High-resolution mapping of a QTL for Fusarium Head Blight resistance on chromosome 2A in Triticum monococcum

Securing wheat production is of prime importance with regard to feeding the earth’s growing population. Wheat is threatened by a lot of abiotic and biotic factors leading to severe yield losses. One important disease is Fusarium Head Blight (FHB), caused by different Fusarium spp. The disease leads to yield losses up to 40 %, a reduction in quality and a health risk for mankind due to toxic secondary metabolites that arise during the infection process. Therefore, FHB belongs to the most important wheat diseases and is extensively studied worldwide. To improve resistance of wheat to Fusarium spp., this study was conducted to get detailed information on the genetics of a new source of resistance, detcted in Triticum monococcum, which is a close relative of bread wheat. To achieve this, a DH-population based on a cross between Triticum monococcum accession mon10-1, which is moderately resistant to FHB and the FHB susceptible Triticum monococcum L. conv. sinskayae (Sinskayae) comprising of 94 DH-lines was analysed. The population was phenotyped in two years field trials and genotyped by DArT analyses resulting in a genetic map of 1987.55 cM. Based on these data, two neighbouring QTLs were mapped in an interval of 45.1 cM on the short arm of chromosome 2A. Further analyses aimed at shortening the QTL interval and the identification of closely linked markers and candidate genes by a map-based cloning approach. A high-resolution mapping population was developd out of 1991 F2-plants, that traced back to crosses between three susceptible and two resistant DH-lines of the original population. 333 RILs were developed of which 268 were used for phenotypic evaluation with F. culmorum (Isolate: Fc46) in field and greenhouse trials. Marker saturation was conducted based on the 90K iSelect chip, genotyping-by-sequencing (GBS) and known genetic maps of Triticum monococcum. Out of these, 21 KASP markers were developed and mapped within the QTL interval. Assigning these markers to the physical map of T. aestivum resulted in an interval of 31.4 Mbp. However, by phenotyping respective segmental RILs, the resistance locus was not located within this interval. A new QTL analysis with a reduced marker set of the DH-mapping population using their physical postitions was conducted and resulted in a switch of the peak markers to a proximal region of chromosome 2A into an interval between 499.25 – 607.96 Mbp. This QTL mapped in the same region like the soft glume (sog)-gene, but it is unclear if the QTL effect is due to tight linkage between sog- and FHB resistance gene or pleiotropy.