Macrophomina phaseolina was isolated more frequently (65.2%) followed by Fusarium spp. (25.0%), Rhizoctonia solani (7.6%) and Sclerotium rolfsii (2.2%) from different samples showing charcoal-rot and root rot symptoms. The highest frequencies of M. phaseolina (94.0%), Fusarium spp. (52.3%), R. solani (37.5%), and S. rolfsii (18.5%) were recorded in Menia, Domiat, Menofiya, and Qalubya,. Eleven isolates of M. phaseolina obtained from different hosts and locations were studied in this work. The obtained isolates differed significantly in linear growth and sclerotial production. Color of fungal colonies was varied from gray to black also and seems to be correlated with density of sclerotial formation. In general, culture filtrates sterilized by autoclave, were more toxic and caused significant reduction in seed germination, shoot and root lengths of sesame seedlings than those sterilized through Sintered glass filter. Culture filtrates of sesame isolates No. 1 and 5 showed the highest and lowest phytotoxocity, respectively. Pathogenicity tests carried out in infested soil and piercing sesame stems with toothpicks proved that, M. phaseolina isolated from sunflower and sesame (isolate No.7) were less virulent, meanwhile sesame-isolate No.3 was more virulent on sesame plants. Studying protein patterns proved that, the highest degree of similarity was detected between M. phaseolina isolates from host plants grown in the warmer soils in Middle and Upper Egypt. The interaction between 5 isolates of M. phaseolina and 5 host plants was studied. Sunflower was the most susceptible host to infection, followed by sesame, soybean, cotton and peanut, respectively. However, isolates of M. phaseolina from sesame, soybean, and sunflower were more aggressive than those isolated from peanut and cotton. Host-plant/pathogen-isolate interactions were studied, the highest disease incidence was associated with peanut/peanut isolate, sesame/sesame isolate, soybean/sunflower isolate, sunflower/soybean isolate, and cotton/sesame isolate combinations. Isolate of M. phaseolina isolated from peanut was more aggressive on sunflower than the other tested host plants.
Key Words: Sesame, charcoal-rot, Macrophomina phaseolina, culture filtrates, soil infestation, toothpick inoculation, electrophoresis, patterns protein. |
