Abstract In breeding for resistance to Fusarium head blight (FHB) there should be precise differentiation between QTL for resistance and those for spike architecture traits that indirectly affect disease. QTL mapping for FHB Type II resistance and spike architecture traits was carried out in a population of 80 RIL. Three QTL for FHB Type II resistance were identified respectively on chromosomes 2A, 4A and 6D, the last of which is reported here for the first time. The number of florets per spike and per spikelet was associated with FHB Type II resistance but there was not co-localization between QTL for these traits. However, QTL for number of spikelets per spike overlapped with those for FHB Type II resistance on chromosomes 2A and 6D. Spike architecture traits - notably, the number of florets per spike and per spikelet - should be considered in the design of breeding strategies to increase Type II resistance to FHB in bread wheat.

Abstract Spike fertility index (SF) is a trait easily measured at maturity and strongly associated with the number of grains per unit area. In order to identify genomic regions involved in SF control, a biparental (Baguette 10 × Klein Chajá) population of 80 recombinant inbred lines (RIL) was used. Seven field trails were conducted to determine the SF BLUP value per RIL. RILs were genotyped using a commercial chip (Axiom® 35K SNP Wheat Breeder's Array, Affimetrix). A linkage map was constructed with 857 SNP markers, and SF QTL mapping was performed. The narrow-sense heritability of SF was 0.89. Three genomic regions (QTL) associated with SF were found on chromosomes 2D, 4A, and 7A. The proportion of genetic variation explained by these three QTL was 32%, with no significant epistatic interaction between QTL.