Identification Of Three Pathogens Causing Soil-borne Diseases On Mung Bean

Mung bean(Vigna radiata(L)Wilczek),which belongs to the Vigna genus of legume,is one of the most important food legume crop in China.It originates from Southeast Asia including China which has a more than 2000 years history of mung bean cultivation.Pests and diseases are important factors limiting the yield and quality of mung bean.To date,more than 20 diseases have been documented on mung bean in China,of which powdery mildew,sclerotium stem rot and bacterial halo blight are the main diseases.Recently,the known diseases are gradually aggravating and the new diseases are emerging constantly,which partly due to climatic condition changes and deployment of excellent varieties leading to cultivar simplification and the regulation of agricultural planting structures.In this study,we focus on the detailed identification of pathogens causing Fusarium wilt,Verticillium wilt,and root and stem rot of mung bean.The main results are as follows:1 ? The pathogen causing mung bean wilt is identified as a new forma specialis of Fusarium oxysporumA total of 170 Fusarium oxysporum-like isolates were obtained from diseased mung bean plants showing typical Fusarium wilt symptom collected from Jilin,Shanxi,Inner Mongolia,Henan,Hebei,Heilongjiang and Shaanxi.Based on the morphological observation,pathogenicity test and specific primer detection of F.oxysporum-species,we confirmed the pathogen causing mung bean wilt to be F.oxysporum.Furthermore,host specificity test and phylogenetic analysis indicated that all isolates from mung bean were different from other known formae speciales of F.oxysporum,thus we designed the pathogen isolated from mung bean as a new forma specialis,named F.oxysporum f.sp.mungcola.2?An emerging disease of mung bean Verticillium wilt is caused by the pathogen Verticillium dahliaeA new disease of mung bean with Verticillium wilt symptoms was observed in the fields located in Inner Mongolia,Shanxi,Shandong and Hebei provinces during 2014-2015.The infected mung bean plants showed typical Verticillium wilt symptoms,including gradual leaf yellowing,wilting,shortened internodes and plant stunting,vascular turning brown after splitting the stem.41 isolates were obtained from collected samples,which were morphologically and molecularly identified to be V.dahliae.All isolates were divided into three types based on colony morphology on PDA.The results of molecular identification for physiological race showed that 27 of 41 isolates were race 2 and no race 1 was detected;Molecular detection of mating types indicated that 28 isolates belong to MAT1-2-1 and no MAT1-1-1 was detected;Detection with specific markers showed that 4 isolates were defoliating and 11 were nondefoliating,and the others were neither defoliating nor nondefoliating;Pathogenicity test and phylogenetic analysis indicated that all isolates from Shandong and Hebei had stronger virulence than those from the other provinces.3?To find a new disease of mung bean,Phytophthora root and stem rot,and identify the pathogen as a new forma specialis,Phytophthora vignae f.sp.mungcolaA new disease showing the symptoms of root and stem rot was discovered on mung bean inMingguang,Anhui Province in 2015.Based on morphological observation and molecular detection,the isolates from mung bean were confirmed as P.vignae.Subsequently,pathogenicity and host range tests indicated the isolates from mung bean were different from those isolated from cowpea and adzuki bean,thus we designed it as a new forma specialis,named P.vignae f.sp.mungcola.