Studies On Pathogenicity Differentiation Of Botrytis Cinerea And The Mycoviruses In Strain JXstr36

Botrytis cinerea causes the grey mold disease on many corps inducing great economic losses. This dissertation investigated the pathogenicity differentiation of B. cinerea strains isolated from six provinces of China and characterized the mycovirus infecting strain JXstr36 of B. cinerea. All results are listed below:Firstly, 566 strains of B. cinerea were isolated form the samples of six provinces including Liaoning, Hebei, Hunan, Jilin, Jiangxi and Shandong in this study. The pathogenicity of these B. cinerea strains were tested on detached Nicotiana benthamiana leaves. The results showed that the proportion of virulent B. cinerea strains(lesion diameter larger than 10 mm)is 96.3%, whereas the hypovirlent strains accounted for only 3.7%. Through repeating the test of pathogenicity on hypovirulent strains, seven phenotypically stable strains were obtained.Secondly, seven hypovirulent strains were determined to be B. cinerea through the PCR detection with B. cinerea-specific primers. Biological analysis showed that the culture characteristics of 7 hypovirulent strains were almost normal; however, the growth rates within these strains were different and slower than that of strain B05.10. Seven hypovirulent strains of B. cinerea could produce conidia except strain SY18, and some strains could even produce more conidia than that of strain B05.10. In the seven strains, only strains SDtom39 and BJstr8 produced sclerotinia. These results indicated the existence of biological diversity in the population of hypovirulent B. cinerea strains.Thirdly, four dsRNAs were detected in the hypovirulent strain JXstr36 with normal culture characteristic, and named them as dsRNA-A, dsRNA-B, dsRNA-C and dsRNA-D. The sequence of four dsRNAs were all subsequently sequenced and analyzed. The results showed that dsRNA-A was 10197 bp in length(without poly-A tail), and its nucleic acid sequence was 67% and 67% identical to those of Phomopsis longicolla hypovirus(PlHV) and Sclerotinia sclerotiorum hypovirus 1(SsHV1), indicating dsRNA-A might be a species of mycovirus, named as Botrytis cinerea hypovirus 1/JXstr36(Bc HV1/JXstr36). BcHV1/JXstr36 contained a large ORF encoding a polypeptide with RdRp, UGT, Prot, Hel domians.Finally, dsRNA-B was 3913 bp in length(without poly A tail), and showed homologous to partial sequence of SsHV1. Moreover, the 5’- and 3’-UTR of dsRNA-B was also homologous to those of BcHV1, whereas no sequence similarity was found in the middle sequence for both of them. Therefore, dsRNA-B might be the satellite RNA of BcHV1. The size of dsRNA-C å'Œ dsRNA-D was 1386 bp and 778 bp, respectively, and they were both determined to be the defective RNA of dsRNA-B.