Genome-wide association study of heat stresstolerance traits in spring-type Brassica napus L.under controlled conditions

摘要

High temperatures have a detrimental effect on growth,development,and yield of Brassica napus.Even a short period of heat stress can lead to yield losses of 15%–20%.A collection of spring-type accessions available in Germplasm Resources Information Network(GRIN)were used to assess the effect of short periods of high-temperature stress at the early flowering stage of B.napus.Two sets of accessions with three replications per set were grown in a greenhouse at 22/18°C day/night temperatures.Plants from the second set at the 6-day flowering stage were exposed to heat-stress conditions(maximum temperature up to 35°C)in a plant growth chamber for five days.The heat-stressed plants were then allowed to recover in a greenhouse.Pollen sterility,sterile/aborted pods,and number of pods on main raceme were recorded for both control(set 1)and heat stressed(set 2)plants.Heat susceptibility indices for all three traits were calculated and an association-mapping study was conducted using 37,539 Single Nucleotide Polymorphisms(SNPs)to identify genomic regions controlling the heat stress traits.A total of 5,8,and 7 quantitative trait loci(QTL)were associated with pollen sterility,sterile/aborted pods,and number of pods on main raceme,respectively.Together they explained respectively 46.3%,60.5%,and 60.6%of phenotypic variation.Candidate genes in the QTL regions included genes associated with flowering,male sterility,pollen abortion,embryo abortion reducing pollen development,and pod development.