A Preliminary Analysis On The Genetic Diversity Of Cotton Verticillium Dahlia Population In Xinjiang Corps Reclamation Area

Verticillium dahlia is a typical soil-borne vascular pathogen and its verticillium wilt is the leading disease threatening cotton production in China.In recent years,with the adjustment of cotton planting structure,Xinjiang has become the largest cotton producing area in China.In 2019,the planting area of Xinjiang accounted for 76.1% of the total in China.Among them,the cotton planting area of Xinjiang production and Construction Corps is 879,400 ha,accounting for 34.62% of the total cotton area in Xinjiang and 42.33% of the output.However,in Xinjiang cotton area,especially in corps cotton planting and reclamation area,there are some special cultivation modes,such as mechanization,continuous cropping all year round,straw returning to the field and so on.In addition,the frequent transfer of seeds leads to a large amount of soil pathogens,especially Verticillium dahliae,and the superposition and mixing of various bacterial strains,which provides conditions for the transmission of dominant population and population variation of Verticillium dahliae,and causes frequent Cotton Verticillium Wilt in Xinjiang corps in recent years The outbreak and damage are becoming more and more serious.Therefore,in order to clarify the population genetic structure and distribution characteristics of Verticillium dahliae in Xinjiang production and Construction Corps,this paper collected Cotton Verticillium wilt samples from the main cotton planting fields of Xinjiang production and Construction Corps in 2016-2017 and isolated Verticillium dahliae.Through genotype identification and population genetic structure analysis,the main research conclusions are as follows:1.2016—2017 strains of Verticillium dahliae were isolated from 40 groups of 9 divisions in 2017,of which 1345 strains(71.66%)were isolated in 2017 and 1158 strains(61.69%)were isolated in North Xinjiang.The most common sclerotium type strains(easily deposited melanin)was 1131 strains(60.25%),followed by the mycelium type strains(570 strains(30.37%),and 176 strains were the intermediate type strains,The results showed that there was no significant difference in culture phenotype between the years and between the north and the south of Xinjiang.The results showed that the main type of Verticillium dahliae was the sclerotium type strains.2.Based on the genetic markers of defoliating / non-defoliating type,physiological races and mating type,the genotypes of the isolates were systematically identified.It was found that 1094 strains(58.28%)were defoliating,703 strains(37.45%)were nondefoliating and 80 strains(4.26%)were neither defoliating nor non-defoliating,In 2017,it was found that the proportion of defoliating strains in North and South Xinjiang was 81.94% and 75.03% respectively,and that in South Xinjiang was 31.76% and 28.40% respectively,which indicated that the proportion of defoliating strains in North Xinjiang was significantly higher than that in South Xinjiang.Further analysis showed that the proportion of defoliating strains in the same / similar sampling points was on the rise,and in 2017,they were isolated from the third,sixth and eighth divisions V.dahliae of defoliating type increased(> 5%)compared with that of 2016.The results of physiological type(race)detection showed that all the isolates of Verticillium dahliae in Xinjiang were physiological type 2(race);The mating type analysis showed that all the isolates were MAT1-2,indicating that they did not have the population structure basis of sexual generation.To sum up,the results showed that the defoliating strains has become the dominant population in Xinjiang cotton area,especially in the north of Xinjiang and spread rapidly.3.The whole genome was re sequenced to identify 231994 genetic variations,including 201986 SNPs and 30008 indels,of which 35433 were non synonymous SNPs,which provided an important data support for the construction of genetic variation map and gene positive selection analysis.Based on the genetic variation of the whole population genome,the phylogenetic tree of Verticillium dahliae population in Xinjiang Corps was constructed for the first time.It was found that there were two distinct evolutionary branches of Verticillium dahliae in Xinjiang corps,two polar populations were directly related to defoliating and non-defoliating types,and there was no obvious genetic variation exchange,indicating that there were still two typical asexual Verticillium dahliae in Xinjiang corps The transmission of the lines(defoliating and non-defoliating).Genetic variation and phylogenetic tree analysis also showed that a few strains were independent of the two evolutionary branches,indicating that there were still new clones or variation types of Cotton Verticillium dahliae in Xinjiang production and Construction Corps.In conclusion,through the investigation of Cotton Verticillium wilt damage and isolation and identification of Verticillium dahliae in Xinjiang corps,this paper provides important data and strain resources for the research of Verticillium wilt etiology.Through genotype identification and genome wide genetic variation analysis,it is found that there are still two distinct clones,defoliating and non-defoliating,in Xinjiang corps It has become a dominant population and spread rapidly,which provides an important theoretical and data support for the variation and evolution of population structure and the control of Verticillium wilt.