Identification Of Three Pathogens Causing Diseases In Pea

Pea(Pisum sativum L.),as food and vegetable widely grown,is one of the important edible legume corps in China.The total planting area and yield of pea in China are the first in the world.Pests and diseases are an important factor limiting pea production.To date,there are more than 20 kinds of diseases on peas in my country,among which the main diseases are Fusarium wilt,root rot,powdery mildew and white mold.However,the pathogens of most diseases have not been identified in detail.Moreover,the adjustment of agricultural planting structure,promotion and planting of single commercial varieties,unreasonable field management and fertilizer application,and changes in climatic conditions have caused many original diseases on peas to aggravate,and new diseases or pathogens have also appeared in recent years.In this study,we aim to identify the pathogens of the pathogens of the increasingly serious Fusarium wilt,white mold and rust.The main results are as follows:1,Identify the physiological races of pathogen of pea Fusarium wilt in my country and 2 cryptic Fusarium species are identified.A total of 83 pathogenic isolates of Fusarium oxysporum have been got though pathogen isolation,specific primers,and pathogenicity tests from pea Fusarium wilt strains collected from 10 provinces of Beijing,Anhui,Guangxi,Guizhou,Hebei,Henan,Jiangsu,Shandong,Sichuan and Yunnan.Then,83 isolates were identified by using pea Fusarium wilt physiological race standard cultivars.The results showed that 52,6,16 and 9 isolates were races 1,2,5 and unknown races,respectively.Host specificity test showed that F.oxysporum isolates from pea were different from other forma specialis of F.oxysporum.The results of SIX gene detection showed that SIX14 gene may be a related gene for pathogenicity of F.oxysporum,and the identification of SIX1-14 gene combination can distinguish race 5.The phylogenetic analysis and genetic diversity identification of Fusarium species indicated that there may be 2 cryptic Fusarium species in this study.2,The pathogens causing white mold of pea are identified as Sclerotinia sclerotiorum,S.minor and S.trifoliorum.We found white mold of pea during the surveys in the some fields located in Chongqing and Sichuan.The infected pea plants showed typical symptoms with water-strained and chlorotic or grayish white,causing soft rot or longitudinal cracks in the stem base,white cotton-like mold growing on the surface of the diseased part,and finally producing black irregular sclerotia.A total of 30 isolates were obtained though pathogen isolation from disease plant tissues or sclerotia.Based morphological characteristics and molecular characterization,30 isolates were identified to three species,6 isolates as S.minor,7 as S.sclerotiorum,and 17 as S.trifoliorum.In pathogenicity tests on pea cultivars “Zhongwan 4” and“Longwan 1”,all 30 isolates caused typical symptoms of white mold on the inoculated plants,and the inoculated pathogens were re-isolated from the diseased plants.It is the first report that S.minor and S.trifoliorum cause white mold of pea in southwest China.3,The pathogens causing pea rust are identified as Uromyces viciae-fabae ex P.sativaum.A total of 4 rust isolates were obtained through the pathogen propagation and morphological characters of the pea rust samples collected from Yuxi City,Yunnan Province.Based on pathogenicity tests and phylogenetic analysis of ITS sequence,all 4 isolates were identified to U.viciae-fabae.In pathogenicity tests,the pea isolate WX1 was highly pathogenic to faba bean and pea and produced abundant aecia on inoculated leaves,but not pathogenic to lentil and chickpea.The phylogenetic analysis indicate that all isolates of U.viciae-fabae from different hosts were clustered into a phylogenetic group;the isolates from pea were clustered into a subgroup according to hosts.Based on the above results,we suggested U.viciae-fabae from pea in Yuxi City,Yunnan Province was named as U.viciae-fabae ex P.sativum.