Genetics and breeding for durable resistance to leaf and stripe rusts in wheat

Abstract

Yellow (or stripe) and leaf (or brown) rusts, caused by Puccinia striiformis and P. triticina, respectively, are important diseases of wheat worldwide. Growing resistant cultivars is the most economical and environmentally safe control measure and has no cost to growers. Wheat (Triticum aestivum) cultivars that have remained resistant for a long time, or in other words carry durable or race-nonspecific resistance, are known to occur. Inheritance of resistance indicates that these cultivars often carry a few slow rusting genes that have small-to-intermediate, but additive, effects. Our genetic studies show that a high level of resistance (approaching immunity) to both rusts could be achieved by accumulating from 4 to 5 such genes. We recommend that a group of winter and spring wheat cultivars known to carry adequate levels of durable resistance to yellow and/or leaf rusts are assembled and further evaluated in the region to identify those cultivars that show resistance stability. Resistance from these cultivars should then be transferred in a planned manner to the susceptible but locally adapted cultivars through a ‘Single Backcross Breeding Approach’, that allows the simultaneous accumulation of desired number of slow rusting genes with increased grain yield potential and other traits.