Pseudo black chaff as evidence for recombination of Sr2 and Fhb1

Resistances conferred by Sr2 and Fhb1 are considered important in the control of stem rust and Fusarium head blight (FHB), respectively, but these genes on chromosome 3BS are known only to occur in repulsion. The objective of this study was to use a doubled haploid (DH) population of Carberry/AC Cadillac to seek a recombinant with the Sr2 and Fhb1 resistance alleles in coupling. Carberry expresses moderate resistance to FHB. AC Cadillac has marker alleles typically linked to the Sr2 resistance allele. Carberry has marker alleles associated with Fhb1. The DH population was genotyped with 578 DArT®, 55 SSR, 2 BAC-derived, 2 CAPS, and 1 STS markers. The parents and 261 DH lines were evaluated for adult plant stem rust response (Ug99) at Njoro, Kenya, and at Swift Current, Canada (Canadian Pgt races). Response to FHB was evaluated in nurseries near Portage la Prairie, Manitoba. Pseudo black chaff (PBC), known to be tightly linked to Sr2, was scored in nurseries when symptoms were expressed. Both cultivars have other Sr and Fhb resistance genes, and QTLs contributing to PBC on chromosomes other than 3BS. Using phenotypic and molecular marker data, and the very tight linkage or pleiotropic relationship of Sr2 with PBC, DHs were classified for presence of PBC and FHB response. Putative recombinant DH candidates were re-evaluated for symptoms of PBC, stem rust, and FHB in three international nurseries and genotyped with markers closest to Sr2 and Fhb1. The results will be presented.

SeCan Association, Canada
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