Powdery mildew, caused by Oidium heveae, is a major threat to rubber plantations worldwide. Population studies are scarce for this pathogen due to the lack of polymorphic molecular markers. In this study, sixteen polymorphic microsatellite loci were identified using DNA extracted from single lesions based on the whole-genome sequences of the pathogen. Primers of these loci were applied to 138 O. heveae samples from five counties in Hainan, China. The number of alleles per locus ranged from 2 to 11 and the gene diversity varied from 0.014 to 0.728. In total, 119 multilocus genotypes (MLGs) were observed for the 138 samples. However, only one sample was significantly distinct from the other samples base on DAPC analysis.Further study indicated that there were three subclusters for the other 137 samples, but no evidence for regional genotypic subdivision was identified. The microsatellite markers developed in this study are very useful to study the genetic structure and dispersal route of O. heveae, especially as it can use DNA extracted directly from infected leaves..
Colletotrichum siamense was demonstrated as the dominant species among Colletotrichum spp. that infected rubber tree, areca palm and coffee in Hainan, China. However, it is not known the extent of genetic differentiation within the species C. siamense in relation to geographical regions and host species. In this study, 112 C. siamense isolates were genotyped with 12 microsatellite markers. In total there were 99 multilocus genotypes (MLGs). Results from permutational multivariate analysis of variance (PERMANOVA) and analysis of molecular variance (AMOVA) indicated that there was no significant genetic differentiation between fungal populations with respect to host, location (county) and year. Discriminant analysis of principal components (DAPC) and STRUCTURE analysis showed that C. siamense isolates grouped into three clusters; further analysis confirmed that there were significant (P < 0.001) genetic differences among the three clusters. However, each cluster had isolates from different hosts, counties or years, supporting the lack of genetic differentiation with respect to host, county and year. Statistical analyses of allelic associations indicated some evidence for recombination within the populations defined on the basis of host or county. The present findings provide insights into the genetic structure of C. siamense on the three perennial host species in Hainan and suggest that the disease on these three crops can be effectively considered as one disease and hence need to be controlled simultaneously in mixed plantations.
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