PATHOLOGICAL STUDIES ON ROOT-ROT DISEASE OF PEANUT (ARACHIS HYPOGAEA L.)IN EGYPT

Abstract

The present work was conducted mainly to isolate the pathogenic fungi causing root-rot of peanut (Arachis hypogaea L.) plants and testing their pathogenicity at different levels of soil infestation. Also, the effect of some fungicides, commercial bioagents and natural plant extracts on root-rot incidence and some plant growth characters under both greenhouse and field conditions were also investigated. The obtained results could be summarized as follow: I. Rhizoctonia so/ani, Sclerotium ro(fi•ii, Fusarium so/ani, Macrophomina phaseolina, F. oxysporum, Bol1yodiplodia theobromae, F. moniliforme, Aspergillus sp., Penicillium sp. and Rhizopus sp. were isolated 'at different frequencies from infected roots of peanut plants grown at different locations. R. so/ani showed the highest frequency at all locations followed by S. rolfsii, F. so/ani and M. phaseolina. 2. Sclerotium ro/fsii and R. so/ani were the most pathogenic and caused the highest percentage, of pre­ emergence damping-off followed by F. so/ani, M phaseolina. Meanwhile F. oxysporum, B. theobrome, F. /11(J11iliji.Jrme caused the lowest percentages of pre­ emergence damping-ofT Increasing inoculum level increased disease incidence caused by these pathogenic