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Horticulturae, Volume 7, Issue 6 (June 2021) – 39 articles

Cover Story (view full-size image): The possible role of an early calcium application via sprays on dormant buds to improve sweet cherry (cv. Ferrovia) fruit quality at harvest was investigated. Fruit quality characteristics were also investigated in response to the age of spurs, the ripening stage, and their interactions. Results indicate that calcium enters the dormant flower buds and the phloem but not to the dormant vegetative buds. This study illustrates that the high dose of calcium application during bud dormancy can effectively improve sweet cherry fruit characteristics, in terms of calcium content, cracking incidence, and fruit set. Overall, the present study contributes to a better understanding of the impact of calcium nutrition in fruit crops. View this paper
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Review
A Narrative Review of the Facts and Perspectives on Agricultural Fertilization in Europe, with a Focus on Italy
Horticulturae 2021, 7(6), 158; https://doi.org/10.3390/horticulturae7060158 - 21 Jun 2021
Viewed by 320
Abstract
Fertilizers stand at the base of current agricultural practices, providing the nutrient sustainment required for growing plants. Most fertilizers are synthetic chemicals, whose exploitation at very high levels poses a risk to cultivated land and the whole environment. They have several drawbacks including [...] Read more.
Fertilizers stand at the base of current agricultural practices, providing the nutrient sustainment required for growing plants. Most fertilizers are synthetic chemicals, whose exploitation at very high levels poses a risk to cultivated land and the whole environment. They have several drawbacks including soil degradation, water pollution, and human food safety. Currently, the urgent need to counterbalance these negative environmental impacts has opened the way for the use of natural and renewable products that may help to restore soil structure, microorganism communities, nutrient elements, and, in some cases, to positively enhance carbon soil sequestration. Here, we endeavor to reinforce the vision that effective strategies designed to mitigate negative anthropic and climate change impacts should combine, in appropriate proportions, solutions addressed to a lower and less energy intensive production of chemicals and to a more inclusive exploitation of renewable natural products as biological soil amendments. After drawing an overview of the agricultural energy demand and consumption of fertilizers in Europe in the last few years (with a particular focus on Italy), this narrative review will deal with the current and prospective use of compost, biochar, and neem cake, which are suitable natural products with well-known potential and still-to-be-discovered features, to benefit sustainable agriculture and be adopted as circular economic solutions. Full article
(This article belongs to the Special Issue Recent Advances in Nutrition and Fertilization of Horticultural Crops)
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Article
Comparative Transcriptome Identifies Gene Expression Networks Regulating Developmental Pollen Abortion in Ogura Cytoplasmic Male Sterility in Chinese Cabbage (Brassica rapa ssp. pekinensis)
Horticulturae 2021, 7(6), 157; https://doi.org/10.3390/horticulturae7060157 - 20 Jun 2021
Viewed by 483
Abstract
Ogura cytoplasmic male sterility (Ogura CMS), originally identified in wild radish (Raphanus sativus), has enabled complete pollen sterility in Brassica plants, but the underlying mechanism in Ogura CMS Chinese cabbage (Brassica rapa ssp. pekinensis) remains unclear. In this study [...] Read more.
Ogura cytoplasmic male sterility (Ogura CMS), originally identified in wild radish (Raphanus sativus), has enabled complete pollen sterility in Brassica plants, but the underlying mechanism in Ogura CMS Chinese cabbage (Brassica rapa ssp. pekinensis) remains unclear. In this study cytological analysis showed that during microsporogenesis the meiosis occurred normally, and the uninucleated pollens subsequently formed, but the development of both binucleated and trinucleated pollens was obviously disrupted due to defects of pollen mitosis in the Ogura CMS line (Tyms) compared with the corresponding maintainer line (231–330). In transcriptome profiling a total of 8052 differentially expressed genes (DEGs) were identified, among which 3890 were up-regulated and 4162 were down-regulated at the pollen abortion stages in an Ogura CMS line. KOG cluster analysis demonstrated that a large number of DEGs were related to the cytoskeleton’s dynamics, which may account for the failure of pollen mitosis during development in the Ogura CMS line. The pivotal genes related to the phenylpropane synthesis pathway (PAL, 4CL and CAD) were significantly down-regulated, which probably affected the formation and disposition of anther lignin and sporopollenin, and eventually led to abnormality in the pollen exine structure. In addition, several key up-regulated genes (GPX7, G6PD and PGD1) related to the glutathione oxidation-reduction (REDOX) reaction indicated that the accumulation of peroxides in Ogura CMS lines during this period affected the pollen development. Taken together, this cytological and molecular evidence is expected to advance our understanding of pollen abortion induced by Ogura cytoplasmic action in Chinese cabbage. Full article
(This article belongs to the Special Issue Advances in Brassica Crops Genomics and Breeding)
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Article
Comparing Visual and Image Analysis Techniques to Quantify Fusarium Basal Rot Severity in Mature Onion Bulbs
Horticulturae 2021, 7(6), 156; https://doi.org/10.3390/horticulturae7060156 - 19 Jun 2021
Viewed by 737
Abstract
Development of resistant cultivars for Fusarium basal rot (FBR), a fungal disease caused by the soil-borne fungus Fusarium oxysporum f.sp. cepae (FOC), is a major breeding goal for onion breeding programs around the world. Currently, the selection of FBR-resistant bulbs is based on [...] Read more.
Development of resistant cultivars for Fusarium basal rot (FBR), a fungal disease caused by the soil-borne fungus Fusarium oxysporum f.sp. cepae (FOC), is a major breeding goal for onion breeding programs around the world. Currently, the selection of FBR-resistant bulbs is based on a visual interval or category scale, which is an entirely subjective method. This study aimed to develop an objective approach using digital image analysis to quantify symptom development in the basal plate of dormant bulbs. Digital image analyses were performed after artificially inoculating dormant bulbs of eighty-five United States Department of Agriculture (USDA) Allium cepa accessions with a virulent FOC isolate, ‘CSC-515’. An analysis with confocal microscopy identified bright blue–green autofluorescence from FOC-infected tissue, effectively differentiating diseased from healthy tissue. Visual scoring of the FBR symptom was aided by stereo fluorescence microscopic images captured using a green fluorescence protein dual filter to quantify accurately FBR severity in the basal plate tissue. An automatic stepwise image segmentation method was developed that was relatively more accurate than a visual estimation. This method exhibited comparable reliability and precision to visual scoring, but it tended to underestimate FOC infection. To our best knowledge, this is the first comprehensive study to investigate the potential use of image analysis as a viable alternative to conventional visual scoring for FBR symptom development. This method could be used for developing resistant cultivars for onion breeding programs in the near future. Full article
(This article belongs to the Special Issue Advances in Allium Breeding and Genetics)
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Article
Detection of a Point Mutation (G143A) in Cyt b of Corynespora cassiicola That Confers Pyraclostrobin Resistance
Horticulturae 2021, 7(6), 155; https://doi.org/10.3390/horticulturae7060155 - 18 Jun 2021
Viewed by 269
Abstract
Point mutation G143A in the cytochrome b (Cyt b) protein commonly confers resistance to quinone outside inhibitor (QoI) fungicides in phytopathogenic fungi, including Corynespora cassiicola, which causes cucumber target spot disease. However, the effect of G143A on the binding between the QoI [...] Read more.
Point mutation G143A in the cytochrome b (Cyt b) protein commonly confers resistance to quinone outside inhibitor (QoI) fungicides in phytopathogenic fungi, including Corynespora cassiicola, which causes cucumber target spot disease. However, the effect of G143A on the binding between the QoI fungicide and the Cyt b protein, and the use of LAMP (loop-mediated isothermal amplification) to detect this point mutation had not been reported previously in C. cassiicola. In this study, the sensitivity of 131 C. cassiicola isolates—collected from Shandong province, China in 2019 and 2020—to pyraclostrobin was determined. The EC50 values ranged from 1.67 to 8.82 μg/mL, and sequencing results showed that all C. cassiicola isolates contained the G143A mutation. Molecular docking results suggested that G143A significantly alters the affinity of pyraclostrobin to the Cyt b protein. Following development of three LAMP primer pairs, the best reaction condition for LAMP analysis was 65 °C for 60 min, and the detection limit was 0.01 ng/μL of DNA containing the point mutation. In conclusion, the G143A mutation conferring pyraclostrobin resistance is widespread in C. cassiicola from Shandong province, and the LAMP method can be used to monitor QoI resistance in C. cassiicola caused by the G143A mutation in the field. Full article
(This article belongs to the Section Plant Pathology and Disease Management (PPDM))
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Article
Signal Intensity of Stem Diameter Variation for the Diagnosis of Drip Irrigation Water Deficit in Grapevine
Horticulturae 2021, 7(6), 154; https://doi.org/10.3390/horticulturae7060154 - 15 Jun 2021
Viewed by 398
Abstract
Precise irrigation management of grapevines in greenhouses requires a reliable method to easily quantify and monitor the grapevine water status to enable effective manipulation of the water stress of the plants. This study describes a study on stem diameter variations of grapevine planted [...] Read more.
Precise irrigation management of grapevines in greenhouses requires a reliable method to easily quantify and monitor the grapevine water status to enable effective manipulation of the water stress of the plants. This study describes a study on stem diameter variations of grapevine planted in a greenhouse in the semi-arid area of Northwest China. In order to determine the applicability of signal intensity of stem diameter variation to evaluate the water status of grapevine and soil. The results showed that the relative variation curve of the grapevine stem diameter from the vegetative stage to the fruit expansion stage showed an overall increasing trend. The correlations of MDS (maximum daily shrinkage) and DI (daily increase) with meteorological factors were significant (p < 0.05), and the correlations with SWP, RWC and soil moisture were weak. Although MDS and DI can diagnose grapevine water status in time, SIMDS and SIDI have the advantages of sensitivity and signal intensity compared with other indicators. Compared with MDS and DI, the R2 values of the regression equations of SIMDS and SIDI with SWP and RWC were high, and the correlation reached a very significant level (p < 0.01). Thus, SIMDS and SIDI are more suitable for the diagnosis of grapevine water status. The SIMDS peaked at the fruit expansion stage, reaching 0.957–1.384. The signal-to-noise ratio of SIDI was higher than that of MDS across the three treatments at the vegetative stage. The value and signal-to-noise ratio of SIDI at the flowering stage were similar to those of SIMDS, while the correlation between SIDI and the soil moisture content was higher than that of SIMDS. It can be concluded that that SIDI is suitable as an indicator of water status of grapevine and soil during the vegetative and flowering stages. In addition, the signal-to-noise ratio of SIMDS during the fruit expansion and mature stages was significantly higher than that of SIDI. Therefore, SIMDS is suitable as an indicator of the moisture status of grapevine and soil during the fruit expansion and mature stages. In general, SIMDS and SIDI were very good predictors of the plant water status during the growth stage and their continuous recording offers the promising possibility of their use in automatic irrigation scheduling in grapevine. Full article
(This article belongs to the Special Issue Study of the Influence of Abiotic and Biotic Stress Factors on Plants)
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Article
Does Participation in Agricultural Value Chain Activities Influence Smallholder Fruit Grower Production Performance? A Cross-Sectional Study of Apple Farmers in Shandong, China
Horticulturae 2021, 7(6), 153; https://doi.org/10.3390/horticulturae7060153 - 15 Jun 2021
Viewed by 312
Abstract
The value chain comprises several factors and activities useful for strengthening production and distribution by connecting producers with suppliers, intermediaries, and marketplaces and collaboratively creating added value for products or goods. However, the values of agricultural products mostly depend on various factors and [...] Read more.
The value chain comprises several factors and activities useful for strengthening production and distribution by connecting producers with suppliers, intermediaries, and marketplaces and collaboratively creating added value for products or goods. However, the values of agricultural products mostly depend on various factors and actors, which should be linked together for fostering added values. Thus, there may be strong ground for facilitating a smooth transition of the agricultural value chain (AVC) within the prospects of emerging countries. It could be a key means of promoting a profound connection between smallholder farmers and modern agriculture facilities. It could be especially crucial for the highly perishable and high-value product such as fruits. The main aims of the study are to evaluate the factors influencing smallholder apple farmers’ participation in the agricultural value chain and determine whether participation in AVC improves farmers’ production performance. The empirical setup of the study was chosen based on survey data of apple growers in Shandong, China. The propensity score matching (PSM) and inverse probability weighted regression adjustment (IPWRA) models were employed to craft the study’s outcomes. The main conclusions are as follows. (1) Fruit farmers’ gender, total household expenditure, housing value, planting scale, planting years, degree of specialization, days of family labour input, and total days of employment have significant effects on their participation in AVC activities. (2) Fruit farmers’ usage of improved fertilizers and organization participation supports a higher yield and net income per acre. (3) Participating in two kinds of AVC can significantly improve the yield per acre and net income per acre compared with only using one type of AVC (improved fertilizer). Policy makers should improve the existing policy by eliminating institutional barriers and enhancing human factors for farmers to participate in high-value chain activities. Governments should extend technical support, and enhance training facilities, and comprehensively promote the AVC among smallholder farmers. Finally, farmers’ organizations (e.g., cooperatives and credit organizations) should come forward to help facilitate the effectiveness of AVC. Full article
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Article
Long-Term Irrigation with Treated Municipal Wastewater from the Wadi-Musa Region: Soil Heavy Metal Accumulation, Uptake and Partitioning in Olive Trees
Horticulturae 2021, 7(6), 152; https://doi.org/10.3390/horticulturae7060152 - 13 Jun 2021
Viewed by 511
Abstract
Utilization of treated wastewater (TWW) for agricultural purposes has grown over the past few years because of limited available water resources. This study was performed to assess the long-term irrigation of treated wastewater from the Wadi-Musa region on the accumulation of heavy metals [...] Read more.
Utilization of treated wastewater (TWW) for agricultural purposes has grown over the past few years because of limited available water resources. This study was performed to assess the long-term irrigation of treated wastewater from the Wadi-Musa region on the accumulation of heavy metals in soil and their uptake and translocation to various parts of olive trees. Fifteen year old trees that had been grown and irrigated with treated wastewater resources since their establishment were used in this study. Irrigation water, soil, and plant samples (root, stem bark, leaves, fruits) were collected and chemically analyzed for their heavy metal content. Accumulation of heavy metals in irrigation water and soil were found to be within the acceptable range for the safe use of treated wastewater according to the standards of the WHO. However, long-term and continuous irrigation with TWW resulted in significant accumulation of heavy metals in plant parts when compared to their levels in irrigation water and soil. Uptake of metals was consistent among plant parts with the highest concentrations for Fe, Mn, Pb and Zn, and the lowest concentrations for Ni, Cr and Cd. Assessment of the bioaccumulation factor (BFC) and translocation factors (TF) of heavy metals into different plant parts indicated selective absorption and partitioning of these heavy metals into different plant parts. High BCF values were observed for Fe, Cu and Ni in roots and fruits, and Fe, Mn, Cd and Pb in leaves. Translocation factors of metal ions were variable among plant parts. Fruits had the highest TF for Cu, Cd and Zn metals, and the lowest for Mn and Fe, while leaves have the highest TF for Fe, Zn and Mn and the lowest for Cd and Pb. The results of this study indicate that olive trees are heavy metal accumulators, caution should be considered in long-term use of TWW and periodic assessment of possible hazards, especially on fruits and oil quality is required. Full article
(This article belongs to the Section Biotic and Abiotic Stress)
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Article
Microbiome and Metagenome Analysis Reveals Huanglongbing Affects the Abundance of Citrus Rhizosphere Bacteria Associated with Resistance and Energy Metabolism
Horticulturae 2021, 7(6), 151; https://doi.org/10.3390/horticulturae7060151 - 13 Jun 2021
Viewed by 487
Abstract
The plant rhizosphere microbiome is known to play a vital role in plant health by competing with pathogens or inducing plant resistance. This study aims to investigate rhizosphere microorganisms responsive to a devastating citrus disease caused by ‘Candidatus Liberibacter asiaticus’ (CLas) [...] Read more.
The plant rhizosphere microbiome is known to play a vital role in plant health by competing with pathogens or inducing plant resistance. This study aims to investigate rhizosphere microorganisms responsive to a devastating citrus disease caused by ‘Candidatus Liberibacter asiaticus’ (CLas) infection, by using 16S rRNA sequencing and metagenome technologies. The results show that 30 rhizosphere and 14 root bacterial genera were significantly affected by CLas infection, including 9 plant resistance-associated bacterial genera. Among these, Amycolatopsis, Sphingopyxis, Chryseobacterium, Flavobacterium, Ralstonia, Stenotrophomonas, Duganella, and Streptacidiphilus were considerably enriched in CLas-infected roots, while Rhizobium was significantly decreased. Metagenome analysis revealed that the abundance of genes involved in carbohydrate metabolism, such as glycolysis, starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism, was significantly reduced in the CLas-infected citrus rhizosphere microbial community. Likewise, the abundance of genes involved in phosphoinositide signaling and phosphoinositide metabolism, which play important roles in energy metabolism (such as carbohydrate metabolism and lipid metabolism), was also decreased in the CLas-infected samples. Taken together, our results indicate that CLas infection could affect the resistance potential and energy metabolism of the citrus rhizosphere microbial community, which may help us to understand the rhizosphere responses to plant disease and thus facilitate the development and application of antagonistic microorganism products in citrus industry. Full article
(This article belongs to the Special Issue Citrus Rhizosphere Microbiome)
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Review
A Sustainable Viticulture Method Adapted to the Cold Climate Zone in China
Horticulturae 2021, 7(6), 150; https://doi.org/10.3390/horticulturae7060150 - 11 Jun 2021
Viewed by 524
Abstract
Due to the particularity of the continental monsoon climate in China, more than 90% of the wine grape cultivation areas require vines to be buried in winter for a burial period that can extend to half a year. Additionally, traditional vine cultivation practices [...] Read more.
Due to the particularity of the continental monsoon climate in China, more than 90% of the wine grape cultivation areas require vines to be buried in winter for a burial period that can extend to half a year. Additionally, traditional vine cultivation practices can expose the surface of the soil during winter, easily leading to soil erosion. To meet the restrictive factors for viticulture in the Chinese cold climate zone, a new sustainable viticulture strategy called crawled cordon mode (CCM) has been developed. CCM includes crawled cordon training (CCT), physical methods of flower and fruit thinning, winter suspension of shoots, the use of a biodegradable liquid film, and covering of grass and branches for simplified management of vineyards. This article summarizes the specific implementation methods of the main measures of CCM and their significant effects on the quality of grapes and wine, ecological environment, and costs, and aims to provide inspiration for the study of sustainable and eco-friendly cultivation measures for vineyards in other cold climate zones. Full article
(This article belongs to the Special Issue Advances in Viticulture Production)
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Article
Genome-Wide Identification and Characterization of Hsf and Hsp Gene Families and Gene Expression Analysis under Heat Stress in Eggplant (Solanum melongema L.)
Horticulturae 2021, 7(6), 149; https://doi.org/10.3390/horticulturae7060149 - 10 Jun 2021
Viewed by 440
Abstract
Under high temperature stress, a large number of proteins in plant cells will be denatured and inactivated. Meanwhile Hsfs and Hsps will be quickly induced to remove denatured proteins, so as to avoid programmed cell death, thus enhancing the thermotolerance of plants. Here, [...] Read more.
Under high temperature stress, a large number of proteins in plant cells will be denatured and inactivated. Meanwhile Hsfs and Hsps will be quickly induced to remove denatured proteins, so as to avoid programmed cell death, thus enhancing the thermotolerance of plants. Here, a comprehensive identification and analysis of the Hsf and Hsp gene families in eggplant under heat stress was performed. A total of 24 Hsf-like genes and 117 Hsp-like genes were identified from the eggplant genome using the interolog from Arabidopsis. The gene structure and motif composition of Hsf and Hsp genes were relatively conserved in each subfamily in eggplant. RNA-seq data and qRT-PCR analysis showed that the expressions of most eggplant Hsf and Hsp genes were increased upon exposure to heat stress, especially in thermotolerant line. The comprehensive analysis indicated that different sets of SmHsps genes were involved downstream of particular SmHsfs genes. These results provided a basis for revealing the roles of SmHsps and SmHsp for thermotolerance in eggplant, which may potentially be useful for understanding the thermotolerance mechanism involving SmHsps and SmHsp in eggplant. Full article
(This article belongs to the Special Issue Advances in Molecular Breeding of Vegetable Crops)
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Article
Remobilization of Storage Nitrogen in Young Pear Trees Grafted onto Vigorous Rootstocks (Pyrus betulifolia)
Horticulturae 2021, 7(6), 148; https://doi.org/10.3390/horticulturae7060148 - 10 Jun 2021
Viewed by 408
Abstract
The remobilization of storage nitrogen (N) is affected by growth characteristics of young pear trees. Aboveground parts of young pear trees grafted on P. betulifolia grew more vigorously than that on dwarfing rootstocks. Therefore, the remobilization of storage N within young pear trees [...] Read more.
The remobilization of storage nitrogen (N) is affected by growth characteristics of young pear trees. Aboveground parts of young pear trees grafted on P. betulifolia grew more vigorously than that on dwarfing rootstocks. Therefore, the remobilization of storage N within young pear trees on vigorous rootstocks may be different from that on dwarfing rootstocks. A 15N tracing experiment, including six groups of one-year-old pear trees grafted on vigorous rootstocks in 2016, was conducted to investigate the mobilization of storage N from 2016 to 2018. Results indicated that about 44%, 31.4% and 24.6% of storage N remobilized in new growth was derived from the trunk, shoots and roots, respectively. Most of storage N remobilized in new organs were supplied by trunks and shoots. About 82.2% of storage N withdrawn from senescent leaves were recovered in the trunk and shoots during autumn. The aboveground parts played a more important role than roots in the cycling process of storage N in young pear trees. However, as compared with young pear trees on dwarfing rootstocks, more storage N recovered in new organs were supplied by roots of that on vigorous rootstocks, due to vigorous growth and more nutrient requirement of aboveground parts. Full article
(This article belongs to the Section Plant Nutrition)
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Review
Aulacaspis yasumatsui Delivers a Blow to International Cycad Horticulture
Horticulturae 2021, 7(6), 147; https://doi.org/10.3390/horticulturae7060147 - 10 Jun 2021
Viewed by 339
Abstract
The literature covering the biology, invasion chronology, host plant responses, and control efforts of the armored scale Aulacaspis yasumatsui Takagi (Hempitera: Diaspididae) is reviewed. The small size of this cycad pest and complex surface morphology of the host cycad organs combine to make [...] Read more.
The literature covering the biology, invasion chronology, host plant responses, and control efforts of the armored scale Aulacaspis yasumatsui Takagi (Hempitera: Diaspididae) is reviewed. The small size of this cycad pest and complex surface morphology of the host cycad organs combine to make visual detection of every cryptic infestation difficult or impossible to achieve. The international movement of Cycas revoluta Thunb. nursery plants and the presence of C. revoluta nursery industries in so many countries have enabled this pest to wreak havoc on the international cycad horticulture trade over the last 25 years. The short pre-oviposition period and considerable female fecundity lead to rapid population expansion on the plants initially infested in newly invaded regions. A depletion of non-structural carbohydrates accompanies long-term infestations and precedes plant death. Enemy escape within the invasive range allows the scale population growth to remain unchecked until anthropogenic efforts establish non-native biological control. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae Ⅱ)
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Article
Investigating Producers’ Preferences for Crapemyrtle and Their Perceptions Regarding Crapemyrtle Bark Scale
Horticulturae 2021, 7(6), 146; https://doi.org/10.3390/horticulturae7060146 - 10 Jun 2021
Viewed by 380
Abstract
Crapemyrtle (Lagerstroemia spp.) is the most popular summer flowering tree in the U.S. Its total value sold has almost doubled since 1998. Consumers prize crapemyrtles for their beauty and being relatively pest free. However, current crapemyrtle production and use might be affected [...] Read more.
Crapemyrtle (Lagerstroemia spp.) is the most popular summer flowering tree in the U.S. Its total value sold has almost doubled since 1998. Consumers prize crapemyrtles for their beauty and being relatively pest free. However, current crapemyrtle production and use might be affected by crapemyrtle bark scale (CMBS; Acanthococcus lagerstroemiae), which has been confirmed in at least 14 U.S. states after its first sighting in Texas in 2004. In this study, we conducted interviews of business representatives. Our survey results indicate that producers anticipate a significant decrease in the value of crapemyrtle if infested with CMBS, and suggest industry demand for CMBS control. An important finding of our research is that a majority of businesses support science-based CMBS control research. Another important finding from our study is that most producers believed that benefits of CMBS control outweigh the costs. We used a relative importance index to illustrate the ranking of different attributes of crapemyrtles that producers consider while making decisions about growing/purchasing the plants. Flower color was found to be the most important attribute, followed by disease resistance. The most popular landscape plants that can potentially serve as alternatives to crapemyrtle, in the opinion of producers we surveyed, are Vitex agnus-castus (Texas lilac), Magnolia spp., and Hibiscus spp. Full article
(This article belongs to the Section Floriculture, Nursery and Landscape, and Turf)
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Article
Synergistic Effect of Preharvest Spray Application of Natural Elicitors on Storage Life and Bioactive Compounds of Date Palm (Phoenix dactylifera L., cv. Khesab)
Horticulturae 2021, 7(6), 145; https://doi.org/10.3390/horticulturae7060145 - 10 Jun 2021
Viewed by 424
Abstract
Despite the immense capabilities of the date palm, maintaining the fruit’s quality, marketability, and shelf life is still a challenge. This study aimed to assess the synergistic effect of a preharvest spray application of a natural elicitor chitosan, (Ch) 1% alone and in [...] Read more.
Despite the immense capabilities of the date palm, maintaining the fruit’s quality, marketability, and shelf life is still a challenge. This study aimed to assess the synergistic effect of a preharvest spray application of a natural elicitor chitosan, (Ch) 1% alone and in combination with salicylic acid (SA) 2 mM and calcium chloride (Ca) 3%; (Ch,SA, Ca,Ch+Ca, Ch+SA, Ch+SA+Ca), on the quality parameters, storage life, and bioactive compounds content of date fruit from ‘Khasab’ cultivar during cold storage for 60 days. The obtained results revealed that all treatments significantly retard senescence/decay of the fruit compared to the control. Ch+SA treated fruit followed by Ch, and Ch+SA+Ca had the lowest weight loss, color change, and the least decay after 60 days of storage. Ch+Ca, SA, Ca treated fruit had significantly lower levels of total soluble solids and highest total phenolic, tannins, and flavonoids contents compared to the control fruit. Antioxidant activities were found in all treatments, with significantly higher effect in Ch+SA+Ca and Ch+SA compared to the control. Our results provide an evidence for a synergistic effect of elicitors combination to extend the shelf life of date fruit during cold storage by preserving its quality and decreasing senescence/decay and recommend it as a promising strategy. Full article
(This article belongs to the Special Issue Propagation and Post-harvest of Fruit Crops)
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Article
Performance of Greenhouse-Grown Beit Alpha Cucumber in Pine Bark and Perlite Substrates Fertigated with Biofloc Aquaculture Effluent
Horticulturae 2021, 7(6), 144; https://doi.org/10.3390/horticulturae7060144 - 09 Jun 2021
Viewed by 682
Abstract
Using aquaculture effluent (AE) to fertigate plants is gaining popularity worldwide. However, in substrate-based systems, the choice of substrate is essential due to their effects on crop productivity. Differences in the retention of nutrients by substrates makes it necessary to assess suitability for [...] Read more.
Using aquaculture effluent (AE) to fertigate plants is gaining popularity worldwide. However, in substrate-based systems, the choice of substrate is essential due to their effects on crop productivity. Differences in the retention of nutrients by substrates makes it necessary to assess suitability for use in AE. This study was conducted from January to July in 2016 and September to October in 2019 to evaluate greenhouse-grown Beit Alpha cucumber (Cucumis sativus L. ‘Socrates’) performance fertigated with AE in pine bark or perlite substrates, grown either as one plant or two plants per pot. A 2 × 2 factorial arrangement in a randomized complete block design with four replications for each season was used. The substrate effect on yield in 2016 depended on the density and season. The pooled yield over seasons in 2016 showed pine bark had a significantly higher yield than perlite by 11% in one plant per pot but lowered by the same amount in two plants per pot. In 2019, pine bark significantly reduced the leachate pH in both plant densities and reduced the leachate EC by about 15% in two plants per pot. The foliar boron was occasionally below sufficiency whilst manganese was above sufficiency in pine bark due to its inherently low pH. We conclude that the effect of the substrates on cucumber yield fertigated with AE is dependent on the season and the number of plants per pot. Therefore, due to the local availability of pine bark, it could be a potential substitute for perlite especially when using one plant per pot for AE. In addition, pine bark could be used as an intermediate substrate to reduce the pH in AE for downstream use. Full article
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Article
Genome Wide Characterization, Comparative and Genetic Diversity Analysis of Simple Sequence Repeats in Cucurbita Species
Horticulturae 2021, 7(6), 143; https://doi.org/10.3390/horticulturae7060143 - 08 Jun 2021
Viewed by 465
Abstract
Simple sequence repeats (SSRs) are widely used in mapping constructions and comparative and genetic diversity analyses. Here, 103,056 SSR loci were found in Cucurbita species by in silico PCR. In general, the frequency of these SSRs decreased with the increase in the motif [...] Read more.
Simple sequence repeats (SSRs) are widely used in mapping constructions and comparative and genetic diversity analyses. Here, 103,056 SSR loci were found in Cucurbita species by in silico PCR. In general, the frequency of these SSRs decreased with the increase in the motif length, and di-nucleotide motifs were the most common type. For the same repeat types, the SSR frequency decreased sharply with the increase in the repeat number. The majority of the SSR loci were suitable for marker development (84.75% in Cucurbita moschata, 94.53% in Cucurbita maxima, and 95.09% in Cucurbita pepo). Using these markers, the cross-species transferable SSR markers between C. pepo and other Cucurbitaceae species were developed, and the complicated mosaic relationships among them were analyzed. Especially, the main syntenic relationships between C. pepo and C. moschata or C. maxima indicated that the chromosomes in the Cucurbita genomes were highly conserved during evolution. Furthermore, 66 core SSR markers were selected to measure the genetic diversity in 61 C. pepo germplasms, and they were divided into two groups by structure and unweighted pair group method with arithmetic analysis. These results will promote the utilization of SSRs in basic and applied research of Cucurbita species. Full article
(This article belongs to the Special Issue Advances in Molecular Breeding of Vegetable Crops)
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Article
Characterization of Japanese Apricot (Prunus mume) Floral Bud Development Using a Modified BBCH Scale and Analysis of the Relationship between BBCH Stages and Floral Primordium Development and the Dormancy Phase Transition
Horticulturae 2021, 7(6), 142; https://doi.org/10.3390/horticulturae7060142 - 08 Jun 2021
Viewed by 651
Abstract
Bud dormancy is an important developmental stage that ensures that trees can tolerate environmental stresses in winter and bloom uniformly in the following spring. Regarding Rosaceae floral buds, exposure to chilling conditions promotes floral primordium development and the transition from endodormancy to ecodormancy. [...] Read more.
Bud dormancy is an important developmental stage that ensures that trees can tolerate environmental stresses in winter and bloom uniformly in the following spring. Regarding Rosaceae floral buds, exposure to chilling conditions promotes floral primordium development and the transition from endodormancy to ecodormancy. A subsequent period of warm conditions induces blooming. In Japanese apricot (Prunus mume), dormancy progression is accompanied by morphological changes that alter the bud appearance and internal structures. We used a modified BBCH scale and conducted microscopy analyses to elucidate the bud developmental stage of three cultivars with contrasting chilling requirements. The floral bud developmental period corresponding to BBCH stages 51–53 includes the transition from endodormancy to ecodormancy in all three cultivars. Male meiosis and microspore development occurred during this transition in high-chill cultivars, but were detected considerably later than the transition in the low-chill cultivar. A slow or suspended developmental phase was observed only for the high-chill cultivars upon completion of floral primordium organ differentiation, suggesting that chilling may be required to induce floral bud maturation and dormancy release only in high-chill cultivars. Possible relationships among BBCH stages, flowering-related morphological characteristics, and the dormancy phase transition in Japanese apricot are discussed. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae Ⅱ)
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Article
Rootstocks Genotypes Impact on Tree Development and Industrial Properties of ‘Valencia’ Sweet Orange Juice
Horticulturae 2021, 7(6), 141; https://doi.org/10.3390/horticulturae7060141 - 08 Jun 2021
Viewed by 508
Abstract
The low diversification of rootstock genotypes in orchards limits the expansion of the citrus industry, restricting increases in productivity and cost-saving via phytosanitary treatments and other horticultural practices. Therefore, the aim of this study was to assess the impact of rootstock genotypes on [...] Read more.
The low diversification of rootstock genotypes in orchards limits the expansion of the citrus industry, restricting increases in productivity and cost-saving via phytosanitary treatments and other horticultural practices. Therefore, the aim of this study was to assess the impact of rootstock genotypes on tree development and industrial properties of ‘Valencia’ sweet orange juice (Citrus sinensis). Twenty rootstock genotypes were evaluated by measuring tree growth and industrial properties of orange juices, including ‘Trifoliata’ hybrids with tangerine (citrandarins) and grapefruit (citrumelos), as well ‘Rangpur’ lime and other potential rootstocks. The experimental orchard was planted in Rancho Alegre, PR, Brazil, under clay soil and subtropical rainfed conditions. A randomized block design with four replicates was used. Trees grown on IPEACS–239 and IPEACS–256 citrandarins, and on ‘US–802’ pummelo hybrid had low vigor, high production efficiency and high industrial properties of orange juice, and are therefore potential alternatives for high-density plantings. The F.80–3 and F.80–5 citrumelos also had good dwarfing potential and high production efficiency, but lower industrial properties of juice compared to the other ‘Trifoliata’ hybrid rootstocks. Trees grown on ‘US–812’ citrandarin rootstock had low vigor, good productive performance, accumulated production and production efficiency similar to ‘Rangpur’ lime, and high industrial properties of juices. Although the ‘Rangpur’ lime and the ‘Florida’ rough lemon allowed high yields, the trees are very vigorous, with low-quality fruits. A Quick Reference Chart was created to provide practical and objective identification of the best rootstock alternatives for ‘Valencia’ orange trees in terms of tree development and industrial properties of juices. Full article
(This article belongs to the Special Issue Rootstock Genetics and Improvement in Breeding)
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Article
The Impact of Salt Stress on Plant Growth, Mineral Composition, and Antioxidant Activity in Tetragonia decumbens Mill.: An Underutilized Edible Halophyte in South Africa
Horticulturae 2021, 7(6), 140; https://doi.org/10.3390/horticulturae7060140 - 07 Jun 2021
Viewed by 528
Abstract
Climate change, expanding soil salinization, and the developing shortages of freshwater have negatively affected crop production around the world. Seawater and salinized lands represent potentially cultivable areas for edible salt-tolerant plants. In the present study, the effect of salinity stress on plant growth, [...] Read more.
Climate change, expanding soil salinization, and the developing shortages of freshwater have negatively affected crop production around the world. Seawater and salinized lands represent potentially cultivable areas for edible salt-tolerant plants. In the present study, the effect of salinity stress on plant growth, mineral composition (macro-and micro-nutrients), and antioxidant activity in dune spinach (Tetragonia decumbens) were evaluated. The treatments consisted of three salt concentrations, 50, 100, and 200 mM, produced by adding NaCl to the nutrient solution. The control treatment had no NaCl but was sustained and irrigated by the nutrient solution. Results revealed a significant increase in total yield, branch production, and ferric reducing antioxidant power in plants irrigated with nutrient solution incorporated with 50 mM NaCl. Conversely, an increased level of salinity (200 mM) caused a decrease in chlorophyll content (SPAD), while the phenolic content, as well as nitrogen, phosphorus, and sodium, increased. The results of this study indicate that there is potential for brackish water cultivation of dune spinach for consumption, especially in provinces experiencing the adverse effect of drought and salinity, where seawater or underground saline water could be diluted and used as irrigation water in the production of this vegetable. Full article
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Article
Effect of Daily Light Integral on Cucumber Plug Seedlings in Artificial Light Plant Factory
Horticulturae 2021, 7(6), 139; https://doi.org/10.3390/horticulturae7060139 - 07 Jun 2021
Viewed by 415
Abstract
In a controlled environment, in an artificial light plant factory during early spring or midsummer, vegetable seedlings can be uniform, compact, and high quality. Appropriate light parameters can speed up the growth of seedlings and save on production costs. Two experiments were carried [...] Read more.
In a controlled environment, in an artificial light plant factory during early spring or midsummer, vegetable seedlings can be uniform, compact, and high quality. Appropriate light parameters can speed up the growth of seedlings and save on production costs. Two experiments were carried out in this study: (1) cucumber seedling growth under different daily light integrals (DLIs) (5.41–11.26 mol·m−2·d−1) and optimum DLI for seedling production were explored (experiment 1: Exp. 1); (2) under the same DLI selected by Exp. 1, the effects of different light intensities and photoperiods on cucumber seedlings were investigated (experiment 2: Exp. 2). The root biomass, root-to-shoot ratio, seedling index, and shoot dry matter rate increased as the DLI increased from 5.41 to 11.26 mol·m−2·d−1, while the shoot biomass and leaf area decreased in Exp. 1. The cucumber seedlings became more compact as DLI increased, but more flowers developed after transplanting when the DLI was 6.35 mol·m−2·d−1. Under the optimal DLI (6.35 mol·m−2·d−1), the optimal intensity was 110–125 μmol·m−2·s−1, and the optimal photoperiod was 14–16 h, in which plant biomass, shoot dry matter rate, seedling index, and photochemical efficiency were higher. Full article
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Article
Morphological, Molecular and Genomic Characterization of Two Inter-Subspecific Hybrids between Olive Cultivars and Olive Subspecies
Horticulturae 2021, 7(6), 138; https://doi.org/10.3390/horticulturae7060138 - 07 Jun 2021
Viewed by 350
Abstract
Two inter-subspecific F1 hybrids have been obtained by crossing olive cultivars (‘Frantoio’ and ‘Coratina’) with pollen donors from olive subspecies (Olea europaea subsp. cuspidata) to enrich the germplasm of cultivated olive in southern China. This study aimed to investigate the [...] Read more.
Two inter-subspecific F1 hybrids have been obtained by crossing olive cultivars (‘Frantoio’ and ‘Coratina’) with pollen donors from olive subspecies (Olea europaea subsp. cuspidata) to enrich the germplasm of cultivated olive in southern China. This study aimed to investigate the characterization of morphological traits and molecular markers in the two hybrids and their parents of crosses. The morphological study showed a significant difference between genotypes according to the main discriminative parameters on qualitative and quantitative traits of leaf, fruit, and endocarp. A set of six co-dominant polymorphic simple sequence repeats (SSRs) were used for molecular identification, and SSR analysis confirmed that two progenies were the offspring of their cited parents based on the presence of parental specific SSR alleles. Three single-copy nuclear loci (SCNL) primer pairs were used for amplification of single-copy genes in the two progenies and their parents and after then PCR products were sequenced. Sequence alignment analysis on the effective data showed a total of 15 different base sites between two progenies, which were confirmed as true inter-specific hybrids between olive cultivars and subsp. cuspidata. Full article
(This article belongs to the Section Genetics, Genomics, Breeding, and Biotechnology (G2B2))
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Article
Effects of Foliage Spraying with Sodium Bisulfite on the Photosynthesis of Orychophragmus violaceus
Horticulturae 2021, 7(6), 137; https://doi.org/10.3390/horticulturae7060137 - 06 Jun 2021
Viewed by 506
Abstract
Sulphurous acid derived from sulfur dioxide (SO2) emission leads to the pollution of irrigation water and the inhibition of plant growth. The safe concentration threshold of NaHSO3 in plants should be clarified to promote agricultural production. In this study, Orychophragmus [...] Read more.
Sulphurous acid derived from sulfur dioxide (SO2) emission leads to the pollution of irrigation water and the inhibition of plant growth. The safe concentration threshold of NaHSO3 in plants should be clarified to promote agricultural production. In this study, Orychophragmus violaceus seedlings were used as experimental materials and five NaHSO3 concentrations (i.e., 0, 1, 2, 5, 10 mmol·L−1) were simultaneously sprayed on the leaf surface of different seedlings separately. Leaf physiology responses under different concentrations were analyzed. The NaHSO3 did not promote photosynthesis in O. violaceus under the 1 and 2 mmol·L−1 treatments. It was conducive to the net photosynthetic rate (PN), photorespiration rate (Rp), chlorophyll content, actual photochemical quantum yield (YII) and photochemical quenching (qP) under the 5 mmol·L−1 treatment. However, quantum yield of regulated energy dissipation (YNPQ) and nonphotochemical quenching (NPQ) were inhibited. Under the 10 mmol·L−1 treatment, PN, chlorophyll content, YII, qP, dark respiration rate (Rd) and electron transport rate (ETR) showed significant decreases, while the photorespiration portion (Sp) significantly increased. Our results demonstrated that NaHSO3 provided a sulfur source for plant growth and interfered with the redox reaction of the plant itself, and its role as a photorespiratory inhibitor might be masked. Full article
(This article belongs to the Special Issue Plant Physiology under Abiotic Stresses)
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Article
Nitrogen Uptake Efficiency of Olive Cultivars
Horticulturae 2021, 7(6), 136; https://doi.org/10.3390/horticulturae7060136 - 06 Jun 2021
Viewed by 480
Abstract
Maximizing nitrogen uptake efficiency is a sustainable objective to reduce the amount of nitrogen fertilizers applied in olive orchards. Many factors affect this parameter, but nothing is known about whether there are differences among cultivars related to nitrogen uptake efficiency in the olive, [...] Read more.
Maximizing nitrogen uptake efficiency is a sustainable objective to reduce the amount of nitrogen fertilizers applied in olive orchards. Many factors affect this parameter, but nothing is known about whether there are differences among cultivars related to nitrogen uptake efficiency in the olive, and if there are interactions with soil type. To clarify these questions, two groups of experiments were conducted. In the first group, four experiments were carried out in which 20 olive cultivars were compared. In the second group, three experiments were carried out to study the interaction with the type of soil. In all experiments, mist-rooted olive cuttings were growing in 1.1 L pots containing a mixture of sand and peat (2:1 by volume). Depending on the experiment, plants were placed in a shadehouse or in growth chambers at 25/15 °C (day/night) with a 14 h photoperiod and 70% humidity. Plants received weekly applications of 100 ppm N throughout the irrigation water, alternating with one or two applications of 150 mL of tap water. Some plants of each cultivar did not receive nitrogen and served as a control for NUE calculation. A nutrient solution without nitrogen was applied every four weeks to prevent nutritional deficiencies. Results indicated that there are differences among cultivars in the efficiency of uptake nitrogen. The Spanish cultivars ‘Picual’, ‘Arbequina’ and ‘Manzanilla de Sevilla’, together with the Greek cultivar ‘Koroneiki’ and the Italian ‘Frantoio’, were the cultivars with high NUE in this work. Soil type did not affect NUE, and no interaction between soil type and cultivar was observed. Full article
(This article belongs to the Section Plant Nutrition)
Article
An Early Calcium Loading during Cherry Tree Dormancy Improves Fruit Quality Features at Harvest
Horticulturae 2021, 7(6), 135; https://doi.org/10.3390/horticulturae7060135 - 06 Jun 2021
Viewed by 543
Abstract
The possible role of an early calcium application via sprays (0.25, 0.5 and 1M CaCl2) on dormant buds to improve sweet cherry (cv. Ferrovia) fruit quality at harvest was investigated. Fruit quality characteristics were also investigated in response to the age [...] Read more.
The possible role of an early calcium application via sprays (0.25, 0.5 and 1M CaCl2) on dormant buds to improve sweet cherry (cv. Ferrovia) fruit quality at harvest was investigated. Fruit quality characteristics were also investigated in response to the age of spurs, the ripening stage, and their interactions. Results indicate that calcium enters the dormant flower buds and the phloem but not to the dormant vegetative buds. At harvest, the levels of Zn, Mn, and Cu were declined in fruits by increasing CaCl2 doses of sprays. Fruit respiratory activity was higher and on–tree fruit cracking was lower in red-colour (unripe) cherries as well as in fruit that was produced by 2-year-old short spurs or by Ca-treated buds. Differences in the sweet cherry skin metabolic profiles were identified. Fruit produced from Ca-exposed spurs exhibited lower levels of ribose and other cell-wall-related sugars and higher sucrose, maltose, and quininic acid levels. Nutrient shift was increased in red cherries, while anthocyanins were boosted in the black ones. PCA analysis was performed between the high dose of calcium spray and a control for mineral element content and cherry quality traits. This study illustrates that the high dose of calcium application during bud dormancy can effectively improve sweet cherry fruit characteristics, in terms of calcium content, cracking incidence, and fruit set. Overall, the present study contributes to a better understanding of the impact of calcium nutrition in fruit crops, which will provide references for alternative nutrient management and quality control in sweet cherry production. Full article
(This article belongs to the Special Issue Improving Quality of Fruit)
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Article
Postharvest Fumigation of Fresh Citrus with Cylinderized Phosphine to Control Bean Thrips (Thysanoptera: Thripidae)
Horticulturae 2021, 7(6), 134; https://doi.org/10.3390/horticulturae7060134 - 05 Jun 2021
Viewed by 488
Abstract
Bean thrips (BT), Caliothrips fasciatus (Pergande), is a pest of concern to certain countries that import fresh citrus fruit from California, USA. A series of laboratory-scale exploratory fumigations with phosphine at 4.9 ± 0.3 °C (mean ± 2 SD; x¯±2s) were conducted to evaluate the postharvest control of adult BT. Models of the duration–mortality response predicted ca. 99% mortality of BT populations when headspace concentrations of phosphine, [PH3], are maintained at levels ≥0.4 g m−3 (250 ppmv (µL L−1)) and ≤1.5 g m−3 (1000 ppmv (µL L−1)) for 12 h, with the duration representing the lower bound of the 95% confidence level (CL). Confirmatory fumigations, each lasting 12 h, were then conducted using BT-infested sweet oranges, Citrus sinensis (L.), at pulp temperature (T) ≤ 5 °C to corroborate the exploratory results. Three formulations of cylinderized phosphine were used: 1.6% phosphine by volume in nitrogen, VAPORPH3OS®, and ECOFUME®, all applied at two levels, ca. 1.5 g m−3 (1000 ppmv (µL L−1)), as well as 0.5 g m−3 (300 ppmv (µL L−1)). Collectively, across the formulations, an applied dose of ca. 1.5 g m−3 (1000 ppmv (µL L−1)) resulted in 0 survivors from 38,993 (probit 8.60, 95% CL; probit 9, 72% CL) treated BT, while an applied dose of 0.5 g m−3 (300 ppmv (µL L−1)) resulted in 0 survivors from 31,204 (probit 8.56, 95% CL; probit 9, 70% CL) treated BT. Results were discussed in the context of commercial and operational features of quarantine and pre-shipment (QPS) uses of phosphine to treat fresh fruit and, specifically, the control of BT in fresh citrus exported from California, USA, to Australia. Full article
(This article belongs to the Special Issue Propagation and Post-harvest of Fruit Crops)
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Review
Methyl Jasmonate Applications in Viticulture: A Tool to Increase the Content of Flavonoids and Stilbenes in Grapes and Wines
Horticulturae 2021, 7(6), 133; https://doi.org/10.3390/horticulturae7060133 - 05 Jun 2021
Viewed by 480
Abstract
Recently, the interest in methyl jasmonate (MeJ) has increased in viticulture due to its effects on the synthesis of phenolic secondary metabolites in grapes, especially of anthocyanins, flavonols, and stilbenes derivatives, naturally occurring or synthesized, in berries in response to MeJ application to [...] Read more.
Recently, the interest in methyl jasmonate (MeJ) has increased in viticulture due to its effects on the synthesis of phenolic secondary metabolites in grapes, especially of anthocyanins, flavonols, and stilbenes derivatives, naturally occurring or synthesized, in berries in response to MeJ application to grapevines. These metabolites help to define sensory characteristics of wines by contributing to their color, flavor and mouthfeel properties, and to derive potential beneficial health effects due to their consumption. This review offers an overview of the importance of these phenolic compounds in grape and wine quality, in association with the MeJ supplementation to grapevines, and also considers their natural biosynthesis in grapes. On the other hand, this review describes the adaptation mechanisms induced after the grapevine elicitation. In addition, this report addresses the effects of MeJ over other aspects of Vitis immunity and its association with phenolic compounds and summarizes the recently published reports about the effects of exogenous MeJ applications to grapevines on grape and wine quality. Full article
(This article belongs to the Section Viticulture)
Review
A Review on Plant Responses to Salt Stress and Their Mechanisms of Salt Resistance
Horticulturae 2021, 7(6), 132; https://doi.org/10.3390/horticulturae7060132 - 03 Jun 2021
Viewed by 549
Abstract
Nowadays, crop insufficiency resulting from soil salinization is threatening the world. On the basis that soil salinization has become a worldwide problem, studying the mechanisms of plant salt tolerance is of great theoretical and practical significance to improve crop yield, to cultivate new [...] Read more.
Nowadays, crop insufficiency resulting from soil salinization is threatening the world. On the basis that soil salinization has become a worldwide problem, studying the mechanisms of plant salt tolerance is of great theoretical and practical significance to improve crop yield, to cultivate new salt-tolerant varieties, and to make full use of saline land. Based on previous studies, this paper reviews the damage of salt stress to plants, including suppression of photosynthesis, disturbance of ion homeostasis, and membrane peroxidation. We have also summarized the physiological mechanisms of salt tolerance, including reactive oxygen species (ROS) scavenging and osmotic adjustment. Four main stress-related signaling pathways, salt overly sensitive (SOS) pathway, calcium-dependent protein kinase (CDPK) pathway, mitogen-activated protein kinase (MAPKs) pathway, and abscisic acid (ABA) pathway, are included. We have also enumerated some salt stress-responsive genes that correspond to physiological mechanisms. In the end, we have outlined the present approaches and techniques to improve salt tolerance of plants. All in all, we reviewed those aspects above, in the hope of providing valuable background knowledge for the future cultivation of agricultural and forestry plants. Full article
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Article
Is There Daily Growth Hysteresis versus Vapor Pressure Deficit in Cherry Fruit?
Horticulturae 2021, 7(6), 131; https://doi.org/10.3390/horticulturae7060131 - 03 Jun 2021
Viewed by 458
Abstract
The growth of cherry fruit is generally described using a double sigmoid model, divided into four growth stages. Abiotic factors are considered to be significant components in modifying fruit growth, and among these, the vapor pressure deficit (VPD) is deemed the most effective. [...] Read more.
The growth of cherry fruit is generally described using a double sigmoid model, divided into four growth stages. Abiotic factors are considered to be significant components in modifying fruit growth, and among these, the vapor pressure deficit (VPD) is deemed the most effective. In this study, we investigated sweet cherry fruit growth through the continuous, hourly monitoring of fruit transversal diameter over two consecutive years (2019 and 2020), from the beginning of the third stage to maturation (forth stage). Extensometers were used in the field and VPD was calculated from weather data. The fruit growth pattern up to the end of the third stage demonstrated three critical steps during non-rainy days: shrinkage, stabilization and expansion. In the third stage of fruit growth, a partial clockwise hysteresis curve of circadian growth, as a response to VPD, appeared on random days. The pattern of fruit growth during rainy days was not distinctive, but the amount and duration of rain caused a consequent decrease in the VPD and indirectly boosted fruit growth. At the beginning of the fourth stage, the circadian growth changed and the daily transversal diameter vs VPD formed fully clockwise hysteresis curves for most of this stage. Our findings indicate that hysteresis can be employed to evaluate the initial phenological phase of fruit maturation, as a fully clockwise hysteresis curve was observable only in the fourth stage of fruit growth. There are additional opportunities for its use in the management of fruit production, such as in precision fruit farming. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae Ⅱ)
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Article
Role of Glutathione-Ascorbate Cycle and Photosynthetic Electronic Transfer in Alternative Oxidase-Manipulated Waterlogging Tolerance in Watermelon Seedlings
Horticulturae 2021, 7(6), 130; https://doi.org/10.3390/horticulturae7060130 - 03 Jun 2021
Viewed by 489
Abstract
Alternative oxidase (AOX) has been documented to mitigate the oxidative stress caused by abiotic stresses. However, it remains unknown how AOX regulates the antioxidant system and photosynthesis under waterlogging. To address this issue, we used two watermelon (Citrullus lanatus L.) cultivars (waterlogging [...] Read more.
Alternative oxidase (AOX) has been documented to mitigate the oxidative stress caused by abiotic stresses. However, it remains unknown how AOX regulates the antioxidant system and photosynthesis under waterlogging. To address this issue, we used two watermelon (Citrullus lanatus L.) cultivars (waterlogging tolerant cultivar ‘YL’ and sensitive cultivar ‘Zaojia8424’) as materials and the AOX inhibitor salicylhydroxamic acid (SHAM) to investigate the effects of AOX on photosynthesis and reactive oxygen species metabolism under waterlogging. We found that waterlogging decreased leaf photosynthesis and quantum yield of photosynthesis in watermelon, and the waterlogging tolerant cultivar ‘YL’ showed higher expression level of ClaAOX than the sensitive cultivar ‘Zaojia8424’. Net photosynthesis rate was higher in ‘YL’ than ‘Zaojia8424’. Moreover, waterlogging induced photoinhibition in ‘Zaojia8424’ but not in ‘YL’. Meanwhile, waterlogging promoted the accumulation of superoxide and peroxide hydrogen, and triggered oxidative damage. ‘YL’ suffered from less severe oxidative damage due to increased contents of ascorbate, a higher ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG), a higher activity of ascorbate peroxidase (APX) and catalase (CAT), and enhanced levels of CAT and APX expression, relative to ‘Zaojia8424’. However, the alleviation of photosynthesis and oxidative damage, increased content of ascorbate and higher GSH/GSSG ratio were abolished by SHAM. Our results suggested that photosynthetic electronic transfer and glutathione-ascorbate cycle are involved in waterlogging tolerance mediated by the AOX pathway in watermelon. Full article
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Article
Shoot Production and Mineral Nutrients of Five Microgreens as Affected by Hydroponic Substrate Type and Post-Emergent Fertilization
Horticulturae 2021, 7(6), 129; https://doi.org/10.3390/horticulturae7060129 - 02 Jun 2021
Viewed by 578
Abstract
As a new specialty crop with high market value, microgreens are vegetable or herb seedlings consumed at a young age, 7–21 days after germination. They are known as functional food with high concentrations of mineral nutrients and health beneficial phytochemicals. Microgreen industry lacks [...] Read more.
As a new specialty crop with high market value, microgreens are vegetable or herb seedlings consumed at a young age, 7–21 days after germination. They are known as functional food with high concentrations of mineral nutrients and health beneficial phytochemicals. Microgreen industry lacks standardized recommendations on cultural practices including species/variety selection, substrate choice, and fertilization management. This study evaluated shoot growth and mineral nutrient concentrations in five microgreens including four Brassica and one Raphanus microgreens as affected by four hydroponic pad types and post-emergent fertilization in two experiments in January and February 2020. The five microgreens varied in their shoot height, fresh, dry shoot weights, and mineral nutrient concentrations with radish producing the highest fresh and dry shoot weights. Radish had the highest nitrogen (N) concentration and mustard had the highest phosphorus (P) concentrations when grown with three hydroponic pads except for hemp mat. Hydroponic pad type altered fresh, dry shoot weights, and mineral nutrients in tested microgreens. Microgreens in hemp mat showed the highest shoot height, fresh, dry shoot weights, and potassium (K) concentration, but the lowest N concentration in one or two experiments. One time post-emergent fertilization generally increased shoot height, fresh, dry shoot weights, and macronutrient concentrations in microgreens. Full article
(This article belongs to the Section Protected Culture)
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