Abstract:

Objective Genetic diversity of pepper germplasm materials was analyzed and molecular markers related to fruit color traits were further explored. Method The genetic relationship and diversity of 57 pepper germplasm materials was evaluated by 7 fruit color traits and 20 SSR markers. The generalized linear model (GLM) and mixed linear model (MLM) of Tassel 5.0 software were carried out to analyze the correlation between traits and SSR markers, which then were used for constructing the germplasm fingerprint maps. Result The range of genetic diversity index of the 7 fruit color traits was from 1.58 (peel-L) to 2.08 (pulp-a) and the range of coefficient of variation was 9.07%-51.84%. There was a certain correlation between E value and Lab values of peel and pulp. A total of 107 polymorphic loci were detected by 20 SSR markers, with an average of 5.1 loci per marker. Primer polymorphism information content (PIC) ranged from 0.221 to 0.864, with an average of 0.624. The average values of Shannon’s information index (I) and Nei’s genetic diversity index (H) were 1.3 and 0.646, respectively. The range of genetic similarity coefficient of the 57 pepper germplasms was from 0.069 to 0.915 1, with an average of 0.294. The 57 germplasms were divided into 2 subclusters by systematic clustering, with 28 and 29 germplasms contained in subcluster I and subcluster II, respectively. The population structure analysis showed that the germplasm was divided into 2 subgroups, with 33 and 24 germplasms in subgroup I and subgroup II, respectively, which had high overlap with the results of cluster analysis. A total of 16 markers related to pepper fruit color traits were detected using both GLM and MLM models, and the phenotypic explanation rate was from 6.6% to 13.8%. Marker SSR4 was extremely significantly associated with E value (P < 0.01). SSR6, SSR9 and SSR17 were detected to be significantly associated with the same trait in both models. The fingerprint maps of 57 pepper germplasms were constructed using 9 pairs of core primers. Conclusion This study comprehensively analyzes the genetic diversity of fruit E value and Lab value of 57 pepper germplasms and the genetic diversity based on SSR markers, and constructes the germplasm fingerprint maps, which may provide a certain theoretical basis for the identification of pepper germplasm resources, the screening of excellent germplasm and molecular-assisted breeding.

Key words: pepper, fruit color traits, SSR markers, genetic diversity, association analysis, fingerprint maps