Slow rusting type of resistance in wheat (Triticum aestivum) to leaf rust (Puccinia recondita tritici) and stripe rust (Puccinia striiformis tritici) is often conferred by a few partially effective, non-hypersensitive type of genes with additive effects. Inheritance studies at CIMMYT have shown that although individually these genes may have small to intermediate effects, combinations of 3 to 5 such genes result in a high level of resistance. We planned a breeding experiment aimed to combine such genes for resistance to both leaf and stripe rusts with high yield potential. Simple crosses were made between parents that had moderate to good levels of slow rusting resistance to both rusts; the F 1S were then top-crossed (three-way) with a third parent that had high yield potential and at least some resistance. Segregating generations were alternated between Ciudad Obregon (28 ºN, 39 m a.s.1., irrigated, high yielding site with high leaf rust pressure) and Toluca (18 ºN, 2640 m a.s.l., high rainfall site with high stripe rust pressure) in Mexico. Selection pressure was mild for resistance but strong for plant morphology in the early segregating generations. Selected plants were advanced to higher generations as bulk. Plants with good morphology and high level of resistance were advanced as pedigree in the F 5 generation. We have identified lines that combine high yield potential with high levels of resistance based on additive genes to both rusts in Mexican and other global environments.

Global Wheat Program

English

0007|AGRIS 0101|R99-00CIMPU|AL-Wheat Program

Jose Juan Caballero

INT0610