Analysis of pathogenic and genetic variability of Corynespora cassiicola based on iPBS retrotransposons

摘要

Corynespora cassiicola is an important plant pathogen with a wide host range. We investigated pathogenic and genetic variation among 69 C. cassiicola isolates from 16 hosts in China. Based on the inter-primer binding sites (iPBS)-retrotransposons, we selected five iPBS primers to analyse the genetic variability of these isolates. All isolates were clustered in two genetic clades (IG1 and IG2). Forty-four C. cassiicola isolates were selected from the collection to investigate their pathogenic profiles. Based on the results of the pathogenicity analysis, these 44 isolates were divided into two pathogenicity groups (PG1 and PG2). A correlation between the genetic and pathogenicity groups was observed in the phylogenetic tree obtained with the iPBS markers, whereas the isolates from rubber tree were clustered in an independent clade. A total of 72 bands were observed, of which 68 were polymorphic (94.44). The Nei's genetic identity index of the 16 host populations varied from 0.5035 to 0.9661. The mean Nei's gene diversity index (H = 0.3042) and the mean Shannon's information index (I = 0.4598) at the species level were higher than at the population level, suggesting that the genetic diversity within the populations was greater than among the populations. The Nei's GST (0.7895) and gene flow (0.1333) showed more considerable genetic differentiation among populations and few gene exchanges. The pathogenicity and molecular marker analyses revealed there was a high level of genetic differentiation and diversity in the C. cassiicola isolates studied.