Development of SNP-Based Markers to Identify Colletotrichum gossypii in Upland Cotton.

Colletotrichum gossypii is a causal agent of anthracnose in upland cotton (Gossypii hirsutum). C. gossypii belongs to the C. gloeosporioides species complex. However, the high level of genetic similarity among the species within the C. gloeosporioides species complex makes the development of a diagnostic assay for C. gossypii challenging. Furthermore, the spore size and cultural characteristics of C. gossypii from different geographical areas can vary. In this study, we examined the morphological variance, growth pattern, and pathogenicity of C. gossypii and developed a molecular diagnostic assay to detect C. gossypii in cotton plants from different regions of China. To overcome any ambiguity in morphological and pathogenic characteristics, a set of primers targeting the β-tubulin (TUB) gene of C. gossypii was designed. Single-nucleotide polymorphisms (SNP) were used to identify C. gossypii at the species level using DNA sequence alignments of the TUB gene. The SPSCG/F and SPSCG/R primer pair only amplified C. gossypii, and was able to amplify C. gossypii in mixtures of other Colletotrichum spp., even when DNA concentrations were up to 10 times lower than that of the other species. This is the first report of the development of SNP-based markers for the specific identification of C. gossypii.