Genetic optimization of seed size, plant height, and tillering traits for enhanced yield in Montana wheat

Abstract

Wheat (Triticum spp.) production is central to Montana State's economy. In 2024, 5.26 million acres of wheat were planted in Montana, accounting for 11.4 % of the United States' total planted acreage. In 2024, nearly half of Montana's wheat acreage was planted with varieties developed by breeding programs at Montana State University. This thesis research directly supports these breeding programs to develop superior wheat varieties for Montana farmers. Natural alleles of Grain Number Increase-1 (GNI-A1) in spring wheat (Triticum aestivum L.) were studied in field experiments to examine their impact on seed size, yield, and protein content. The alleles GNI-A1-105K and GNI-A1-105Y increase seed number without reducing grain quality. Ethyl methanesulfonate (EMS) derived mutant alleles of the Green Revolution gene Reduced Height-1 (Rht-1) were examined in durum wheat (Triticum turgidum L. subsp. durum) and in spring wheat to show how manipulating plant height can improve yield and other traits. Specifically, the alleles Rht-B1b-E529K and Rht-A1-E63K impart an intermediate height phenotype, improving seedling emergence and grain protein content, and increasing grain yields in some environments. Finally, natural and EMS derived mutant alleles of Teosinte Branched-1 (TB1) were tested in durum wheat, spring wheat, forage winter wheat (Triticum aestivum L.), and triticale (Triticosecale spp.) to develop lines with higher tillering potential, and consequently higher grain yields and forage biomass. Introducing one or two nonsense alleles of TB1 into polyploid wheat crops reduces TB1 function, increasing tiller number and tillering plasticity, ultimately improving yields in certain environments. Research on these genes has led to the development of superior Montana adapted germplasm that will help breeding programs to accelerate gains in yield while maintaining high cereal quality. In addition, this research provides wheat breeders around the world with genetic stock and background data they can use to optimize seed size, height, and tillering potential according to their specific goals.