The Study On Pathogen And Pathogenicities Of Wheat Black Point Disease And Resistance Evaluation To Wheat Varieties In Xinjiang

According to results on pathogen isolation, identification and pathogenicity, there are threepathogens, Alternaria consortiale (Thüm.) Hughes,Alternaria alternate (Fr.) Keissler and Bipolarissorokiniana (Sacc et Sorokin) Shoems., which causing black point diseases of wheat were determined inXinjiang. It was the first report in China that A. Consortiale infected kernel and became to thepredominantpathogen.Resultsalsoshowedthatthepathogenicitiesofthreepathogensweredifferent. Thepathogenicity of B. sorokiniana on seedling was stronger than that of the other two pathogens, but thesituation changed to the opposite after the heading stage. The pathogenicities of A. consortiale and A.alternateonkernelwerestrongerthanthatof B.sorokiniana,theirinfectionperiodsarefrommilkstagetothe yellow ripe stage and fromheading stage to milk stage, respectively. On the pathogens of wheat blackpointdisease infection mechanismStudyisobserved. Pathogens always infectthe rachilla first, there aftermyceliuminfected embryo throughthe bottomof ear then causing the whole embryo getting black. it wasproved that high temperature and air humidity in field are the principal reasons of high frequency ofdisease. A 2-yr field studies have been conducted, at the experimental station in Xinjiang agricultureuniversity. There are 25 wheat cultivars including the main cultivars and regional trial wheat varietieswere evaluated on susceptibility and resistance to black point disease. The varieties showed differentabilityto disease caused bydifferentpathogen. Regarding the disease caused byA.alternate., there are noimmunevarietiesbeendetected,whereas9varietiesaccountfor36%outoftotaltestedvarieties,includingXinchun6, 7, 8 and etc. showed high susceptibilityto the disease, 11 varietiesaccountfor48%outoftotaltested varieties, including Xinchun2, 5, 8131 and etc. showed middle susceptibility to the disease.However, there are only 4 varieties account for 16% out of total tested varieties, including Xinchun15,945-304,64-1and1-147,showedresistancetothedisease. Tothediseasecausedby B.sorokiniana,thereare no immune varieties been detected too, only 3 varieties, including Ningchun 4, Xinchun 13 and 9,showed high susceptibility to the disease, 7 varieties including Xinchun 2 and etc. showed middlesusceptibilitytothedisease;15varietiesaccountfor60%outoftotaltestedvarieties,includingXinchun15,64-1andetc.,showedresistancetothedisease. Resultsalsosuggestedthatthegrowthfactorsincluding theheightofwheatplant, the lengthsoftheearand thearista,displayed minusrelativity with the incidence ofwheat black point disease.The observation on dissected embryo of grains showed that, the hyphainvadedthe inner area just below the coat layer without extending to the center area. The infested area wascontainminatedtohoneyyellowwithfewspores.