The Pathogenicity Of Rhizococtonia Solani To Soybean And The Resistance Of Soybean Varieties To Rhizoctonia Solani

Soybean is one of the important crops in our country,and it is the main source of plant fats and oil crops for mankind.Our country is the largest soybean consumer,but self-sufficiency rate is low and soybean mainly relies on imports.Since 2019,our country has implemented a soybean revitalization plan to expand the planting area in multiple ways.Huang Huai region is the main area for rice cultivation in our country.In order to implement the national soybean revitalization plan and restore the soybean planting area in Huang Huai region.In order to expand the soybean planting area,it is necessary to relatively reduce the rice planting area or implement the rice-bean rotation model in rice planting area.Because soybean wilt caused by Rhizoctonia solani is one of the main diseases in soybean seedling stage,the pathogenicity of this pathogen to soybean and the resistance of soybean varieties to this pathogen are still lacking systematic research in our country.Soybean is one of the economically most important crops in China,providing the main source for vegetable oil and protein.China consumes the biggest proportion of global soybeans but domestic soybean production is far from needs,so that soybean plays a major role in Chinese international business.To increase domestic soybean productions,China initiate a soybean revive project and expand soybean producing area.In this situation,Huang Huai region,a former rice growing region,is now turning back to the traditional soybean producing region.As such,the local planting strategy is changing to meet soybean producing need.Soybean is known as one of the host plants of fungal pathogen Rhizoctonia solani,but the pathogenicity of this pathogen to soybean remains unclear.In this study,a total of 62 R.solani strains were isolated and collected from Huang Huai region and Northeast China.The fungal pathogenicity is determined by soybean hypocotyl inoculation method on soybean cultivar Zhonghuang 13.After scoring the pathogenicity of 62 strains,25 strains were highly virulent,26 strains were moderately virulent,and 11 strains were weakly virulent.In addition,we selected 4 representative R.solani strains from 62 strains to inoculate soybean seedlings in pots.The results of this pathogenicity assay are basically consistent with the results of soybean hypocotyl inoculation assay.Over all,our results indicate that R.solani in Huang Huai region are highly virulent on soybeans,pointing to a possibility that the fungal pathogens of rice sheath blight may expand their host ranges and in particular infect soybeans in rice-bean rotation in rice planting area.To investigate the resistance of soybean varieties to R.solani in Huang Huai region will provide insights for rational soybean disease-resistant utilization.In this study,the soybean hypocotyl inoculation method is used to determine the resistance of 45 soybean varieties from Huang Huai region to R.solani strains isolated from both rice and soybean.The results showed that all the 45 soybean varieties are highly susceptible to the highly virulent strain Rss-3 isolated from soybean.However,all these soybeans show good resistance to the Rsr-37 strain that are virulent on rice,the moderately virulent strains Rss-9on soybean and Rsr-33 on rice,the weakly virulent strain Rss-5 from soybean and Rsr-56 from rice.Although a few soybean varieties are highly susceptible to R.solani isolated from rice,our results suggest that soybean varieties in Huang Huai region harbor rich natural disease-resistance to this fungal pathogen.We reason that when rice-bean rotation is carried out in areas where rice sheath blight occurs severely,susceptible soybean varieties should be avoided to decrease the persistence of R.solani,as such to reduce the possibility of soybean wilt epidemic.This study highlights the mechanistic basis for soybean wilt management by using the rice-bean rotation model.