Evaluation Of Hulless Barley Germplasm Resources Originated From Qinghai-Tibet Plateau And Cause Analysis Of The High?-Glucan Content Adessertation

In Qinghai-Tibet plateau,hulless barley is the most important staple food,therefore the breeding activity of hulless barley has been carried out for nearly 70 years.More than one hundred varieties were bred at this period,promoting the yield increase of hulless barley.With the rapid development of Tibetan society and economy,the need of high quality hulless barley has been increased.Therefore,quality has become the main breeding target of barley breeding.?-glucan has been believed to greatly reduce the risk of serious human diseases,including type II diabetes,cardiovascular disease and colorectal cancer.To breed varieties with high?-glucan content has become a hot target in the hulless barley breeding activity.The lack of excellent germplasm resources and the effective breeding methods has hindered the progress.In order to promote the breeding process,it has been necessary to evalute the genetic diversity and the quality characters of hulless barley germplasm resources,select the excellent germplasms and explore the efficient breeding method.In this study,105 bred hulless barley varieties grown commonly and broadly across Qinghai-Tibet plateau,which has been surveyed since 1950,and 3 introduced varieties were selected as representative materials.The genetic diversity of the bred hulless barley varieties in Qinghai-Tibet plateau was estimated by coefficient of parentage(COP).Based on the results of COP analysis and local field performance,the selected bred varieties and some hulless barley accessions were selceted to evalute the quality traits.Based on evaluation results,11 accessions with different?-glucan content were selected as research materials to analyse the association between the?-glucan content and the Hv Csl F6 gene.The following results have been obtained:(1)5778 variety combinations were produced by 108 varieties.16.49%of variety combinations were genetically related.The COP of all combinations ranged from 0.000to 0.750,with an average of 0.054,which was significantly higher than that of the main barley varieties grown in the rest of China and North American.At different era,there was significant difference about the average COP of the combinations.This index was higher at 1970s and 1980s,reaching 0.131 and 0.115,respectively,while this index was lower at the 1990s and the recent decade,reaching 0.045and 0.037,respectively.At different areas,the average COP of the combinations made by the varieties from Gansu Province was highest,reaching 0.260,while this index for Tibet Autonomous Region,Qinghai Province,and Sichuan Province were similar,reaching 0.098,0.131 and 0.155,respectively.Based on the COP analysis,9 bred varieties were identified as important core parents in Qinghai-Tibet plateau,from which,67 varieties had been derived.9 core parents and their 67 derivatives account for 72.38%of investigated bred varieties,the utilization of introduced germplasms has been inefficient,therefore.The genetic diversity of hulless barley cultivated across the Qinghai-Tibet plateau is relatively lower.(2)The?-glucan content of 203 hulless barley accessions was ranged from3.22%-9.50%,with an average of 5.11%.The?-glucan content of 96.06%accessions was ranged from 4.00%to 7.00%.The starch content of the investigated accessions was ranged from 42.28%to 59.91%,with an average of 50.46%.The starch content of93.10%accessions was ranged from 45.00%to 55.00%.The average?-glucan content of the accessions derived from Tibet,Qinghai,Sichuan and Gansu was 5.23%?5.07%?5.05%and 5.21%,respectively.There was no significant difference among the average?-glucan contents of accessions from different areas.The average starch content of the accessions derived from Tibet,Qinghai,Sichuan and Gansu was 50.30%?50.86%?50.53%and 48.91%,respectively.There was significant difference between the average starch content of accessions from Qinghai and Gansu province.11 hulless barley accessions with significant difference in?-glucan content were selected from the 203hulless barley accessions,including 3 varieties and 8 landraces,which were used to analyse the association between the?-glucan content and the Hv Csl F6 gene.(3)16 polymorphic sites of Hv Csl F6 gene were detected within the selected accessions.Two SNPs were located at 5'UTR,8 SNPs at intron 1,5 SNPs at intron 2and 1 SNP at exon 3.A phylogenetic tree was constructed on the basis of the sequences of Hv Csl F6 gene.According to the phylogenetic tree,the investigated accessions were divided into three groups.there was no significant difference among the average?-glucan contents of different groups.Therefore,it was concluded that the relationship between the polymorphic sites of Hv Csl F6 gene and the?-glucan content in matured grain was not obvious.(4)During the endosperm development,at the sampling time of 22^nd DAP(Day After Pollination),there was significant positive correlation between the transcript abundance of Hv Csl F6 gene and the?-glucan content in the matured grain.For waxy or non-waxy barley accessions,at the sampling time of 22^nd DAP,there was significant or highly significant positive correlation between the transcript abundance of Hv Csl F6gene and the?-glucan content in the matured grain,which indicated that the high transcript abundance of Hv Csl F6 gene during the middle stage of endosperm development was one of the causes that led to the high?-glucan content of some hulless barley accessions.(5)At the sampling time of 22^nd DAP,the Hv Csl F6 gene's transcript abundance of waxy accessions was lower than that of the non-waxy accessions,whereas the?-glucan content was higher than or similar with that of the non-waxy accessions.Therefore,the trait of waxy might be the another cause that led to the high?-glucan content.Moreover,there might be a superimposed efffect created by the trait of waxy and the trait of high transcript abundance of Hv Csl F6 gene during the middle stage of endosperm development,which led the?-glucan content of Z999 reach 9.50%.(6)To verify this speculation,waxy barley accession Z1191 and non-waxy barley varieties ZQ25 were used as parents to develop a population of 101 F₆-derived RILs.Based on the results of two-year field experiments of this RILs,4 quality traits of this RILs were analysed,including?-glucan and starch content,the ratio of amylose and the weight of thousand grains.The average?-glucan content of waxy parent and non-waxy parent was 5.78%and 6.83%,respectively and the?-glucan content of this RILs was ranged from 4.11%to 9.08%,with an average of 6.51%.For 65 non-waxy lines,the?-glucan content was ranged from 4.11%to 7.79%,with an average of 5.62%,and for36 waxy lines,the?-glucan content was ranged from 6.69%to 9.08%,with an average of 8.11%.There was highly significant negative correlation between the?-glucan content and the ratio of amylose(r=-0.83).Therefore,it was concluded that the trait of waxy was one of the causes that led to the high?-glucan content.The average?-glucan content of the waxy lines was 44.31%significantly higher than that of the non-waxy lines,which was 40.31%and 18.74%higher than that of their waxy and non-waxy parents,respectively;there were 3 waxy lines with extremely high?-glucan content(>9.00%);which was 55.71%and 31.77%higher than that of their waxy and non-waxy parents,respectively.This results indicated that for the waxy lines,there was the superimposed effect between the trait of waxy and the trait of high transcript abundance of Hv Csl F6 gene during the middle stage of endosperm development.Based on the results of the RILs,making a cross between a waxy barley accession and a non-waxy barley accession with higher?-glucan content could be a feasible method of breeding hulless barley varieties with higher?-glucan content.