Identifying Potential Avenues for Increasing GRAIN Number UNDER Post Anthesis HEAT Stress Condition.

The genetic progress of grain yield in wheat ranged from 0.3% to 1.0% per year during the last century, but needed to be increase by 1.8% to meet global food demand by 2050. High temperature is a major limitation to achieve that goal. High temperature stress during post anthesis stage is a common phenomenon in the USA and other wheat growing areas globally. Efforts to make effective genetic gain in yield will require identification of potential traits that aids in increasing grain number per m^-2 and an increase in harvest index. An effective avenue to increase grain number will be through increased partitioning of useful biomass towards sink during post anthesis stage.  We aim to identify traits and markers enabling breeders to discriminate such useful biomass for better spike partitioning. Fruiting efficiency, the ratio between grain number and spike chaff dry weight, has been reported as potential trait for improving spike partitioning and thus increasing grain number. Our preliminary data revealed significant genotypic variation for fruiting efficiency in 246 US soft wheat association panel under post anthesis high temperature stress condition. We found significant positive correlations between fruiting efficiency with grains m^-2, grains spike^-1, yield, spike harvest index, grain filling duration, and negative correlation with chaff weight m^-2. Our results will demonstrate the noble traits which are associated with grain partitioning and the genetic loci controlling those noble traits, and improve harvest index and grain yield under high temperature stress condition.