Genetic research as the valid base of strategies for breeding rust resistant wheats

Abstract

It is known that few wheat cultivars maintain their resistance to rust diseases for a long period of time, particularly when crop populations become genetically more uniform. A number of genetically diverse, so far unexploited, sources of rust resistance in the natural as well as mutagenized population of wheat cultivars were identified. Several of these genes were placed in agronomically superior well-adapted backgrounds so that they could be used as pre-breeding stocks for introducing genetic diversity for resistance in a crop population. Some of these stocks when employed as parents in several cross combinations in a breeding programme have generated a number of promising cultivars with diversity for resistance.Many presently grown wheats in India, near-isogenic lines each with Lr14b, Lr14ab, Lr30 and certain international cultivars were identified as possessing diverse sources of adult plant resistance (APR) to leaf rust. Prolonged leaf rust resistance in some of the Indian cultivars was attributed to the likely presence of Lr34 either alone or in combination with other APR components. Tests of allelism carried out in certain cultivars that continue to show adequate levels of field resistance confirm the presence of Lr34, which explains the role that this gene has played in imparting durability for resistance to leaf rust. Also, Lr34 in combination with other APR components increases the levels of resistance, which suggests that combination of certain APR components should be another important strategy for breeding cultivars conferring durable and adequate levels of resistance. A new adult plant leaf rust resistance source that seems to be associated with durability in 'Arjun' has been postulated. Likewise, cultivars possessing Sr2 in combination with certain other specific genes have maintained resistance to stem rust.Further, non-specific resistances that were transferred across widely different genotypes into two of the popular Indian wheats provided easily usable materials to the national breeding programmes for imparting durable resistance to stripe rust.

Occurrence of the rust resistance gene Lr37 from Aegilops ventricosa in Argentine cultivars of wheat

“…Greater knowledge on the identity of rust resistance genes present in cultivars that can be used as donors of resistance in wheat breeding programs could greatly improve the efficiency of developing resistant cultivars by using these genes per se or by stacking different resistant genes in a given cultivar (Sawhney and Joshi, 1996). In this context, there are no reports about the presence, frequency and origin of Lr37 in Argentinean wheat cultivars.…”

Development of Alloplasmic Lines of Spring Soft Wheat and Study of Their Resistance to Leaf Rust

“…Recently, the idea to transfer resistance genes of barley to the soft wheat genome was also raised and the strategies for breeding rust resistant was discussed on the basis of genetic researches (Sawhney and Joshi, 1996).…”