Identification Of Sclerotium Rolfsii Causing Southern Blight Disease Of Macleaya Cor Data And Characterization Of RNA Mycovirus-mediated Hypovirulence

M. cordata (Wild.) R. Br is a perennial erect large herb with high medicinal value in agriculture, which belongs to the Papaveraceae, Macleaya. In August and September of 2014 the pink plumepoppy planted in Chinese herbal medicine planting bases in Yongan County, Liuyang City, Hunan Province, appeared the phenomenon of wilting and turned to dead of the whole plant in a large area suspected caused by S. rolfsii. Therefore, in this study the pathogens was isolated and identified from infected plants, and the relationship between dsRNA mycoviruses and hypovirulence about the hypovirulence strain BLH-1 isolated from infected pink plumepoppy was researched. The main conclusions were as follows:1?After Koch's postulates verification, combined with molecular biology and morphology determination, the two strains BLH-1 and BLH-2 isolated from susceptible plants were identified as S.rolfsii, causing southern blight in pink plumepoppy. At that time, China has not yet been reported about southern blight disease of M. cordata caused by S. rolfsii.2?Detected by dsRNA extracted from hypovirulence strain BLH-1 showed that the strain BLH-1 contains a series of dsRNAs ranging from 1-15Kbp. Through protoplast regeneration and picking hyphae tip to eliminate this dsRNAs of strain BLH-1, then horizontally transmitting it to virus-free strain BLH-1-P1. The comparison of dsRNA before and after infection of host strain mycelium growth and differences in virulence, the results showed that the strain infected with dsRNAs mycelium growth rate slowed down and had not been producing sclerotia, while also significantly reduced virulence, proved by eliminating the dsRNA virus and then transmitting it, indicated it can affect the mycelial growth and pathogenicity of strain BLH-1.3?Scanning electron microscopy and transmission electron microscopy showed that the strain infected with dsRNA virus mycelium surface appeared sunken, shriveled, twisting and other abnormal phenomenon, besides, mycelium breaks into small fragments; in addition its cell ultrastructure also changed significantly, such as cytoplasm declined and formed small vesicles recession-like structure, the number of mitochondria reduced, became smaller and deformity, moreover the crest of mitochondria degenerated.4?The dsRNA virus infected host can obviously reduce the ability of producing pathogenic factor. The laccase and acids production capacity of the hypovirulence strain BLH-1 contained dsRNA decreased significantly compared with virus-free strain BLH-1-P1, and didn't produce cellulase on cellulose Congo red medium.5?Measured partial genomic sequence of dsRNA virus contained strain BLH-1, the results showed that the strain mixed infected by at least three viruses which were named as: SrHV1, SrRV1, SrV1. The SrHV1 was predicted similarity to SsHV2 isolated from Sclerotinia sclerotiorum associated with hypovirulence, so we suggested that thia virus maybe is the main factor associated with hypovirulence of host strain BLH-1.