Identifying Molecular Markers for Resistance to Septoria tritici Blotch in Bread Wheat

Abstract

Abstract Septoria tritici blotch (STB) is a foliar disease of wheat (Triticum aestivum L.) caused by the ascomycete fungus Zymoseptoria tritici. STB is a polycyclic disease and represents a significant threat to wheat production, reducing yield and grain quality. The control of STB is mainly based on fungicides. Unfortunately, Z. tritici populations have evolved high resistance levels to some of these fungicides, causing them to lose their efficacy. Therefore, increasing STB resistance through plant breeding is the most cost-effective and environmentally friendly method for control. A recombinant inbred line (RIL) population was developed from a cross between a cultivar moderately susceptible to STB, ‘Madsen’ (PI 511673), and ‘Foote’ (PI 599663), which has provided moderate resistance to STB in the Pacific Northwest (PNW) region of the U.S. The RIL population, consisting of 217 lines, was phenotyped across multiple environments for STB response and genotyped using Illumina HiSeq 3000 Sequencing. The STACKS program was used to select SNPs. The best linear unbiased prediction (BLUP) value for each accession across different environments for STB severity was used for QTL mapping. Results of quantitative trait loci (QTL) analysis indicated minor genes associated with resistance in chromosomes 4B, 5A, 6B, 6D, and 7DS. Presence of all seven QTL in RILs reduced STB severity by over 70% compared to RILs lacking any of the QTL. These QTL could be used develop breeder-friendly molecular markers for genotypic selection of improved STB resistance in wheat in the PNW.