Identify Genomic Regions Associated with Membrane Integrity in Wheat Under High Temperature Stress Conditions.

Identify genomic regions associated with membrane integrity in wheat under high temperature stress conditions

 M.A. Babar, K. Vijayalakshmi, A.K. Fritz,, B.S. Gill and G Paulsen

 High temperature stress during grain filling is a common limitation in many wheat growing regions of the world including Central and Southern Great Plains of the USA. One of the major effects of high temperature on plants is to alter different membrane structure, such as plasmamembrane (also called plasmalemma or cell membrane) and photosynthetic membranes (Thylakoid membrane). Thylakoid membranes and Photosystem II are very thermolabile and their activity is either greatly reduced or damaged under high temperature stress. Thylakoid membrane (TMD) and cell membrane (CMS) damage have been reported to be important traits associated with heat tolerance in wheat. Molecular characterization of those traits can help wheat breeders to make effective genetic gain for heat tolerance. The objectives of study were to identify genomic regions associated with membrane integrity. A F5-derived recombinant inbred line population (RILs) was developed from elite Kansas line Karl 92 (heat sensitive) and Australian wheat line, Ventnor (heat tolerant). Initial QTL mapping project demonstrated that several QTLs were associated with senescence in this population. In the follow up study, the population was evaluated for TMD (estimated by chlorophyll fluorescence), CMS and SPAD-chlorophyll content in F₉ and F₁₀ generations under long-term post-anthesis heat stress conditions. Plants were exposed to post anthesis the high temperature stress under 36^o/30^oC day/night temperature with 80% relative humidity and 16/8 hours photoperiod. TMD and SPAD-chlorophyll content was estimated after 0, 4, 7 and 10 days after post-anthesis high temperature stress, while CMS was measured at 7 and 10 days only. The genetic map was developed based on 450 molecular markers which included 259 AFLPs, 189 SSRs, and a STS. Two quantitative trait loci (QTLs) were significantly associated with those traits. Two QTLs demonstrated significant association with all traits and are located on 7AL and 6AL. The QTL located on 7AL explained 15% to 18%, of total phenotypic variation for those traits, while the other QTL located on 6AL explained 10% to 14% phenotypic variability. The results demonstrated that the two QTLs have pleiotropic effects for the three traits. Markers associated with those QTLs have potential to be used in marker-assisted selection for high temperature stress tolerance in wheat.