Venturia Inaequalis Research Articles (Page 1)

The cultivated apple is a traditional crop for Abkhazia. However, the humid subtropical climate here promotes the intensive development of fruit diseases, such as scab (caused by Venturia inaequalis (Cooke) G. Winter) and moniliosis (caused by Monilinia fructigena (Pers.) Honey). Research efforts today are aimed at searching for formulations capable of enhancing the natural immunity of plants against these diseases. In this work, we assess the possibility of extending the protection system against apple scab and monilial rot by including a single treatment with growth regulators during the budding phase. The studies were conducted in 2022–2024 in Golden Rangers apple tree plantations in the Gulrypsh district of the Republic of Abkhazia using a generally accepted methodology. The immune-stimulating effect of the Zerebra agro©, Biosil©, and Stimmunol EF© growth regulators against fruit scab was observed in the second and third years of application. With regard to monilial rot, the effect was observed in the third year of application. Yantarin BAU© demonstrated an increased biological effectiveness against scab and moniliosis already after the first application. A single application of the Zerebra agro©, Biosil©, Stimmunol EF©, and Yantarin BAU© growth regulators during the budding period did not increase the apple yield. Energiya-M, KRP© did not exhibit an immune-stimulating effect against either scab or moniliosis. However, a single treatment of the plants with this preparation during the budding period resulted in a 23.4 % increase in the apple yield compared to the control.

ABSTRACTApple scab, caused by Venturia inaequalis, is the most economically important fungal disease impacting apple production globally. Most commercial apple cultivars are susceptible to scab, although several sources of genetic resistance have been identified. The availability of genetic markers tightly linked with the functional resistance alleles is one of the factors limiting the breeding of scab‐resistant cultivars. ‘Honeycrisp’, one of the popular North American apple cultivars, is a source of Vhc1 scab resistance on linkage group 1, but the associated locus spans 12.6 cM and harbours over 200 genes. Here, we present the fine‐mapping of the Vhc1 locus, the development of haplotype‐specific simple sequence repeat (SSR) markers and the identification of candidate resistance alleles. Chromosome‐level phased genome assemblies of the scab‐resistant parent ‘Honeycrisp’ and scab‐susceptible ‘Gala’ were used to design nine novel polymorphic markers, along with two previously reported markers, spanning the Vhc1 QTL region. An F1 population derived from the two cultivars was developed and was evaluated for scab resistance across two consecutive years using the V. inaequalis isolate Vi‐19‐004 collected from Malus floribunda 821. Broad‐sense heritability was estimated at 0.66 across experiments. Phenotype–genotype association analysis fine‐mapped a moderate‐effect apple scab resistance QTL, explaining 5.2%–11.8% of phenotypic variance, to a 4.2‐cM genetic interval and a corresponding 0.85‐Mb physical region. SSR markers mdCu_2500, mdCu_3000 and CH‐Vf1 collocated with the Vhc1 QTL and can be used in future marker‐assisted selection studies for Vhc1. Six LRR‐encoding genes underlying the QTL region with enhanced expression upon inoculation with V. inaequalis were identified as scab resistance candidate alleles. These newly developed markers and candidate genes will accelerate the development of ‘Honeycrisp’ based scab‐resistant cultivars.

Venturia inaequalis, a hemibiotrophic ascomycete, is the causal agent of apple scab, a major disease affecting apple production worldwide. The widespread use of fungicides in orchard management has led to the selection of resistant strains. To limit the spread of these resistant strains, it is essential to understand their competitive fitness within the population. In this study, we evaluated the resistance profiles and fitness components of 23 V. inaequalis isolates from both treated and untreated orchards in Northern Italy, focusing on five fungicides: dodine, cyprodinil, trifloxystrobin, boscalid, and myclobutanil. Fitness parameters, including mycelial growth, conidia number, and conidia size, were assessed in relation to fungicide resistance and environmental factors, such as altitude. The results revealed that, overall, resistant and sensitive strains showed no significant differences in fitness, except for cyprodinil-resistant strains, which exhibited enhanced mycelial growth and increased conidia size, and dodine-resistant strains, which produced smaller conidia. Additionally, altitude influenced conidial size, with higher elevation sites correlating with smaller conidia. These findings suggest that both genetic and environmental factors contribute to conidial variation, which may impact pathogen dispersal and infection dynamics. This study highlights the resilience and potential for spread of fungicide-resistant strains and underscores the need for integrated resistance management strategies to maintain sustainable and high quality apple production.

Endophytic Diaporthe citrichinensis as a new source to alleviate post-harvest fungal infections in apple (Malus x domestica Borkh.).

BackgroundApple scab, caused by the hemibiotrophic fungus Venturia inaequalis (cooke) Wint., is a globally prevalent disease that severely threatens apple yield and fruit quality. Although the key resistance gene Rvi6 (resistance to Venturia inaequalis 6) has been widely deployed in apple scab-resistant breeding programs, the molecular mechanisms underlying its resistance phenotype remain poorly characterized.ResultsIn this study, we generated transgenic apple calli overexpressing Rvi6 and systematically investigated both its resistance phenotype and underlying molecular mechanisms. The Rvi6 gene presented high expression levels in leaves and fruits throughout the growth cycle, and aligning with the infection window of V. inaequalis. Rvi6 overexpression significantly reduced the levels of IAA (indole-3-acetic acid), ABA (abscisic acid), and JA (jasmonic acid), and auxin signaling, as well as the callus growth, which directly evidencing the “growth-defense trade-off” hypothesis on Rvi6-mediated apple scab resistance. The marked inhibition of V. inaequalis infection in Rvi6-overexpressing calli was attributed to increased ROS (reactive oxygen species) scavenging capacity, increased osmolyte accumulation, and maintenance of plasma membrane integrity. Additionally, Rvi6 induction depressed apple growth by reducing auxin accumulation and attenuating auxin signaling. Transcriptome analysis revealed that multiple biological processes and signaling pathways are involved in Rvi6-mediated disease resistance. Pathways related to plant‒pathogen interactions, lipid and amino acid metabolism, and flavonoid biosynthesis were significantly enriched among the upregulated pathways. Conversely, plant hormone signal transduction, protein processing and modification, and carbohydrate metabolism were enriched predominantly in the downregulated pathways.ConclusionsRvi6 exhibits high expression in leaves and fruits across the growth cycle, aligning with the infection window of V. inaequalis. Rvi6 enhances ROS scavenging capacity, osmolyte accumulation, and plasma membrane integrity, as well as suppresses apple growth, thereby restricting V. inaequalis invasion. Plant immune responses mediated by Ca2⁺ or MAPK cascade reactions, plant hormone signaling and multiple secondary metabolic mechanisms, contribute to Rvi6-mediated resistance against apple scab. This study provides novel insights into the biological functions of Rvi6.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12870-025-07117-1.

ABSTRACTApple scab, caused by Venturia inaequalis, is a major disease of cultivated apples (Malus × domestica) worldwide. Annually, there is one cycle of sexual reproduction (ascospores) in V. inaequalis between strains of two opposite mating types. Sexual reproduction mainly occurs on leaf litter over the winter, and mature ascospores readily infect young leaves the following spring. We do not yet know whether sexual reproduction is initiated before or after leaf‐fall in autumn. The timing of sexual reproduction initiation can significantly impact the exchange of genetic information among pathogen strains. In this study, we used scanning electron microscopy (SEM) to determine the timing of sex initiation, in particular, whether sex can initiate between lesions on the same leaf prior to leaf‐fall. SEM images showed that pseudothecial structures begin to develop before leaf‐fall on leaves with either multiple lesions or a single lesion. Following an overwintering period under laboratory conditions, however, the pseudothecia on leaves with multiple lesions were larger and more mature than those on leaves with a single lesion, where initial pseudothecial structures were present but did not develop further. Thus, the results suggest that the initiation of sexual reproduction in V. inaequalis can occur prior to leaf‐fall in autumn, limiting the opportunities for sexual recombination among strains from different leaves.

Apple (Malus × domestica Borkh.) production is threatened by scab, caused by the fungus Venturia inaequalis. One defense mechanism of apple trees against fungal pathogens such as V. inaequalis is the biosynthesis of antifungal compounds. Amongst these, phenolic compounds are particularly hypothesized to correlate with scab resistance, thereby offering a putative route to breed new apple cultivars with enhanced resistance. To characterize the involvement of phenolics in scab resistance, as conferred by either the Rvi6 resistance gene or through increased somatic ploidy, we monitored the phenolics profile in the leaves of apple genotypes harboring Rvi6 or increased ploidy that show enhanced levels of scab resistance compared to susceptible genotypes. Our study revealed differences in total and specific phenolic contents across the tested genotypes with significant correlation to Rvi6-based resistance and a minor effect of polyploidy herein. In particular, procyanidin dimer levels appeared positively correlated with the level of resistance, indicating a putative functional role in scab resistance. In contrast, the majority of other phenolics were negatively correlated with the resistance. Finally, our study did not identify a significant correlation between reduced phloridzin:flavanol ratio and Rvi6 resistance. These findings are discussed in the context of the role of phenolic metabolism in apple scab resistance.

This review article analyzes the prospects of DNA markers in apple breeding and presents the results of testing DNA markers linked to scab resistance genes in Russian and international practice. Rvi6 was identified to be the most common gene in Russian varieties, with over 80 varieties carrying this gene having been approved for use in the Russian Federation. Genetic sources of three or more resistance oligogens are of interest for prompt pyramiding of resistance genes in hybrid offspring. Among the carriers of the three identified resistance genes were found to be the Venyaminovskoye, Orlovskoye Polesie, Start, Zarya Stavropol’ya, Nika, Kandil Orlovsky varieties and 12/2-20-75, 17/1-6-72, 17/1-6-1, 17/2-6-7, 17/1-7-17, 17/1-6-73, 94-13/39, 2007-19/15 forms of Russian origin. Among those of foreign selection were the Realka, Redfree, Korobovka Krupnoplodnaya, Navavita, Sakavita varieties, as well as the 84-39/58 and 84-59 forms. The following genetic sources with four resistance genes were identified: Firiki Vermiou (Rvi2, Rvi4, Rvi8, Rvi11) and 2000-45/70 (Rvi2, Rvi4, Rvi5, Rvi6). The research results obtained to date, in particular the identification of a number of genetic sources of one or more oligogens using DNA markers, indicate progress in breeding work toward increasing scab resistance and achieving stable resistance through identification of genotypes with single and pyramided target genes for further breeding work.

Diffuse apple scab symptoms on the abaxial leaf surface are caused by the fungal pathogen Venturia inaequalis and occur even in well-managed orchards. The disease is challenging to manage, as the symptoms emerge on aging leaves later in the season and only develop on some leaves, suggesting the involvement of intrinsic defense mechanisms. We studied the development of diffuse abaxial scab symptoms on 'Jonagold' leaves in an orchard at three different shoot positions and at four different time points during the growing season to identify leaf-specific defense mechanisms. We identified infection moments by tracking the ascospore load and formation of new shoot leaves and determined the period required for proliferation of diffuse abaxial scab symptoms. Then, we correlated gene expression and phenolics profiles with the V. inaequalis DNA content to identify those inhibiting scab proliferation in asymptomatic leaves. Leaves in the middle of shoots showed higher symptom expression compared with shoot base and tip leaves. Disease inhibition in asymptomatic leaves was negatively correlated with several defense-related genes and phenolics. Altogether, our observations highlight that diffuse abaxial scab is one of the key challenges in apple growing and that the leaf ontogenic status during the infection process affects the development of these symptoms, with putative regulation by phenolic metabolism and ontogeny-related defense genes.

Apple scab, caused by Venturia inaequalis, remains a major challenge for apple production in Morocco, where disease management heavily depends on fungicide applications. However, increasing reports of resistance have raised concerns about the long-term efficacy of commonly used products and the economic sustainability of apple orchards. In this study, we evaluated the sensitivity of five V. inaequalis isolates from the Fes-Meknes region, a key apple-producing area in Morocco, to three fungicides: difenoconazole, trifloxystrobin, and thiophanate-methyl. The identity of the isolates was confirmed based on both morphological characteristics and by molecular analysis of the ITS region. In vitro and in vivo assays revealed significant differences in isolate responses. Difenoconazole consistently showed the highest efficacy, with EC50 values ranging from 0.05 to 1.46 µg/mL, and preventive applications reducing disease severity by up to 85.8% at 10 µg/mL. In contrast, trifloxystrobin and thiophanate-methyl exhibited much higher EC50 values (2.94–29.62 µg/mL and 14.84–1237.20 µg/mL, respectively), indicating widespread resistance, particularly to thiophanate-methyl, whose curative and preventive efficacy rarely exceeded 44%. Preventive treatments were significantly more effective than curative applications for all fungicides tested. These findings highlight the urgent need to revise apple scab management strategies in Morocco, including the rotation of fungicides with different modes of action and the integration of non-chemical approaches. Broader sensitivity monitoring and the use of molecular diagnostics are recommended to better inform sustainable disease control programs.

Venturia inaequalis, the cause of apple scab, readily develops resistance to fungicides with specific modes of action. Knowledge of the spatial and temporal pattern of resistance development is therefore relevant to fruit producers and their consultants. In the Lower Elbe region of Northern Germany, a two-year survey based on a conidial germination test was conducted, examining fungicide resistance in 35 orchards under Integrated Pest Management (IPM), 16 orchards of susceptible cultivars as well as a further 12 orchards of scab-resistant (Vf) cultivars under organic management, and 34 abandoned or unmanaged sites. No evidence of resistance to SDHI compounds (fluopyram, fluxapyroxad) was found after >5 yr of their regular use. Resistance to anilinopyrimidines (cyprodinil, pyrimethanil) had disappeared 15 yr after its widespread occurrence. Isolates from a few IPM orchards showed a reduced sensitivity to dodine. Double resistance to the MBC compound thiophanate-methyl and the QoI trifloxystrobin was rare in V. inaequalis strains that had achieved breakage of Vf-resistance, but very common (>50%) on scab-susceptible cultivars in IPM, organic and abandoned orchards in the 'Altes Land' core area of the Lower Elbe region, and in IPM orchards in the periphery. We conclude that resistance to QoI and MBC fungicides is persistent even decades after their last use, and that the core area harbours a uniform population adapted to intensive crop protection, whereas isolated orchards in the periphery are colonised by discrete populations of V. inaequalis.

Efficacy of biofungicides based on Bacillus against apple scab (Venturia inaequalis) and their influence on rhizosphere fungal communities

The root-derived syringic acid and shoot-to-root phytohormone signaling pathways play a critical role in preventing apple scab disease.

Phytosanitary treatments are massively used in orchards to fight apple scab, a disease caused by the fungus Venturia inaequalis (Vi). To reduce these treatments, resistant varieties are largely deployed but their effectiveness can decrease over time. The combination of complementary molecular mechanisms within new varieties could enhance the durability of genetic resistance however, the underlying resistance mechanisms remain poorly understood. An apple pseudo-F1 progeny was previously widely investigated for its quantitative trait loci (QTL) controlling resistance to scab and at least three of them seem to act complementarily; notably, one of them is specific to some Vi isolates while the others have a broader spectra of action. The aim of this approach is to better understand the underlying molecular mechanisms and metabolites associated with resistance alleles by exploring apple leaf specialized metabolism. A total of three experiments was conducted: one experiment included non-inoculated leaves whereas in the two other experiments, leaf samples were collected five days after inoculation with two different Vi isolates, including one known to overcome one QTL. Metabolic content was extracted in aqueous methanol before performing an untargeted metabolomic analysis using an Orbitrap IDXTM mass spectrometer, allowing high-resolution mass spectrometry (HRMS) detection. This approach without a priori enables the detection of potentially new chemical families involved in resistance to apple scab. The current data article includes 1) the protocol of plant sample production with a table summarizing key elements of the experimental designs, 2) overview of the raw metabolomic profiles from all three experiments and 3) assessment of metabolic feature reproducibility between replicates in each dataset through Principal Component Analysis. The raw data files are available on the recherche.data.gouv repository (10.57745/XJBD8V). These datasets are valuable resources to further investigate the molecular mechanisms underlying genetic resistance to apple scab, with a focus on specialized metabolism. In the long term, it should improve apple breeding strategies by informing on how to combine appropriate genetic and biochemical factors in new varieties to ensure a more durable resistance.

Apple scab is a disease caused by Venturia inaequalis; it alters the vegetative cycle of apple trees and affects the fruits in orchards or during post-harvest storage. Utilizing rotten apples in cidermaking is a promising technique to mitigate crop losses; nonetheless, uncertainties persist regarding the beneficial effects of damaged fruits. This study involves a thorough chemical analysis of cider produced from both healthy and scab-infected fruits to identify compositional changes caused by microbial proliferation and to assess their impact on cider quality. Apples infected by post-harvest apple scab, as opposed to uninfected apples, were employed in cidermaking. The peel microbiota was described by plate count, and next-generation sequencing-based metabarcoding methods were used to describe the peel microbiota, while HPLC and GC MS-MS were used to characterize the cider compositions. Apples infected with post-harvest scab host a specific fungal consortium with higher biodiversity, as evidenced by the Shannon evenness index, especially in the fungi kingdom. The presence of apple scab slows fermentation by up to 23%, lowers ethanol accumulation by up to 0.4%, and affects certain cider constituents: sugars, alcohols, amino acids, fatty acids, and esters. The statistical treatment of data relative to the chemical profile (PLS and PCA on the 31 compounds with VIP > 1) distinguishes ciders made from altered or safe fruits. Scab-infected apples can be valorized in the agri-food industry; however, microbiota alterations must not be underestimated. It is necessary to implement adequate mitigation strategies.

Evaluating cultivar susceptibility to biotic stressors in apple orchards is essential for selecting genotypes adapted to local conditions and for designing effective plant protection strategies. This study conducted a comparative assessment of five apple cultivars (‘Florina’, ‘Jonathan’, ‘Golden Delicious’, ‘Pinova’, and ‘Idared’) in response to major fungal diseases (Venturia inaequalis, Podosphaera leucotricha, and Monilinia spp.) and insect pests (Eriosoma lanigerum, Quadraspidiotus perniciosus, Anthonomus pomorum, Aphis spp., and Cydia pomonella). The cultivars were monitored over a five-year period in six orchards located in Central Transylvania, Romania. Significant differences in phytosanitary behavior were recorded among cultivars and locations. ‘Florina’ consistently showed the highest tolerance to pathogens and pests across all sites and years, while ‘Jonathan’ and ‘Golden Delicious’ proved highly susceptible, particularly to apple scab, powdery mildew, aphids, and codling moth. Pest incidence was strongly influenced by temperature, while disease occurrence was more closely linked to precipitation patterns. Heritability analysis indicated that genetic factors played a substantial role in shaping cultivar responses to most biotic stressors. The integrated approach to cultivar–location–pathogen and pest interactions offers practical insights for optimizing orchard protection strategies under variable ecological conditions.

Apple scab, caused by Venturia inaequalis, is one of the most economically significant diseases of apples worldwide. Severe infections can cause extensive defoliation and fruit with multiple lesions, rendering the apples unmarketable for fresh market sales. Commercial producers rely heavily on intensive fungicide spray programs to prevent disease outbreaks in susceptible cultivars. This report evaluates the efficacy of five fungicides for the management of primary scab and fruit scab. The trial was conducted in 2023 on six-year-old ‘Golden Delicious’ apple trees. Results from these trials can be used to advise apple producers on developing fungicide spray programs for the management of apple scab in Ohio.

Resistance evolution and local adaptation of Venturia inaequalis to old and new generation SDHI fungicides.

Comparison of the actual release dates of ascospores of the fungus Venturia inaequalis with those predicted by selected simulation models in an apple orchard in Central Poland

Classifying early apple scab infections in multispectral imagery using convolutional neural networks