Improvement Of Heat Tolerance And Identification Of QTLs Conferring Heat Tolerance Using Advanced Backcrossing Introgression Lines In Rice

In this study, four BC2F4advanced backcrossing populations were developed bya widely used elite indica restorers Shuhui527as recurrent parent, Zihui100, Bg90-2,Fuihui838and Gui99as donors which contain24,20,19and20lines respectively.SAS and one-way ANOVA software were used to analyze phenotypic data and detectQTLs for8target traits, including plant height, the number of filled grains per paniclepanicle number per plant, thousand grain weight, yield per plant and spikelet fertility.The main results were as follows:1. Phenotypic performance of advanced backcrossing introgression lines undernormal and high temperature conditions.Based on the performance of mean value and ratio of one trait under twoconditions, panicle number per plant, spikelet fertility and yield per plant were moresusceptible to high temperature than other traits. The number of filled grains perpanicle and total number of spikelets per panicle took the second place. Heading date,plant height and thousand grain weight were more stable than other traits under hightemperature condition. Plant height were increased under high temperature conditionin four populations, It indicated that high temperate may promote the longitudinalgrowth of rice. In addition, yield per plant was highly sensitive to high temperature;panicle number was also sensitive to high temperature, spikelet fertility showedrelatively stable performance under high temperature.Correlation analysis indicated that panicle numbers per plant and spikeletfertility were positive or significant positive correlated with yield per plant in fourpopulations under two conditions. Therefore, it suggested that the reduction of paniclenumber per plant and spikelet fertility might result in the loss of yield per plant. Thematerials were subjected to high temperature for a long duration since the early stagein their whole life, this might be the reason why the panicle number was decreasedunder high temperature condition.2. Analysis of QTLs mapping in advanced backcrossing introgression lines undertwo conditions was studied.A total of37QTLs were mapped in Shuhui527/Zihui100population, of which,8QTLs were detedted under high temperature condition,25QTLs were detected undernormal condition, only4QTLs were mapped under two conditions.21QTLs were mapped in Shuhui527/Bg90-2population,11QTLs were detedted under hightemperature condition,7QTLs were detected under normal condition, and3QTLswere mapped under two conditions.20QTLs were identified in Shuhui527/Fuhui838population,9QTLs were mapped under high temperature condition,11QTLs weremapped under normal condition and no QTLs were mapped under both conditions.12QTLs were mapped in Shuhui527/Gui99population,6QTLs were mapped under hightemperature condition,4QTLs were mapped under normal condition, and2QTLswere mapped under both conditions.In this study, all identified QTLs were located on12chromosomes. qtgw2c andqtgw3b, which were located on chromosomes2and chromosomes3, were detected indifferent populations. What is more, these two QTLs showed negative additive effect.Qtgw2c was detected in Shuhui527/Zihui100and Shuhui527/Gui99population, and itwas also dectected under both conditions in Shuhui527/Zihui100population. Qtgw3bwas detected in Shuhui527/Zihui100and Shuhui527/Bg90-2population and it wasdectected in both high temperature and normal conditions in Shuhui527/Zihui100population. These two QTLs showed negative additive effects, it was suggested thatthe favorable alleles were derived from the recurrent parent. Qtgw3b were more stablethan others which would be very important in rice breeding program.