Capturing new genetic variation for rust resistance among the Watkins collection of pre- Green Revolution wheats - discovery to deployment and cloning
The Green Revolution involved the deployment of reduced height (Rht) genes to generate shorter wheat varieties with increased grain yields. It also contributed to a reduction in genetic diversity in the modern gene pool. Therefore, the pre- Green Revolution tall wheat landraces may provide a reservoir of genetic variation for economic traits such as rust resistance. Considering the breakdown of a suite of rust resistance genes through the emergence of currently predominant pathotypes (e.g. Ug99 and high temperature adapted isolates of the stripe rust pathogen) after three decades of Green Revolution, the discovery, characterisation and deployment of diverse sources of resistance remains a high priority. We have screened the Watkins wheat landrace collection and discovered, characterised and formally named a suite of new rust resistance genes including Yr47, Yr51, Yr57, Yr63 and Sr49. In addition, genotypes carrying potentially new genes for resistance to three rust pathogens are currently being investigated by students from seven nations representing three continents (Australia, Asia and Africa). Yr47, Yr51, Yr57 and Lr52 have been backcrossed into modern cultivars including the widely adapted cultivar PBW343 (Atilla) using markers developed in our research program. Development of triple rust resistant derivatives in modern wheat backgrounds is in progress. Stocks carrying Yr47, Yr51, Yr57 and Lr52 have been mutated to facilitate cloning of these loci for their eventual use in development of multi-gene cassettes for transformation.