MOLECULAR MAPPING OF DURABLE RUST RESISTANCE IN WHEAT AND ITS IMPLICATION IN BREEDING

Abstract

Genetic characterization of sources of durable resistance enables their strategic deployment in breeding programs. Genomic locations of uncharacterized adult plant resistance (APR) sources to leaf rust and stripe rust diseases of wheat were determined. Two genomic regions, 3DS (Halberd) and 5DS (Cranbrook) controlled APR to both leaf rust and stripe rust. Chromosomes 6B (Cranbrook) and 7B (Halberd) reduced leaf rust severity. Chromosomes 2DS, 3BS and 7A also reduced stripe rust severities in at least one crop season. Stem rust resistance genes Sr2 (3BS) and Sr30 (5DL) from Cranbrook explained stem rust response variation. Regression analysis also indicated strong positive interaction of these two loci in controlling stem rust. Expression of Sr2-linked psuedo black chaff (Pbc) was controlled by a major gene on chromosome 3BS and three modifiers located on chromosomes 6A, 3D and 7A. The chromosome 7A located region was not consistent across all seasons and sites. QTLs detected consistently in different experiments were temporarily designated as QYr/Lr3D, QYr/Lr5D, QLr6B and QLr7B.