QUANTITATIVE TRAIT LOCI MAPPING OF FUSARIUM HEAD BLIGHT RESISTANCE IN ADVANCED BACK CROSS POPULATION (BC1F6) DERIVED FROM TUN 34 × LEBSOCK TETRAPLOID WHEAT

Fusarium head blight (FHB) caused by Fusarium graminearum has resulted in signifi cant reduction in grain yield, quality and farm income in durum wheat growing areas of North America. There are a few known sources of resistance for FHB mostly derived from the Chinese hexaploid sources like Sumai3 and Wangshuibai. Distinct sources of resistance were identifi ed by NDSU in Tunisian pedigrees. It has been shown that Tunisian lines have no relation to Chinese genotypes and therefore can be used to en- hance the resistance in durum wheat by pyramiding resistant genes from different genetic backgrounds. To expedite identifi cation of durum lines carrying these resistant alleles in earlier generations, use of molecular markers associated with FHB is essential. Genomic regions associated with FHB were examined in 168 progenies of tetraploid Tun34 × Lebsock advanced back cross (BC 1 F 6 ) population. To construct the genetic map, a total of 2300 DArT markers were tested for polymorphism between parents. The polymorphic markers were assembled into link- age groups at likelihood ratio statistic (LOD) greater or equal to three and followed by assembly of a consensus map using Kosambi mapping function. Of the total DArT markers screened for polymorphism between parent lines Tun34 and Lebsock, 379 clones (15.1%) were polymorphic. Segregation ratios were compared to expected ratios for all markers using chi-square goodness of fi t test. Results indicate segregation distortion of 5.2% (P<0.01) for this population. Of 379 markers, 359 were assigned (LOD≥3.0) into 44 linkage groups with the minimum number of three markers. Following the grouping, genetic maps were constructed. Almost all of the linkage groups except two could be assigned to durum wheat chromosomes by alignment to previous published maps. Genomic scan using Kruskal-Wallis rank-sum test identifi ed signifi cant (P≤0.001) putative QTL as- sociated with FHB on chromosomes 5B, 2A, 6B, 7A and 7B. A region on chromosome arm 5BL (4cM interval) showed the highest K score and an increase in resistance to FHB due to alleles of Lebsock parent. Composite interval mapping confi rmed the presence of this signifi cant (LOD=6.1) QTL explain- ing 14.7% of phenotypic variation for FHB. Since this population was phenotyped at two different seasons in replicated experiments, information from these QTL can be used in marker assisted selection (MAS) to control FHB.