Molecular Mapping of Adult Plant Resistance Gene to Leaf Rust and Its Relationship with Plant Height in Wheat Cultivar AGS 2038.

Leaf rust disease, which is caused by the fungal pathogen Puccinia triticina, is the most destructive foliar disease of wheat worldwide, and can cause significant yield losses over many cereal geographical regions. Genetic resistance is the most effective, economic, and environmentally safe method to reduce losses caused by this disease. Plant height is an important agronomic trait in wheat that has been found to be associated with many economic traits, including disease resistance. In this study, a mapping population was developed by crossing resistant tall (AGS 2038) and susceptible short (UGA 111729) cultivars to characterize the leaf rust resistance genes in AGS 2038, and to study its relationship with plant height. While both genotypes were susceptible to leaf rust in seedling stage, AGS 2038 was resistant at adult plant stage. Phenotypic evaluation of the parents and the populations (F3 and F4) was conducted under field conditions and natural infection at Plains, GA in 2015 and 2016 growing seasons. While the average disease severity (DS) of AGS 2038 and UGA 111729 was 20 and 70%, their plant height was 84 and 68 cm, respectively. The distribution of the F3/F4 population DS and F4 population plant height showed a transgressive segregation with a mean of 33% (range of 5-90%) and 78 cm (range of 62-93 cm), respectively. Correlation study showed a low and negative (r = -0.34, p<0.0001) correlation between plant height and DS in F4 population. Furthermore, preliminary result from bulk segregant analysis (BSA) indicated that 2 SSR markers are most likely linked to leaf rust resistance in AGS 2038. Currently, we are advancing this population to develop recombinant inbred lines (RILs), which will ultimately be used for QTL mapping using 90K SNPs.