Rising global temperature is perhaps the single most critical factor in wheat production, as every degree Celsius rise in temperature reduces grain yield by more than 5%. CIMMYT possesses an extraordinary germplasm collection as well as sequence information on a majority of the lines. In addition, a collection of lines identified after years of field testing for variable response to heat and water stresses is available from breeders and physiologists. A set of 300-400 lines will constitute a diversity panel for genetic association mapping of stress tolerance. The panel will be grown in growth chambers and subjected to various day and night temperature treatments. Seedling biomass at the 4-6 week stage will be one of the components to map, the other being leaf photosynthate (fructose, glucose, starch, and sucrose). As photosynthate production capacity is the primary determinant of biomass accumulation, of which grain yield is a component, its continued production under stressful conditions will be the focus of our work. Aside from identifying lines for immediate use in setting up crosses to breed for stress tolerance, this project will provide QTL for various photosynthate components under normal and stressful conditions. In some cases, the QTL might be significant enough and on short enough of a chromosomal interval that candidate genes could be identified for validation either by gene editing or a transgenic approach.
Compile a diversity panel of bread wheat lines based on historical field data available and sequence information. Determine growth chamber conditions that result in a 20-30% reduction in seedling biomass at elevated temperature (day as well as night) as compared to normal growing conditions. Grow the diversity panel in the growth chamber (Biosafety Laboratory), collect leaf samples before and after temperature treatment in the morning (to measure photosynthate remobilization and utilization efficiency at night) and evening (photosynthate production and storage capacity). Dry leaf samples, grind in a GenoGrinder, extract metabolites, and measure photosynthetic components using 96-well assays. Harvest seedlings after 4-6 weeks, dry, weigh, and carry out metabolite assays on the leaves and stems (for reserves). Identify QTL for photosynthate production under normal and heat stress conditions through genetic association mapping. Several publications (photosynthate profile of a growing plant, QTL for photosynthetic components, QTL for stem reserves, QTL for heat tolerance) could be prepared by this stage. The follow-up project would aim to: (1) employ these QTL directly to identify additional lines in the CIMMYT germplasm collection to provide additional options to breeders; (2) validate QTL by generating near-isogenic lines in a series of genetic backgrounds; and (3) identify potential gene candidates to be validated by gene editing or transgenic expression.
Ph.D. in genetics, physiology, biochemistry, or a related field