Genetic Variation,QTL And QTL-by-environment Interactions For Seed Vitamin E In Soybean

Vitamin E?VE?is an important antioxidant supplement for human health.Soybean?Glycine max?Linn.?Merr?seed extracts are the main source of VE supplements.Therefore increasing the VE content of soybean seeds is important issue in breeding programs.In this study,238 F6:7 recombinant inbred lines?RILs?were created by single-seed-descent from a cross between a high VE cultivar,‘Beifeng 9' and a low VE cultivar,‘Freeborn'.Based on the RILs that were planted in three locations across two years,genetic analysis and correlation analysis of individual and total VE in soybean seeds were performed.A genetic map was constructed using 174 polymorphic simple sequence repeat markers?SSR?.QTL associated with individual and total VE were identified by composite interval mapping analysis?CIM?.The mixed model-based composite interval mapping?MCIM?was used to analyse the additive QTL,additive × additive epistatic QTL pairs,additive QTL × environment,and epistatic QTL pair × environment interactions respectively.The major results were as follows:?1?The phenotypic variation of RILs for individual and total VE contents was broad.Individual and total VE of soybean seeds were not only affected by genes,but also were largely affected by environments.?2?Among individual and total VE contents,except the correlation between ?-tocopherol and ?-tocopherol was not consistent across locations and years,all tocopherol contents were significantly correlated with each other.There was a significant negative correlation between ?-tocopherol and node number,while was not consistently correlation between ?-tocopherol and other agronomic traits across multiple environments.Other tocopherols and total VE were not consistently correlated with agronomic traits across multiple environments.Protein and oil were not consistently correlated with ?-tocopherol and ?-tocopherol,respectively.?3?Sixty-six QTL for contents of individual and total VE,twenty-one for ?-tocopherol,seventeen for ?-tocopherol,thirteen for ?-tocopherol and fifteen for total VE were detected by composite interval mapping analysis.The QTL were located on chromosomes 9,10,15,18 and 19,respectively.Phenotypic variance underlain by each QTL ranged from 2.4% to 32.6%.Two major QTL?BARCSOYSSR₁0₁140-BARCSOYSSR₁0₁188 and BARCSOYSSR₁5₀855 to BARCSOYSSR₁5₀887?associated with ?-Toc,?-Toc,?-Toc and total VE contents were mapped on chromosomes 10 and 15,respectively.They explained 12.0% and 32.6% of phenotypic variance for ?-tocopherol;5.5% and 13.0% for ?-tocopherol;6.6% and 23.6% for ?-tocopherol;and 19.6% and 21.8% for total VE.QTL intervals BARCSOYSSR₁5₀790-BARCSOYSSR₁5₀855?Q?15₁,Q?15₁?,BARCSOYSSR₁5₁113-BARCSOYSSR₁5₁159?Q?15₃,Q?15₂,QTVE15₄?and BARCSOYSSR₁5₁159-BARCSOYSSR₁5₁190?Q?15₄,Q?15₅,QTVE 15₅?were associated with ?-tocopherol and explained 22.2%,23.8% and 24.4% of the phenotypic variation in multiple environments.BARCSOYSSR₀9₁098BARCSOYSSR₀9₁128?QTV E9₁?and BARCSOYSSR₁5₀887-BARCSOYSSR₁5₀935?QTVE15₂,Q?15₃?associated with total VE content explained 21.8% and 16.4% of the phenotypic variation in two environments.These QTL allowed for marker-assisted selection for cultivars with high VE contents.?4?Using mixed model-based composite interval mapping?MCIM?of QTLNetwork V2.0,eleven additive QTLs associated with individual and total VE contents were detected.Among them,five QTLs were confirmed by CIM analysis,and six QTLs were only identified by MCIM analysis.Three QTL intervals?Q?10₃,Q?18₃ and Q?18₄?associated with ?-tocopherol,one QTL intervals?Q?15₃?associated with ?-tocopherol,one QTL intervals?Q?10₄?and one QTL intervals?QTVE10₂?associated with total VE showed additive × environment interaction effects?AE?in different environments.Moreover,2,3 and 4 epistatic pairs of QTLs were found to be associated with ?-tocopherol,?-tocopherol and?-tocopherol contents.Among them,two epistatic pairs of QTLs associated with ?-tocopherol content?Q?e₁ and Q?e₂?showed epistasis × environment interaction effects?AAE?.The QTLs identified in multienvironments could provide more information about QTL by environment interactions and could be useful for the marker-assistant selection of soybean cultivars with high seed VE or/and ?-tocopherol contents.?5?Using MCIM model,twelve additive QTLs associated with plant high,node number,branch number,pod number,seed number per plant,seed weight per plant and 100-seed weight were detected.Among them,eleven QTLs?seven marker intervals?were associated with individual and total VE contents.These marker intervals would have great potential value for marker assisted selection for high VE content and promotions for agronomic traits.