Evaluation Of Genetic Diversity And Ecological Adaptability In Tibet Barley Germplasm

Tibet barely germplasm had high genetic diversity.Semi-wild barley and landraces were major sources of genes new barley varieties.Growing area and production account for 60%and 55%of the total grain in Tibet,respectively,and therefore the sustainable development of barley plays an important role in food safety in Tibet.Heading date is an important domesticated and agronomic trait,which directly affects yield and quality of barley.Diversity analysis of heading date,identification of growth habit and comprehensive evaluation of main agronomic traits will help us to better understand the wild adaptabtion of Tibetan barley germplasm in highland agricultural eco-environment.Phenotypic variation and its evaluation under different environments provides the basic information for effective utilization of highland barley germplasm.In this study,Tibetan barley germplasm including semi-wild barley,landraces,cultivars from different breeding periods,and elite barley variety of Qing-Tibetan highland was used to identify the growth habit,agronomic traits,and phenotypic variation in different environments.The main results are summarized as follows.1.Assessment of growth habit and ecological adaptationTo improve the utilization of Tibetan barley germplasm and select appropriate parents in hybridization breeding,the growth habit and heading date diversity of 1,605 Tibetan barley germplasm were evaluated under the spring and autumn sowing conditions in Nyingchi and Lhasa,Tibet.The growth habit was determined by the difference in heading date observed in two spring sowing time in Lhasa,i.e.normal spring sowing I and 10 days later spring sowing II.The results showed that 96.2%of the landraces are spring barley,which distributed in all three ecological regions;the winter barley accessions are mainly originated from the southeastern ecological region of Tibet.Shannon-Wiener’s analysis showed that the heading date diversity under spring-sown environment had higher diversity than did the autumn-sown environment.The Lhasa region had the highest diversity in spring sowing,followed by the Nyingchi spring-sown environment,and the Nyingchi autumn-sown environment had the lowest diversity.In the same environment,landraces had higher diversity than did the modern varieties.A total of 368spring-type landraces and 21 varieties were stable across environments,and the cultivar Kangqing 3 had the highest stability among all tested materials.2.Diversity analysis for agronomic traitsMost characteristics in newly-bred barley varieties are superior to those of landrace,due to the positive selection on yield-related traits modern hydridezation breeding.Genetic gain of breeding is mainly reflected in the increase in grain number and weight per panicle.Compared with other regions in Qing-Tibetan highland,lower genetic diversity was observed in Tibetan varieties,while the overall performance of traits is superior.Tibetan barley germplasm was divided into four categories according to cluster analysis.Class I had the best overall performance,class II had the most tiller number,and class III had the least tiller number,the other traits were medium in clases II and III.The overall performance of class IV is the worst.Principal component analysis and stepwise regression analysis showed that except for panicle length which has a lower impact on comprehensive phenotype,five other traits could be used as the main indicators for phenotypic identification in barley,explaining most variation,i.e.R~2 of 0.999.3.Analysis of molecular markers of vernalization genes Hv VRN1 and Hv VRN2Six haplotypes were identified in Tibetan barley germplasm totally,those is Hvvrn1(v1),Hv VRN1-1(V1-1),Hv VRN1-4(V1-4),Hv VRN1-6(V1-6),Hv VRN1-8(V1-8),and Hv VRN1-9(V1-9).The dominant Hv VRN2(V2)was major genotype and only 10 accession were recessive Hvvrn2(v2).Haplotypes in semi-wild barley and landraces were more abundant than other types of cultivars.V1-8 and V1-4 were the main haplotypes in wild barley,accounting for 90.2%and 7.4%respectively,and the remaining haplotypes account for 2.4%.V1-8 and V1-9 are the main haplotypes in landraces,local old landraces and improved cultivaes.Haplotype V1-8 accounted for 95.3%,92.4%and 95.2%,and V1-9accounted for 4.2%,6.8%and 5.4%respectively.In Tibetan varieties,V1-8 and V1-9 were the dominant haplotypes in winter and spring type,accounting for 79.1%and 16.3%respectively.We also found that haplotype V1-8 was distributed in all ecological regions.V1-9 of located in landraces and the V1-4 located in semi-wild barley were mainly distributed in the Nyingchi,and the remaining haplotypes were distributed in the ecological areas such as Chamdo,Lhoka,and Lhasa.