Genomic and pathogenic diversity in Colletotrichum gloeosporioides from wild native Mexican Stylosanthes spp., and taxonomic implications

RAPD amplifications of 119 Mexican Colletotrichum gloeosporioides isolates from wild native Stylosanthes plants, of two Australian (internal reference isolates of type A and type B) and of two African (previously demonstrated as different from the A and B types) allowed the generation of four polymorphic clusters. The RAPD cluster I contained the Australian type A and 103 Mexican isolates from other species than S. guianensis. The cluster II contained the Australian type B isolate and 14 Mexican isolates from S. guianensis. The clusters III and IV contained one African and one Mexican isolate each. A phylogenetic study was performed using the ITS1 sequences from 32 representative Mexican isolates selected in the four RAPD clusters, from the two Australian and the two African used as references, from 13 C. gloeosporioides from various hosts and origins available in the EMBL databank and from three phylogenetically related species of Colletotrichum. Two clusters (S and VHO) were generated. Cluster S contained the 30 isolates clustered in RAPD I and II, and the type A and B isolates from Stylosanthes selected in EMBL. Cluster VHO contained the two isolates belonging to RAPD clusters III and IV as well as the remaining Colletotrichum spp. and C. gloeosporioides isolates from various hosts and origins selected in EMBL. Severe type A lesions were observed on several Stylosanthes species, including S. guianensis, after inoculation with the 26 Mexican isolates selected in RAPD cluster I. The four Mexican isolates selected in RAPD cluster II induced extensive type B lesions only on S. guianensis genotypes. The virulence spectra of the isolates was not linked to variations in their ITS1 region sequence. A wide range of anthracnose lesions was induced by the Mexican isolates in interactions with the various Stylosanthes genotypes. On the basis of results obtained from the molecular and pathogenic experiments in the present study, of morphological and molecular data from previous work, as well as from other authors, a taxonomic infraspecific differentiation was proposed, as C. gloeosporioides f. stylosanthis f. sp. stylosanthis and f. sp. guianensis.