Analysis On Combining Ability And Heterosis Of Eight Spring Cabbage Inbred Lines

Cabbage（Brassica oleracea var.capitata L.）is one-year-old or two-year-old herbaceous plant of Brassicaceae and Brassica.Spring cabbage has less pests and good commodity,so it is loved by people.Through combining ability and heterosis,excellent parents and hybrid combinations of spring cabbage were screened,which provided reference for the selection of spring cabbage varieties in actual production,and improved the yield and quality of spring cabbage.At the same time,SSR and other molecular markers were used to predict heterosis,which can improve breeding efficiency.It is of great significance for future breeding work and actual production of cabbage.In this study,eight spring cabbage inbred lines were used as parents,and 28hybrid combinations were prepared by complete diallel cross method for two years of field experiment.The agronomic traits of parents and F₁ generation were measured,and their combining ability and heterosis were analyzed.Determination of nutritional quality traits of some hybrid combinations.The yield heterosis was predicted by SSR molecular marker technology.The results are as follows:1.The results of correlation analysis,principal component analysis,variance analysis and Core length performance analysis of agronomic traits showed that there was a significant correlation between each agronomic trait,and the yield was greatly affected by the head width and head height and core length.Principal component analysis reduced 13 agronomic traits into 4 main comprehensive evaluation indexes.Its cumulative contribution rate is 80.805%.Twenty-eight hybrid combinations had extremely significant indigenous differences in agronomic traits except degree of compactness,and most agronomic traits were greatly affected by the environment.The core length of 28 hybrid combinations were all less than one-half of the head height.2.The analysis of combining ability showed that the GCA of parents had significant or extremely significant differences in each agronomic trait.The SCA of 28crosses had significant or extremely significant differences in agronomic traits except whole plant weight and degree of compactness,and GCA and SCA under most traits were greatly affected by environmental factors.Two excellent parents,Gp97-1 and DH198,were screened out.The two parents had higher GCA yield and higher yield potential than other parents.At the same time,they were also better than other parents in the comprehensive GCA performance of traits.They can be used as backbone parents for subsequent breeding research.The combination with the highest SCA in the whole plant weight and the single ball weight was Gp37-4×DH02-5 and Gp37-4×DH198,respectively.The combination with better performance in the comprehensive SCA of13 traits was Gp97-1×Gp585-3,DH198×DH23-3,DH123-8×Gp151,Gp37-4×DH198,DH23-3×Gp585-3 and DH23-3×Gp97-1.3.The results of heterosis analysis showed that 26 combinations showed significant positive heterosis in MPH,HPH and CKH of yield,and the heterosis of Gp37-4×DH198 and DH23-3×Gp97-1 was higher than that of other combinations.According to the characters,Gp97-1×Gp585-3,DH198×DH23-3,Gp37-4×DH198,Gp37-4×DH02-5 and Gp37-4×Gp151 were strong heterosis combinations.Combining the special combining ability and heterosis performance of the combinations under various agronomic traits,five hybrid combinations with excellent yield performance,Gp97-1×Gp585-3,Gp97-1×DH02-5,DH198×DH23-3,Gp37-4×DH198 and Gp37-4×DH02-5.At the same time,three combinations Gp97-1×Gp585-3,DH198×DH23-3and Gp37-4×DH198 with the best comprehensive performance on each trait were screened out.These combinations are better parental combinations and can improve the comprehensive performance of spring cabbage on multiple traits.Gp97-1×Gp585-3 and DH198×DH23-3 performed well in nutritional quality traits.Except for individual traits,there is basically a significant or extremely significant positive correlation between SCA and heterosis.The sum of GCA of parents is positively correlated with extremely significant or extremely significant heterosis over standard heterosis.4.Genetic distance and cluster analysis showed that at the genetic similarity coefficients of 0.60 and 0.69,the eight parents can be divided into three and four groups,respectively.There is no difference between DH198 and DH23-3 at the genetic similarity coefficient of 0.88.The genetic relationships of inbred lines Gp97-1,Gp37-4,DH198 and DH23-3 are close,and the genetic relationships of DH123-8 and Gp151are also close,while the genetic relationships of DH02-5 and other parents are far.In the MGD range of 0.29–0.69,the yield strong heterosis combinations were more distributed,and the probability of breeding high yield strong heterosis combinations under medium genetic distance was greater.