IDENTIFICATION OF QUANTITATIVE TRAIT LOCI (QTL) FOR RESISTANCE TO SOIL- BORNE PATHOGENS FUSARIUM CULMORUM AND HETERODERA FILIPJEVI IN WHEAT (TRITICUM AESTIVUM L.)
Thompson, Yvonne Alexandria
MetadataShow full item record
Wheat (Triticum aestivum L.) is one of the world’s staple crops essential to global food security; however, its profitable production can be threatened by soil-borne diseases. The fungus, Fusarium culmorum, and cereal cyst nematode, Heterodera filipjevi, are two types of soil-borne pathogen/pest that drastically reduce yield in wheat production areas worldwide. However, few sources of plant resistance have been identified for either, making knowledge of genetic regions associated with resistance imperative. An integrated approach, requiring the use of host plant resistance, is necessary for management of these diseases. Our aim is to contribute to this integrated approach by identifying sources of resistance for applied use. We sought to identify quantitative trait loci (QTL) related to genetic resistance against F. culmorum in diverse germplasm. A population of 600 wheat accessions was phenotyped for disease using an enhanced screening system to better separate susceptible and resistant responses. The accessions screened showed differential responses among genotypes of wheat, reflecting genetic variability under disease pressure. Genotypic data was acquired using the Illumina wheat 9K iSelect SNP chip. A Genome-wide Association Study (GWAS) was conducted using the R software and FARM CPU package to evaluate marker-trait associations. Marker-trait associations at or above the Bonferroni threshold of 0.05 were identified on chromosomes 1A, 5A, and 6B. Chromosomes 5A and 6B may likely reflect novel sources of resistance. We also aimed to identify quantitative trait loci (QTL) related to genetic resistance against H. filipjevi in spring wheat breeding lines and cultivars adapted to the Pacific Northwest. Naturally infested soils, containing predominately H. filipjevi, were used to screen 138 wheat varieties, revealing variability in response to nematode infection. The selected germplasm was genotyped using a genotype-by-sequencing approach and marker-trait associations were evaluated using the R software and FARM CPU package. Marker-trait associations at or above the Bonferroni threshold of 0.05 were identified on chromosomes 2B, 5B, and 7B. The identified QTL for resistance should be validated and further explored for their usefulness in marker assisted breeding.