Genetic diversity within Colletotrichum acutatum sensu Simmonds

Isolates of Colletotrichum acutatum from several hosts were characterized b y various molecular methods in comparison with morphological identification . Species-specific primer analysis was reliable for grouping C. acutatum is olates to their designated species. Arbitrarily primed polymerase chain rea ction and A+T-rich DNA analyses identified four subgroups within C. acutatu m. Subgroup I contained U.S. isolates from almond, apple, peach, and pecan, subgroup II contained isolates from anemone, olive, and strawberry, subgro up III contained isolates from almond (Israel) and strawberry (Spain), and subgroup IV contained a single isolate from anemone (the Netherlands). Like wise, sequence analysis of the internal transcribed spacer (ITS) 2 region a lone or the complete ITS (ITS 1-5.8S-ITS 2) region grouped the isolates int o the same four subgroups. Percent similarity of the complete ITS region wi thin each cluster ranged from 99.6 to 100.0, 99.8 to 100.0, and 98.6% among subgroups I, II, and III, respectively. DNA sequence analysis of the ITS 2 region alone or the entire ITS 1-2 region was more informative than that o f the ITS 1 region, which could only group the isolates into two main clust ers. The molecular methods employed for studying genetic variation in popul ations of C. acutatum determined that this species is diverse, indicating t hat isolates within populations of each subgroup are not host specific.