Potato leaf infection caused by Colletotrichum coccodes and C. nigrum.

Colletotrichum coccodes is an important pathogen of potatoes. Recently, the closely related C. nigrum has been reported as an important pathogen of solanaceous crops but not as a pathogen of potato. This study confirms C. coccodes as the most prevalent Colletotrichum species infecting foliar and tuber tissue of potatoes in Australia and the USA. In addition, three isolates from the USA, previously identified as C. coccodes, were re-identified as C. nigrum. The gene loci TUB2, ACT, GAPDH, CHS-1 or HIS3 were all suitable for differentiating C. nigrum from C. coccodes. Australian and USA tuber and foliar isolates of C. coccodes and C. nigrum had similar pathogenicity on detached potato leaves. This is the first report of C. nigrum as a pathogen of potato. Moreover, the recently described C. dianense was revealed to be a synonym of C. nigrum. [ABSTRACT FROM AUTHOR]