Preliminary Study On The Biological Control Potential Of The Hypovirus CHV1-CN280 And Functional Analysis Of P29

Chestnut blight fungus(Cryphonectria parasitica) is one of the major diseases of chestnut and has caused serious damage in orchards and in forests.The hypovirulence, which is an attenuation of fungal pathogenis, has reduced the impact ofthis disease and has been used as a biological control method in Europe. So study on biological control of the chestnut blight is possible to provide a new method to control and design the new disease control strategy to give the new theory of direction.CHV1-CN280 is a hypovirus strain isolated in China. In this paper we report the colonization capability of CHV1-CN280 in the field, and the biological characteristics of the hypoviruses CHV1-CN280,CHV1-EP713 and CHV1-Euro7 in the laboratory. Compared to the other two hypoviruses, CHV1-CN280 resulted in a white colonial phenotype of C. parasitica (loss of orange pigmentation), but a moderate reduction in asexual sporulation, and less reduction in fungal virulence. Furthermore, CHV1-CN280 was found established in the field two years later of inoculation, and successfully transmitted into wild virulent strains of C. parasitica which belong to different vegetative compatibility group. Accordingly, CHV1-CN280 showed a better biocontrol capacity of chestnut blight in China.Viral double-stranded RNAs (dsRNAs) responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus, Cryphonectria parasitica, profoundly influence a range of host functions in addition to virulence.There have reported that the papain-like protease, p29, present in hypovirulent strain EP713, was shown by DNA-mediated transformation analysis to suppress fungal sporulation, pigmentation, and accumulation of the enzyme laccase. Bioinformatics analysis results show that the amino acid sequences of p29 were quite different between EP713 and CN280.We mapped the p29 gene of CHV1-CN280,and transformate it into virus-free virulent strains EP155.The fungal transformation results presented in this report demonstrate that the expression of viral papain-like protease p29 elicits some similar hypovirus symptoms like the increasing growth rate, the reducing fungal sporulation, pigmentation and the production of the enzyme laccase. Besides, there also have obvious different phenotype between transformant of Cryphonectria parasitica and Magnaporthe oryzae. The combined results suggest that papain-like protease p29 plays a different role when it was transformed into different srain.At the same time, papain-like protease p29 of EP713 and CN280 show different characterizations because of the different sequence.