Mycelial compatibility groups in Sclerotium cepivorum

Abstract

Isolates of Sclerotium cepivorum from the Holland-Bradford Marsh, Ontario, Canada (n = 146) and other locations (n = 23) were evaluated for mycelial compatibility in agariculture and by transmitted light microscopy. In compatible interactions, hyphae of paired colonies anastomosed without cell deterioration or death at the point of fusion. In some incompatible interactions, hyphae of paired colonies were initially similar to those of compatible interactions but were later followed by deterioration or death of the fused cells. Incompatible interactions were associated with a red-brown colour that, n-mass, produced a dark line at the junction of the two colonies. In other incompatible interactions, hyphae were observed to bypass or repel each other without fusing. Compatible and incompatible reactions were used to define nine mycelial compatibility groups (MCGs) among the isolates examined. An ong isolates from Ontario, no incompatibility responses were observed among isolates from individual fields (e.g. no intrafield variability) but two MCGs were found among isolates from different fields (e.g. interfield variability). Among isolates from other regions, seven additional MCGs were detected that consisted of one to eight isolates. Two isolates were variable in reaction and were not assigned to any MCG. Three isolates from Switzerland were compatible with MCG-1 isolates from Ontario: and one isolate from Switzerland, two from England, two from New Zealand, and two from Australia were all intercompatible. The results establish that mycelial compatibility can be used to reflect genetic heterogeneity among isolate, of S. cepivorum.