Evaluation On Genetic Diversity And Cross Combination Of Tobacco Germplasm Resources In Sichuan Province

Sunflower germplasm represents a large proportion of tobacco genetic resources,and at the same time,it provides material for genetic breeding of sunflower.In this study,37 phenotypic traits of 52 newly collected sun-dried tobacco germplasm from Sichuan were analysed for genetic diversity,and correlation and principal component analyses were conducted to determine the richness of genetic diversity and the degree of variation in this material.At the same time,the phenotypic data were investigated for 40 sunflower crosses,and the scores of 23 indicators and each principal component were analyzed using principal component analysis and subordinate function analysis to evaluate the crosses.The main research results are as follows:(1)The results of phenotypic traits showed that the genetic diversity indices of 11 botanical traits ranged from 0.33 to 1.14,indicating that the collected materials were rich in genetic diversity and had a large degree of variation;the results of correlation analysis showed that most of the 18 agronomic traits had significant or highly significant interrelationships;the principal component analysis of plant traits extracted a total of three principal components,with a cumulative contribution of 83.715%.The cumulative contribution of the first four principal components extracted for leaf traits was 86.42%;21varieties were screened as having strong resistance to three field diseases,namely cyanobacteria,black stem disease and potato Y virus,accounting for 40.02% of the total number of resources.(2)20 pairs of core SSR markers with high polymorphism were screened and used for SSR typing.74 alleles were detected,with an average of 3.7 alleles;the average Nei’s diversity and Shannon’s diversity were 0.5728 and 0.8928 respectively;the polymorphic information content The variation in polymorphic information content(PIC)ranged from0.3503 to 0.7946,with an average of 0.6104;the variation in genetic distance ranged from0.127 0 to 0.6897,with an average genetic distance of 0.417 2.The 52 germplasm resources were clustered into seven taxa based on SSR markers,containing one,nine,five,seven,eight,four,seven and 11 materials,respectively.(3)The coefficients of variation of 18 agronomic trait indicators in the F1 generation of 40 sun-dried tobacco cross combinations ranged from 11.02% to 42.91%,and the coefficient of variation of the angle between the main and lateral veins was relatively high,with a mean value of 58.81°;the coefficients of variation of the chemical composition of the modulated tobacco ranged from 5.36% to 78.52%,with the largest coefficient of variation being nicotine.On the basis of the principal component analysis,the top 10 Sichuan sun-dried tobacco crosses with the best overall performance were selected by using a comprehensive evaluation of the affiliation function.