Two new species of Colletotrichum (Glomerellaceae, Glomerellales) causing walnut anthracnose in Beijing.

Colletotrichum species are plant pathogens, saprobes and endophytes on various plant hosts. It is regarded as one of the 10 most important genera of plant pathogens in the world. Walnut anthracnose is one of the most severe diseases affecting walnut productivity and quality in China. In this study, 162 isolates were obtained from 30 fruits and 65 leaf samples of walnut collected in Beijing, China. Based on morphological characteristics and DNA sequence analyses of the concatenated loci, namely internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase ( GAPDH ), actin ( ACT ), chitin synthase 1 ( CHS-1 ) and beta-tubulin (TUB2), these isolates were identified as two novel species of Colletotrichum , i.e. C.juglandicola and C.peakense . Koch's postulates indicated that both C.juglandicola and C.peakense could cause anthracnose in walnut.