Diversity Of Pathogens Of Gray Mold From The Main Strawberry Production Regions In China

As a crucial disease of strawberry, strawberry gray mold, with severe harm and wide range influence, is a main factor resulting to a decreased yield and declined quality of strawberry. In this study, the species of pathogen causing strawberry gray mold was identified, in addition, the colony characteristics, transposable element type, mating type, pathogenicity, resistance to the common fungicides and population genetic diversity were also under research and analysis. The results are as follows:1. There were 255 single spore strains isolated from strawberry gray mold samples collected from 6 main producing areas of strawberry in China, namely, Liaoning, Hebei, Beijing, Anhui, Sichuan and Xinjiang Antonomous Region. Based on the results of morphology, enzyme digestion analysis of the Bc-hch and the phylogenetic analysis of gene G3PDH、HSP60 and RPB2, it showed that the pathogen of the strawberry gray mold was consisted of at least three phylogenetic species:B. cinerea, B. sinoviticola and B. pelargonii. B. cinerea was dominant population, B. sinoviticola and B. pelargonii was found on strawberry for the first time in China. Therefore, strawberry was the new record host in China. It was the first study about the population composition of B. cinerea from strawberry in China.2. Comparisons were conducted between strains of B. cinerea and B. sinoviticola on the aspects of colony characteristics, colony growth rate, conidium size, sporulation, pathogenicity and sensitivity to fenhexamid. The results showed that compared with B. cinerea, the sclerotia of B. sinoviticola were smaller but larger in quantity; the conidium were longer, while the pathogenicity was weaker. There was no obvious difference in colony growth rate and sporulation quantity, both B. cinerea and B. sinoviticola were sensitive to fenhexamid.3. Diversity of B. cinerea was proved on transposable element type, colony characteristics, pathogenicity and other aspects. In this research, there were 4 transposable element types: transposa(containing both Flippe and Boty), vacwma(with neither Flipper nor Boty), boty(only Boty) and flipper(only Flipper), in which transposa was the main type with proportion of 61.7%. Mating type was MAT1-1 or MAT1-2, with a ratio of approximate 1:1. Colony characteristics manifested three types: the mycelial type, the conidia type and the sclerotial type, in which the sclerotial type was at most. The pathogenicity to strawberry leaves could be divided three types:weak, medium and strong, and the strong virulent was at most. Based on the resistance to carbendazim, procymidone and diethofencarb, there were 8 phenotypes, CarsProsDieR was the dominating type, with proportion of 28.3%. Different strains displayed a marked difference on these characteristics, thus it refected that the diversity of B. cinerea from strawberry in our country was rich.4. The population genetic diversity was analyzed by means of SSR. There were 165 multilocus genotypes (MLGs) among the 6 geographic populations, with averaged gene and genotypic diversity of 0.662 and 0.994, respectively. All the isolates could be divided into two genetic groups according to the results of PCoA, included population from Hebei and populations from other 5 regions. Analysis of AMOVA revealed that genetic variation within populations accounted for 97% of the total genetic variation. Asexual reproduction was the main mode of reproduction according IA. The Genetic fixed index Rst was estimated to range from 0.002 to 0.07, low to moderate genetic differentiation was detected among most populations.