| In this research,93 germplasms of Bromus inermis Leyss.from China and other countries were selected as study object.Genetic diversity at phenotype and molecular level was studied.Genetic structure was analysized to define the direction of genetic evolution.The germplasms of Bromus inermis Leyss.were screened for constructing core germplasm to excavate high yield materials with excellent characteristics and high potential,and to create and utilize new germplasm rationally.This work was of great significance for accelerating the breeding process of Bromus inermis Leyss.,solving the problems of grassland ecological construction and strengthening the protection of biodiversity.The main results were as followed:1.At the phenotypic level,there was a high genetic diversity in 93 germplasm resources of Bromus inermis Leyss.(1)The order of genetic Shannon's information index(H')from large to small was:stem weight > dry weight > pitch number > fresh weight > leaf weight > plant height > leaf length > stem diameter > leaf width > ear length.The genetic variations of fresh weight,dry weight,stem weight,pitch number and plant height were reletively abundant.(2)The comprehensive ranking of genetic progress was:stem weight > pitch number > plant height > leaf weight > leaf width > ear length > leaf length > fresh weight > stem diameter > dry weight.(3)comprehensive ranking of 93 germplasms was conducted by the principal component analysis of characterstics,10 excellent germplasms were selected.2.At the molecular level,there were weak genetic correlation and high genetic diversity among the 93 germplasms of Bromus inermis Leyss.(1)Three groups were obtained through the phylogenetic tree analysis.Germplasms of group I was the ancestor population,and that of group II and group III were evolutionary subgroups.The originated location of the ancestral population(group I)was at the junction of Eurasia and West Asia in Russia.(2)23 germplasms of group II were divided into 6 subgroups,among which the bred cultivar Wuyi of Russia at the subgroup 5(II-5)was at a high level of evolution.3 germplasms of group III were divided into 12 subgroups,among which the Chinese bred cultivars at a high level of evolution,they were Xilingol marginal brome,Gong-nong awless brome,Qitai awless bromeand Wusu NO.1in the subgroups 7,9,10 and 11 respectively.Wusu NO.1 from Xinjiang showed the highest level of evolution.(3)Germplasms of group II had higher grass yield,while those of group III had wider adaptability.Parents can be selected from the above two groups.Hybrid breeding should be adopted to create more genetic variation,strengthen selection pressure and improve breeding efficiency in the future.3.Based on the genome-wide association analysis,five SNP markers with significant correlation to leaf weight traits were screened out.The phenotypic contribution rate to leaf weight of Marker 11780,Marker 12723,Marker 15908,Marker 185742 and Marker 31669 was 3.12%,2.46%,4.15%,2.31% and 3.31% respectively.Their cumulative phenotypic contribution rate was 15.53%.Due to the small number of samples,no positive SNP markers were obtained for the other 9 traits.The SNP core markers were sceened were analyzed.The number of SNP core markers for plant height,ear length,stem diameter,pitch number,leaf length,leaf width,fresh and dry yield,stem and leaf weight was 20?24?19?21?29?19?25?26?31 and 33 respectively.The?r cumulative phenotypic contribution rate was 53.21%?8.35%?52.34%?60.56%?49.38%?50.21%?46.67%?54.37%?39.39% and 62.12% respectively.A total of 247 core SNP markers were obtained,which could help advancing the efficiency of molecular identification for Bromus inermis Leyss.new culvitars.41 core germplasms were obtained by sampling in groups II and III.4.There were extensive genetic variations in the yield-related seed traits among 41 obtained core germplasms.(1)5 traits with higher coefficient of variation than the mean were ear interpitch length,number of florets,number of spikelet,number of spindle branches,and seed yield.The coefficient of variation was respectively 35.14%,29.32%,26.98%,22.78% and 22.71%.(2)The number of florets(0.75),spikelets(0.653),number of spikelet(0.505)and number of ears(0.454)had a significant positive correlation with the seed yield.(3)The comprehensive ranking of genetic parameters was:number of florets,seed yield,number of spindle branches,number of spikelet,ear interpitch length,caryopsis length,glumelle length,first interpitch length of ear,spikelet length,number of spikelet florets,first glume length,second glume length,ear length,first interpitch length of rachis,number of ear pitch,lemma length,glumelle width,lemma width.(4)41 core germplasm were comprehensively ranked by principal component analysis,10 excellent germplasms were selected.Therefore,there was extensive genetic variation,rich genentic diversity,obvious genetic differentiation and clear systematic evolution in Bromus inermis Leyss.In the future,hybridization and breeding should be carried out in group ?and ? to create more genentic variation,constantly strengthen selection pressure and improve breeding efficiency. |
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