Selective response of Ricinus communis seedlings to soil borne Rhizoctonia infection

Seedlings of Ricinus communis tolerated soil-borne Rhizoctonia infection in strain dependent manner. There was no connection revealed between pathogenicity of strains and their origin or taxonomic position, however, the castor plant proved to be susceptible to most strains highly pathogenic to other host plants as well. Rhizoctonia zeae (teleomorph: Waitea circinata), a species new for European flora, was less aggressive to R. communis as the most potent R. solani strains. The effect of Rhizoctonia infection on mass accumulation of hypocotyls was more prominent than that on cotyledons. The protein content and glutathione S-transferase (GST) activity increased in parallel with evolution of disease syndrome. Metalaxyl, an acetanilide type systemic anti-oomycete fungicide induced locally the GST activity in R. communis cotyledons with 24 hours lag phase, and this induction was altered in the seedlings grown in Rhizoctonia infested soil by strain dependent manner. It might be concluded, that the stress response related detoxication mechanisms of plants in tolerant host/parasite pairs take effect at higher level than in highly susceptible relationships

Effect of acibenzolar-S-methyl, strobilurins and other fungicidetreatments on phylloplane fungi of crops

Strobilurins, broad-spectrum fungicides used to control various diseases, may also inhibit the growth of nontarget fungi in the natural environment. Acibenzolar-S-methyl (ASM) is a plant activator; however, the effect of ASM on the growth of microflora on the leaf surface is not clear yet. ASM, strobilurins and other fungicides were sprayed on Japanese pear and cucumber plants in the field. Variations in the morphological characteristics and rDNA-ITS nucleotide sequence of isolated phylloplane fungi were evaluated. The isolation frequency of Alternaria spp., Aureobasidium spp., Cladosporium spp. and Myrothecium spp. on Japanese pear leaves treated with kresoxim-methyl and polycarbamate was lower than on nontreated pear leaves. Moreover, the frequency of Alternaria spp., Cladosporium spp., Epicoccum spp. and Fusarium spp. on leaves of two cucumber cultivars treated with azoxystrobin, triflumizole and mancozeb was lower than the frequency of fungal isolation on nontreated cucumber leaves. The effect of ASM on fungal isolation frequency was not significantly different from that on nontreated pear or cucumber leaves. The fungal genera observed and isolation frequency on the leaves treated with polycarbamate, azoxystrobin, triflumizole and mancozeb tended to be reduced compared to the no-spray treatment

Antisporulant activity of leaf extracts of Indian plants against Sclerospora graminicola causing downy mildew disease of pearl millet

Methanolic extracts of forty plant species commonly growing across India were collected and have been screened for antisporulant activity against Sclerospora graminicola (Sacc.) Schroet., the causative agent of pearl millet downy mildew. The collection represented 38 genera of 30 families. The methanolic extracts of nine species did not show any effect, whereas the activity of the extracts of Clematis gouriana, Evolvulus alsinoides, Mimusops elengi, Allium sativum and Piper nigrum were commensurable to that of the marketed botanical fungicides. The extracts of 11 species (Agave americana, Artemisia pallens, Citrus sinensis, Dalbergia latifolia, Helianthus annus, Murraya koenigii, Ocimum basilicum, Parthenium hysterophorus, Tagetes erecta, Thuja occidentalis and Zingiber offinale) exhibited remarkable antisporulant effect even after 10-fold dilution of the crude extracts while in the case of remaining 15 plants the crude extracts loosed activity after 10-fold dilution. The antisporulant activity of commercialised Azadirachta preparation (Nutri-Neem) was more pronounced than that of Reynutria based one (Milsana) and Sabadilla (veratrin), however, these botanical preparations held off the extracts of C. gouriana and E. alsinoides and synthetic fungicides