Characterisation and mode of Action of natural plant products against leaf fungal pathogens

The medicinal uses and chemical diversity of bryophytes, spices and herbs are long known, but their potential application in crop protection seems largely unexplored. The objectives of this study were to find crude extracts, new fungicide leads, and resistance incucers to meet the current uprising demands in the discovery of biopesticides Research schemes were carried out to isolate and determine antifungal compounds from 20 bryophytes and from 23 spices and herbs. These were used as crude ethanolic extracts to investigate their bioactivity on globally important 16 different pathogens and 8 important host plants under in vitro and in vivo conditions. The screening of extracts for their antifungal effects exhibited that activity of products varied significantly according to their sources. Extracts of broyphytes, especially Bazzania trilobata, Diplophyllum albicons, Sphagmum quinquefarium, Dicramum demdatum and Hylocomium splendens showed higher antifiungal efficacy against Botrytis cinerea. Alternaria solani, Phytophthora infestans, and Blumeria graminis. Similarly, extracts of Piper nigrum, Carum carvi, Cassia spp., Artemisia dracunculus, Urtica dioica, Foeniculum vulgare and Coriandrum sativum were found as the best antifungal products among spices and herbs. The extracts of B. trilobata and P. nigrum were investigated in more detail. The B. trilobata extract inhibited fungal stages like germination of conidia, germ-tube formation, elongation and mycelial growth. Plants received the product (1% m/v) at different time intervals befor inoculations with pathogens. Application of the extract 2 days befor fungal inoculation showed reduction of disease severity against diverse pathosystems up to 98%. Under such circumstances, the extract gave high efficacy in 9 of the 13 tested pathosystems, though the biotrophic pathosystems were more sensitive than the perthotrophic ones. the extract of P. nigrum showed both protective and curative mode of action, whereas the efficacy of the extract from B. trilobata was reduced by 50% for its curative application against Puccinia recondita on wheat. Bioassays determining systemicity of the B. trilobata extract demonstrated that the product showed a translaminar and at distant effectivity against P. infestans, Podosphaera leucotricha, Uncimula necator and Uromyces appendiculatus. Incubations were processed using LLOs with sporangia and zoospores of P. infestans, conidia and mycelia of A solani, unrediospores of U. appendiculatus and teliospores of Ustilago nuda. Unspecific degeneration of fungal cell walls and entire protoplasms were detected. Germination, basidia formation and sporidia differentation of teliospores of Tilletia caries were delayed on a medum amended with the LLOs. The protective spraying of LLOs significantly impaired the infection structure of pathogens on the leaf pathogens were reduced irrespectively of variation in their taxonomy and host pathogen interactions. Thus, pretreatments of susceptible plants with LLO preparations of mosses provide a new perspective for an integrated disease management of fungal pathogens of different crop plant.