Dynamic QTL Analysis Of Stay Green Related Traits Of Leaf And Non-leaf Organs During Grain Filling Stage In Wheat (Triticum Aestivum L.)

Drought stress is a major environment constraint greatly impacting wheat(Triticum aestivum L.) production. Studies have shown that photosynthetic efficiency can be improved by delaying leaf senescence during grain filling stage. Additionally, stay green wheat exhibited improved resistance to biotic and abiotic stresses. Genes associate with stay green are complex and dynamic process during grain filling period. Based on the combined analysis by conditional and unconditional QTL mapping of stay green related traits of different green organs under different grain filling stage, this study provides new insights into understanding the genetic mechanism underlying the development of stay traits of different organs in wheat and also benefits genetic manipulations through molecular marker-assisted selection (MAS).In this study, a recombinant inbred line (RIL) population consisting of 306 lines was used to analyze the SPAD value, GLAD value and senescence related parameters during grain filling stage under two water regions. Furthermore, the dynamic quantitative trait loci (QTLs) for chlorophyll content of flag leaves were detected by a combination of unconditional and conditional mapping method. A doubled haploid (DH) population consisting of 150 lines was used to analyze the chlorophyll content of flag leaf and nonleaf organs during grain filling stage under two water regions. And the dynamic quantitative trait loci (QTLs) for chlorophyll content of flag leaves and nonleaf organs were detected by a combination of unconditional and conditional mapping method. The results showed that:1. The change of SPAD value and GLAD value of flag leaves during the grain filling stage was a complex process, showing the characteristics of "slow-fast-slow". The phenotypic correlation analysis showed that SPAD was positively significantly correlated with YPP, SNPP and GNPS in the middle stage of grain filling, and SPAD was positively significantly correlated with GW, GT, TGW and YPP in the final stage of grain filling. SPAD was more suitable for rapid screening of stay green materials.2. In the entire grain-filling period, five additive QTLs and seven additive QTLs were detected by unconditional mapping and conditional mapping, respectively. The phenotypic variation explained by individual QTLs ranged from 2.12% to 12.80%. The expression of QTLs for chlorophyll content during grain filling exhibited temporal specificity, most of the QTLs expressed at one certain stage/period, none of the genes controlling chlorophyll content expressed throughout the entire period of chlorophyll development. There were different QTLs expression patterns under different water regimes. A major QTL (Qchl-5A.1) was detected at multiple stages during grain filling, unaffected by genetic background and environmental conditions and might have great prospects for use in marker-assisted selection (MAS) breeding.3. In the entire grain-filling period, fifty-four additive QTLs and twenty-nine pairs of epistatic QTLs were detected by a combination of unconditional and conditional mapping method. The phenotypic variation explained by individual QTLs ranged from 1.02% to 20.95%. The expression of QTLs for chlorophyll content of different green organs during grain filling exhibited temporal and specific. Major QTLs closely linked with marker interval WMC74-Xgwm291-Xgwm410 on chromosome 5 A and Xgwm181-Xgwm340-xgwm247 on chromosome 3B were detected. These important hot-spot chromosome regions played critical roles to QTL functional research and clone.