The impact of Elsinoë ampelina-infection on key metabolic properties in Vitis vinifera cv. Red Globe berries via multi-omics approaches

Grape anthracnose caused by Elsinoë ampelina (Shear) is one of the most serious fungal diseases that lead to the quality reduction and yield losses of grape (Vitis vinifera cv. Red Globe) berries. In the present study, metabolome and transcriptome analyses were conducted using grape berries in the field after infection with E. ampelina at 7, 10, and 13 days to identify the metabolic properties of berries. A total of 132 metabolites with significant differences and 6877 differentially expressed genes were detected and shared by three comparisons. The analyses demonstrated that phenylpropanoid, flavonoid, stilbenoid and nucleotide metabolisms were enriched in E. ampelina-infected grape berries but not amino acid metabolism. Phenolamide, terpene and polyphenole contents also accumulated during E. ampelina infection. The results provided evidence of the enhancement of secondary metabolites involved in plant defence, such as resveratrol, α-viniferin, ε-viniferin, and lignins. The results showed the plant defence-associated metabolic reprogramming caused by E. ampelina infection in grape berry and provided a global metabolic mechanism under E. ampelina stimulation.

Anthracnose risk establishment based on age-related susceptibility of grape leaves, flowers and berries to infection by Elsinoë ampelina

Anthracnose is an important disease of grapevines caused by the fungus Elsinoë ampelina. In recent years, there have been regular outbreaks in humid grape-growing regions around the world. Young leaves and berries are reported to be highly susceptible to E. ampelina, but detailed and seasonal development of age-related susceptibility remains unclear. Experiments were conducted under greenhouse and vineyard conditions by inoculating 1 to-19-day-old leaves, flowers and berries at different phenological stages of three grapevine cultivars (Vandal-Cliche, Marquette and Vidal). Leaf susceptibility was highest when inoculated at 1-2 days old, and inoculated leaves were moderately susceptible at 3-6 days old and almost resistant when older than 6 days. The influence of leaf age on anthracnose relative severity was adequately described by an exponential decay model. The susceptibility of the inflorescences was high when inoculated from their initiation to the full flowering (50% fall of the caps), and the inflorescences/flowers were moderately susceptible until veraison, after which the berries were practically resistant. The flower/berry susceptibility as a function of degree-days accumulated since April 1 was modeled using a sigmoid model. Based on this model, 50% disease incidence is reached when 656, 543 and 550 degree days are accumulated for the cultivars Vandal-Cliche, Marquette and Vidal, respectively. These results suggest that the risk of anthracnose development is high from bud-break to fruit set, and on newly-emerged leaves either early in the season or following pruning. More knowledge on anthracnose epidemiology is needed, but these results could be used to improve timing of fungicide applications and pruning activities.

Development and evaluation of a model that predicts grapevine anthracnose caused by Elsinoë ampelina

Grapevine anthracnose caused by Elsinoë ampelina is a serious threat in many vineyards, and its control requires repeated application of fungicides, usually on a calendar basis. A better understanding of the pathogen life cycle would help growers to manage anthracnose more safely and effectively. After conducting a systematic literature search of grape anthracnose, we used the retrieved information and data to develop a mechanistic model based on systems analysis. The model simulates (i) production and maturation of primary inoculum; (ii) infection caused by both primary and secondary conidia; and (iii) lesion formation and production of secondary inoculum. The model was validated for its ability to predict i) first seasonal onset of anthracnose lesions by using 8 years of data collected at Auckland, New Zealand, and ii) disease progress during the season by using 3 years of data collected at Frelighsburg, Canada. Overall, the model provided accurate predictions of infection occurrence, with 0.96 accuracy, 0.91 sensitivity, and 0.97 specificity. The model also showed good accuracy for predicting disease progress, with a concordance correlation coefficient between observed and predicted disease severities of CCC=0.92, a root mean square error of RMSE=0.14, and a coefficient of residual mass of CRM=0.06. Although the model failed to predict 10 of 110 real infection periods, these missed infections led to only mild disease symptoms. We therefore conclude that the model is reliable and can be used to reduce the costs of anthracnose management by improving the timing of fungicide applications.

Transcriptome Analysis of the Grape-Elsinoë ampelina Pathosystem Reveals Novel Effectors and a Robust Defense Response

Elsinoë ampelina is an ascomycetous fungus that causes grape anthracnose, a potentially devastating disease worldwide. In this study, a dual RNA-seq analysis was used to simultaneously monitor the fungal genes related to pathogenesis and grape genes related to defense during the interaction at 2, 3, 4, and 5 days postinoculation. Consistent with their potential roles in pathogenicity, genes for carbohydrate-active enzymes, secondary metabolite synthesis, pathogen-host interaction, and those encoding secreted proteins are upregulated during infection. Based on Agrobacterium tumefaciens–mediated transient assays in Nicotiana benthamiana, we further showed that eight and nine candidate effectors, respectively, suppressed BAX- and INF1-mediated programmed cell death. The host response was characterized by the induction of multiple defense systems against E. ampelina, including synthesis of phenylpropanoids, stilbenes, and terpenoid biosynthesis, cell-wall modifications, regulation by phytohormones, and expression of defense-related genes. Together, these findings offer new insights into molecular mechanisms underlying the grape–E. ampelina interaction. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Influence of Leaf Wetness Duration and Temperature on Infection of Grape Leaves by Elsinoë ampelina under Controlled and Vineyard Conditions

On susceptible varieties, indirect damage to vines infected by Elsinoë ampelina range from reduced vigor to complete defoliation while, on berries, damage ranges from reduced quality to complete yield loss. Limited knowledge about the relationship between weather conditions and infection makes anthracnose management difficult and favors routine application of fungicides. The influence of leaf wetness duration and temperature on infection of grape leaves by E. ampelina was studied under both controlled and vineyard conditions. For the controlled conditions experiments, the five youngest leaves of potted vines (Vidal) were inoculated with a conidia suspension and exposed to combinations of six leaf wetness durations (from 0 to 24 h) and six constant temperatures (from 5 to 30°C). A week after each preset infection period, the percent leaf area diseased (PLAD) was assessed. At 5°C, regardless of the leaf wetness duration, no disease developed. At 10 and at 15 to 30°C, the minimum leaf wetness durations were 4 and 6 h, respectively. Above the minimum wetness duration, at temperatures from 10 to 30°C, PLAD increased linearly, with increasing leaf wetness up to 12 h, and then at a lower rate from 12 to 24 h. The optimal temperature for infection was 25°C. Relative infection was modeled as a function of both temperature and wetness duration using a Richards model (R2 = 0.93). The predictive capacity of the model was evaluated with data collected in experimental vineyard plots exposed to natural wetness durations or artificial wetness durations created using sprinklers. In total, 264 vineyard infection events were used to validate the controlled experiments model. There was a linear relationship between the risk of infection estimated with the model and the observed severity of anthracnose (R2 = 90); however, the model underestimated disease severity. A risk chart was constructed using the model corrected for vineyard observations and three levels of risk, with light, moderate, and severe risks corresponding to ≤5, >5% to ≤25, and >25% leaf area diseased, respectively. Overall, 93.9% of 132 independent observations were correctly classified, with 100, 29.4, and 9.4% of the light, moderate, and severe risks, respectively.

Pathogenesis and immune response in resistant and susceptible cultivars of grapevine (Vitis spp.) against Elsinoë ampelina infection

Elsinoë ampelina is the main cause of grape anthracnose, and the majority of grapevine cultivars are susceptible to this fungus. Some Chinese wild grape cultivars are resistant, however. It is therefore apt to compare the pathogenesis and immune responses in susceptible and resistant cultivars of grapevine to explore the detailed molecular and biochemical mechanisms of resistance to this fungus. In this study, ultrastructural and histopathological observations were used to demonstrate the resistance responses to E. ampelina in the resistant Chinese wild cultivar Vitis quinquangularis clone ‘Shang-24’ and the susceptible cultivars Vitis davidii cv. ‘Tangwei’ and Vitis vinifera cv. ‘Thompson Seedless’. Seventy-two hours post-inoculation (hpi) with E. ampelina, brown necrotic spots were clearly visible on the leaves of the susceptible cultivars ‘Tangwei’ and ‘Thompson Seedless.’ The infection was characterized by rapid colonization of the host cells by hyphae and massive spread of the pathogen in the intercellular spaces, ultimately leading to host cell collapse, cuticle dissolution, and extensive hyphal growth. In the resistant clone ‘Shang-24’, the conidia were lysed, a large quantity of electronically dense matter appeared, the hyphal growth was suppressed, and the host cells remained intact. In addition, six genes associated with disease resistance were differentially expressed in the susceptible and resistant cultivars. These disease-related genes were significantly up-regulated following infection with E. ampelina. This study illustrates the differences in infection and colonization of E. ampelina in resistant and susceptible grape leaves.