Search Results (35)

This study examines the economic feasibility of adopting digital technologies for the early detection of Verticillium wilt in olive cultivation in Northern Evia, Greece. A Net Present Value (NPV) framework with different scenarios was employed to derive three adoption thresholds: the minimum effectiveness required to break even, the maximum tolerable cost at a target effectiveness, and the break-even olive-oil price. The results reveal substantial variability across scenarios, reflecting uncertainty in both disease dynamics and market conditions. Key determinants of feasibility include detection effectiveness, adoption costs, olive oil prices, and disease incidence. Larger holdings consistently face more favourable thresholds due to economies of scale, while smaller farms remain constrained unless collective actions or policy support reduces costs. The preliminary evidence indicates that early detection technologies can strengthen the resilience of olive farms, especially in high-incidence areas, though feasibility remains highly sensitive to costs, prices, and pathogen pressure. Finally, the findings underscore the need for targeted policy interventions to facilitate broader adoption. Full article

Verticillium wilt of olive (VWO), caused by the vascular soilborne fungus Verticillium dahliae, is one of the most devastating diseases of olive cultivation in the Mediterranean area. The adoption of tolerant genotypes is considered an efficient strategy to reduce its impact in the absence of effective chemical control. In the present study we assessed the response of seventy-seven olive cultivars (Olea europaea L.) to the defoliating pathotype of V. dahliae under controlled inoculation conditions. Five plants per cultivar were inoculated and compared with non-inoculated controls. Disease progression was monitored weekly for ten weeks and measured through three complementary parameters: Relative Area Under the Disease Progress Curve (RAUDPC), Final Mean Severity (FMS), and Percentage of Dead Plants (PDP). Statistical analyses, including ANOVA followed by Tukey’s HSD, correlation evaluation, and principal component analysis (PCA), were applied to classify cultivars into five susceptibility classes. Notable variability was observed among cultivars, with 7.8% classified as Highly Resistant (HR), 24.7% as Resistant (R), 46.8% as Moderately Susceptible (MS), and 20.8% as Susceptible (S) or Extremely susceptible (E). The cultivar Ghiacciolo showed the highest level of tolerance, displaying only slight symptoms and no statistically significant difference from the non-inoculated control, whereas ‘Carbuncion’, ‘Giogolino’, and ‘Pampagliosa’ exhibited more severe disease than the susceptible reference ‘Picual’. Strong correlations among RAUDPC, FMS, and PDP confirmed the consistency of the disease assessment framework, while PCA revealed distinct clustering patterns according to resistance level. Overall, these findings provide reliable evidence for the selection of olive cultivars suitable for areas vulnerable to V. dahliae. Full article

Verticillium wilt, caused by Verticillium dahliae, poses a significant threat to olive trees (Olea europaea L.). The isolation of endophytic Streptomyces strains from olive roots has led to the discovery of several strains showing strong antifungal activity against V. dahliae, as demonstrated through in vitro and small-scale soil experiments. Molecular analyses confirmed that strain OE54 belongs to Streptomyces iranensis. The main antifungal compound identified in this strain was rapamycin. Rapamycin displayed potent antifungal effects, notably inhibiting conidiospore germination (IC₅₀ = 87.36 μg/mL) and the hyphal growth of V. dahliae, with a minimum inhibitory concentration (MIC₅₀) of 3.91 ng/mL. Additionally, a second rapamycin-producing strain, OE57^T, was isolated. Phenotypic and genotypic analyses indicated that OE57^T represents a new species, which is proposed to be named Streptomyces lacaronensis sp. nov., with OE57^T designated as the type strain (=DSM 118741^T; CECT 31164^T). The discovery of two endophytic rapamycin-producing Streptomyces strains residing within olive roots is especially notable, given the rarity of rapamycin production among microorganisms. These findings highlight the potential of rapamycin-producing Streptomyces strains in developing biofertilizers to manage V. dahliae and reduce the impact of Verticillium wilt on olive trees and other crops. Full article

Olive trees are generally considered a species well-adapted to drought, but the impact of water shortage is of critical importance on olive production. For this reason, developing tolerant cultivars could be an effective strategy to mitigate the impact of drought in the future. Characterizing drought stress tolerance in olive is a complex task due to the numerous traits involved in this response. In this study, plant growth, pressure–volume curves, gas-exchange and chlorophyll fluorescence traits, and stomata characteristics were monitored in nine cultivars to assess the effects of mild and severe drought stress conditions induced by withholding water for 7 and 21 days, respectively, and were compared to a well-watered control treatment. The plant materials evaluated included traditional cultivars, as well as new developed cultivars suited for high-density hedgerow olive orchards or resistant to verticillium wilt. Significant differences between cultivars were observed for most evaluated traits, with more pronounced differences under severe drought conditions. A multivariate analysis of the complete dataset recorded throughout the evaluation period allowed for the identification of promising cultivars under stress conditions (‘Sikitita’, ‘Sikitita-2’, and ‘Martina’) as well as highly discriminative traits that could serve as key selection parameters in future breeding programs. Full article

Verticillium wilt of olive, caused by Verticillium dahliae Kleb., is a serious disease with no highly effective control methods currently available. Consequently, biological control strategies are being explored as viable and environmentally friendly alternatives. A natural recovery phenomenon has been observed in certain olive varieties following infection by low-virulence isolates of the pathogen, likely due to plant resistance mechanisms that may enhance defense against more virulent isolates. Based on these findings, a study was conducted to determine whether plants that had recovered from infection by a low-virulence isolate could exhibit increased resistance to highly virulent isolates. ‘Picual’ plants were first inoculated with a non-defoliating isolate, followed by inoculation with a defoliating isolate at different time intervals. The results demonstrate that prior infection with a non-defoliating isolate reduced disease severity caused by a defoliating isolate, particularly in susceptible cultivars like ‘Picual’. Treated plants exhibited slower disease progression and no mortality, whereas untreated plants developed severe symptoms and showed high mortality rates. A minimum interval of four months between inoculations with isolates of different virulence was crucial for achieving a significant reduction in disease severity. While this methodology has proven effective, further research is needed to elucidate the underlying mechanisms and identify additional biocontrol agents to enhance disease management strategies. Full article

Verticillium wilt caused by the soil-borne fungus Verticillium dahliae causes severe losses to a broad range of economically important crops worldwide. Chemical disease management is ineffective; thus, alternative control strategies are needed. Olive-producing countries face the challenge of managing olive mill wastewater (OMW) in an environmentally friendly and agronomically beneficial manner. The proper use of OMW supported by scientific research has been proposed as a valuable means for successful disease management. In this respect, we tested whether soil application of raw OMW can protect vegetable crops against V. dahliae and investigated the potential disease-suppressive mechanisms. OMW inhibited significantly fungal growth, sporulation, hyphae width, and conidial and microsclerotial germination in vitro, and these effects were dose-dependent. Moreover, the addition of OMW in the soil provided sufficient protection of eggplant and tomato against V. dahliae in planta. The high OMW-conferred protection of eggplant was gradually decreased, possibly due to the decreased phenolic content in OMW over time. Bioassays with sterilized soil substrate and OMW, along with isolated microbial strains, revealed that soil- and OMW-originated microbes had no role in disease suppression. Moreover, split-root set-ups suggested a non-systemic OMW-induced resistance mechanism. Root-drench application of OMW in eggplant and tomato plants did not cause significant alterations in the structure of the plant microbiome that could be associated with disease suppressiveness. Full article

Verticillium wilt of olive (VWO), caused by Verticillium dahliae (Vd), represents a significant threat to olive cultivation, particularly to the Moroccan cultivar “Picholine Marocaine”, by reducing yield, tree survival, and overall productivity. Current chemical and cultural control strategies provide limited efficacy, highlighting the need for alternative approaches such as biological control. This study investigated the potential of Rhizophagus irregularis (RI) as a biological agent to mitigate VWO over a 10-month period following V. dahliae inoculation. Disease severity, incidence, and defoliation rate as well as oxidant stress markers, antioxidant enzyme activities, and the phenolic pathway were evaluated in a greenhouse experiment. Our results showed that R. irregularis significantly reduced (p < 0.05) disease severity and incidence by about 31% and 26%, respectively, and decreased defoliation rates by 35% in RI-infected plants (RIV). The presence of R. irregularis triggered enhanced antioxidant enzyme activities (e.g., superoxide dismutase, catalase, and polyphenoloxidase), increased lignin deposition, elevated phenylalanine ammonia-lyase activity, and increased total phenol content in olive tissues. These biochemical and structural changes reduced lipid peroxidation, oxidative stress, and physiological damage, resulting in delayed disease progression. Enhanced accumulation of lignin and total phenolic compounds, particularly in aboveground tissues, was observed. This likely reinforced cell walls and enhanced resistance to pathogen infection. This study demonstrates that R. irregularis offers a promising biocontrol agent for combating soil-borne diseases in olives and other susceptible crops by mitigating VWO, boosting antioxidant defenses, and modulating the phenolic pathway with tissue-specific responses. Full article

Olive trees are a cornerstone of Mediterranean agriculture but face significant threats from diseases such as Verticillium wilt and olive anthracnose. These diseases, caused by Verticillium dahliae and Colletotrichum spp., respectively, result in significant economic losses and degrade olive oil quality. While traditional chemical treatments present environmental risk, sustainable alternatives such as biological control agents (BCAs) are gaining attention. Epicoccum nigrum, an antagonistic fungus, has shown potential as a BCA due to its production of antimicrobial secondary metabolites. This study aimed to observe whether E. nigrum has an antagonistic ability against V. dahliae and C. acutatum, and to elucidate the metabolic interactions between these fungi using NMR-based metabolomics. E. nigrum showed inhibitory effects on the growth of C. acutatum and V. dahlia of 44.97% and 38.73% respectively. Metabolomic profiling revealed distinct biochemical responses in E. nigrum, V. dahliae, and C. acutatum under mono- and dual-culture. Multivariate statistical analysis highlighted the metabolic shifts in mycelia and identified the primary metabolites, such as glutamine, 4-aminobutyrate, and phenylalanine that are involved in adaption for survival in stress conditions such as the presence of a competitor. The results could be important for a better understanding of the primary fungal metabolism, which is still poorly characterized. Further investigation is needed, but these results suggest that E. nigrum could serve as a BCA, offering a more sustainable approach to managing olive diseases. Full article

The olive tree is crucial to the Mediterranean agricultural economy but faces significant threats from climate change and soil-borne pathogens like Verticillium dahliae. This study assesses the dual role of an onion extract formulation, rich in organosulfur compounds, as both biostimulant and antifungal agent. Research was conducted across three settings: a controlled climatic chamber with non-stressed olive trees; an experimental farm with olive trees under abiotic stress; and two commercial olive orchards affected by V. dahliae. Results showed that in the climatic chamber, onion extract significantly reduced MDA levels in olive leaves, with a more pronounced reduction observed when the extract was applied by irrigation compared to foliar spray. The treatment also increased root length by up to 37.1% compared to controls. In field trials, irrigation with onion extract increased the number of new shoots by 148% and the length of shoots by 53.5%. In commercial orchards, treated trees exhibited reduced MDA levels, lower V. dahliae density, and a 26.7% increase in fruit fat content. These findings suggest that the onion extract effectively reduces oxidative stress and pathogen colonization, while enhancing plant development and fruit fat content. This supports the use of the onion extract formulation as a promising, sustainable alternative to chemical treatments for improving olive crop resilience. Full article

Verticillium wilt of olive (VWO) caused by Verticillium dahliae is considered a major olive (Olea europaea) disease in Mediterranean-type climate regions. The lack of effective chemical products against VWO makes it necessary to search for alternatives such as biological control. The main goal of this study was to evaluate the effect of six Streptomyces spp. strains as biological control agents (BCAs) against VWO. All of them were molecularly characterized by sequencing 16S or 23S rRNA genes and via phylogenetic analysis. Their effect was evaluated in vitro on the mycelial growth of V. dahliae (isolates V004 and V323) and on microsclerotia (MS) viability using naturally infested soils. Bioassays in olive plants inoculated with V. dahliae were also conducted to evaluate their effect against disease progress. In all the experiments, the reference BCAs Fusarium oxysporum FO12 and Aureobasidium pullulans AP08 were included for comparative purposes. The six strains were identified as Streptomyces spp., and they were considered as potential new species. All the BCAs, including Streptomyces strains, showed a significant effect on mycelial growth inhibition for both V. dahliae isolates compared to the positive control, with FO12 being the most effective, followed by AP08, while the Streptomyces spp. strains showed an intermediate effect. All the BCAs tested also showed a significant effect on the inhibition of germination of V. dahliae MS compared to the untreated control, with FO12 being the most effective treatment. Irrigation treatments with Streptomyces strain CBQ-EBa-21 or FO12 were significantly more effective in reducing disease severity and disease progress in olive plants inoculated with V. dahliae compared to the remaining treatments. This study represents the first approach to elucidating the potential effect of Streptomyces strains against VWO. Full article

Verticillium wilt of olive (VWO) is one of the most widespread and devastating olive diseases in the world. Harnessing host resistance to the causative agent is considered one of the most important measures within an integrated control strategy of the disease. Aiming to understand the mechanisms underlying olive resistance to VWO, the metabolic profiles of olive leaves, stems and roots from 10 different cultivars with varying levels of susceptibility to this disease were investigated by liquid chromatography coupled to mass spectrometry (LC-MS). The distribution of 56 metabolites among the three olive tissues was quantitatively assessed and the possible relationship between the tissues’ metabolic profiles and resistance to VWO was evaluated by applying unsupervised and supervised multivariate analysis. Principal component analysis (PCA) was used to explore the data, and separate clustering of highly resistant and extremely susceptible cultivars was observed. Moreover, partial least squares discriminant analysis (PLS-DA) models were built to differentiate samples of highly resistant, intermediate susceptible/resistant, and extremely susceptible cultivars. Root models showed the lowest classification capability, but metabolites from leaf and stem were able to satisfactorily discriminate samples according to the level of susceptibility. Some typical compositional patterns of highly resistant and extremely susceptible cultivars were described, and some potential resistance/susceptibility metabolic markers were pointed out. Full article

Developing models to understand disease dynamics and predict the risk of disease outbreaks to facilitate decision making is an integral component of plant disease management. However, these models have not yet been developed for one of the most damaging diseases in Mediterranean olive-growing areas (verticillium wilt (VW), caused by the fungus Verticillium dahliae Kleb.), although there are parameters (e.g., level of V. dahliae inoculum in the soil, level of susceptibility of the olive cultivar, isothermality, coefficient of variation of seasonal precipitation, etc.) that have previously been correlated with the severity of the disease. Using the data from previous VW studies conducted in the Guadalquivir Valley of Andalusia (one of the most damaged areas worldwide), in this work, a set of fuzzy logic (FL) models is developed with the aforementioned disease and climatic parameters, and the results are compared with machine learning (ML) models, of known effectiveness, to predict the risk levels of VW appearance in an olive orchard. Under these conditions, both groups of models were less effective than those previously studied with simpler models or models used under controlled conditions. However, the accuracy achieved with the most efficient FL model (60%; classification system based on fuzzy rules using the Ishibuchi method with a weighting factor) was somewhat greater than the efficiency achieved with the most efficient ML model (59.0%; decision tree classifier), in addition to being more appropriate (from a practical point of view) for the incorporation into a decision support system by allowing the risk of appearance of each observation to be known by providing rules for each of the combinations of the different parameters with similar precision. Therefore, in this study, we propose the FL methodology as suitable to act as an expert system for the future creation of a decision support system for VW in olives. Full article

Verticillium wilt is a soil-borne fungal disease that affects olive trees (Olea europaea) and poses a serious threat to their cultivation. The causal agent of this disease is Verticillium dahliae, a pathogen that is difficult to control with conventional methods. Therefore, there is a need to explore alternative strategies for the management of Verticillium wilt. In this study, we aimed to isolate and characterize actinobacteria from the rhizosphere of olive trees that could act as potential biocontrol agents against V. dahliae. We selected a Streptomyces sp. OR6 strain based on its in vitro antifungal activity and its ability to suppress the pathogen growth in soil samples. We identified the main active compound produced by this strain as albocycline, a macrolide polyketide with known antibacterial properties and some antifungal activity. Albocycline was able to efficiently suppress the germination of conidiospores. To our knowledge, this is the first report of albocycline as an effective agent against V. dahliae. Our results suggest that Streptomyces sp. OR6, or other albocycline-producing strains, could be used as a promising tool for the biological control of Verticillium wilt. Full article

The olive tree (Olea europaea), a non-tropical woody crop that occupies the largest area in the world, is severely affected by the fungus Verticillium dahliae worldwide. In this regard, there is currently detailed information on the level of resistance to this pathogen in the main olive varieties. However, there is little information on quantitative aspects of its anatomy and on the existence of anatomical differences between varieties that could be related to the differential resistance response observed. In the present work, a quantitative study of the xylem of ‘Picual’, susceptible, and ‘Frantoio’, resistant, to V. dahliae is carried out. This study also provides quantitative data on the xylem in different areas of the plant, an aspect on which there is not much information for the olive tree. Among the parameters evaluated, it is probably the greater conductive capacity in the xylem tissue that ‘Frantoio’ presents, mainly due to the greater density of its vessels, which has a more relevant role in the resistance and natural recovery that this cultivar manifests to the disease. In any case, these constitutive anatomical differences, and those others that can be induced in plants during infections, should be investigated in future work that includes inoculation with the pathogen. Full article

It is known that high N doses, N/K imbalances, and frequent irrigation favor Verticillium wilt. The influence of fertilization and its interaction with the frequency of irrigation on the development of Verticillium wilt of olive (VWO) has been evaluated. A split-split-plot design in microplots with two naturally infested soils of different texture was established for studying three fertilization treatments (NO₃Ca, NPK and without fertilization), plus two irrigation frequencies (daily and deficit). The treatments were applied by means of fertigation, evaluating the susceptible cultivar Picual. Final disease incidence in plants subjected to NO₃Ca daily treatment was 100% regardless of soil texture. However, final mortality in these plants was 37% and 85.2% in clay and sandy loam soils, respectively. In addition, the area under the disease progress curve values were significantly higher (49.1%) in plants subjected to NO₃Ca fertilization compared to those not fertilized or fertilized with N-P-K when plants were grown in clay soil. This value in the sandy loam soil was significantly higher in the NO₃Ca daily irrigation treatment (94.3%), followed by the N-P-K-daily treatment (61.1%) which also was significantly higher than the unfertilized daily, N-deficit and NPK-deficit treatments (37.8, 42.6 and 44.9%, respectively). The plants submitted to unfertilized-deficit treatment reached the lowest value (9.6%). In this work it can be concluded that the application of fertilizer or the application of fertilizer with daily irrigation in naturally infested soils increases the development of VWO in Picual. Full article