| The unique terrain,landforms,and ecological environment of Guizhou have nurtured rich rice seed resources.As a type of local rice variety that adapts to special natural habitats such as deep valley shade and deep rot and cold soak in the mountainous areas of southeastern Guizhou,"He" has strong regional characteristics,good quality,and strong stress resistance,and high breeding value.With the widespread promotion of high-yield hybrid rice and the lack of awareness of protecting grass germplasm resources among people,the planting area of grass in southeastern Guizhou has decreased,resulting in the loss of a large number of excellent grass germplasm resources.Although there have been numerous reports on the research and utilization of gramineae germplasm for a long time,there have been few systematic and comprehensive studies on genetic diversity analysis and construction of core germplasm from both phenotypic and molecular levels.This study conducted genetic diversity analysis on 402 cereal germplasm resources based on phenotypic traits and SSR molecular markers,and constructed core germplasm.The aim is to provide reference for the collection and preservation of germplasm resources,germplasm innovation,and rice genetic improvement.The main research findings are as follows:1.The analysis of 9 quality traits showed that most of the cereal germplasm resources exhibited characteristics such as drooping panicles,awning,scattered panicle branches,less prone to lodging,medium maturity,broad egg grain type,yellow glume,white seed coat,and brown glume tip;The genetic variation of 17 quantitative traits reached a highly significant level;Most of the 17 quantitative traits have significant or extremely significant correlations;Principal component analysis showed that 17 quantitative traits were transformed into 6 principal components,with a cumulative contribution rate of 75.89%;Cluster analysis divided 402 germplasm resources into 5 groups,with only 1 germplasm resource in Group I,19 germplasm resources in Group II,59 germplasm resources in Group III,183 germplasm resources in Group IV,and 140 germplasm resources in Group V.2.Genotype analysis was conducted on 402 cereal germplasm resources using 37 pairs of SSR primers.A total of 191 alleles were detected,with an average number of effective alleles of 2.0836,an average number of unbiased effective alleles of 0.7963,an average observed heterozygosity of 0.0486,an average expected heterozygosity of0.3835,an average immobilization index of 0.914,and 22 low degree polymorphic loci.Genetic diversity is not abundant.The analysis of population differentiation coefficient and gene flow showed that the average value of inbreeding coefficient within the population was 0.937,the average value of inbreeding coefficient between populations was 0.942,and the average value of differentiation coefficient between populations was 0.110.11% of genetic variation came from between populations,89% of genetic variation came from within populations,and there was moderate genetic differentiation between populations.There was a difference between 37 pairs of primers in gene flow,with an average of 5.582.gene flow was enough to resist the effect of genetic drift,homogenize,prevent population differentiation,and there was one-way gene flow between populations.Molecular variance analysis showed that the genetic variation between populations and within populations was 10.971% and89.029%,respectively.The genetic differentiation within populations was greater than that between populations.This is consistent with the results of population differentiation based on SSR loci,indicating that genetic variation in grasses mainly originates from individual differences within populations.UPGMA cluster analysis divided 402 cereal germplasm resources into 2 groups,with Group I including 351 germplasm and Group II including 51 germplasm.The group structure analysis based on Structure software shows that when K=2,Δ K shows a clear peak,with 402 germplasm resources divided into 2 groups.K1 group contains 385 germplasm resources,and K2 group contains 17 germplasm resources.The classification of germplasm resources for the two classification methods is roughly the same.Principal coordinate analysis shows that materials originating from Rongjiang have a distant genetic relationship with materials from Liping,Congjiang,and Guangxi.3.Based on 26 phenotypic traits of cereal germplasm resources,the original germplasm was divided into 5 groups according to the difference in spikelet tip color,with 10% being the optimal overall sampling size.The logarithmic proportion method was the best for intragroup sampling,and the cluster sampling method was the best for intragroup sampling.Under the optimal scheme,47 core collections of grass were constructed,retaining 11.69% of the original materials.The mean difference percentage,range coincidence rate,coefficient of variation change rate,variance difference percentage,and phenotypic retention ratio were 12.70%,88.31%,106.41%,23.50%,and 95.77%,respectively.The constructed core germplasm has good abundance and average,which can better represent the original germplasm.4.By comparing and analyzing the effectiveness of the stepwise clustering sampling method and the allele maximization method in constructing core collections,80 core collections were constructed using the stepwise clustering sampling method with a sampling ratio of 20%.The retention rates for the number of alleles,effective alleles,observed heterozygosity,expected heterozygosity,diversity index,and polymorphism information content were 82.34%,101.26%,98.15%,101.22%,101.31%,and 101.08%,respectively.The t-test showed that there was no significant difference in the number of effective alleles,observed heterozygosity,expected heterozygosity,diversity index,and polymorphism information content between the core germplasm and the original germplasm.Principal coordinate analysis shows that the core germplasm is evenly distributed among the original germplasm and has good representativeness. |
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