Association Analysis Of Drought Resistance Characters And Drought Resistance Candidate Genes And Identification Of Superior Alleles In Barley

Barley(Hordeum vulgare L.)is one of the most important crops in China,especially in Tibet,where it accounts for more than half of the total grain production and is a healthy food for human consumption and animal feed.In this experiment,174 barley test materials were selected,and nine measurements of germination rate,germination potential,germination index,shoot length,root length,shoot fresh weight,shoot dry weight,root fresh weight and root dry weight at the germination stage of barley were identified for drought resistance using PEG-6000 simulated drought stress.In addition,the same materials were planted in drought shelters set up in the field with two treatments of drought and irrigation,and nine trait indexes of single plant biomass,effective spike number,plant height,spike length,main spike weight,main spike grain weight,main spike grain number,thousand grain weight and single plant yield were measured at the establishment stage.Using the drought resistance candidate genes obtained from the previous barley transcriptome screening as the basis,we designed primers to PCR amplify the barley genomic DNA,sequenced the amplification products by Sanger,and correlated the measured indicators with the SNP sequencing results in two different fertility periods to mine the SNP loci associated with drought stress in barley.While screening drought-tolerant germplasm at the germination and establishment stages of barley for positive trait indicator identification in response to drought stress,superior alleles in response to drought stress were mined.The main findings were as follows.(1)By comparing the drought resistance metric values(D values)of174 barley materials at the germination stage,the materials with the strongest drought resistance were h183(0.776)and h189(0.673),and 51 barley materials with very strong drought resistance,62 materials with moderate drought resistance,and 61 materials with weak drought resistance were obtained by cluster analysis of D values;gray correlation analysis showed that the drought resistance coefficients of root fresh weight and root dry weight had the highest correlation with the drought resistance metric values,and root fresh weight and root dry weight could be used as important indicators of drought resistance at the germination stage.The correlation between the drought resistance coefficients of root fresh weight and root dry weight and the drought resistance metric values were the highest,and root fresh weight and root dry weight could be used as important indicators of drought resistance during the germination period.(2)The principal component analysis of the nine indicators of barley at maturity showed that the economic traits(main spike weight,main spike grain weight and yield per plant)were highly loaded on the first principal component;the correlation analysis showed that the main spike weight was positively correlated with all indicators except for the effective number of spikes,which was significantly negatively correlated with most of the indicators;the gray correlation analysis showed that the drought resistance coefficient(DC)of main spike weight had the highest gray correlation with the D value.The results of gray correlation analysis showed that the coefficient of drought resistance(DC value)of main spike weight had the highest gray correlation with the D value,and the main spike weight could be used as an important trait index of drought resistance in barley at the adult stage,and the measurement was conducted for the trait index with high correlation,which was not only a simple identification method,but also could effectively identify the drought resistance of barley germplasm while reducing the workload.(3)The correlation analysis between the values of drought tolerance coefficients of sprouting traits and the values of drought tolerance coefficients of adult plant traits showed that the plant height at the adult plant stage was highly significantly and positively correlated with the shoot fresh weight,shoot dry weight and shoot length at the sprouting stage,and whether the shoot length and above-ground biomass of barley at the sprouting stage determined the plant height at the adult plant stage needed to be further investigated and verified in the subsequent experiment.By cluster analysis,it was observed that the materials with consistent drought resistance in two different fertility periods were 13 materials with strong drought resistance,15 materials with moderate drought resistance and 22 materials with weak drought resistance.(4)Through association analysis of traits in different periods of barley,a total of 19 pleiotropic loci were identified,among which 6 loci were associated at both germination and establishment stages.The Chr6H＿239 locus was associated with several traits in different periods,including main spike grain weight,plant height and root length and root fresh weight at the establishment stage,indicating that this locus may be a key locus in response to drought stress and needs to be focused on in further studies.All five traits in the adult stage association analysis were significantly associated with Chr5H＿647 on LOC122395995 drought resistance gene,and when one locus was associated with multiple traits at the same time,it indicated that this locus was a key SNP locus and was involved in response to drought stress in barley.The significantly associated SNP locus markers for drought traits obtained in this study provide an important reference for drought breeding research in Tibetan barley.