ANASTOMOSIS GROUPS OF RHIZOCTONIA SOLANI ISOLATED FROM SUGARBEET AND THEIR VIRULENCE IN RELATION TO CROP SEQUENCE

Document Type : Original Article

Author

Research Plant Pathologist, Sugar Crops Research Institute, Agricultural Research Centre, Giza, Egypt.

10.21608/ejar.1994.450699

Abstract

Eight isolates of Thanatephorus cucumeris Frank (Dank) (Rhizoctonia solar?, Kuhn) isolated from sugarbeet seedlings and roots were multinuclate. Considering anastomosis, the isolates fell into two groups corresponding to AG-2 and AG-4. A greenhouse test was conducted to determine the effect of cotton, soybean, sugarbeet, beams and corn as crops preceding sugar-beet on Rhiroctonia seedling disease of the latter. All isolates of AG-2 and AG-4 showed different degrees in infec‌tion percentage and disease severity on seedling stage (15 and 30 days) on all,crops. Cotton, soybean and sugarbeet significantly increased pre- and post-emergence damping-off, while beans and corn were less conducive. Therefore, lower disease incidence in pre- and post-emergence stages could be obtained by not following cotton, soybean, or sugarbeet. Advantage of reduced damping-off in sugarbeet following corn in rotation is apparent.