Drought Tolerance Gene Mining Of Sweet Sorghum Based On Principal Component Regression

As one of the most drought-tolerant C₄crops,sweet sorghum has higher photosynthetic rate than maize and wheat.It has good adaptability to different types of abiotic stresses,and the genome is small.It is an ideal model crop for studying crop resistance mechanisms.At the same time,because of its characteristics of drought tolerance and saline-alkali tolerance,it is of great significance to alleviate the lack of local water resources and the improvement of saline-alkali land in southern Xinjiang.In this study,nine phenotypic traits including plant height,stem thickness,fresh weight of main stem,panicle length,panicle stalk length,panicle stalk diameter,panicle extension,stay green,and grain weight per panicle were selected under normal irrigation and drought stress at late growth stage.The principal components under two environmental conditions were extracted,and genome-wide association analysis was performed on the phenotypes and corresponding principal component scores,aiming to explore the genes related to drought tolerance of sweet sorghum and provide new ideas for drought tolerance gene mapping of sweet sorghum germplasm in southern Xinjiang.The main findings include:（1）The results of correlation analysis and principal component analysis showed that under normal irrigation conditions,the stay-green trait was positively correlated with peduncle length,and negatively correlated with other traits.The cumulative contribution rate of the first five principal components was84.4%.Under drought treatment conditions,the stay-green trait was negatively correlated with the remaining eight traits.The cumulative contribution rate of the first five principal components was 85.6%,which could represent the vast majority of important information.（2）The results of genome-wide association analysis based on phenotypic traits and their principal components showed that 54 significant loci were detected under normal irrigation conditions,41 significant loci were detected under drought treatment conditions,and 27 significant loci were detected under normal irrigation conditions.Four significant loci（chromosome＿1-66669707,chromosome＿2-60880966,chromosome＿3-10788549,super＿506-229）were detected in both cases.Five significant loci（chromosome＿1-45079712,chromosome＿1-54974032,chromosome＿1-66669707,chromosome＿7-6855479,super＿33-195192）were detected under the two conditions.The normal irrigation treatment and its principal component results detected 14 significant loci（chromosome＿1-17128169,chromosome＿1-20237568,chromosome＿1-45079712,chromosome＿1-54427410,chromosome＿1-66669707,chromosome＿3-12995488,chromosome＿3-63949295,chromosome＿5-53559861,chromosome＿6-22967016,chromosome＿7-50073034,chromosome＿7-60970528,super＿265-5270,super＿31-205253,super＿506-229）;eleven significant loci（chromosome＿1-54974032,chromosome＿1-66669707,chromosome＿3-18244518,chromosome＿5-54372634,chromosome＿5-56804936,chromosome＿6-153673,chromosome＿6-40248711,super＿15-2036269,super＿31-168637,super＿33-195192,super＿72-97762）were detected by drought treatment and its principal component results.The results of association analysis are different under different environmental conditions.The results of genome-wide association analysis based on principal component regression and the results of genome-wide association analysis based on phenotypic traits can verify and complement each other,and then more candidate genes can be mined.（3）A total of 117 significant loci were detected in 9 phenotypic traits and their principal components of sweet sorghum,which were distributed on 10 chromosomes and super chromosome segments,and 38genes were annotated.The significant SNP site chromosome＿1-663053 may be a candidate gene for drought tolerance.