AB-QTL mapping of Fusarium head blight resistance

Fusarium head blight (FHB) of wheat is a destructive disease causing severe yield and quality losses, but the most serious concern is the possible mycotoxin contamination of cereal food and feed. The cultivation of resistant varieties has great potential to reduce the negative impact of Fusarium diseases on cereals. Unfortunately the majority of the current European wheat cultivars are susceptible to the disease. Only limited molecular genetic information is available on sources of resistance to FHB, other than spring wheat sources from China (e.g. Sumai-3 and relatives). The objective of this proposal is to characterize FHB resistance of two wild relatives of wheat: Triticum macha (genome AABBDD, 2n=42) and T. dicoccoides (genome AABB, 2n=28) through molecular mapping. The resistant lines possess apart from their high level of FHB resistance many undesired traits like tall straw, susceptibility to lodging and a low yield potential. Back-cross populations were derived from the BC1 or BC2 generation of crosses of the two resistant lines with well-adapted bread and durum wheat lines, respectively. These populations (of about 300 recombinant lines each) will be evaluated in artificially inoculated experiments for resistance to FHB. In parallel the recombinant lines will be genotyped with molecular markers. The combined analysis of the marker data and the resistance data should allow the detection of quantitative trait loci (QTL) which contribute to FHB resistance in these crosses. Effect and location of QTL contributing to FHB resistance will be estimated. This is the first project to utilise an advanced back-cross QTL mapping scheme for analysing FHB resistance. The project contributes to the utilization of novel sources in FHB resistance breeding. The ultimate goal of the project is to develop tools for use in marker assisted selection and simultaneously to develop wheat lines with improved FHB resistance in an agronomically acceptable genetic background.

In years where moist weather conditions promote infections by fungi of the genus Fusarium, not only severe yield and quality losses will be the consequence, the most concerning problem is the accumulation of mycotoxins in cereal food and feed. The most promising control measure is the development of disease resistant cultivars. Several resistance sources are available in bread wheat but only little information is available for durum wheat. Within this project an advanced backcross QTL (AB-QTL) approach was used for conjoined mapping and QTL detection in two different backcross populations. Aim of the project was to identify novel quantitative trait loci (QTL) for Fusarium head blight resistance in wheat. For bread wheat a BC 2 population was developed from a cross between the well adapted bread variety Furore and Triticum macha, a Transcaucasian landrace, as donor parent of the resistance source. For durum wheat three related BC 1 derived populations were developed by crossing the Austrian varieties Helidur, Floradur and DS-131621 with the resistant line T. dicoccum#161. The populations were genetically analysed with SSR and AFLP markers and their positions on the chromosomes were calculated. Except for the chromosome 4D in the hexaploid population, markers could be assigned to all wheat chromosomes and their arrangements on the chromosomes were in most cases coherent to maps retrieved from the literature, which approves a good and accurate genotyping. All populations were scored for resistance after artificial inoculation with Fusarium in seven field experiments over 4 years. The compiled results showed that five different chromosomal regions associated with Fusarium head blight were detected in the Furore x T. macha population and 3 different chromosomal regions in the durum wheat x T. dicoccum populations. High broad sense heritability for FHB and repeated detection of the QTLs among the different experiments confirmed the reliability and repeatability of the obtained results. Because of the different origin of the resistant parent Triticum macha to the already well investigated Asian-, Latin American-, and European gene pools, we were able to detect novel QTLs on chromosomes 5A, 2A, 2B, and 5B for bread wheat. Unfortunately the QTL on 5A with the highest impact on resistance improvement was strongly connected to the spelt type of the lines, and is close or at the location of the Q-gene, which is known to regulate the spelt- or non spelt type of wheat. QTL analysis for the durum populations revealed associations for several genomic regions with resistance to FHB. The major effects associated with FHB resistance mapped to chromosomes 4B, 3B and 6B. Because of the novel character of the detected QTLs they broaden the genetic basis of FHB resistance. The fact, that in these populations 87.5 % and 75 % of the genome descend from a well adopted variety, lines suitable for practical breeding can be developed within a short time, and can be used for pyramiding resistance to FHB by practical breeders, which enhances sustainable resistance management.