Riboflavin (Vitamin B2) induces defence responses and resistance to Plasmopara viticola in grapevine

Grapevine (Vitis vinifera) is susceptible to a variety of pathogenic fungi that affect yield and wine quality. Their control is generally achieved by widespread application of fungicides in the vineyards. The economic costs and negative environmental impact associated with these applications has led to a quest for alternative strategies, focusing on manipulation of host defence mechanisms. Here, we evaluated the ability of riboflavin (i.e. Vitamin B₂) to induce resistance against downy mildew in grapevine. Our results showed that 2 mM riboflavin applied 1–3 days before pathogen inoculation provided a disease reduction efficiency of 86 %. A microscopic analysis of the time course of P. viticola colonization in riboflavin-treated leaf discs suggests early inhibition of hyphae spreading in the intercellular space. This resistance does not result from a direct fungitoxic effect of riboflavin. However, this vitamin activates host-defence responses including H₂O₂ generation, upregulation of an array of defence-related genes and synthesis of callose in stomata cells, while stilbene synthesis is not affected. Using a pharmacological approach, we deduced that both jasmonic acid and callose biosynthesis pathways are significantly involved in riboflavin-induced resistance against downy mildew in grapevine.     

Auswirkungen des Herbizids Basta® auf die Weinrebe und den Falschen Mehltau

A field experiment was conducted in order to analyse the effects of the herbicide Basta^® with glufosinate-ammonium as the active ingredient (that inhibits specifically the enzyme glutamine-synthetase) on the grapevine plant and the infestation with Plasmopara viticola, the downy mildew pathogen. The herbicide was applied at sublethal concentrations and the toxic effects on leaves and berries based on different quality parameters were estimated. Low concentrations of glufosinate-ammonium (<?0,625?mM) did not affect the chlorophyll and amino acid concentrations in leaves. This was also the case for the content of salicylic acid and phenolic compounds. Furthermore, must parameters such as sugars (glucose and fructose), acids (tartaric acid, malic acid, total acids and volatile acids), and alcohol (ethanol and glycerine) also remained unchanged compared to the fungicide-treated or untreated control, whereas the concentrations of nitrogenous components metabolically available to yeasts increased with increasing concentrations of glufosinate-ammonium. The amount of berries harvested at the end of the experiment depended on the glufosinate-ammonium concentration applied. The harvest was highest when glufosinate-ammonium was applied as a 0.1?mM solution and differed not significantly from the fungicide-treated control, but decreased with increasing herbicide doses. However, the infestation of leaves with P. viticola was significantly reduced by the application of the herbicide, even though not each infection was eradicated due to the non-systemic mode of action of the herbicide. The particular influence of the herbicide onto this host-parasite interaction still remains unclear. Since applications of glufosinate-ammonium at low concentrations seem not to affect grapevine plants negatively, but were able to reduce the infestation with downy mildew, the specific mode of action may reveal new alternatives for the control of fungal pathogens.     

An Aqueous Extract of the Dry Mycelium of Penicillium chrysogenum Induces Resistance in Several Crops under Controlled and Field Conditions

We have examined the effect of Pen, an aqueous extract of the dry mycelium of Penicillium chrysogenum, on plant–pathogen interactions. Pen controlled a broad range of pathogens on several crop plants under greenhouse and field conditions. Pen protected grapevine from downy and powdery mildew (caused by Plasmopara viticola and Uncinula necator), tomato from early blight (caused by Phytophthora infestans), onion from downy mildew (Peronospora destructor) and apple trees from apple scab (caused by Venturia inaequalis) to a similar extent as fungicides such as copper and sulphur or well-known inducers such as benzothiadiazole or β-aminobutyric acid. Pen had no major direct fungicidal effect and is thus supposed to protect plants by activating their defense mechanisms. The raw material for extraction of Pen was available in constant quality, a prerequisite for commercial application. Under certain conditions, Pen caused phytotoxic side effects. The symptoms mostly consisted of small necrotic spots or, more rarely, of larger necrotic areas. The development of the symptoms was dependent on several parameters, including concentration of Pen, the number of applications, the persistence on the plant tissue, the plant species and variety and environmental conditions. In grapevine, a partially purified fraction of Pen was much less toxic than the crude Pen extract, but protected the plants to a similar extent against P. viticola. Our data show that Pen has interesting and unique properties as a plant protection agent, but more research is needed to further reduce its phytotoxic side effects.     

Effect of aerated compost tea on grapevine powdery mildew, botrytis bunch rot and microbial abundance on leaves

Aerated compost tea (ACT), prepared from immature compost, was applied to foliage and fruit of grapevines (Vitis vinifera) to assess its potential for suppressing two important diseases: botrytis bunch rot, caused by Botrytis cinerea, and powdery mildew, caused by Erysiphe necator. An ACT applied to leaves of Cabernet Sauvignon vines in pots 7 days before inoculation with E. necator conidia reduced mean powdery mildew severity on the three youngest expanded leaves (at inoculation) to less than 1 %; mean severity on non-treated, inoculated leaves was 15 %. Multiple applications of ACTs at two vineyards in different growing seasons suppressed powdery mildew to <1 % mean severity on Chardonnay leaves (non-treated 79 % severity) and bunches (non-treated 77 % severity), and on Riesling leaves (non-treated 24 % severity). The same treatments reduced the incidence of Chardonnay bunches with latent B. cinerea and Riesling bunches with sporulating B. cinerea, although the level of botrytis bunch rot in both experiments was not economically damaging. The numbers of culturable bacteria, fungi and yeasts on Chardonnay leaves were higher than pre-treatment levels 10 days after ACT application, as were fungal numbers on Riesling leaves 21 days after treatment. Suppression by ACTs of two fruit and foliar pathogens of grapevine with different biology and epidemiology indicated potential for their use as a tactic in integrated disease management. Further testing of ACTs in a range of viticultural environments and application regimes will contribute to a better understanding of the impact of this tactic on disease, grape and wine quality.     

Frequency distribution of sensitivity of Ustilaginoidea virens to four EBI fungicides, prochloraz, difenoconazole, propiconazole and tebuconazole, and their efficacy in controlling rice false smut in Anhui Province of China

False smut, caused by Ustilaginoidea virens, is an important emerging disease of rice (Oryza sativa L.) in China. Up to now, as most varieties with high yielding and good quality are susceptible or even highly susceptible to false smut in most rice-growing ecological regions, especially in Anhui Province, chemical control with fungicides would be an important measure for the control of this disease. The ergosterol biosynthesis inhibitor (EBI) fungicides, such as prochloraz, difenoconazole, propiconazole and tebuconazole, are extensively used in China for the control of rice diseases, such as rice sheath blight and rice blast. In this study, a total of 102 U. virens isolates (from Anhui Province of China) were tested for their sensitivity to these four EBI fungicides during the stage of mycelial growth. The EC₅₀ ranges of values for prochloraz, difenoconazole, propiconazole and tebuconazole inhibiting mycelial growth of the 102 U. virens isolates were 0.04–0.75, 0.04–1.08, 0.04–0.38 and 0.03–0.57 μg?ml^?1, with the average EC₅₀ values of 0.32?±?0.08, 0.45?±?0.08, 0.19?±?0.03 and 0.21?±?0.06 μg?ml^?1, respectively. These values suggested that the tested U. virens isolates were very sensitive to these four EBI fungicides. Results of field trials showed that two sprays of three of the fungicides exhibited greater control efficacy than a single spray for the control of rice false smut. Two sprays of each was better than a single spray for the control of rice sheath blight. Two sprays of 50% propiconazole EC at 300 g a.i. ha^?1 gave the best control of rice false smut at both two sites during the two consecutive years, 2010 and 2011, with the control efficacy ranging from 71.5 to 74.3%. Sensitivity of the field U. virens isolates to EBI fungicides should be monitored. Mixtures, as well as alternation with other fungicides with different modes of action, should be tested.     

Effect of epoxiconazole on rice blast and rice grain yield in China

Sensitivity to epoxiconazole of 90 single-spore isolates of Magnaporthe oryzae was determined. The EC₅₀ values for epoxiconazole in inhibiting mycelial growth of the 90 M. oryzae isolates were 0.11–0.86 μg/ml, with an average EC₅₀ value of 0.260?±?0.082 μg/ml. There was no correlation between sensitivity to epoxiconazole and sensitivity to carbendazim or iprobenfos. In protective and curative tests, epoxiconazole applied at 200 μg/ml provided over 70 % control efficacy, while tricyclazole exhibited better protective than curative activity. The results of four field trials performed in 2010 and 2011 at two sites showed that epoxiconazole at 112.5 g a.i/ha provided over 75 % control efficacy, which was similar to tricyclazole with 300 g a.i./ha and better than carbendazim with 562.5 g a.i./ha.     

Baseline sensitivity to proquinazid in Blumeria graminis f. sp. tritici and Erysiphe necator and cross‐resistance with other fungicides

BACKGROUND: Proquinazid is a new quinazolinone fungicide from DuPont registered in most European countries for powdery mildew control in cereals and vines. The aim of this paper is to present baseline sensitivity data in populations of Blumeria graminis f. sp. tritici EM Marchal and Erysiphe necator (Schw) Burr as well as results from cross‐resistance studies with other fungicides. RESULTS: Proquinazid exhibited a high intrinsic activity on B. graminis f. sp. tritici isolates at rates ranging from 0.000078 to 0.02 mg L^?1. Erysiphe necator isolates were comparatively less sensitive to proquinazid, with EC₅₀ values ranging from 0.001 to 0.3 mg L^?1. Proquinazid controlled equally well B. graminis f. sp. tritici isolates sensitive and resistant or less sensitive to tebuconazole, fenpropimorph, fenpropidin, cyprodinil and kresoxim‐methyl. A positive correlation (r = 0.617) between quinoxyfen and proquinazid sensitivities was found among 51 B. graminis f. sp. tritici isolates. Quinoxyfen‐resistant B. graminis f. sp. tritici isolates were slightly less sensitive to proquinazid than the quinoxyfen‐sensitive isolates; however, proquinazid remained much more active than quinoxyfen on these isolates. A stronger sensitivity relationship (r = 0.874) between proquinazid and quinoxyfen was found among 65 E. necator isolates tested in a leaf disc assay. The sensitivity values for proquinazid were significantly lower than those for quinoxyfen, confirming the higher intrinsic activity of proquinazid on both pathogens. CONCLUSION: Given the history of resistance development in powdery mildew and the observed sensitivity relationship with quinoxyfen, specifically in E. necator, we conclude that the risk of resistance developing to proquinazid might be influenced by the use of quinoxyfen. Based on these results, the authors recommend that proquinazid and quinoxyfen be managed together for resistance management. Copyright © 2009 Society of Chemical Industry     

„VitiMeteo Plasmopara“ – Prognosemodell zur Bekämpfung von Plasmopara viticola (Rebenperonospora) im Weinbau

Downy mildew, caused by Plasmopara viticola, is the most important disease of European grapevine (Vitis vinifera) in humid climates. On the basis of weather data the forcasting model “VitiMeteoPlasmopara” calculates the most important steps of the life cycle of downy mildew. A growth model for the simulation of leaf development is integrated in the pure forcasting model for downy mildew. “VitiMeteoPlasmopara” was elaborated by the Swiss Research Station ACW, Changins-Wädenswil and the State Institute of Viticulture and Enology Freiburg in Germany. Since 2003 the system is scientifically tested in Switzerland and Baden-Württemberg and applied in practice. Once or twice a day, the actual results of the forecasting system are visualised on the Internet. “Vitimeteo Plasmopara” is used to forecast downy mildew in Switzerland and in the south of Germany (Baden Württemberg), comprising approx. 42,000?ha of grapevine (15,000?ha CH, 27,000?ha D), and about 100 weather stations located in the area. The forecasting system is widely used by both advisory service and growers. It has proven a very useful tool to estimate the epidemiological situation and it allows the definition of spray intervals in relation with the epidemics. The open structure of the database allows the use and the integration of weather data into any other expert software moduls to forecast the development of other fungal diseases, pests or completely other models, for example irrigation models. “VitiMeteo Growth ”, a vine growth model, “VitiMeteo Insects”, a model for pests and “VitiMeteo DataGraph”, a software to analyze and present weather data, are already developed. The expert software moduls are summarized under designation “VitiMeteo Suite”.     

Investigations on the role of cuticular wax in resistance to powdery mildew in grapevine

Cuticular wax on the plant epidermis inhibits or enhances prepenetration events of powdery mildew (Erysiphe necator Schwein). We examined the role of cuticular leaf and berry waxes as a resistance mechanism in four grapevine genotypes (Italia?×?Mercan-174, Gürcü, Isabella, Özer Karas?) resistant to powdery mildew after natural infection and inoculation. To understand cuticular wax properties, we determined the amount of wax and antifungal effects of thin layer chromatography (TLC) fractions from cuticular leaf and berry waxes, then assessed the chemical composition of fractions with different antifungal activities using gas chromatography/mass spectrometry (GC/MS). Susceptible genotypes Cabernet Sauvignon and Italia were used for comparison. Resistant and sensitive genotypes did not differ significantly in the total amount of wax on leaves and berries; however, 27 fatty acids, 26 alkanes, 6 terpenes, 4 indole derivatives and 4 ketones, and 3 amides, 3 phenols and 3 steroids were detected in fractions with high antifungal activity (≥75% inhibition of germination) in leaf and/or berry cuticular waxes of resistant genotypes only. These compounds may be evaluated as markers for powdery mildew resistance during genotype selection in a grapevine breeding program.     

Sensitivity of Rhizoctonia solani causing rice sheath blight to fluxapyroxad in China

Fluxapyroxad,3-(difluoromethyl)-1-methyl-N-(3’,4’,5’-trifluorobiphenyl-2-yl) pyrazole-4-carboxamide (C₁₈H₁₂F₅N₃O, Fig. 1), is a SDHI fungicide, which is a new active ingredient that interferes with succinate ubiquinone reductase in the electron transport chain of fungi. Between 2008 and 2010, a total of 128 isolates of Rhizoctonia solani from Anhui Province of China were characterized for the baseline sensitivity to fluxapyroxad. The isolates collected between 2008 and 2010 all showed similar sensitivity to fluxapyroxad. Baseline sensitivity was distributed as unimodal curves with an average EC₅₀ value of 0.054?±?0.014 μg ml^?1. However, EC₅₀ values of boscalid for inhibition of mycelial growth of R. solani isolates ranged from 1.89 to 2.68 μg/ml and the average (±SE) EC₅₀ value was 2.212?±?0.228 μg/ml, indicating that the R. solani isolates were less sensitive to boscalid than that of fluxapyroxad. Fluxapyroxad exhibited excellent protective and curative activity against rice sheath blight and provided 82.6–94.2 % protective or curative control efficacy. In field trials, control efficacy of fluxapyroxad at 100 g a.i/ha 15 days and 30 day after second application was 83.4–88.0 %, suggesting excellent activity against sheath blight. Control efficacy of boscalid at a dosage of 600 g a.i/ha 15 days and 30 day after second application was about 51.7–57.0 %. There was a significant difference in the efficacy between fluxapyroxad and boscalid or jinggangmycin. These results suggested that fluxapyroxad is a good alternative fungicide to jinggangmycin for the control of rice sheath blight.     

Characterization of European Plasmopara viticola isolates with reduced sensitivity to cymoxanil

Cymoxanil has been used for over 30 years to control grape downy mildew (Plasmopara viticola) in European vineyards, prevalently in mixture with other fungicides active on this disease. In the 1990’s cases of P. viticola resistant to cymoxanil were detected using a leaf disc assay. In this study, we establish that the presence of only 1 % of resistant isolates in a P. viticola population will allow the detection of cymoxanil resistance in the leaf disc assay. A poor correlation (R?=?0.194) was observed between the leaf disc assay and a whole- plant test for 38 P. viticola field populations collected in 2004. Over 60 % of these populations were characterized as fully sensitive in a whole-plant assay compared to 10 % in the leaf disc assay. Five P. viticola field isolates resistant to cymoxanil reverted to full sensitivity after six to nine transfers to untreated vines, indicating that cymoxanil resistance in P. viticola is unstable. Two European P. viticola populations sensitive to cymoxanil became resistant when transferred 12–14 times on vines treated with cymoxanil. In contrast, two populations originating from the USA and three monozoospore isolates from France retained full sensitivity to the fungicide after 13 cycles on cymoxanil-treated plants. Whole-plant experiments were conducted in the laboratory to compare the efficiency of spray programs to delay the development of cymoxanil resistance. Whereas the continuous use of cymoxanil alone quickly selected for resistance, the mixture of cymoxanil and folpet applied either continuously or in strict or block alternation effectively prevented the development of resistance over 10 generations of the fungus. These results demonstrate that resistance to cymoxanil in P. viticola can be managed with appropriate spray programs.     

Method for rapid detection of the PvCesA3 gene allele conferring resistance to mandipropamid, a carboxylic acid amide fungicide, in Plasmopara viticola populations

BACKGROUND: The occurrence of carboxylic acid amide (CAA)‐fungicide‐resistant Plasmopara viticola populations is becoming a serious problem in the control of grapevine downy mildew worldwide. RESULTS: The authors have developed a method, which utilises PCR‐RFLP, for the rapid detection of resistance to the CAA fungicide mandipropamid in P. viticola populations. With this method, a glycine‐to‐serine substitution at codon 1105 of the cellulose synthase gene PvCesA3 of CAA‐fungicide‐resistant P. viticola was easily detected, although no resistant P. viticola was detected from 398 isolates in Japan. CONCLUSION: It is proposed that the PCR‐RFLP method is a reliable tool for the rapid detection of CAA‐fungicide‐resistant P. viticola isolates. Only 4 h was required from the sampling of symptoms to the phenotyping of fungicide resistance. Copyright © 2011 Society of Chemical Industry     

New tools for studying epidemiology and resistance of grape powdery mildew to DMI fungicides

Using a Random Amplified Polymorphic DNA (RAPD) assay, we investigated the genetic polymorphism existing among 62 European isolates of the grape powdery mildew fungus (Uncinula necator [Schw.] Burr.). Isolates overwintering as mycelium in buds were genetically distinct from isolates overwintering as ascospores, suggesting the existence of two genetically isolated powdery mildew populations, and consequently of two independent sources of inoculum in the vineyard. Isolates resistant to fungicides inhibiting sterol 14α-demethylation (DMIs) were found in both populations, suggesting that resistance to DMIs may arise independently in the two powdery mildew populations. A PCR assay targeting the gene encoding U. necator 14α-demethylase has been developed which will permit an early, specific detection of U. necator infections, and may be useful for spraying programmes. ©1997 SCI     

葡萄叶提取物对葡萄霜霉病的防治作用及有效成分分析

为探究葡萄叶提取物对葡萄霜霉病的防治作用,测定了葡萄叶提取物及其有效物质对葡萄生单轴霉Plasmopara viticola孢子囊和游动孢子的抑制作用以及对葡萄霜霉病的防治效果,观察了其对葡萄生单轴霉在叶片中扩展、产生孢子囊能力的影响,并对葡萄叶提取物组成成分进行了分析。结果表明,葡萄叶提取物对葡萄生单轴霉孢子囊的形成和萌发均有明显的抑制作用。当葡萄叶提取物浓度为10 mg/mL时,其对孢子囊形成的抑制率为82.4%,葡萄生单轴霉孢子囊和游动孢子的萌发率仅为7.6%和1.1%,均显著低于无菌水处理。荧光显微观察发现,葡萄叶提取物可以抑制葡萄生单轴霉在叶片内的扩展。当葡萄叶提取物浓度为10 mg/mL和50 mg/mL时,对葡萄霜霉病的室内防治效果分别为80.1%和100.0%;且浓度为10 mg/mL的葡萄叶提取物对葡萄霜霉病的田间预防效果为67.8%,与烯酰吗啉处理无显著差异。液质联用技术检测显示,葡萄叶提取物中含有白藜芦醇和紫檀芪,其对葡萄生单轴霉均有显著的抑制作用,且紫檀芪的抑制效果强于白藜芦醇。     

Detection and analysis of genetic variations in GOB locus of Plasmopara viticola by DNA sequence analysis

The population genetic structure of Plasmopara viticola in Japan was analyzed using grapevine downy mildew specimens collected from two islands, Honshu and Hokkaido. By simple sequence repeat analysis with the GOB microsatellite marker and DNA sequencing, an accurate copy number of the (CT) _n (CTAT) _n repeat was determined. Consequently, we found a large number of genetic variations in (CT) _n and (CTAT) _n repeats. Also, a single nucleotide polymorphism in the (CTAT) _n repeat of the GOB locus was detected. These genetic variations may serve as a valuable tool to understand the population structure of P. viticola.     

Monitoring of QoI fungicide resistance in Plasmopara viticola populations in Japan

BACKGROUND: The increasing occurrence of QoI fungicide resistance in Plasmopara viticola (Berk. & MA Curtis) Berl. & DeToni populations is becoming a serious problem in the control of grapevine downy mildew. In Japan, the existence of QoI‐fungicide‐resistant P. viticola was reported in 2009. RESULTS: The QoI fungicide resistance in P. viticola samples collected from vineyards in Japan in 2008 and 2009 was monitored. Resistant P. viticola were detected in the regions where QoI fungicides have been introduced in accordance with the pest management programme, whereas in Hokkaido vineyards, where QoI fungicides have not yet been introduced, QoI‐fungicide‐resistant P. viticola were not found. CONCLUSION: Japan comprises thousands of islands and is physically isolated from other countries by the sea. Monitoring the emergence, incidence and distribution of QoI fungicide resistance in P. viticola populations in Japan is necessary to improve pest management strategies for downy mildew disease in Japanese vineyards. Copyright © 2010 Society of Chemical Industry     

The reliability of leaf bioassays for predicting disease resistance on fruit: a case study on grapevine resistance to downy and powdery mildew

This study was designed to assess the reliability of grapevine leaf bioassays for predicting disease resistance on fruit in the field. The efficacy of various grapevine quantitative trait loci (QTLs) for conferring resistance to downy and powdery mildew was evaluated in bioassays and in a 2‐year field experiment for downy mildew. The resistance genes studied were inherited from Muscadinia rotundifolia (Rpv1 and Run1) and from American Vitis species through cv. Regent (QTLRgP and QTLRgD). In bioassays, genotypes carrying Run1 blocked powdery mildew development at early stages. Genotypes combining Run1 with QTLRgP displayed no greater level of resistance. For downy mildew, genotypes carrying Rpv1 and/or QTLRgD were more resistant than the susceptible cv. Merlot, and showed a high level of leaf resistance in the field (<10% severity). Disease levels on bunches were much higher than those on leaves, with a high variability between Rpv1 genotypes (1–48%). A Bayesian decision theory framework predicted that an OIV‐452 threshold of 5 in leaf bioassays allowed accurate selection of grapevine genotypes (P = 0·83) with satisfactory disease severity on bunches. Therefore, this study validates that the use of early bioassays on leaves, as currently performed by grapevine breeders, ensures a satisfactory level of resistance to downy mildew of bunches in the field.     

Thiophanate-methyl sensitivity and fitness in Lasiodiplodia theobromae populations from papaya in Brazil

Stem-end rot, caused by Lasiodiplodia theobromae, is an important postharvest disease of papaya in Brazil. The use of fungicides is one of the main disease management measures. However, there are no data available on the sensitivity of L. theobromae to thiophanate methyl (methyl benzimidazole carbamate), the most common fungicide used in papaya orchards in northeastern Brazil. Thus, the effective concentration that results in 50 % of mycelial growth inhibition (EC₅₀) of 109 isolates, representing five populations of the pathogen was estimated in vitro. Seven components of fitness were measured for the 10 isolates with lower and high values of EC₅₀. Of the 109 isolates, 20.2 % were resistant to the fungicide with EC₅₀ values greater than 300 μg ml^?1, whereas the remaining 79.8 % were sensitive with an average EC₅₀ of 1.87 μg ml^?1. The EC₅₀ values for the resistant isolates were significantly (P?≤?0.05) higher than those for the sensitive isolates. When the fitness components were evaluated, only in relation to the spore production was significant difference among sensitive and resistant isolates, and resistant isolates showed sporulation capacity significantly lower than the S isolates, indicating a fitness cost.     

不同栽培模式下葡萄霜霉病菌遗传结构的时间动态分析

为明确不同栽培模式下葡萄霜霉病菌Plasmopara viticola的遗传结构、遗传多样性及遗传分化水平,于2014-2015年定期采集露地和避雨2种栽培模式下的葡萄霜霉病菌菌株,利用6对SSR引物对该病菌基因型、遗传多样性及遗传分化进行对比分析。结果表明,露地和避雨栽培模式下葡萄霜霉病菌群体的Nei’s基因多样性指数大于0.14,香农多样性指数大于0.31,2种栽培模式下群体具有丰富的遗传多样性,但避雨栽培模式可显著降低群体等位基因数和等位基因频率。露地栽培模式下该病菌群体的流行模式呈现中等水平无性繁殖,2年初侵染和再侵染对病害流行的贡献率分别约占26.1%和73.9%;避雨栽培模式下葡萄霜霉病菌群体的流行模式则呈现高等水平无性繁殖,初侵染和再侵染对病害流行的贡献率分别约占4.3%和95.7%。卵孢子的形成对于葡萄霜霉病菌种群遗传变异和有效越冬起着关键的作用。2014-2015年露地栽培模式下葡萄霜霉病菌群体的主效流行基因型对病害流行的贡献率分别为44.5%和51.8%;而其在避雨栽培模式下葡萄霜霉病菌群体的贡献率分别可达84.2%和87.1%。同一年份的露地和避雨栽培模式下葡萄霜霉病菌群体的主效基因型种类相同,2个群体间的等位基因频率呈现显著正相关性,且二者之间存在频繁的基因交流,推测避雨栽培模式下葡萄霜霉病的初侵染源自于避雨设施附近的露地栽培病株上再侵染形成的飞散传播孢子囊。