Studies on the resistance of grapevine to powdery mildew

Studies of 68 cultivars of Vitis vinifera and two interspecific hybrids inoculated with four naturally occurring isolates of Uncinula necator demonstrated variation for pathogenicity between isolates and variation in resistance between cultivars. There was no specific interaction between the cultivars and the isolates. The progenies produced either by selling or hybridization of cultivars of V. vinifera always contained some resistant individuals regardless of the parental resistance ratings. However, the proportion of resistant plants was positively correlated to the level of resistance of the parent(s). The results indicate that 'minor' resistance genes exist in the cultivars of V. vinifera , and that resistance to U. necator could be improved by recurrent selection.     

Effects of sunlight exposure on grapevine powdery mildew development

Natural and artificially induced shade increased grapevine powdery mildew (Erysiphe necator) severity in the vineyard, with foliar disease severity 49 to 75% higher relative to leaves in full sun, depending on the level of natural shading experienced and the individual experiment. Cluster disease severities increased by 20 to 40% relative to those on check vines when ultraviolet (UV) radiation was filtered from sunlight reaching vines in artificial shading experiments. Surface temperatures of leaves in full sunlight averaged 5 to 8°C higher than those in natural shade, and in one experiment, filtering 80% of all wavelengths of solar radiation, including longer wavelengths responsible for heating irradiated tissues, increased disease more than filtering UV alone. In controlled environment experiments, UV-B radiation reduced germination of E. necator conidia and inhibited both colony establishment (hyphal formation and elongation) and maturity (latent period). Inhibitory effects of UV-B radiation were significantly greater at 30°C than at 20 or 25°C. Thus, sunlight appears to inhibit powdery mildew development through at least two mechanisms, i.e., (i) UV radiation's damaging effects on exposed conidia and thalli of the pathogen; and (ii) elevating temperatures of irradiated tissues to a level supraoptimal or inhibitory for pathogen development. Furthermore, these effects are synergistic at temperatures near the upper threshold for disease development.     

A host-pathogen simulation model: powdery mildew of grapevine

An epidemiological model simulating the growth of a single grapevine stock coupled to the dispersal and disease dynamics of the airborne conidia of the powdery mildew pathogen Erysiphe necator was developed. The model input variables were either climatic (temperature, wind speed and direction) or related to the pathogen (location and onset of primary infection). The environmental input variables dictated plant growth and pathogen spread (latent period, infection, lesion growth, conidial spore production and release). Input parameters characterized the crop production system, the growth conditions and the epidemiological characteristics of the pathogen. Output described, at each time step, number, age and pattern of healthy and infected organs, infected and infectious leaf area and aerial density of spores released. Validation of the model was achieved by comparing model output with experimental data for epidemics initiated at different times of host growth. Epidemic behaviour for two contrasting years of crop development and 7 phenological stages at the time of primary infection (PI) was examined. For PI occurring at day 115 a vine with late budbreak (1998) showed 58% of primary leaves diseased at flowering compared with only 19% for a vine with early budbreak (2003). Depending on the phenological stage at PI (1–4 leaves), the proportion of diseased primary leaves decreased from 42% to 6% at flowering. Simulations suggested that differences resulted from the interplay between the timing of the first sporulation event, the phenological stage at the time of initial infection, and the age structure and spatial distribution of the leaf population.     

Effects of humidity on the development of grapevine powdery mildew

ABSTRACT The effects of humidity on powdery mildew development on grape seedlings and the germination of Uncinula necator conidia in vitro were examined. Studies were conducted at an optimum temperature of 25 +/- 2 degrees C. Disease on foliage was markedly affected by humidity levels in the test range of 39 to 98% relative humidity (RH), corresponding to vapor pressure deficits (VPD) of 1,914 to 61 Pa. Incidence and severity increased with increasing humidity to an optimum near 85% RH, and then appeared to plateau or decrease marginally at higher values. Conidial density and chain length also were proportional to humidity, but were influenced less strongly. There was a strong, positive linear relationship between humidity level and frequency of conidium germination with RH treatments of 相似文献   

紫萁白粉病发生规律及其防治

紫萁白粉病是近年发生在鄂西南地区的一种新病害。调查表明 ,该病在该地区每年在5月上、中旬和7月中、下旬有两次发病高峰。其发生程度与光照、田间管理水平关系密切 ,不同海拔高度上的发病高峰期有一定的差异。提高管理水平 ,清除病残体 ,同时结合喷施低毒药剂是控制该病的有效措施。     

Role of stilbenes in the resistance of grapevine to powdery mildew

Stilbene phytoalexins are identified as defence response in pathogen–grapevine interactions, but little information is available on the role of stilbenes on Erysiphe necator, causal agent of grapevine powdery mildew. Analysis of stilbenes in artificially infected leaf discs from susceptible to highly resistant cultivars was performed and compared to the development of the pathogen. Results indicate that stilbene synthesis is confined in infected cells, penetrated by an appressorium–peg. Stilbene amounts expressed by infection site allow discriminating susceptible and resistant cultivars. Highest viniferins concentrations on resistant cultivars are in correspondence with the observed inhibition of the pathogen growth. The analysis of stilbenes at the infection site and viniferins accumulation in grapevine defence reaction is discussed.     

A standardised method for the quantitative analysis of resistance to grapevine powdery mildew

Powdery mildew caused by Erysiphe necator is one of the most important diseases affecting grapevine (Vitis vinifera, L.). Control of this pathogen is based on the use of fungicides, which cause environmental damage and increase production costs. A cost-effective and environmentally friendly alternative to control the disease relies on using resistant varieties. While most V. vinifera cultivars are susceptible to powdery mildew, several species belonging to the Vitaceae have been described as resistant. Several loci for resistance to grapevine powdery mildew have been identified through genetic analysis of segregating populations derived from different resistance sources. Identifying quantitative trait loci (QTL) with minor effects on the resistance may prove valuable in a strategy of pyramiding, which aims at increasing the durability of the resistance. However, current methods for evaluation of resistance either do not take into account quantitative variations, or, if they do, are not adapted to large sample sets. Here we develop a method for the analysis of quantitative resistance to grapevine powdery mildew in large populations. We devised a semi-quantitative resistance scale and confirmed the usefulness of a cell counter to quantify sporulation. We compared three inoculation methods and identified dry inoculation using a settling tower as the one giving the best infection. Finally, we confirmed the value of the method by applying it to a set of plants segregating for resistance to E. necator. Using the method described here for the quantitative analysis of the resistance to powdery mildew will prove valuable for breeding for durable resistance.     

Susceptibility of grapevine buds to infection by powdery mildew Erysiphe necator

Bud colonization and perennation of powdery mildew ( Erysiphe necator ) was studied by inoculating shoots of grapevine ( Vitis vinifera cv. Carignane) at different phenological stages. Disease incidence and severity assessments indicated that buds were most susceptible at the three- to six-unfolded-leaf stage. Incidence of powdery mildew colonies on the surface of buds collected from these shoots 7 weeks postinoculation was highest at these stages (68 and 62%, respectively), which indicates that colonization of the bud interior via the infected bud surface is likely to occur within this period. Histological analyses of buds revealed hyphae with haustoria, conidiophores and conidia on all parts of the bud interior except for the meristems. In particular, trichomes were frequently parasitized by haustoria. In total, 13·2% of all buds analysed, and 32·3% of all buds originating from shoots inoculated at the three-unfolded-leaf stage, were infected by E. necator . In the spring of the following year, buds from inoculated shoots yielded 18 flag shoots (1·6% of all emerging shoots). These primary infections caused an epidemic 28 days after the appearance of the first flag shoot. A linear regression analysis on the frequency of infections of the bud exterior, bud interior and flag shoots revealed that incidence of external bud infection in the first season is strongly correlated with flag shoot incidence in the following season ( R ² = 0·94). Hence predictions of flag shoot incidence may be reliably based on the incidence of infection on the outer bud scales in the preceding season.     

葡萄白粉病抗性鉴定方法优化及品种抗性评价

本研究通过对叶盘保湿方法的改进,不同菌源接种后发病严重度的分析,抗、感病对照品种的确定,建立了一种更为便捷、可靠、稳定的葡萄白粉病室内抗性鉴定方法:取葡萄藤自上而下第2～4片幼嫩叶片,打取直径15 mm的叶盘置于1.5％水琼脂平板进行保湿,采集田间菌源直接制备孢子浓度为2×105个/mL的孢子悬浮液接种,选定抗、感病葡...     

Contribution of molecular studies to botanical epidemiology and disease modelling: grapevine downy mildew as a case-study

After being accidentally introduced from the USA at the end of the 19^th century, downy mildew caused by Plasmopara viticola (Berk. et Curt.) Berlese et De Toni became one of the most damaging diseases affecting Vitis vinifera in Europe. Downy mildew causes both direct and indirect losses and can lead to severe reduction of yield. Our understanding of the life cycle and epidemiology of P. viticola has been recently altered by molecular studies that revealed that the overwintering inoculum (i.e., the oospores) does more than initiate disease, as was previously thought. A mechanistic model was developed for predicting the entire chain of processes leading to primary infections, and this primary infection model was linked to other models of secondary infection cycles. The model for primary infections defines the length of the primary inoculum season and a seasonal oospore dose consisting of several cohorts of oospores that progressively mature. The model was evaluated by means of Bayesian analysis in both Italy and eastern Canada, and showed high sensitivity, specificity, and accuracy both for potted plants and vineyards. Fungicide applications are necessary to control downy mildew because preventive agronomic practices are not very effective, including host resistance. The use of warning systems based on weather-driven models leads to a reduction in the use and cost of chemicals and a reduction in their environmental impact.     

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.     

防治西葫芦和黄瓜白粉病的生物制剂的筛选

瓜类白粉病是蔬菜上的重要病害之一,为加大对该病害的生物防治力度,本研究采用课题组研发的1×109cfu/g玫瑰黄链霉菌水剂和10亿芽胞/g枯草芽胞杆菌悬浮剂以及市场上常用的枯草芽胞杆菌、哈茨木霉菌、寡雄腐霉、武夷菌素、多抗霉素等多种生物制剂进行田间药效试验,比较几种生物制剂的防治效果。结果表明,供试生物制剂对西葫芦白粉病的防效为57.65%~84.98%,其中3%多抗霉素水剂600倍液的防效最好,为84.98%,且具有明显的促生长作用,增产率达12.65%。其次为1 000亿芽胞/g枯草芽胞杆菌可湿性粉剂(武汉天惠)400倍液、2%武夷菌素水剂600倍液和3×108 cfu/g哈茨木霉菌可湿性粉剂300倍液,可作为西葫芦白粉病防治的选用药剂。1×109 cfu/g玫瑰黄链霉菌水剂对西葫芦和黄瓜白粉病均具有较好的防效,分别为78.68%和73.59%,具有开发和应用的市场价值。     

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.     

Biological control of cucumber powdery mildew by Tilletiopsis minor

Samenvatting Onder optimale omstandigheden konT. minor de ontwikkeling van komkommermeeldauw (Sphaerotheca fuliginea) tegengaan.Spuiten met 2×10⁷ sporen ml^–17 dagen na inoculatie met komkommermeeldauw gaf een reductie van meeldauwontwikkeling van ongeveer 90%. Wanneer een tweede bespuiting met dezelfde concentratie sporen 3 dagen na de eerste werd toegepast bleven de planten vrij van meeldauw tot ze werden opgeruimd 3 weken later.Bij een R.L. lager dan 70% en een temperatuur boven 30 °C had geen van de behandelingen succes. T. minor bleek ongevoelig voor dimethirimol (Milcurb) bij een concentratie van 125 g ml^–1, terwijl er gemakkelijk een mutant kon worden verkregen, die resistent was tegen 100 g fenarimol ml^–1, bij gelijk blijvende groeikracht en pathogeniteit ten opzichte van komkommermeeldauw, waardoorT. minor ingepast kan worden in een schema voor geïntegreerde bestrijding.     

杂交酸模白粉病的发生与防治

经对鲁梅克斯K- 1杂交酸模白粉病发生调查、病原鉴定和防治研究结果表明 ,该病由蓼白粉菌 (Erysiphe polygoni DC .)引起 ,在分枝期、叶簇期、拔节期、开花期、刈割期均可发病 ,与田间杂草巴天酸模白粉菌相互侵染。通过清除杂草、枯枝落叶 ,合理增施肥料 ,适期播种 ,合理刈割等农业防治措施 ,结合高脂膜200倍液与50%多菌灵、50%甲基托布津600～800倍液复配 ,每隔 10d喷雾1次 ,2～3次防效达 95%以上。     

Biological control mechanisms of D-pinitol against powdery mildew in cucumber

D-pinitol is an effective agent for controlling powdery mildew (Podosphaera xanthii) in cucumber. In this study, we determined the mechanisms of D-pinitol in controlling powdery mildew in cucumber plants. We compared P. xanthii development on cucumber leaf surface treated with D-pinitol or water (2 mg ml⁻¹) at different time points after inoculation. The germinating conidia, hyphae, and conidiophores of the pathogen were severely damaged by D-pinitol at any time of application tested. The highest level of suppression of fungal development was obtained at 3 days after inoculation. The contents of chlorophyll, total phenolics, flavonoid, and gallic acid and its derivatives (GAD); the activities of phenylalanine ammonialyase (PAL), polyphenoloxidase (PPO), peroxidase (POX), and superoxide dismutase (SOD); and the expression of the genes encoding for PR-1, peroxidase (POX), lipoxygenase (LOX1), chitinase (Chit1) were higher in the cucumber leaves treated with D-pinitol and inoculated than in the leaves either treated with D-pinitol or inoculated with the pathogen. These results suggest that D-pinitol triggers several plant defense responses in cucumber leading to pathogen suppression and resistance to powdery mildew.     

A mechanistic model simulating ascosporic infections by Erysiphe necator,the powdery mildew fungus of grapevine

A new dynamic model for Erysiphe necator ascosporic infections on grapevine was developed. Between budbreak of vines and the time when the pool of ascospores is depleted, the model uses weather data for calculating, at daily intervals: curve of ascospore maturation; ascospore discharge events and relative proportion of the discharged ascospores; infection periods and their relative infection severity; and progress of latency period and time when secondary infections should begin. The model was validated over a 4‐year period (2005–2008) in 26 vineyards in Italy by comparing model predictions with actual observations of the first seasonal symptoms of powdery mildew. The model showed high sensitivity, specificity and accuracy. Proportions of true and false positive predictions were TPP = 0·94 and FPP = 0·26, respectively. Because a proportion of predicted infection periods did not result in actual disease onset, confidence was higher for prediction of non‐infections than for prediction of infections. Most of the false positive predictions occurred in the earlier growth stages of the host, when the surface area of susceptible tissue may be very small so that the probability that ejected ascospores land on susceptible tissue is low. An equation was then developed to describe the probability that a predicted infection period results in disease onset as a function of the growth stage of vines at the time of prediction. The new model should improve early season powdery mildew management by helping vineyard managers schedule fungicide sprays or schedule the scouting of the vineyard for detection of first disease signs.     

40%百可得可湿性粉剂防治黄瓜白粉病药效试验

合浦县有种植黄瓜的习惯 ,农业产业结构调整后 ,种植面积逐年增大。黄瓜白粉病是瓜类的重要病害之一 ,在温湿度适宜的条件下 ,病菌繁殖迅速 ,严重影响黄瓜生产。为筛选一种防治该病的高效药剂 ,我们于 2 0 0 2年 3～ 4月在本县廉州镇大江村进行了40 %百可得 (双胍三辛烷基苯黄酸盐 )可湿性粉剂防治黄瓜白粉病药效试验。现将结果报告如下。1　试验材料与方法1 .1　供试药剂　　 40 %百可得可湿性粉剂 (日本大日本油墨化学株式会社提供 )、 75 %百菌清 (先正达投资有限公司上海分公司生产、市售 )、 5 0 %速克灵 (日本住友化学工业株式社生产 …