Management of Charcoal Rot of Sesame by Seed Soaking in Medicinal Plant Extracts and Hot Water

Abstract

Macrophomina phaseolina causing charcoal rot was isolated from sesame seeds (cvs. Giza 32 and Shandawel-3) collected from different localities of Assiut, Sohage and El-Minia Governorates. The fungus was found in the highest frequently in samples collected from Assiut Governorate followed by Sohag and finally EL Minia Governorate. The obtained isolates were different in their virulence on the tested sesame cvs. Also, they differed in their growth nature including colony color and sclerotial production. The color of colonies of the pathogen seem to be correlated with density of sclerotial formation. Aqueous extracts of Majorna, Wild chamomile, Geranium oil and Nees plants were highly toxic to tested isolates of M. phaseolina, in vitro. On the other hand the rest of the tested aqueous extracts had no effect. Under greenhouse conditions in 2005 and 2006 seasons, soaking seeds of sesame before sowing in aqueous extracts of Eucalyptus, Nerium, Ocimum and Roesmary plants decreased the disease incidence. Aqueous extracts of Eucalyptus and Ocimum were the most effective treatment. Dipping sesame seeds in hot water at <TEX>$60^{\circ}C$</TEX> for 5 minutes increased seed germination of Giza 32 and Shandawel-3 cvs. followed by <TEX>$55^{\circ}C$</TEX>, <TEX>$50^{\circ}C$</TEX> and <TEX>$45^{\circ}C$</TEX>, while <TEX>$40^{\circ}C$</TEX> treatment resulted the lowest seed germination rate. Dipping sesame seeds in hot water at different temperature before planting decreased seed, seedling and charcoal rots. Soaking seeds in hot water at <TEX>$60^{\circ}C$</TEX> increased greatly plant height and decreased seed, seedling rot and charcoal rot followed by <TEX>$55^{\circ}C$</TEX> and <TEX>$50^{\circ}C$</TEX>, under greenhouse condition.