High Genetic Diversity and Limited Regional Population Differentiation in Populations of from Plantations.

causes a serious and widespread disease known as Calonectria leaf blight in plantations of southern China. Little is known regarding the population biology or reproductive biology of this pathogen in the affected areas. The aims of this study were to investigate the genetic diversity, population structure, and reproductive mode of . from affected plantations of southern China. Ten polymorphic simple sequence repeat markers were developed for the species and were used to genotype 311 isolates from eight populations. The mating types of all isolates were identified using the gene primers. The results revealed a high level of genetic diversity of the pathogen in all investigated populations. Of the 90 multilocus genotypes detected, 10 were shared between at least two populations. With the exception of one population from HuiZhou, GuangDong (7HZ), the most dominant genotype was shared in the seven remaining populations. Discriminant analysis of principal components and population differentiation analyses showed that the 7HZ population was well differentiated from the others and that there was no significant differentiation between the remaining populations. Analysis of molecular variance suggested that most molecular variation was within populations (86%). Index of association analysis was consistent with a predominantly asexual life cycle for . in the studied regions. Although both mating types were detected in seven of the eight populations, the / ratios in these populations deviated significantly from the 1:1 ratio expected in a randomly mating population.