Morphogenesis of microsclerotia and sasakii-type sclerotia in Rhizoctonia solani, anastomosis group 1, intraspecific groups IA and IB

Abstract

Soybean plants with Rhizoctonia web blight ( Rhizoctonia solani , anastomosis group 1) were collected from fields in Louisiana. Microsclerotia were isolated from diseased tissues and cultured on 2 % water agar. Initiation and development of microsclerotia are described using optical and scanning electron microscope techniques. A lateral growth type of development was observed for microsclerotia which was different from the loose growth type observed for sasakii-type sclerotia. Microsclerotia arose vertically from growing points out of main hyphae. The growing point stopped developing vertically after differentiating seven or eight levels of lateral side branches. These branches became continuously interwoven until the sclerotia reached full size. One growing point from one main hypha was involved in the formation of a single microsclerotium. The relationship between microsclerotia and sasakii-type sclerotia is discussed.