Water Soluble Antifungal Metabolites of Pea (pisum Sativum) Leaves Determine Infection by Erysiphe Pisi

Antifungal activity of water soluble exudates of pea leaves was assayed. Exudates of different nodal leaves were collected by dipping them in sterilized distilled water for different length of time and conidial germination of four non-pathogenic to pea fungi (Alternaria solani, Curvularia lunata, Helminthosporium penniseti and H. echinocloa) and one pea pathogenic to pea fungus (Erysiphe pisi) was observed in the collected exudates. The leaf exudates inhibited differently conidial germination and A. solani and C. lunata were found highly susceptible. Conidial germination on exudate-depleted pea leaves showed better germination of E. pisi than on non-depleted leaves. Bipolar germination was the highest on II and III nodal leaves dipped in distilled water for 18 h while after 24 h it was the highest on I nodal leaves following dipping in distilled water. Similarly, conidial germination of E. pisi was observed on different nodal leaves of pea of different age. It was very clear that young leaves did not support germination at all and on the same nodal leaves conidia germinated after the leaves became older. No germination was observed on less than 20-day-old leaves. Moreover, 30-day-old leaves were found to be highly susceptible as bipolar germination of E. pisi conidia was maximum on such leaves and did not increase with aging.