Effect of Sulphuric Acid Amendments on Soil-Borne Pathogenic Fungi Associated with Root Rot of Two Dry Bean Cultivars

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Damping-off of common bean (Phaseolus vulgaris L.) is considered to be of paramount importance causing yield losses that exceed 50% and has been reported in many countries worldwide. In this study, damping off and root rot fungi and others associated with common bean root rot in Egypt were isolated and were identified as Rhizoctonia solani Kuhn, Macrophomina phaseolina (Tassi) Goid and Sclerotium rolfsii Sacc. Non-traditional control measures with chemicals as sulphuric acid were tried in literature. It has been shown in the present study that application of high rates of H2SO4 to bean plants have had indirect effect on disease(s) progress. Plants, 45 days after the treatment, were evaluated pathologically. Two dry bean Nebraska and Nahda cultivars reacted differently to the isolated pathogenic fungi. Pre and Post emergence damping off caused by mixture of the isolated fungi on Nahda cv. treated with sulphuric acid compared to Nebraska cultivar showed greater susceptibility to the disease. The results showed significant differences in shoot /root ratio(s) either on fresh or dry weights bases as influenced by H2SO4 strength, i.e., the concentration. Different intensity values of nodulation in both varieties were found to follow the recorded difference in damping off susceptibility. The same conclusion may be applied to the inherent difference in varietal susceptibility to infection by nodule bacteria. Root rot severity was significant and also determination of microbial density, 45 days after application. The concentration (0.2N) of sulphuric acid resulted in the decrease of each of N, P and K in most cases. Further studies are needed to include the possible effect of induced resistance in common bean induced by sulphuric acid. Field trials may be advised.

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