Genome-wide association study of heat stress-tolerance 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℃ 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℃) 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.