an analysis of genetic diversity in hyphal tip isolates of promising mycoherbicide alternaria alternata for control of amaranthus retroflexus

the potential mycoherbicide alternaria alternata was isolated from one lesion on a leaf of amaranthus retroflexus which had been inoculated with conidia of the fungus. the isolate was cultured on v-8 agar medium. hyphal tip isolates (hti) were derived from young germ tubes of single spores and cultured on a semidefined culture medium with a c:n ratio of 15:1. amplified fragment length polymorphism analysis detected genetic variation in four htis and revealed 29% polymorphism. selected htis that were different in at least one dna fragment pattern varied in degree of sporulation, length of conidial germ tube, virulence and desiccation tolerance. the results indicated that the original culture of a. alternata is heterogeneous and, thus, cannot be considered as a suitable candidate for development as a commercial biocontrol agent.