Identification To Pathogens Of Woods Canker, Genetic Differentiation Research To Its Main Species Valsa Mali And Rapid Detection To Primary Infection Source Of V. Mali In Xinjiang

Object:In order to clarify the pathogen species of woods canker of shelterbelt and economic forests in Xinjiang and clarify pathogenicity differentiation and genetic diversity of its main species Valsa mali.Meantimes,for confirm the primary source of infection of canker pathogen in apple and korla pear orchard in Xinjiang.Finally,there results were used to guide woods canker management in Xinjiang.Methods:Canker samples of wood were collected and isolated by tissue isolation in Xinjiang,and pathogenicity of these pathogen were determinated according to Koch's rule.These isolates were identified by means of the morphological features of culture,18S rDNA-ITS and?-Tubulin gene sequences analysis.Pathogenicity and genetic differentiation of main specie Valsa mali were detected in vitro shoot inoculation and ISSR methods;Based on?-Tubulin sequence of the Valsa genus,specific primers were designed,and a rapid PCR assay for detection the primary source of infection of canker pathogen in apple and korla pear orchard in Xinjiang.Result:1.A total of 281 isolates were obtained from woods canker come from 17 kinds of hosts in Xinjiang,all isolates are anamorph,and pathogenicity of these isolated were tested according to Koch's rule.These isolates were identified as 5 species,they are Valsa mali(anamorph:Cytospora mali),Valsa sordida(anamorph:Cytospora chrysosperma),Valsa macolica(anamorph:Cytospora schulzeri),Leucostoma niveum(anamorph:Cytospora nivea)and Cryptosphaeria pullmanensis(anamorph:Cytosporina pullmanensis)respectively..The V.mali and V.sordida are main pathogens of economic forest and shelter forest,respectively.2.Pathogenicity differentiation of the main specie V.mali were studied.The color of V.mali are white,milk-white and yellow.The growth rates of white strains were faster than milk-white and yellow strains,but growth rates of yellow strains were the slowest.The optimum growth conditions of V.mali is temperature 20 ~oC to 30 ~oC and pH 5 to pH 6.Milk-white and yellow strains had stronger pathogenicity than white strains.The pathogenicity of V.mali strains were medium and weak,no strong pathogenicity strains in pathogenicity test.Pathogenicity differentiation of V.mali was observed in Xinjiang.3.The results of genetic diversity of different geographical groups showed that Nei's(1973)gene diversity index(H)and Shannon's information index(I)were both higher than 0.2 and0.4,respectively,which indicated that the genetic diversity of V.mali in Xinjiang was considerably abundant.The results of population genetic structure of different geographical groups showed that the genetic variation within the populations was the main source of genetic variation.The dendrogram based on ISSR markers revealed that different natural populations were grouped into two clusters by UPGMA.Populations of V.mali were grouped into South Xinjiang and North Xinjiang.The populations belonged to the same geographical groups could be clustered into different clusters,which indicated that there was no significant correlation between the genetic relationships and their geographical originals.4.A rapid PCR assay for detection of woods Valsa canker was developed in Xinjiang.Four pairs of species-specific primers could be used to amplifiy 144 bp,180 bp,240 bp,and 324 bp DNA fragments from V.mali,V.sordida,L.niveum and V.malicola,respectively.And the detection sensitivity was 10pg/mL.5.Results of detection of primary infection source of Valsa canker showed that among 39samples from serious canker in Korla pear orchard,the species of V.mali was detected in 7samples,which had a proportion of 17.95%;there were 33 samples of serious canker in Aksu apple orchard,19 samples were detected in V.mali and the proportion was 22.94%.V.sordida,L.niveum,V.malicola in pear orchard and apple orchard were not detected.Test results demonstrated that pruning,trees tissues,soil samples,woods outside the orchard may be overwintering sites and primary infection source of apple and korla pear orchard in Xinjiang.Conclusion:A totla of 5 canker pathogens come from 17 woods were identified and V.mali is the main pathogen causing canker of economic forest,and V.sordida is the main specie causing canker of shelter forest in Xinjiang.The pathogenicity of V.mali was medium and weak strains,no strong pathogenicity strains.differentiation among the pathogenicity of V.mali was presented in Xinjiang.A rapid PCR detection technique was developed for detection of four species Valsa canker in Xinjiang and the detect results show that pruning,trees tissues,soil samples,woods outside the orchard may be overwintering sites and primary infection source of apple and korla pear orchard in Xinjiang.