Molecular and morphological characterization of Colletotrichum gloeosporioides from native Mexican Stylosanthes species

A total of 264 Stylosanthes spp. plants collected from 78 Stylosanthes spp. populations in seven southern Mexican states were analysed for the presenc e of Colletotrichum spp. Isolates were obtained from 64 plants collected fr om 36 Stylosanthes populations; 198 isolates produced straight conidia, whi le 72 isolates produced falcate conidia. Molecular identification was perfo rmed to confirm the identity of C. gloeosporioides for the straight-spored isolates. PCR amplifications using the primer CgInt, synthesized from an IT S1 fragment specific to C. gloeosporioides, and the universal primer ITS4 g enerated the target fragment for 120 Mexican isolates with straight conidia . The endonucleases Ava II and Sma I were used for restriction of the entir e amplified ITS1 region of these 120 isolates. The tree constructed from th e restriction data grouped 118 Mexican C. gloeosporioides isolates into thr ee clusters containing reference isolates from Africa and Australia, and ge nerated two additional clusters for two Mexican isolates. Conidial shape an d growth rate on solid medium were used as the major morphological criteria for distinguishing types A and B. On the basis of 32 other morphological c haracteristics, a phenogram grouped the colonies into three main clusters. These clusters were partially related to the Stylosanthes species from whic h they were isolated, and to the molecular groups.