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Article

Biostimulant Application as a Tool to Improve Rooting of Olive Tree Cuttings in Brazil

by
Rodrigo José de Vargas
1,*,
Daniela Farinelli
2,*,
Larissa Hiromi Kiahara Sackser
1,
Renan Araujo Sonego
1,
Esperança Paulo Homo
1,
Debora Regina Ferreira da Silva
1,
Simona Lucia Facchin
2,
Chiara Traini
2,
Daniel Fernandes da Silva
3,
Silvia Portarena
4,5 and
Fabiola Villa
1
1
Marechal Cândido Rondon Campus, State University of Western Paraná (Unioeste), Rua Pernambuco, 1777, Marechal Cândido Rondon 85960-000, Brazil
2
Department of Agricultural, Food and Environmental Sciences (DSA3), University of Perugia, Via Borgo XX Giugno 74, 06121 Perugia, Italy
3
Departamento de Botânica (DBOT), Universidade Federal do Paraná (UFPR), Avenida Coronel Francisco Heráclito dos Santos, 100, Jardim das Américas, Curitiba 81531-980, Brazil
4
Institute of Research on Terrestrial Ecosystems (IRET), National Research Council (CNR), Via G. Marconi 2, 05010 Porano, Italy
5
National Biodiversity Future Center, 90133 Palermo, Italy
*
Authors to whom correspondence should be addressed.
Horticulturae 2026, 12(2), 218; https://doi.org/10.3390/horticulturae12020218
Submission received: 12 January 2026 / Revised: 27 January 2026 / Accepted: 9 February 2026 / Published: 10 February 2026
(This article belongs to the Special Issue Agrobiological Means for Sustainable Production in Controlled Environment Agriculture)
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Abstract

In Brazil, the olive tree (Olea europaea) is propagated by cuttings using indole-3-butyric acid (IBA) for rooting and sand as the substrate. Auxin-producing microorganisms may enhance this process when applied together with IBA. This study evaluated the rooting capacity of cuttings from four olive cultivars—Arbequina, Maria da Fé, Ascolano 315, and Koroneiki—treated with commercial products based on microorganisms, plus IBA. The biostimulants used were Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus subtilis, Trichoderma harzianum, and the commercial product Bioraiz® (a mixed mineral fertilizer) in liquid formulation. Trichoderma harzianum and Bacillus spp. improved the quality of rooted cuttings, promoting the formation of more roots per cutting (about 10) and longer roots, on average of 8.1 cm in the cultivars Maria da Fé, Ascolano 315, and Arbequina. Cuttings treated with Trichoderma harzianum, Bacillus subtilis, and Bacillus licheniformis produced higher percentages of rooted cuttings, over 50%, and more developed root systems. Conversely, the control and Bioraiz® showed weaker rooting performance, producing fewer than seven roots per cutting. Overall, the results highlight the potential of biostimulant applications, such as Trichoderma and Bacillus subtilis, as promising tools to optimize the rooting of olive tree cuttings, whereas the fertilizer showed limited effectiveness in promoting rooting.

1. Introduction

Brazil currently has around seven thousand hectares of olive groves and produces approximately 0.2% of the olive oil consumed domestically, with Rio Grande do Sul as the main national producer [1]. The production of olive tree seedlings, and consequently, olive oil cultivation and per capita consumption, is still very limited, highlighting the significant growth potential within the country. In this context, to foster sector development, it is essential that Brazil invests in expanding olive cultivation, prioritizing the application of new technologies in both seedling nurseries and in the field [2]. Seedling production is one of the initial stages in the development of olive cultivation and, at present, is the main problem in olive production in Brazil [1]. As with other fruit species, the quality of commercial olive tree seedlings—whether for establishing new orchards or renewing existing ones—plays a crucial role. Moreover, the use of certified-origin seedlings ensures varietal uniformity and identity, characteristics that directly impact plant productivity [3,4,5].
Commercially, olive seedlings are produced through asexual multiplication, also known as vegetative propagation, a technique that enables greater homogeneity among fruit plants [5]. The most applied method is cutting propagation, using leafy cuttings from healthy, mature mother plants [6]. Several intrinsic and extrinsic factors can influence the rooting of cuttings, such as cultivar selection and the use of phytohormones [7,8,9,10,11]. Endogenous auxin is a limiting factor in the rooting of olive cuttings. Among the class of phytohormones the most used synthetic one in olive propagation is indole-3-butyric acid (IBA), with concentrations ranging from 2000 mg L−1 to 4000 mg L−1, depending on the cultivar, with a percentage of olive tree cuttings rooted ranged, highly variable, for example from 30% in Mission cultivar up to 90% in Alto D’Ouro cultivar [12]. Despite the use of IBA, some cultivars still exhibit low rooting rates, probably due to their woody nature, genetic characteristics, or lack of adaptation to asexual propagation methods [11,13]. In fact, in Brazil, Dalla Rosa et al. reported rooting rates of only 16.25% for Arbequina cultivar cuttings and 37.5% for Maria da Fé cultivar cuttings [13].
Some biostimulants have been studied as alternatives or complements to phytohormones to increase the rhizogenic potential of olive cuttings and possibly reduce nursery time [8,14,15]. For instance, in Brazil, Ferreira et al. [14] have investigated the inoculation of olive tree cuttings from the cultivars Arbequina, Grappolo 541, and Maria da Fé with Rhizophagus clarus, Gigaspora rosea, or Acaulospora scrobiculata, either combined with IBA or not, and concluded that the use of microorganisms for olive tree rooting is not yet an alternative to currently used propagation methods. In fact, without using IBA, the highest proportion of rooting was for cultivar Maria da Fé, with 5.46% rooting [14].
In any case, in Brazil, the number of studies remains low; however, there is significant potential for further research [12,13,16]. Specifically, biostimulants are defined as mixtures of plant regulators—natural or synthetic—algal extracts, microorganisms, and amino acids, and may contain auxins, cytokinins, and gibberellins [17]. The production of these plant regulators is associated with interactions between microorganisms and various plant species. Plants harbor a microbiome with which they maintain an interdependent relationship mediated by signaling pathways. These pathways act in an integrated manner in the formation of these regulators and can enhance plant physiological conditions [18]. This occurs through a complex cellular communication between plants and microorganisms, sustaining a mutualistic relationship that benefits both partners [19]. Biostimulants can improve plant development, specifically in rooting, through different mechanisms, such as the production of indoleacetic acid (IAA) [20]. Almost all groups of microorganisms present in the soil, whether or not associated with plants or not, such as fungi and pathogenic microorganisms, can produce auxins. Their use in preparation for agricultural production is related to bacterial strains capable of synthesizing auxins. This synthesis in microorganisms can occur in various ways, with the gradual conversion of tryptophan to IAA (tryptophan-dependent pathway) being the best known [21]. Recent research has shown that the rooting process of olive cuttings is significantly improved when IBA is combined with biostimulant treatments [11,13,22,23]. For example, in Spain, Montero-Calasanz et al. [23] used several bacterial isolates—namely Pantoea sp. AG9, Chryseobacterium sp. AG13, Chryseobacterium sp. CT348, Pseudomonas sp. CT364, and Azospirillum brasilense Cd (ATCC 29729)—to induce rooting in semi-hardwood cuttings of Arbequina, Hojiblanca, and Picual olive cultivars. They found that under nursery conditions, all tested bacterial strains induced rooting in olive cuttings to a similar or greater extent than control cuttings treated with indole-3-butyric acid (IBA).
In Brazil, Ferreira et al. [14] evaluated the effect of using different Arbuscular Mycorrhizal Fungi (AMF), such as Glomus clarum and Gigaspora rosea, on the growth of seedlings of different olive cultivars with potential for cultivation in the southern region of Minas Gerais. The AMF group provided higher shoot and root dry matter mass in the seedlings. Silva et al. [24] evaluated the effect of Plant Growth-Promoting Rhizobacteria (PGPR) inoculation on the rooting of cuttings of the olive tree cultivars Ascolano 315, Arbequina, and Grappolo 541 under controlled conditions in Maria da Fé (MG, Brazil), with varying results.
Mariosa et al. [25] evaluated the potential of rhizobacteria (isolates 32, 39, 42, and 48) and the type-strains Azospirillum brasilense, Azospirillum amazonense, Herbaspirillum seropedicae, and Burkholderia brasilensis to promote rooting and growth of olive seedlings from semiligneous cuttings of the Grappolo 541 cultivar, and Herbaspirillum seropedicae achieved the best result with a rooting percentage of 50% compared to 20% with IBA. The effect of AMF and PGPR co-inoculation on olive seedling growth was first observed in 2019 and has scarcely been explored in Brazil [26]. Costa and Melloni [27] evaluated, in the cultivars Arbequina and Maria da Fé, the role of cross-inoculation with the rhizobacteria Pseudomonas sp, Paenibacillus, and the AMF group Acaulospora scrobiculata, Gigaspora rosea, and Rhizophagus clarus, showing that for some attributes, there was an isolated effect of FMA or co-inoculation of FMA and rhizobacteria, which provided significant increases in the growth and development of olive tree seedlings.
In Brazil, the most commonly used method for propagating and producing olive tree seedlings is cuttings, although the rooting rate is limited for some cultivars. Some authors [6] evaluated the use of AMF and plant growth-promoting rhizobacteria (PGPR) testing cuttings from four cultivars (Ascolano 315, Koroneiki, Maria da Fé, and Picual) of four-year-old plants, which were inoculated with three species of AMF (Gigaspora margarita, Glomus clarum, and Glomus etunicatum). These were compared with three concentrations of commercial inoculant containing Azospirillum brasilense after treatment with 3000 mg L−1 of indolebutyric acid (IBA). After 75 days, the authors found that the use of AMF in the cultivars Maria da Fé and Picual had a positive effect on rooting.
Recent studies have highlighted how the use of biostimulants may result in plants of better nursery quality, which can enhance rooting success after transplantation into the field [28]. Moreover, the use of microbial stimulants such as Azospirillum brasilense led to higher growth rates, which may indicate a potential reduction in the time seedlings spend in the nursery [28]. A recent review reported that, in Brazil, the effects of the following microorganisms on olive tree cuttings have been studied, in chronological order: Glomus clarum, Gigaspora rosea, Azospirillum brasilense, Azospirillum amazonesnse, Herbaspirillum seropedicae, and Burkholderia brasilensis, Pseudomonas sp., Paenibacillus sp., Acaulospora scrobiculata, Rhizophagus clarus, Glomus margarita, Glomus etunicatum, Azospirillum scrobiculata, Paenibacillus polymyxa, and Pseudomonas protegens [29].
So, according to literature [26], Trichoderma harzianum, which is commonly used to reduce phytohormones and fungicides and is used in agriculture as a biological control agent [30,31,32,33,34], has not applied to olive cutting rooting yet. In fact, although Trichoderma harzianum has been used in nursery production of young olive trees, it has not yet been tested as a biostimulant to promote rooting in olive cuttings [14,31]. Considering that IBA has been commonly used and regarded as essential for rooting olive cuttings [30,31,32,33,34] and that several studies [6,13,15,24] have highlighted the importance of biostimulants in improving the olive cutting rooting efficiency, though with highly variable results and not always positive results; it is necessary to evaluate the effect of other microbial biostimulants on the rooting of olive cuttings, which have not yet been assessed under Brazilian nursery conditions. This study aimed to evaluate the effect of microbial biostimulants (Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus subtilis, and, for the first time, Trichoderma harzianum) and a commercial mixed mineral fertilizer, used in nurseries, always in combination with IBA, on improving the rooting capacity of olive cuttings from four potential olive cultivars in the southwest of Brazil. Since several studies have shown that the rooting process of olive cuttings is significantly improved when IBA is combined with biostimulant treatments [11,13,22,23] and, in contrast, without IBA application, rooting success is very low [14], untreated cuttings were not considered as a control. The evaluation considered both quantitative aspects, such as percentage of rooting and number of roots, and qualitative aspects, such as root length.

2. Materials and Methods

2.1. Location and Climatic Conditions

The experiment was carried out at the “Professor Doutor Mário Cesar Lopes” Protected Cultivation and Biological Control Station belonging to the State University of Western Paraná (Unioeste), Marechal Cândido Rondon Campus, Paraná (Brazil) (latitude 24°33′22″ S, longitude 54°03′24″ W, altitude of 420 m a.s.l.). The climate, according to the Köppen classification, is type Cfa, humid mesothermal subtropical, with hot summers, infrequent frosts, and concentrated rainfall in the summer months, with no defined dry season [35].

2.2. Plant Material, Treatments, and Growing Conditions

The olive branches were collected after pruning in September 2024, from seven-year-old mother plants maintained in the orchard of Unioeste’s Experimental Farm. Four olive cultivars (Arbequina, Maria da Fé, Ascolano 315, and Koroneiki) were used in the experiment with four microbial biostimulants for rooting the cuttings and a commercial fertilizer commonly used in nurseries. The biostimulants used were Bacillus-based (Bacillus amyloliquefaciens, CCT7466; Bacillus licheniformis, CCT0032; Bacillus subtilis, ATCC6051; later B. amyloliquefaciens, B. licheniformis, and B. subtilis), Trichoderma harzianium, IB19/17 (later Trichoderma), and a commercial product Bioraiz® (a commercial mixed mineral fertilizer, later Bioraiz) in liquid formulation.
Bioraiz (Biosul Vacaria Rio Grande do Sul, Brazil) contains zinc (Zn), a micronutrient directly associated with the formation of the amino acid tryptophan, which is enzymatically transformed into auxin or indoleacetic acid, an important growth hormone. It also contains molybdenum (Mo) and manganese (Mn), which activate important enzymes in plant metabolism, in addition to the essential macronutrients of nitrogen (N) and sulfur (S). Bioraiz was applied once with a dose of 15 mL L−1 according to the manufacturer’s recommendations.
The Bacillus formulations had a concentration of 108 CFU, and the applied dosage was 5 mL L−1 of water, according to the manufacturer’s recommendations. The Trichoderma formulation had a concentration of 109 CFU and was applied at a dosage of 5 mL L−1 of water, also following the manufacturer’s guidelines. For each treatment, a total volume of 2 L of water was used. The experiment was initiated in the spring, a period characterized by milder temperatures and increased plant metabolic activity. Treatments were applied only once, at the beginning of October 2024, directly to the sand substrate. Sand was selected as the rooting medium because it is an inert, low-cost material that maintains stable pH and provides excellent drainage compared to other substrates.
All biostimulants used in the experiments were diluted, according to the manufacturer’s instructions, resulting in a final total volume of 2000 mL, which was applied directly to the sand according to the respective treatments. The semi-hardwood olive tree cuttings were collected from the olive mother plants and brought to the seedling nursery to prepare the cuttings for rooting, with an average length of 12 cm and an average diameter of 4 mm, maintaining two pairs of leaves in the upper part and a straight cut at the base [11,14]. The experiment was conducted under greenhouse conditions, allowing approximately 70% of incident solar radiation thanks to a shade net (ChromatiNET®, Ginegar, Lem, São Paulo, Brazil), using a masonry propagation bed filled with washed, medium-textured sand, previously sterilized with 2.5% sodium hypochlorite two days prior to the establishment of the experiment. A mini-greenhouse with transparent plastic (polyvinyl chloride “PVC”) was built over the seedbed, and an irrigation system was installed, with the cuttings irrigated daily, by intermittent misting, with a frequency of 5 min and an interval of 1 h (Figure 1).
Throughout the experiment, phytosanitary control was performed visually and, when necessary, agrochemicals were applied.
Since, without an IBA application, rooting success is very low [14], untreated cuttings were not considered as a control. The control thesis is represented by cuttings treated only with IBA, later named only control.
Biostimulants were considered as treatments, applied to the sand/treatment + 3000 mg L−1 of indolebutyric acid per treatment to standardize the treatments [32,33,34], since the rooting rate of all cultivars is low without the use of IBA [11,13,22,23], being: control (indolebutyric acid only—IBA), Bacillus amyloliquefaciens + IBA, Bacillus licheniformis + IBA, Bacillus subtilis + IBA, Trichoderma harzianium + IBA, and Bioraiz® + IBA. The IBA was diluted in a solution of 250 mL of 70% alcohol and 250 mL of distilled water, where the cuttings were immersed for 15 s [36].

2.3. Experimental Design, Parameters, and Data Analysis

The experimental design used was randomized blocks, in a 6 × 4 factorial scheme (6 biostimulants times 4 olive cultivars), where for each variety, each biostimulant was applied to 100 cuttings divided into four randomized blocks. The cuttings within each block shared the same micro-environmental conditions, and the measurements were taken on all the cuttings in the trial (Figure 1).
After 70 days, some non-destructive parameters were evaluated, such as rooted cuttings (%) unrooted cuttings (%) (meaning cuttings that had formed neither roots nor callus, effectively no longer viable) and cuttings with callused (percentage of calluses), expressed as the number of rooted cuttings, the number of unrooted cuttings without callus and the number of cuttings with callus relative to the 25 cuttings present in each block per 100 (Figure 2). Moreover, the total number of roots formed above 1 cm and the number of shoots per cutting were counted; the length of the longest root and the average length of shoots of each cutting were measured using a ruler, and the diameter of the shoot was measured using a caliper (Figure 3).
To evaluate the effect of biostimulants on root formation and shoot formation, two indices were processed: Root Index and Shoot Index.
Root Index = number of roots × length of the longest root.
Shoot Index = number of shoots × shoot length × shoot diameter.
Data were analyzed using a multifactor ANOVA with the factors being the cultivar and the biostimulant. Significant differences were detected using Duncan’s test at α = 0.05, using the Infostat software version 2020 [3]. In the figures and tables, the mean values for each cultivar and treatment are accompanied by the standard error (S.E.).
The normality of the residuals was checked and confirmed with the Shapiro–Wilk test implemented in the R statistical environment (MetStaT, v 1.0, 2013, R Development Core Team, 2014).
Moreover, a correlation between the total number of roots and the length of the longest root in rooted cuttings of olive cultivars was evaluated. In fact, in the case of woody cuttings, the correlation can be used to demonstrate a favorable relationship between the number of roots and their length [37]. Specifically, the Pearson correlation coefficient is used between two quantitative variables provided that their distribution is normal and exhibits a linear behavior [38]. In the agricultural sector, it is applied in various studies across different segments, such as floriculture and fruit growth. In fruit growing, the correlation can be used for different variables, both in the aerial part of the plant and in the root system [39]. A study presented by [39] with Tectona grandis evaluated specific root areas of fine and medium roots. The study showed that this correlation differed between variables, demonstrating that fine roots have a greater specific root area, representing a higher growth and renewal rate.
Principal Component Analysis (PCA) was used to evaluate multivariate relationships among rooting- and shooting-related traits and to explore variability among samples. The data matrix consisted of block means for each treatment × cultivar combination, resulting in a total of 96 observations. Four variables (rooted cuttings (RC), root index (RI), callus formation (C), and shoot index (SI); columns). Before analysis, all variables were mean-centered and scaled to unit variance (z-score standardization), and PCA was performed on the resulting correlation matrix. The analysis reduced data dimensionality by summarizing the original variables into a smaller set of independent principal components, defined as linear combinations of the original variables and ordered according to the amount of variance explained.

3. Results

3.1. Percentage of Rooted Cuttings and Unrooted Cuttings

Cuttings treated with Trichoderma showed the highest percentage of rooted cuttings, equal to 58.5%, followed by those of B. licheniformis and B. subtilis, which showed the rooting rates of cuttings not significantly different from that of the control, respectively 51%, 49.3%, and 46.3% (Table 1). While cuttings treated with B. amyloliquefaciens and Bioraiz showed the significantly lowest rooted rate as percentage compared to the other treatments, respectively 36% and 37.5% (Table 1).
The Maria da Fé and Ascolano 315 cultivars have achieved a good rooting rate as a percentage of rooted cuttings, on average, 51%. On the contrary, the Koroneiki and Arbequina cultivars showed significantly lower rooting (Table 1). A significant interaction was observed between biostimulants and cultivar on rooted cutting percentage (Table 1).
In the Arbequina cultivar, the percentage of rooted cuttings was positively affected by Trichoderma application, significantly different from that of the control (Table 1). In the Ascolano 315 cultivar, the percentage of rooted cuttings was significantly lower in cuttings treated with Bioraiz compared to the others (Table 1). In the Maria da Fè cultivar, the biostimulant applications improved the percentage of rooted cuttings, except with B. amyloliquefaciens, which obtained rooting values like those of the control plants (Table 1). On the contrary, in the Koroneiki cultivar, the percentage of rooted cuttings was not significantly improved by biostimulant application (Table 1).
Cuttings treated with B. amyloliquefaciens and Bioraiz showed the highest percentage of unrooted cuttings, equal to 59.3% in average (Figure S1a). While cuttings treated with Trichoderma showed the significantly lowest unrooted rate compared to the other treatments, equal to 43.9% (Figure S1a). The Arbequina cultivar showed the highest percentage of unrooted cuttings, over 60%, followed by the Koroneiki one of 51.8%. On the contrary, the Maria da Fé and Ascolano 315 cultivars reported significantly lower unrooted cutting percentage, on average 47.2% (Figure S1b). In the Arbequina cultivar, the percentage of unrooted cuttings was significantly lower in cuttings treated with Trichoderma, significantly different from that of the control (Figure S1c). On the contrary, in the Ascolano 315 cultivar, the percentage of unrooted cuttings was significantly higher in the cutting treated with Bioraiz compared to all other treatments and also the control (Figure S1d). In the Maria da Fé cultivar, the percentage of unrooted cuttings was significantly higher in cuttings treated with B. amyloliquefaciens than in the control (Figure S1e). In the Koroneiki cultivar, the percentage of unrooted cuttings varied a lot according to the treatment; in fact, it was significantly higher in cuttings treated with B. amyloliquefaciens, followed by those treated with Bioraiz and B. licheniformis, while the lowest percentages were observed under control and Trichoderma application (Figure S1f).

3.2. Number of Roots and Length of Roots

Concerning the effects of treatments on the rooting of the cuttings, significant differences were observed in the number of new roots obtained with Trichoderma (10 roots), with respect to those with the control, while B. amyloliquefaciens and Bioraiz produced, on average, only 6.9 roots (Figure 4a).
The Arbequina, Maria da Fé, and Koroneiki cultivars formed a not significantly different number of roots, on average, 5.9 roots. While the Ascolano 315 cultivar formed significantly higher roots, equal to 14.4 (Figure 4b).
A significant interaction was observed for the number of roots between cultivar and treatments. In the Arbequina and Maria da Fé cultivars, Trichoderma significantly improved the number of new roots (Figure 4c,e). In the Ascolano 315 cultivar, B. amyloliquefaciens produced a significantly greater number of roots than the control (Figure 4d), while in the Koroneiki cultivar, it resulted in a lower number of roots (Figure 4f).
Regarding the effect of the treatments on the length of the longest root, significant differences were observed among cultivars and treatments (Figure 5). The treatments of B. subtilis, B. licheniformis, Trichoderma, and the control showed an average root length of 8.1 cm, whereas B. amyloliquefaciens and Bioraiz presented a lower average of 5 cm (Table 2). The cultivars Ascolano 315, Koroneiki, and Maria da Fé produced roots with similar lengths, with an average of 7.9 cm (Table 2). In contrast, the cultivar Arbequina exhibited a significantly shorter root, with an average of 4.3 cm (Table 2).
In the Arbequina cultivar, the shortest roots were observed on cutting treated with B. amyloliquefaciens and Bioraiz (Table 2). In the Ascolano 315 cultivar, treatment with B. subtilis produced the longest roots, reaching up to 12.8 cm, although this was not significantly different from the control, which measured 10.3 cm. However, both were much longer than the roots of cuttings treated with B. licheniformis and Bioraiz (Table 2). In the Maria da Fè cultivar, Trichoderma and B. subtilis produced the longest roots, on average 8.8 cm, although this was not significantly different from the control (Table 2). In the Koroneiki cultivar, B. licheniformis significantly increased the root length, reaching up to 14.3 cm (Table 2).
A positive and significant correlation was observed between the number of roots and their length in the Arbequina, Maria da Fé, and Koroneiki cultivars, indicating that greater root length was associated with a higher number of roots (Table 3).

3.3. Number of Shoots, Shoot Length, and Shoot Diameter

Regarding the effects of the treatments on the number of shoots, significant differences were observed among them. The treatments of B. amyloliquefaciens, B. licheniformis, Trichoderma, and the control produced an average of 0.14 shoots, whereas B. subtilis and Bioraiz showed a lower average of shoots, only 0.03 (Figure 6a). All cultivars exhibited a not different number of shoots, with an average of 0.10 shoots (Figure 6b). In the Arbequina cultivar, the treatments did not significantly affect the number of shoots (Figure 6c). In the Ascolano 315 cultivar, B. licheniformis and Trichoderma positively affected the number of shoots, although this was not significantly different from the control (Figure 6d). The Maria da Fé cultivar exhibited more shoots with B. amyloliquefaciens (Figure 6e), while in the Koroneiki cultivar, no effect was observed (Figure 6f).
For shoot length, Bacillus amyloliquefaciens showed higher mean values compared to the other treatments; however, no statistical difference was observed between this treatment, B. licheniformis, Trichoderma, and the control (Table 4). Among the cultivars, the Maria da Fé cultivar produced longer shoots than the others, while the Arbequina cultivar produced shorter shoots (Table 4). When evaluated separately in relation to the treatments, the cultivars Arbequina and Koroneiki showed no statistically significant differences among treatments (Table 4). In contrast, for the cultivar Ascolano 315, a statistically significant difference was observed with B. licheniformis compared to the others (Table 4). For the cultivar Maria da Fé, a significant difference was observed in the cuttings treated with B. amyloliquefaciens (Table 4).
Regarding the effects of the treatments on the shoot diameter, significant differences were observed among treatments. The control, B. amyloliquefaciens, and B. licheniformis treatments produced an average shoot diameter of 0.3 mm (Figure 7a). In addition, all cultivars exhibited similar shoot diameter, around 0.3 mm, with no statistically significant differences among them (Figure 7b). The cultivar Arbequina showed no statistically significant differences among treatments (Figure 7c). For the Ascolano 315 cultivar, significant statistical differences were observed on the cuttings treated with the B. licheniformis (Figure 7d). The B. amyloliquefaciens exhibited a statistically significant difference in the cultivar Maria da Fé (Figure 7e). In the Koroneiki cultivar, the best response was observed with the control treatment, which differed significantly from the other treatments (Figure 7f).

3.4. Number of Calluses and Percentage of Calluses

Regarding the effects of the treatments on the number of calluses, the Trichoderma treatment yielded significantly higher results, producing an average of 0.34 calluses compared to the mean of 0.13 calluses observed in the other treatments (Table 5). In contrast, all cultivars presented similar callus numbers, with no statistically significant differences (Table 5). For the cultivars Arbequina and Koroneiki, no significant differences were observed among treatments (Table 5). In the cultivars Ascolano 315 and Maria da Fé, a statistically significant difference was observed in the cuttings treated with Trichoderma, although the number of calluses was very low (Table 5).
Treatment with Trichoderma resulted in a significantly higher callus formation rate, with an average of 1.35%, compared to the mean of 0.52% observed in the other treatments (Figure 8a). Across cultivars, the percentage of callus formation was similar, with all genotypes showing an average of 0.66%, and no significant differences were detected (Figure 8b). However, when evaluated separately, an interesting result was found for the cultivar Ascolano 315, in which the Trichoderma treatment showed a big statistical difference compared to the other treatments (Figure 8d).

3.5. Shooting Index and Root Index

Treatment with B. amyloliquefaciens resulted in a significantly higher shoot formation rate according to the shoot index (Table 6). Among the cultivars, Maria da Fé showed the highest value, while the Arbequina cultivar showed the lowest (Table 6). However, when the cultivars were evaluated separately, they exhibited significantly different responses to the treatments. The cultivars Arbequina and Koroneiki showed no significant differences in shoot formation according to the shoot index (Table 6). In contrast, the cultivar Ascolano 315 showed greater shoot formation under the B. licheniformis treatment, with a significant difference compared to the other treatments based on the shoot index (Table 6). The cultivar Maria da Fé produced a higher number of shoots in the B. amyloliquefaciens treatment compared with the other treatments, according to the shoot index (Table 6).
According to the rooting index, only Bioraiz showed a significant difference compared with the other treatments, with a lower rooting rate (Figure 9a). Among the cultivars, the Root Index was highest for Ascolano 315, with significant differences compared with the other cultivars (Figure 9b). When the cultivars were evaluated separately, they exhibited distinct responses according to the Root Index. The cultivar Arbequina showed a significantly high value with the Trichoderma treatment and low values under B. amyloliquefaciens and Bioraiz (Figure 9c). The cultivar Ascolano 315 showed a significant Root Index under B. amyloliquefaciens and B. subtilis treatments, with no significant difference from the control (Figure 9d). The cultivar Maria da Fé exhibited the highest Root Index, with significant values under the Trichoderma treatment (Figure 9e). The cultivar Koroneiki showed significant results for the B. licheniformis treatment (Figure 9f).

3.6. PCA

The scatter plots illustrate the geometric distances among samples in the two-dimensional space defined by PC1 and PC2. The first two PCs explained 64.3% of the total variability, with PC1 accounting for 36.9% and representing the main axis of separation among treatments. Rooted cuttings % (RC) and root index (RI) were the descriptors contributing most strongly to PC1, while calluses Percentage (C) and shoot index (SI) loaded mainly on PC2 (27.4%) (Figure 10).
The distribution of samples clearly differentiated the effect of the biostimulant treatments. Cuttings treated with the Trichoderma, B. subtilis, and B. licheniformis clustered toward the positive side of PC1, corresponding to higher rooting cutting percentages and more developed root systems. Conversely, the control and Bioraiz groups were predominantly located in the negative PC1 region, consistent with their weaker rooting performance. The B. amyloliquefaciens displayed a broader dispersion across the PCA space, with some cuttings aligning with improved rooting capacity (positive PC1), but many positioned toward the negative direction (Figure 10).

4. Discussion

In general, the rooting of olive cuttings, regardless of the cultivar studied, is low due to intrinsic and extrinsic factors, such as the cultivar’s genetics, the presence of oxidative compounds, and hormonal balance [40,41]. Rooting cuttings for fruit seedling production is an important propagation method; however, root development may vary according to the species and local environmental conditions [42]. In the production of olive rooted cuttings, Pio et al. [32] demonstrated that the use of IBA at 3 g L−1 affects the root system characteristics, especially the number of roots and root length. Even with hormone treatment, olive tree cuttings are difficult to root, and the results vary according to the cultivar, time of year, and plant phenological status [14]. The adventitious rooting in olive cuttings is understood as a multifactorial physiological process involving hormonal, metabolic, and molecular mechanisms [42,43]. Auxin is the “master regulator” of root induction. In olive cuttings, Indole-3-butyric acid (IBA) is typically applied to trigger the process.
Biostimulants have a potential role in the development of adventitious root formation [7,44]. In fact, they enhance adventitious rooting by acting as signaling molecules that boost endogenous phytohormone synthesis—particularly auxins—and modulating auxin-responsive genes. They stimulate root initiation, increase root density/length, and improve nutrient uptake, often acting through brassinosteroid-mediated pathways or by improving carbohydrate metabolism. They act on the metabolism, signaling, and conjugation of hormones to create an optimal environment for root development, particularly by elevating auxin levels, which are critical for root induction [45].
In the present study, regardless of the biostimulant used, the cultivars showed a rooting potential of around 48%, a promising result considering that most olive cultivars exhibit low rooting rates during cutting propagation [43].
Maria da Fè and Koroneiki cultivars achieved better and higher rooting results compared to those observed by [3,14] and in a previous study carried out by [13]. Ascolano 315 also achieved better rooting (around 51%) than reported in a previous study [6]. The Arbequina cultivar showed a low rooting rate (38.4%), although still better than observed by [13,14], confirming the findings of [45], who stated that this cultivar has low rooting potential, depending directly on the substrate used. This contrasts, however, with [45], who reported improved results when a perlite bed is used, while the current study was conducted on sand. The rooting percentage obtained in the Arbequina cultivar from cuttings taken in spring is consistent with the findings of Denaxa et al. [46] in Greece, suggesting that better results may be achieved by taking cuttings in summer, although treatment with Tricoderma resulted in a significant increase in rooting.
In agreement with [12], the cuttings of the other cultivars root easily, even when the substrate is sand, due to its good moisture retention, which is essential for the root system formation.
Although endogenous hormone levels were not quantified, the literature suggests that the low rooting observed in Arbequina cuttings may be associated with a high concentration of endogenous cytokinins, which is unbalanced relative to the auxins responsible for root formation. Additionally, differences in enzymatic activity and anatomical structures may also contribute to this response compared with the other cultivars evaluated [31,46]. In contrast, the Maria da Fé cultivar is well-adapted to Brazilian climatic conditions, which favors the rooting of cuttings and the formation of quality seedlings [44].
When comparing the control (in which only indole-3-butyric acid—IBA—was used) with the other treatments, a significant increase in rooting rate was observed when biostimulants were applied. Among the various biostimulants, Trichoderma was the most effective, while B. amyloliquefaciens and Bioraiz, a commercial mixed mineral fertilizer, did not result in good rooting. None of these processes was directly measured in this experiment, but, according to the literature, these results may be attributed to the ability of Trichoderma spp. to secrete secondary metabolites that suppress the growth of phytopathogenic microorganisms, thereby promoting plant growth [47,48]. In addition, Trichoderma promotes plant growth through the production of growth-regulating hormones, mainly from the auxin and gibberellin groups [49]. Furthermore, its application can regulate the root architecture of cuttings, increasing the growth of primary and lateral roots [50].
In seedling production in protected environments, this biostimulant has been used to reduce the use of phytohormones and fungicides [14,31]. Generally, cuttings of the Arbequina cultivar have shorter and fewer roots compared to other cultivars. According to some studies, the cutting period for Arbequina should be longer than for other cultivars, around 100 days [51].
It has been observed that cuttings of the Ascolano 315 cultivar produced a higher number of roots when treated with microbial biostimulants, regardless of the species used. Research shows that Bacillus can produce auxins [52], and B. subtilis, B. licheniformis, and B. amyloliquefaciens, when combined with IBA, can increase the number of roots and shoots, as well as improve root hair growth, thereby increasing the absorption area [53].
The positive effect of B. subtilis on olive cutting production may be attributed to its ability to produce up to 231 different types of secondary metabolites, thus revealing a complex interaction capacity between these metabolites and the environment in which they act, thereby influencing the efficiency of cutting rooting [54]. Due to its antioxidant properties, it may also help reduce oxidative effects on roots, protecting them in situations of biotic and abiotic stress [55].
The commercial product Bioraiz®, a mixed mineral fertilizer composed of 5% nitrogen (N), 3% sulfur (S), 4% zinc (Zn), 0.2% molybdenum (Mo), 2% manganese (Mn), 10% amino acids, 50% plant extracts and 6% algal extracts, elements important for the adventitious rooting of cuttings, did not significantly influence the rooting process after 70 days [56]. This may be because mineral nutrition can directly influence the rooting of cuttings, but only in correlation with the nutritional status of the mother plant. Therefore, more frequent applications or higher doses could yield better results [57]. This result does not agree with that reported by [58], who observed a positive effect on the rooting of Ascolano 315 and Arbequina cuttings using different fertilizers. This could be explained by the different dosage used, which was 25 mL L−1 or 25 g L−1, higher than that used in this study.
A positive correlation was observed between the number of roots and the length of the longest root in cuttings of olive cultivars, except in the Ascolano 315 cultivar. This may be explained by this cultivar’s strong ability to produce many long roots in a short time, as previously observed by [6].
Shoot formation was very limited compared to other studies [6,15], but was slightly higher in cuttings of the Maria da Fé cultivar than in those of other cultivars and increased when treated with B. amyloliquefaciens. This suggests that, for this cultivar, interaction with this microbial biostimulant is more effective in stimulating lateral shoot production than root formation. These findings highlight the cultivar-specific nature of microbial interactions and the importance of tailoring inoculation strategies to the genetic and physiological characteristics of each olive cultivar, as previously observed by [15] with other bacteria.
Callogenesis was very limited in the present study, with rates below 1%, which is much lower than those reported by [6], 10.97% in the Arbequina cultivar, and 19.58% in the Koroneiki cultivar, and 1.33% in the Ascolano 315 cultivar. The number of calluses, between 0.1 and 0.3, was also much lower than those reported by [14] for Arbequina (2.75) and Maria da Fé (5.75) cultivars. It can therefore be inferred that in this study, treatment with Trichoderma stimulated rapid rooting of the cuttings, as indicated by the low percentage of cuttings with callus after 70 days. The formation of calluses in cuttings is possibly an event associated with rooting, as it is a process of regeneration of the cutting, due to the injury caused by the cut at the base [59]. Rooting is more expected than callusing, but callusing is not considered undesirable, as in some commercial nurseries, if the cutting is alive and has calluses or shows basal thickening, it is returned to the rooting bed [30].
Among the four microbial biostimulants tested, Trichoderma was the most effective, followed by B. subtilis and B. licheniformis. Ref. [60] reported that delivering Trichoderma spp. to soil increases the population dynamics of augmented fungal antagonists, thereby suppressing the establishment of pathogenic microbes at the infection site. The endophytic bacteria Pseudomonas fluorescens and Bacillus sp., as well as fungal species of Trichoderma sp., are considered important biocontrol agents against olive diseases such as Verticillium wilt, root rot, and anthracnose. Applying biocontrol agents to olive trees during the initial propagation stage is recommended, as early treatment with bio-fungicides can significantly reduce symptoms caused by pathogens in the field [61,62]. Therefore, the use of microorganisms can be considered beneficial, as it contributes to plant rooting [63].

5. Conclusions

The use of olive cuttings is effective for producing quality seedlings; however, each cultivar has its own rooting characteristics. This can be a problem for nurserymen, as large-scale production is necessary in Brazil. Given this situation, the use of biostimulants could help to improve the rooting of olive cuttings and increase both the number and quality of roots, as well as reduce the nursery time. The combination of microbial biostimulants, such as Trichoderma harzianum, Bacillus subtilis, and Bacillus licheniformis, with IBA has positively affected the rooting of olive cuttings, enabling the production of plants with better development, which may, in turn, increase the success of rooting after transplanting to the field. However, field tests should be conducted.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/horticulturae12020218/s1, Figure S1. Unrooted cutting percentage according to different treatments (a), cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in unrooted cutting percentage (p < 0.05) among the mean values of the treatments and cultivars. Each mean value is ±S.E.

Author Contributions

Conceptualization, R.J.d.V., F.V. and D.R.F.d.S.; methodology, F.V. and D.R.F.d.S.; software, R.J.d.V. and S.P.; validation, R.J.d.V., F.V. and D.R.F.d.S.; formal analysis, R.J.d.V.; investigation, R.J.d.V., L.H.K.S., R.A.S., E.P.H. and D.F.d.S.; resources, F.V.; data curation, R.J.d.V., S.L.F., C.T. and D.F.d.S.; writing—original draft preparation, R.J.d.V. and D.F.; writing—review and editing, R.J.d.V., D.F.d.S., C.T., S.P. and F.V.; visualization, D.F.d.S. and R.J.d.V.; supervision, F.V.; project administration, F.V.; funding acquisition, F.V. and D.F.d.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brazil (CAPES)—Finance Code 001.

Data Availability Statement

The original contributions presented in this study are included in the article/supplementary material. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Chacon-Ortiz, A.; Maia, L.C.; Oliveira, A.C.; Perruolo, G.; Pegoraro, C. Olive trees in the world. Past and present with future perspectives. Rev. Ciências Agroveterinárias 2024, 23, 143–152. [Google Scholar] [CrossRef]
  2. Rocha, T.P.; Barata, A.J.T.S.S.; Alves, R.R. Sale of Extra Virgin Olive Oil in The World. Sci. J. Appl. Soc. Clin. Sci. 2024, 4, 2–6. [Google Scholar] [CrossRef]
  3. Ali, M.H.; Ahmad, W.; Usman, M. Rooting ability of different olive cultivars through cuttings in basal heating system. Int. J. Res. Sch. 2019, 3, 1–4. [Google Scholar]
  4. Schuch, M.W.; Tomaz, Z.F.P.; Casarin, J.V.; Moreira, R.M.; Silva, J.B. Advances in vegetative propagation of olive tree. Rev. Bras. Frutic. 2019, 41, e-003. [Google Scholar] [CrossRef]
  5. Foladori-Invernizzi, S.; Maggioni, R.; Zuffelato-Ribas, K.C. Estado da arte da propagação vegetativa por estaquia de espécies arbustivo-arbóreas. Rev. Eletrônica Científica UERGS 2021, 7, 50–63. [Google Scholar] [CrossRef]
  6. Ritter, G.; Villa, F.; Silva, D.F.; Alberton, O.; Menegusso, F.J.; Eberling, T.; Dória, J. Microbiological biostimulant promotes rooting of olive cuttings. Int. J. Agric. Biol. Eng. 2021, 14, 207–212. [Google Scholar] [CrossRef]
  7. Citernesi, A.S.; Vitagliano, C.; Giovannetti, M. Plant growth and root system morphology of Olea europaea L. rooted cuttings as influenced by arbuscular mycorrhizas. J. Hortic. Sci. Biotechnol. 1998, 73, 647–654. [Google Scholar] [CrossRef]
  8. Montero-Calasanz, M.C.; Göker, C.; Rohde, M.; Spröer, C.; Schumann, P.; Busse, H.J.; Schmid, M.; Tindall, B.J.; Klenk, H.P.; Camacho, M. Chryseobacterium hispalense sp. nov., a plant-growth-promoting bacterium isolated from a rainwater pond in an olive plant nursery, and emended descriptions of Chryseobacterium defluvii, Chryseobacterium indologenes, Chryseobacterium wanjuense and Chryseobacterium gregarium. Int. J. Syst. Evol. Microbiol. 2013, 63, 4386–4395. [Google Scholar] [CrossRef]
  9. Rashedy, A.; Hamed, H.H.; Eldeeb, W.A.M. Antioxidant procedure improve olive cuttings rooting during the cool season. Egypt. J. Hortic. 2021, 48, 267–275. [Google Scholar] [CrossRef]
  10. Shereen, A.S. Rooting ability of some olive genotypes by sub-terminal cuttings. J. Hortic. Sci. Ornam. Plants 2019, 11, 27–37. [Google Scholar]
  11. Lambardi, M.; Fabbri, A.; Micheli, M.; Vitale, A. Olive propagation and nursery. In The Olive Botany and Production; Fabbri, A., Baldoni, L., Caruso, T., Famiani, F., Eds.; CAB International: Wallingford, UK, 2023; pp. 228–256. [Google Scholar] [CrossRef]
  12. Villa, F.; Silva, D.F.; Dall’Oglio, P.; Potrich, C.; Menegusso, F.J. Performance of substrates in rooting capacity of olive tree cuttings. Rev. Ciências Agroveterinárias 2017, 16, 95–101. [Google Scholar] [CrossRef]
  13. Dalla Rosa, D.; Silva, D.F.; Corbari, F. Rooting semihardwood cuttings of olive: Indolbutyric acid, calcium and Azospirillum brasilense. Comun. Sci. 2018, 9, 34–40. [Google Scholar] [CrossRef][Green Version]
  14. Ferreira, G.M.R.; Silva, L.F.O.; Pasqual, M.; Melloni, R.; Luz, J.M.Q.; Dória, J. Microbial biostimulants as alternatives for the rooting of olive tree cuttings. Biosci. J. 2022, 38, e38091. [Google Scholar] [CrossRef]
  15. Areek, F.; Seifi, E.; Alizadeh, M.; Olamaee, M.; Malekzadeh, E. Effects of PGPR inoculation on adventitious rooting and growth attributes in olive microcuttings of ‘Mission’ and ‘Koroneiki’ cultivars. J. Hortic. Postharvest Res. 2025, 8, 335–350. [Google Scholar] [CrossRef]
  16. Costa, S.M.L.; Melloni, R. Relação de fungos micorrízicos arbusculares e rizobactérias no crescimento de mudas de oliveira (Olea europaea). Ciência Florest. 2019, 29, 169–180. [Google Scholar] [CrossRef]
  17. Meyer-Ficca, M.; Kirkland, J.B.N. Niacin. Adv. Nutr. 2016, 7, 556–558. [Google Scholar] [CrossRef]
  18. Trivedi, P.; Leach, J.E.; Tringe, S.G.; Sa, T.; Singh, B.K. Plant–microbiome interactions: From community assembly to plant health. Nat. Rev. Microbiol. 2020, 18, 607–621. [Google Scholar] [CrossRef]
  19. Biswas, A.; Sarkar, D.; Ullah, H.; Himanshu, S.K.; Praseartkul, P.; Tisarum, R.; Datta, A. Exogenous application of silicon and methyl jasmonate alleviates drought-induced stress in sweet Basil plants by improving morpho-physio-biochemical attributes. J. Soil Sci. Plant Nutr. 2025, 25, 9713–9727. [Google Scholar] [CrossRef]
  20. Ramos-Cruz, D.; Troyee, A.N.; Becker, C. Epigenetics in plant organismic interactions. Curr. Opin. Plant Biol. 2021, 61, 102060. [Google Scholar] [CrossRef]
  21. Pirog, T.P.; Piatetska, D.V.; Klymenko, N.O.; Iutynska, H.O. Ways of auxin biosynthesis in microorganisms. Microbiol. J. 2022, 84, 57–72. [Google Scholar] [CrossRef]
  22. Ali, O.; Adesh, R.; Jayaraj, J. Biostimulant properties of seaweed extracts in plants: Implications towards sustainable crop production. Plants 2021, 10, 531. [Google Scholar] [CrossRef] [PubMed]
  23. Montero-Calasanz, M.C.; Santamaría, C.; Albareda, M.; Daza, A.; Duan, J.; Glick, B.R.; Camacho, M. Alternative rooting induction of semi-hardwood olive cuttings by several auxin-producing bacteria for organic agriculture systems. Span. J. Agric. Res. 2013, 11, 146–154. [Google Scholar] [CrossRef]
  24. Silva, T.F.; Melloni, R.; Melloni, E.G.P.; Goncalves, E.D. BACTÉRIAS DIAZOTRÓFICAS NÃO SIMBIÓTICAS E ENRAIZAMENTO DE ESTACAS SEMILENHOSAS DE OLIVEIRA (Olea europaea L.). Ciência Florest. 2017, 27, 61–71. [Google Scholar] [CrossRef]
  25. Mariosa, T.N.; Melloni, E.G.P.; Melloni, R.; Ferreira, G.M.R.; Souza, S.M.P.; Silva, L.F.O. Rizobactérias e desenvolvimen-to de mudas a partir de estacas semilenhosas de oliveira (Olea europaea L.). Amazon. J. Agric. Environ. Sci. 2017, 60, 302–306. [Google Scholar] [CrossRef]
  26. Melloni, R.; Cardoso, E.J.B.N. Microbiome Associated with Olive Cultivation: A Review. Plants 2023, 12, 897. [Google Scholar] [CrossRef]
  27. Lopes, J.I.; Correia, C.M.; Gonçalves, A.; Silva, E.; Martins, S.; Arrobas, M.; Rodrigues, M.Â. Arbuscular mycorrhizal fungi inoculation reduced the growth of pre-rooted olive cuttings in a greenhouse. Soil Syst. 2021, 5, 30. [Google Scholar] [CrossRef]
  28. Ritter, G.; de Vargas, R.J.; Farinelli, D.; Cinosi, N.; Traini, C.; Facchin, S.L.; Villa, F. Application of Azospirillum brasilense and Humic Substances Improves the Nursery Quality of Olive Seedlings in Pots. Horticulturae 2025, 11, 48. [Google Scholar] [CrossRef]
  29. Fosso, E.; Gizzi, G.; Tartaglia, M.; Prigioniero, A.; Ranauda, M.A.; Maisto, M.; Labella-Ortega, M.; Zuzolo, D.; Guarino, C. Management affects the diversity and functions of root and leaf-associated microbiomes: Implications for olive resilience. Front. Plant Sci. 2026, 16, 1699667. [Google Scholar] [CrossRef]
  30. Di Vaio, C.; Testa, A.; Cirillo, A.; Conti, S. Slow-release fertilization and Trichoderma harzianum-based biostimulant for the nursery production of young olive trees (Olea europaea L.). Agron. Res. 2021, 19, 1396–1405. [Google Scholar] [CrossRef]
  31. Mackenzie, A.J. Trichoderma harzianum as a Growth Enhancer of Pot and Cut Floriculture Crops. Master’s Thesis, University of Tennessee, Knoxville, TN, USA, 1995. Available online: https://trace.tennessee.edu/utk_gradthes/6849/ (accessed on 30 December 2025).
  32. Pio, R.; Bastos, D.C.; Berti, A.J.; Scarpare Filho, J.A.; Mourão Filho, F.D.A.A.; Entelmann, F.A.; Bettiol Neto, J.E. Enraizamento de diferentes tipos de estacas de oliveira (Olea europaea L.) utilizando ácido indolbutírico. Ciência Agrotecnologia 2005, 29, 562–567. [Google Scholar] [CrossRef]
  33. Rahman, S.U.; Shah, B.H.; Qamar, S.; Alam, R.; Akhtar, W.; Ahmed, I.; Iqbal, M. Comparative influence of different concentrations of indole butyric acid (IBA) on the propagation success of two olive varieties. Sarhad J. Agric. 2025, 41, 709–715. [Google Scholar] [CrossRef]
  34. Fernandes Serrano, J.M.; Serrano, M.C.; Amaral, E. Effect of different hormone treatments on rooting of Olea europaea cv. Galega vulgar cuttings. In IV International Symposium on Olive Growing; International Society for Horticultural Science: Leuven, Belgium, 2000; Volume 586, pp. 875–877. [Google Scholar] [CrossRef]
  35. Alvares, C.A. Köppen’s climate classification map for Brazil. Meteorol. Z. 2014, 22, 711–728. [Google Scholar] [CrossRef] [PubMed]
  36. Di Rienzo, J.A.; Casanoves, F.; Balzarini, M.G.; Gonzalez, L.; Tablada, M.; Robledo, C.W. InfoStat, versión 2020; Centro de Transferencia InfoStat, Facultad de Ciencias Agropecuarias (FCA), Universidad Nacional de Córdoba: Córdoba, Argentina, 2020. [Google Scholar]
  37. Burin, C.; Batistel, S.C.; Lohmann, G.; Bisognin, D.A. Rooting competence of mini-cuttings of Cabralea canjerana clones in different seasons. Ciência Rural 2020, 50, e20190451. [Google Scholar] [CrossRef]
  38. Lapa, L.G., Jr. Correlação: Medida de associação entre variáveis. Rev. Mais Educ. 2024, 7, 800–811. [Google Scholar] [CrossRef]
  39. Behling, M. Relações entre parte aérea e raízes em povoamentos de teca. Rev. Ceres 2018, 65, 463–473. [Google Scholar] [CrossRef]
  40. Porfírio, S.; da Silva, M.D.G.; Cabrita, M.J.; Azadi, P.; Peixe, A. Reviewing current knowledge on olive (Olea europaea L.) adventitious root formation. Sci. Hortic. 2016, 198, 207–226. [Google Scholar] [CrossRef]
  41. Inocente, V.H.H.; Nienow, A.A.; Tre, L. Time of treatment with IBA in olive cultivars rooting. Rev. Bras. Frutic. 2018, 40, e-800. [Google Scholar] [CrossRef]
  42. De Jesus, J.S.; Dorléans, V.R.; Ribeiro, D.P.; Sodré, G.A.; Barbosa, R.M. Mini-cuttings of forest and fruit species. Científica 2020, 48, 67–75. [Google Scholar] [CrossRef][Green Version]
  43. Rotondi, A.; Lapucci, C.; Morrone, L.; Neri, L. Autochthonous cultivars of Emilia Romagna region and their clones: Comparison of the chemical and sensory properties of olive oils. Food Chem. 2017, 224, 78–85. [Google Scholar] [CrossRef]
  44. Kaur, A.; Devgan, M.; Sharma, R.; Kumar, A.; Choudhary, A.; Singh, R.P.; Husen, A. Role of biostimulant in adventitious rooting via stimulation of phytohormones. In Biostimulants in Plant Protection and Performance; Elsevier: Amsterdam, The Netherlands, 2024; pp. 237–254. [Google Scholar] [CrossRef]
  45. Oliveira, M.C.D.; Vieira, J.; Oliveira, R.D.S.; Pio, R.; Oliveira, N.C.D.; Ramos, J.D. Enraizamento de estacas de duas cultivares de oliveira submetidas à aplicação de diferentes fertilizantes. Bragantia 2010, 69, 99–103. [Google Scholar] [CrossRef]
  46. Maciejewski, P.; Assis, A.M.; Ramm, M.; Oliveira, B.A.S.; Espinosa, S.I.L.; Schuch, M.W. Collection positions in the branch, humic substances and indolebutyric acid in Arbequinaolive minicuttings. Rev. Bras. Frutic. 2021, 43, e-803. [Google Scholar] [CrossRef]
  47. Denaxa, N.K.; Vemmos, S.N.; Roussos, P.A. The role of endogenous carbohydrates and seasonal variation in rooting ability of cuttings of an easy and a hard to root olive cultivars (Olea europaea L.). Sci. Hortic. 2012, 143, 19–28. [Google Scholar] [CrossRef]
  48. Denaxa, N.K.; Roussos, P.A.; Vemmos, S.N.; Fasseas, K. Assessing the effect of oxidative enzymes and stem anatomy on adventitious rooting of Olea europaea (L.) leafy cuttings. Span. J. Agric. Res. 2019, 17, e0803. [Google Scholar] [CrossRef]
  49. Klaram, R.; Jantasorn, A.; Dethoup, T. Efficacy of marine antagonist, Trichoderma spp. as halo-tolerant biofungicide in controlling rice diseases and yield improvement. Biol. Control 2022, 172, 104985. [Google Scholar] [CrossRef]
  50. Abdelmoaty, S.; Khandaker, M.M.; Mahmud, K.; Majrashi, A.; Alenazi, M.M.; Badaluddin, N.A. Influence of Trichoderma harzianum and Bacillus thuringiensis with reducing rates of NPK on growth, physiology, and fruit quality of Citrus aurantifolia. Braz. J. Biol. 2022, 82, e261032. [Google Scholar] [CrossRef]
  51. Mehri, H.; Mhanna, K.; Soltane, A. Root growth of arbequina cuttings as influenced by organic and inorganic substrates under the conditions of Al-Jouf (KSA). Am. J. Plant Physiol. 2013, 8, 74–83. [Google Scholar] [CrossRef][Green Version]
  52. Nadal, M.C.; Ferreira, G.M.R.; Andrade, G.V.S.; Buttrós, V.H.; Rodrigues, F.A.; Silva, C.M.; Martins, A.D.; Rufato, L.; Luz, J.M.Q.; Dória, J. Endophytic bacteria can replace the need for synthetic auxin during In vitro rooting of pyrus communis. Agronomy 2022, 12, 1226. [Google Scholar] [CrossRef]
  53. Maniriho, F.; Askin, M.; Serdar, H. Effect of Indol-3-butyric acid associated with Bacillus subtilis bacteria on rooting of some Prunus spp rootstock hardwood cuttings. J. Hortic. Postharvest Res. 2021, 4, 1–10. [Google Scholar] [CrossRef]
  54. Kai, M. Diversity and distribution of volatile secondary metabolites throughout Bacillus subtilis isolates. Front. Microbiol. 2020, 11, 559. [Google Scholar] [CrossRef]
  55. Azeem, M.; Haider, M.Z.; Javed, S.; Saleem, M.H.; Alatawi, A. Drought Stress Amelioration in Maize (Zea mays L.) by Inoculation of Bacillus spp. strains under sterile soil conditions. Agriculture 2022, 12, 50. [Google Scholar] [CrossRef]
  56. Guirra, B.S.; Silva, M.F.; Silva, J.E.S.B.; Guirra, K.S. Nutrição da planta matriz determina a qualidade de propágulos. Cad. Ciências Agrárias 2021, 13, 1–6. [Google Scholar] [CrossRef]
  57. Pires, P.; Wendling, I.; Auer, C.; Brondani, G. Sazonalidade e soluções nutritivas na miniestaquia de Araucaria angustifolia (Bertol.) Kuntze. Rev. Árvore 2015, 39, 283–293. [Google Scholar] [CrossRef]
  58. Rodrigues, M.Â.; Piroli, L.B.; Forcelini, D.; Raimundo, S.; da Silva Domingues, L.; Cassol, L.C.; Correia, C.M.; Arrobas, M. Use of commercial mycorrhizal fungi in stress-free growing conditions of potted olive cuttings. Sci. Hortic. 2021, 275, 109712. [Google Scholar] [CrossRef]
  59. Fachinello, J.C.; Hoffmann, A.; Nachtigal, J.C. Propagação de Plantas Frutíferas; Embrapa Informação Tecnológica: Brasília, Brazil, 2005; 221p. [Google Scholar]
  60. Ritter, G.; Villa, F.; da Silva, D.F.; Eberling, T.; Guimardes, V.F.; da Silva, E.C.; Dória, J. Humic substances and modes of application in the rooting of semihardwood cuttings of two olive cultivars. Comun. Sci. 2023, 14, 1–7. [Google Scholar] [CrossRef]
  61. Nicoletti, R.; Di Vaio, C.; Cirillo, C. Endophytic fungi of olive tree. Microorganisms 2020, 8, 1321. [Google Scholar] [CrossRef]
  62. Bizos, G.; Papatheodorou, E.M.; Chatzistathis, T.; Ntalli, N.; Aschonitis, V.G.; Monokrousos, N. The role of microbial inoculants on plant protection, growth stimulation, and crop productivity of the olive tree (Olea europea L.). Plants 2020, 9, 743. [Google Scholar] [CrossRef]
  63. Hanane, B.; Abdelilah, M.; Said, W.; Abdelmajid, M.; Zainab, E.A.T. Improvement of growth and development of olive tree by mycorrhizal autochthonous inoculum. Res. J. Biotechnol. 2020, 15, 76–84. [Google Scholar] [CrossRef]
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Figure 1. Mini-greenhouses where the tests were conducted.
Figure 1. Mini-greenhouses where the tests were conducted.
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Figure 2. Unrooted cutting.
Figure 2. Unrooted cutting.
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Figure 3. Measuring the longest root of the cutting.
Figure 3. Measuring the longest root of the cutting.
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Figure 4. Number of roots according to different treatments (a), cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in the number of roots (p < 0.05) among the mean values of the treatments and cultivars. Each mean value is ±S.E.
Figure 4. Number of roots according to different treatments (a), cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in the number of roots (p < 0.05) among the mean values of the treatments and cultivars. Each mean value is ±S.E.
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Figure 5. Rooted cuttings of the Arbequina cultivar, on the left cutting treated only with IBA (control), and on the right cutting treated with Trichoderma plus IBA.
Figure 5. Rooted cuttings of the Arbequina cultivar, on the left cutting treated only with IBA (control), and on the right cutting treated with Trichoderma plus IBA.
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Figure 6. Shoot number according to different treatments (a), of the cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in the number of shoots (p < 0.05) among the mean values of the treatments and cultivars. Each mean value is ±S.E.
Figure 6. Shoot number according to different treatments (a), of the cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in the number of shoots (p < 0.05) among the mean values of the treatments and cultivars. Each mean value is ±S.E.
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Figure 7. The diameter of shoots according to different treatments (a), of the cultivars (b), and the interaction in panels (c–f). Different letters indicate significant differences in shoot diameter (p < 0.05) between the mean values of the treatments and cultivars. Each mean value is ±S.E.
Figure 7. The diameter of shoots according to different treatments (a), of the cultivars (b), and the interaction in panels (c–f). Different letters indicate significant differences in shoot diameter (p < 0.05) between the mean values of the treatments and cultivars. Each mean value is ±S.E.
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Figure 8. Percentage of calluses according to different treatments (a), of the cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in percentage of calluses (p < 0.05) between the mean values of the treatments and cultivars. Each mean value is ±S.E.
Figure 8. Percentage of calluses according to different treatments (a), of the cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in percentage of calluses (p < 0.05) between the mean values of the treatments and cultivars. Each mean value is ±S.E.
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Figure 9. Root index according to different treatments (a), cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in the root index (p < 0.05) between the mean values of the treatments and cultivars. Each mean value is ±S.E.
Figure 9. Root index according to different treatments (a), cultivars (b), and interaction in panels (c–f). Different letters indicate significant differences in the root index (p < 0.05) between the mean values of the treatments and cultivars. Each mean value is ±S.E.
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Figure 10. PCA scatterplot of olive samples on the PC1–PC2 plane. Colors indicate different biostimulant treatments. Arrows represent the loading vectors of the variables: rooted cuttings (RC), root index (RI), callus formation (C), and shoot index (SI).
Figure 10. PCA scatterplot of olive samples on the PC1–PC2 plane. Colors indicate different biostimulant treatments. Arrows represent the loading vectors of the variables: rooted cuttings (RC), root index (RI), callus formation (C), and shoot index (SI).
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Table 1. Rooted cutting percentage according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in rooted cutting percentage (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in rooted cutting percentage (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Table 1. Rooted cutting percentage according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in rooted cutting percentage (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in rooted cutting percentage (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Cultivar/TreatmentsArbequinaAscolano 315Maria da FèKoroneikiMean’s Treatments
Control33.3±4.8 bc55.6±0.2 a50.0±2.2 b55.6±0.2 a48.6±1.6 B
B. amyloliquefaciens25.0±3.8 c55.5±0.2 a47.2±3.3 b30.6±4.2 d39.6±2.1 C
B. licheniformis41.7±5.5 b55.6±0.4 a55.5±0.2 a47.2±3.3 bc50.0±1.7 B
B. subtilis41.7±5.5 b55.5±0.2 a55.6±0.4 a52.3±1.1 ab51.4±1.5 B
Bioraiz33.3±5.4 bc27.8±2.8 b55.4±0.2 a44.4±3.1 c40.3±2.1 C
Trichoderma55.6±0.1 a55.6±0.3 a55.6±0.3 a55.6±0.2 a55.6±0.3 A
Mean’s cultivar38.4±2.0 C50.9±1.1 A53.2±1.3 A47.7±0.7 B
Table 2. Length of the longest root (cm) according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the length of the longest root (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the length of the longest root (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Table 2. Length of the longest root (cm) according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the length of the longest root (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the length of the longest root (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Cultivar/TreatmentsArbequinaAscolano 315Maria da FèKoroneikiMean’s Treatments
Control4.6±1.2 ab10.3±1.3 ab5.6±0.9 ab9.2±1.0 b7.4±0.6 AB
B. amyloliquefaciens3.1±1.0 b9.6±1.1 abc6.9±1.5 ab4.6±1.2 b6.1±0.7 B
B. licheniformis5.2±1.0 ab6.9±1.0 c7.1±1.4 ab14.3±3.1 a8.4±1.0 A
B. subtilis4.1±0.9 ab12.8±0.9 a8.7±0.9 a9.5±1.8 b7.8±0.7 A
Bioraiz2.8±0.7 b3.1±1.0 d4.7±0.6 b5.1±0.9 b3.9±0.4 C
Trichoderma6.3±0.7 a7.8±1.2 bc9.0±1.3 a7.7±0.8 b7.7±0.5 AB
Mean’s cultivar4.3±0.4 B8.4±0.5 A7.0±0.5 A8.4±0.7 A
Table 3. Pearson correlation coefficient between the number of roots and the length of the longest root in cuttings of olive cultivars.
Table 3. Pearson correlation coefficient between the number of roots and the length of the longest root in cuttings of olive cultivars.
CultivarPerson CoefficientSignificance
Arbequina0.3570p = 0.0009
Ascolano 3150.0548p = 0.5690
Maria da Fé0.2130p = 0.0225
Koroneiki0.2180p = 0.0268
Table 4. Shoot length (cm) according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the shoot length (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the shoot length (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Table 4. Shoot length (cm) according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the shoot length (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the shoot length (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Cultivar/TreatmentsArbequinaAscolano 315Maria da FèKoroneikiMean’s Treatments
Control0.05±0.03 a0.11±0.12 b0.00±0.00 b0.29±0.08 a0.11±0.06 B
B. amyloliquefaciens0.11±0.03 a0.00±0.00 b0.85±0.10 a0.29±0.06 a0.31±0.03 A
B. licheniformis0.02±0.03 a0.48±0.08 a0.10±0.08 b0.00±0.00 a0.15±0.05 B
B. subtilis0.25±0.03 a0.00±0.00 b0.00±0.00 b0.00±0.00 a0.06±0.04 B
Bioraiz0.00±0.00 a0.00±0.00 b0.15±0.15 b0.00±0.00 a0.04±0.09 B
Trichoderma0.00±0.00 a0.25±0.17 ab0.22±0.11 b0.18±0.09 a0.16±0.06 B
Mean’s cultivar0.07±0.04 B0.14±0.04 AB0.22±0.05 A0.12±0.05 AB
Table 5. Number of calluses according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the number of calluses (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the number of calluses (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Table 5. Number of calluses according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the number of calluses (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the number of calluses (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Cultivar/TreatmentsArbequinaAscolano 315Maria da FèKoroneikiMean’s Treatments
Control0.15±0.05 a0.15±0.10 ab0.00±0.00 b0.10±0.10 a0.10±0.04 BC
B. amyloliquefaciens0.15±0.10 a0.20±0.08 ab0.15±0.05 b0.20±0.08 a0.18±0.04 B
B. licheniformis0.20±0.08 a0.15±0.05 ab0.10±0.06 b0.10±0.10 a0.14±0.04 BC
B. subtilis0.20±0.05 a0.15±0.05 ab0.25±0.10 b0.25±0.05 a0.21±0.03 B
Bioraiz0.05±0.05 a0.00±0.00 b0.00±0.00 b0.05±0.05 a0.03±0.02 C
Trichoderma0.30±0.10 a0.35±0.17 a0.50±0.13 a0.20±0.08 a0.34±0.06 A
Mean’s cultivar0.18±0.03 A0.17±0.04 A0.17±0.05 A0.15±0.03 A
Table 6. Shoot index according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the shoot index (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the shoot index (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Table 6. Shoot index according to different treatments (last column), cultivars (bottom line), and interaction (from the second to the fourth column). Different capital letters indicate significant differences in the shoot index (p < 0.05) among the mean values of the treatments and cultivars. Different lowercase letters indicate significant differences in the shoot index (p < 0.05) among the mean values of the treatments within each cultivar. Each mean value is ±S.E.
Cultivar/TreatmentsArbequinaAscolano 315Maria da FèKoroneikiMean’s Treatments
Control0.043±0.03 a0.098±0.01 b0.000±0.00 b0.401±0.24 a0.135±0.07 B
B. amyloliquefaciens0.105±0.01 a0.000±0.00 b1.064±0.63 a0.301±0.30 a0.367±0.08 A
B. licheniformis0.035±0.04 a0.457±0.27 a0.060±0.06 b0.000±0.00 a0.138±0.08 B
B. subtilis0.208±0.04 a0.000±0.00 b0.000±0.00 b0.000±0.00 a0.052±0.05 B
Bioraiz0.000±0.00 a0.000±0.00 b0.153±0.15 b0.000±0.00 a0.038±0.04 B
Trichoderma0.000±0.00 a0.025±0.03 b0.163±0.16 b0.263±0.26 a0.113±0.08 B
Mean’s cultivar0.065±0.04 B0.097±0.05 AB0.240±0.13 A0.161±0.08 AB
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MDPI and ACS Style

Vargas, R.J.d.; Farinelli, D.; Sackser, L.H.K.; Sonego, R.A.; Homo, E.P.; Silva, D.R.F.d.; Facchin, S.L.; Traini, C.; Silva, D.F.d.; Portarena, S.; et al. Biostimulant Application as a Tool to Improve Rooting of Olive Tree Cuttings in Brazil. Horticulturae 2026, 12, 218. https://doi.org/10.3390/horticulturae12020218

AMA Style

Vargas RJd, Farinelli D, Sackser LHK, Sonego RA, Homo EP, Silva DRFd, Facchin SL, Traini C, Silva DFd, Portarena S, et al. Biostimulant Application as a Tool to Improve Rooting of Olive Tree Cuttings in Brazil. Horticulturae. 2026; 12(2):218. https://doi.org/10.3390/horticulturae12020218

Chicago/Turabian Style

Vargas, Rodrigo José de, Daniela Farinelli, Larissa Hiromi Kiahara Sackser, Renan Araujo Sonego, Esperança Paulo Homo, Debora Regina Ferreira da Silva, Simona Lucia Facchin, Chiara Traini, Daniel Fernandes da Silva, Silvia Portarena, and et al. 2026. "Biostimulant Application as a Tool to Improve Rooting of Olive Tree Cuttings in Brazil" Horticulturae 12, no. 2: 218. https://doi.org/10.3390/horticulturae12020218

APA Style

Vargas, R. J. d., Farinelli, D., Sackser, L. H. K., Sonego, R. A., Homo, E. P., Silva, D. R. F. d., Facchin, S. L., Traini, C., Silva, D. F. d., Portarena, S., & Villa, F. (2026). Biostimulant Application as a Tool to Improve Rooting of Olive Tree Cuttings in Brazil. Horticulturae, 12(2), 218. https://doi.org/10.3390/horticulturae12020218

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