RAPD markers as a system for differentiating among isolates of the anthracnose fungus Colletotrichum graminicola

Abstract

Random amplified polymorphic DNA markers were used to investigate the genetic composition of a selection of Colletotrichum graminicola isolates from sorghum, maize and johnsongrass. The sorghum isolates were collected from around the world, while the maize and johnsongrass isolates came from the U.S.A RAPDs were able to differentiate a high proportion of isolates examined. The degree of diversity within populations varied with geographical origin; some populations showed very little variation, while others exhibited a high degree of heterogeneity. Geographical origin was found to be more important than was resistance or susceptibility of the source cultivar, in determining relationships among isolates. The isolates were grouped into 12 pathotypes by disease response of six inoculated differential cultivars, but no pathotype-related RAPD banding patterns were found. Use of RAPD patterns to identify selected isolates after passage through and re-isolation from the host was only partially successful. Our data indicate that Colletotrichum graminicola from maize should be classified as a species separate from that on sorghum. Preliminary data. Our data indicate that Colletotrichum graminicola from maize should be classified as a species separate from that on sorghum. Preliminary data from appressorial morphology also indicate that johnsongrass isolates may be distinct from sorghum isolates.