Ethephon elicits protection against Erysiphe necator in grapevine.

The grapevine (Vitis vinifera) is susceptible to many pathogens such as Botrytis cinerea, Plasmopara viticola, Erysiphe necator, and Eutypa lata. Phytochemicals are used extensively in vineyards to reduce pathogen infections, but the appearance of pesticide-resistant pathogen strains and the need for environmental protection require the use of alternative strategies. The phytohormone ethylene is assumed to play a role in the development of disease resistance. In the present study, we have treated grapevine foliar cuttings (Cabernet Sauvignon) with ethylene-releasing ethephon. This resulted in an increase in the number of pathogenesis-related protein (CHIT4c, PIN, PGIP, and GLU) gene copies and in an enhancement of phytoalexin biosynthesis by inducing the PAL and STS genes that correlated with the accumulation of stilbenes (antimicrobial compounds). Moreover, ethephon treatment triggered the protection of grapevine detached leaves and grapevine foliar cuttings against Erysiphe necator, the causal agent of powdery mildew (64% and 70%, respectively). These studies emphasize the major role of ethylene in grapevine defense.

Effect of methyl jasmonate in combination with carbohydrates on gene expression of PR proteins, stilbene and anthocyanin accumulation in grapevine cell cultures.

Grapevine (Vitis vinifera L.) is subject to a number of diseases which affect yield and wine quality. After veraison, berries become strongly susceptible to pathogens due to different physiological changes including the accumulation of glucose and fructose, on the one hand, and to the decrease of anti-microbial compounds called stilbenes, on the other. To obtain berry protection, pesticides are excessively used leading to important cost to the grower and to undesirable environmental impact of the residues, especially in grape, soil and water. As a consequence, alternative strategies have to be developed. Exogenously applied biotic elicitors induce defense responses. We studied the effects of methyl jasmonate in combination with sucrose on defense-related gene expression, stilbene and anthocyanin production in grapevine cell suspensions. The methyl jasmonate/sucrose treatment was effective in stimulating phenylalanine ammonia lyase, chalcone synthase, stilbene synthase, UDP-glucose: flavonoid-O-glucosyltransferase, proteinase inhibitor and chitinase gene expression, and triggered accumulation of both piceids and anthocyanins in cells, and trans-resveratrol and piceids in the extracellular medium. Methyl jasmonate treatment might be an efficient natural strategy to protect grapevine berries in vineyard.

Methyl jasmonate induces defense responses in grapevine and triggers protection against Erysiphe necator.

Grapevine is subject to a number of diseases that affect yield and wine quality. To limit the excessive use of phytochemicals in the vineyard, alternative strategies have to be developed. Plant treatment with signaling molecules like elicitors stimulates their natural defense mechanisms. To improve grapevine tolerance against fungal pathogens, Vitis vinifera plants were treated with a natural exogenous elicitor, methyl jasmonate (MeJA). MeJA-treated leaves (Cabernet Sauvignon foliar cuttings) reacted by increasing transcript levels coding pathogenesis-related proteins (acidic class IV chitinase, serine protease inhibitor, polygalacturonase-inhibiting protein, and beta-1,3-glucanase) and coding enzymes involved in phytoalexin biosynthesis (one phenylalanine ammonia lyase and one stilbene synthase). This was correlated with the accumulation of stilbenes (antimicrobial compounds). The eliciting activity of MeJA was confirmed by enhanced tolerance of grapevine foliar cuttings and vineyard against powdery mildew (75% and 73%, respectively). On the basis of these original results, MeJA can therefore act as an efficient elicitor in an alternative strategy of grapevine protection.

Occurrence and distribution of Microdochium nivale and Fusarium species isolated from barley, durum and soft wheat grains in France from 2000 to 2002.

Fusarium Head Blight of small grain cereal is a disease of growing concern in Europe. Along with Microdochium nivale, several species of Fusarium may be associated with the disease, including species that are potentially toxigenic. This paper describes the results of a large scale survey of the variety and frequency of different Fusarium species and M. nivale in France. A total of 749 soft wheat, durum wheat and barley samples were collected and analyzed from 2000 to 2002. The most frequent species isolated were F.graminearum, F. avenaceum and F. poae. The frequency of F. poae seems to have increased while M.nivale and F. culmorum appear less frequent than previously described in France. Other Fusarium species detected in decreasing prevalence were F. tricinctum, F. equiseti, F. acuminatum, F. sambucinum, F.sporotrichioides, F. moniliforme, F. heterosporum, F. subglutinans and F. oxysporum. All the most frequent pathogenic species and also the less pathogenic ones were frequently associated with individual fields. The implications of these associations for the protection of cereals crops and for contamination by mycotoxins are discussed.