玉米纹枯病菌中新减毒病毒RsHV4的特征研究

Characterization of a Novel Hypovirus RsHV4 in the Phytopathogenic Fungus Rhizoctonia solani

寻找立枯丝核菌(Rhizoctonia solani)中新的弱毒病毒,为玉米纹枯病提供新的生物防治资源。采用dsRNA技术从玉米纹枯病菌菌株ZYFG11中发现一种新的病毒RsHV4(Rhizoctonia solani hypovirus4),通过基因组克隆、系统发育分析、菌株生长特性测定及致病性测定等试验,对新病毒RsHV4的分类地位、减毒活性等生物学特征进行测定。结果表明,RsHV4的基因组全长为18702 nt,编码一个含5540个氨基酸的多聚蛋白(Polyprotein);系统发育分析显示,RsHV4与减毒病毒科(Hypoviridae)θ-减毒病毒属(Thetahypovirus)病毒聚为一支,其编码的蛋白质与该属的Sclerotium rolfsii hypovirus 1编码的蛋白质同源性最高,为59.46%;立枯丝核菌正常菌株JSJH6与含毒菌株ZYFG11的菌丝生长速度分别为0.50cm/d和0.41 cm/d,菌核大量形成的时间分别为培养5 d和7 d,培养10 d时50颗最大菌核的总质量分别为0.27 g和0.11 g,显示含毒菌株ZYFG11的菌丝生长速度减慢、菌核形成时间延迟、菌核体积和质量变小;接种到玉米植株2周后,接种含毒菌株ZYFG11的玉米植株第2叶鞘病斑面积占30%、第3叶鞘病斑面积占10%,接种无毒菌株JSJH6的植株第2叶鞘和第3叶鞘病斑面积达100%,说明含毒菌株ZYFG11的致病力显著降低。综上,在玉米纹枯病菌中发现了一种新的减毒病毒RsHV4,能够影响寄主真菌的生物学特征和致病力,为玉米纹枯病的防治提供了潜在的病毒资源。

In order to find a new hypovirus in Rhizoctonia solani and to provide a new biological control resource for corn sheath blight,a new virus RsHV4(Rhizoctonia solani hypovirus 4)was discovered by dsRNA extraction from the R.solani strain ZYFG11.The taxonomic status and biological characteristics such as hypovirulence activity of the new virus RsHV4 were determined by genomic cloning,phylogenetic analysis,growth characterization and biological inoculation.The result showed that RsHV4 was a positive single‐stranded RNA virus with the genome of 18702 nt,encoding a polyprotein of 5540 aa.Phylogenetic analysis showed that RsHV4 belonged to the genus Thetahypovirus of the family Hypoviridae and shared the highest identity of 59.46%with the polyprotein of Sclerotium rolfsii hypovirus 1.The mycelial growth rates of avirulent strain JSJH6 and virulent strain ZYFG11 were 0.50 cm/d and 0.41 cm/d,the time of mass formation of sclerotium was 5 and 7 d,the total weights of the 50 largest sclerotia were 0.27 g and 0.11 g after ten days of strain growth,respectively,these results indicating that the mycelial growth of the virulent strain ZYFG11 was slowed down,the sclerotium formation was delayed,and the sclerotium size was reduced.Two weeks after biological inoculation,the disease spot area of the second sheath and the third sheath of maize plants inoculated with virulent strain ZYFG11 accounted for 30%and 10%respectively,while the disease spot area of the second sheath and the third sheath of plants inoculated with avirulent strain JSJH6 accounted for 100%,indicating that the pathogenicity of virulent strain ZYFG11 decreased significantly.In conclusion,this study identified a novel hypovirus RsHV4 from R.solani,which can affect the biological characteristics and pathogenicity of host fungi,providing a potential virus resource for the control of corn sheath blight.