Rust resistance in newly bred lines of wheat (Triticum aestivum L.)

Abstract

Of the three rusts, leaf rust caused by Puccinia triticina is the most important because of its wide spread nature [1]. A total of 60 genes conferring resistance to leaf rust have been identified and designated as Lrl through Lr60 [2]. The best strategy for the control of leaf rust lies in combining the genes with major and minor effects. Many virulent races of brown rust have rendered the resistance provided by Lr26 ineffective. The confinement of epidemic outbreak was largely due to the presence of alien genes like Lr26 which combines well with adult plant resistance gene like Lr34 [1, 3] or some unidentified genes with minor effects. Alien genes like Lr9, Lr19, Lr24 etc. with effective resistance against most of the leaf rust races available in India have been utilized only in a few of genotypes grown commercially [4]. At the same time, the appearance of new race like 77-7 with combined virulence on Lr9 and Lr26 has risked the durability of individual alien genes. It is, therefore, high time to pyramid genes which have been knocked down by a single virulence with some of the adult plant resistance genes like Lr34. Some of these alien genes have already been pyramided in a few popular wheat cultivars through backcrossing [5].