Association Mapping Of Root Knot Nematode Resistance Traits In Tobacco

Root knot nematode was one of the important diseases which can constraint and harm agricultural production.In the meantime,this disease can infect a large amount of plants and own many of route of transmission.So it was one of the soil borne disease in crops that is difficult to control.And the root knot nematode can jeopardize tobacco.Because of soil crop rotation system and multiple crop index,the loss of production areas has been on the rise.Generally this disease can cause 30% to 50% loss per annum.Now the control effect of many prevention method was not obvious,at the same time have polluted the soil environment.Not only increasing the burden of government,but also not being able to solve the problem fundamentally.Cultivating disease-resistant variety can enhance tobacco itself disease-resistance,that was the most cost-effective solution.There are the rich tobacco germplasm resources in our country,which provides a material basis for the tobacco resistance breeding.Association mapping was a new method that developed gradually in recent years,and molecular markers of associated with plant traits can be found directly.Therefore this study try to find the molecular markers associating with tobacco root knot nematode resistance using association mapping,which can provide the theoretical basis for tobacco root knot nematode resistance breeding task.The materials of this paper were 81 tobacco germplasm materials of five types.The root knot nematode resistance of them are characterized for the set of materials.At the same time,analysis of genetics diversity and population structure were conducted by using SSR markers,and in addition,the linkage disequilibrium(LD)of chromosomes was calculated.At the end,association test between SSR marker polymorphisms with phenotype variation were performed in to identify loci that are responsible to phenotype variations with yield.The major results are as follows: The main results were as follows:1.The resistance characterization of 81 tobacco materials was identified by root knot nematode in 2015 and 2016.There were 5 high sense,45 middle sense,20 middle resistance and 11 resistance in 2015.There were 4 high sense,46 middle sense,22 middle resistance and 9 resistance in 2016.The results showed that characteristic coefficient of variation ranged from 32.96% to 32.96% and the selected materials group had larger phenotypic characters diversity.2.A total of 81 tobacco assections were evaluated for genetic diversity and population structure based on 70 SSR loci.The results showed that a total of 443 allelic variations were detected with an average allele number of 6.2.The PIC(polymorphism information content)ranged 0.18 to 0.91,the average PIC were 0.63.The results showed that the genetic diversity was relatively high among the assecions used in this study.3.By the STRUCTURE 2.3.4 software analysis,the 81 selected tobacco germplasm materials were divided into two main groups P1 and P2,which respectively contained 45 and 36 materials.By Nei genetic cluster analysis,the 81 materials also were clustered into 2 main group.Most of tobacco are of admixture kinship,and the result of population structure analysis was similar to cluster analysis.4.The linkage disequilibrium analysis was carried out on the group,r2 distribution ranged from 0 to 0.2,the average r2 was 0.034,the results showed there existed linkage disequilibrium in the 81 tobacco germplasm materials group.5.Marker-trait association analysis was calculated by General linear model and MLM model in TASSEL 2.1.Four SSR loci were detected significant associated with the tobacco varieties resistant to root-knot nematodes trait.In which,three SSR loci were detected by MLM model.And the PT30123?PT30296 marker were significant associated with the trait,which was detected by GLM ? Q ? K and Q+K simultaneously.