Plasmopara viticola compounds

Novel cyclohexenones, acremines A-F (109-114), were isolated from a mycoparasitic Acremonium sp. from the oomycete pathogen Plasmopara viticola on Vitis vinifera cv. Regina blanca. Compounds 109-112 inhibited germination of the pathogen, and the most activity was shown by acremine C (111). This work may lead to a mechanism for the mycocidal activity of mycoparasitic fungi. 

Compounds 97 and 5,7-dihalo-l, 2,4-triazolo[l, 5-a]pyrimidines act as agrochemical fungicides and cause protection against Plasmopara viticola (87GEP3533050 94MIP1). Compounds 121 are superior fungicides (83 GEP3130633). 

Aliette (aluminum tris-0 ethylphosphonate) has been reported to enhance defense reactions and phytoalexin accumulation in grapes and tomatoes in response to infection by Plasmopara viticola and Phytophthora spp., respectively, and to trigger phenolic accumulation and hypersensitive cell death in tomatoes, peppers, and beans in response to infection while possessing little direct fungitoxicity (116,117). However, recent data cast doubt on the earlier reports of the low activity of Aliette as an inhibitor of Phytophthora sporulation mi vitro (118), and have attributed the protective properties of the compound to phosphorous acid which is formed in plant tissues or in certain buffer solutions of Aliette (119,120). Toxicity of phosphorous acid to Oomycetes is reversible by phosphate ion, and this may explain Aliette s lack of fungitoxicity in certain growth media. 

Although this compound has been intensively used for nearly 30 years, resistance development of fungal pathogens to fosetyl-aluminium is very limited. Some studies, though, indicate a significant decrease in sensitivity of Plasmopara viticola to fosetyl-aluminium with resistance factors between 5 and 24 [29]. Moreover, decreased sensitivity against lettuce downy mildew, Bremia lactucae, has been observed [30]. However, resistance development to fosetyl-aluminium seems to have only a limited impact on the overall product performance. 

Stilbenoids are highly inducible in leaves using a number of chemicals, UV-C treatment, and infectious agents [25]. To date, the majority of stilbenoids from leaves have been identified from stressed leaves. In some of the preliminary studies by Langcake and Pryce using leaves infected by Botrytis cinerea, the main stilbenoids detected were -resveratrol, -a-viniferin (Fig. 73.2), and a-viniferin [26]. The res-veratrol dehydrodimer, 5-viniferin, and piceids were detected in leaves induced by UV irradiation [27,28]. More recently, Mattivi et al. isolated and identified 14 stilbenoids from the leaves of a hybrid V. vinifera infected with Plasmopara viticola [23]. These compounds included two new dimers and two new to V. vinifera -co-viniferin. 

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