MAPPING OF QUANTITATIVE TRAIT LOCI FOR FHB AND DON RESISTANCE IN A DOUBLED HAPLOID POPULATION OF EVEREST X ART

摘要

The current project is aimed at mapping and identifying quantitative trait loci for resistance in wheat to spread of Fusarium head blight (FHB) symptoms (type II resistance) and spread and accumulation of deoxynivalenol toxin (DON) (type III resistance) throughout the spike. The mapping population consists of 148 doubled haploid lines from an Everest x Art cross. The disease study was performed using a point inoculation technique in a greenhouse with a 14 hour 30°C day and 10 hour 18.9° C night. Inocula of F. graminearum consisted of a conidial suspension using field isolate GZ 3639 native to Kansas. The conidial suspension was adjusted to 100 muL~(-1) for inoculations. Pots were arranged in a completely randomized design on four greenhouse benches. Twenty to forty heads were randomly selected from each line and inoculated after the heads emerged from the leaf sheath. Selected spikes were injected with 10 muL~(-1) of conidial suspension, via a micropipette; into a central spikelet (approximatelythe tenth fully developed spikelet from the base). Spikes were rated for percent infection after 14 days. Kernels were harvested separately from each spikelet in order to determine how DON moves throughout the spike. DON spread and accumulation were measured using a single kernel near-infrared spectroscopy (SKINR) instrument. FHB resistance was significantly correlated with DON resistance (r = 0.82, p = <0.001). Genotyping-by-sequencing (GBS) was used to discover and genotype SNP markers. TASSEL software was then used to call and filter markers resulting in 7,311 SNPs that were bi-allelic between the parents. A linkage map was created with MSTMap~R software using a LOD threshold of 8 and a no mapping distance threshold of 15 cM. The final linkage map consisted of 2,211 markers covering 31 linkage groups (LG) with an average of 71 markers per LG, average LG length of 93.6 cM, and average marker spacing of 1.3 cM. Standard interval mapping and composite interval mapping were performed separately for FHBand DON via the QTL package in RStudio v0.98.1080~R. Four QTL for type II resistance were found on LGs 1,2, 10, and 17. The QTL on LGs 1 and 2 were associated with alleles from Everest and explained 13.4% and 10.0% of the additive phenotypic variance, respectively. The QTL on LG 10 was associated with alleles from Art and explained 21.3% additive phenotypic variation. There were two LOD peaks on LG 17 at 52 cM using SIM (LOD = 3.12, p = 0.0501) and 79 cM using CIM (LOD = 3.36, p = 0.032). The more significant peak obtained from CIM was used as the location of the QTL and explained 11% of the additive phenotypic variation. The narrow-sense heritability estimate for type II resistance was slightly low at 0.13. There were no significant QTL observed fortype III resistance to spread of DON toxin. This experiment is being repeated and the results will be useful in determining if the sources of type II and type III resistance in the cultivars Art and Everest evolved independent of each other. This will allow for the potential to combine QTL for the release of germplasm with high resistance.