Genetics and breeding for rust resistance in wheat

• Pakistan Agricultural Research Council, Pakistan
• Indian Agricultural Research Institute, India

Indian and Pakistan, like many other developing countries, have become major wheat producers, and they are reaping the benefits of using new high-yielding strains developed for subtropical and temperate climates. But the use of a range of cultivars with a common genetic background increase the risk of a widespread epidemic of rust disease.
Plant breeders can lower the risk of a rust epidemic by introducing new strains of wheat carrying rust-resistant properties. But this resistance is not durable, because of continuing changes in the pathogen population. Effective durability requires a sound knowledge of the race structure of the pathogen population and an understanding of the genetic bases for resistance.
The Plant Breeding Research Institute at Castle Hill, Sydney, has studied stem and leaf rusts of wheat for the past 60 years. Rust-resistant cultivars developed there have kept Australia's rust-prone northern wheat zone free of serious stem rust epidemics for the past 30 years. The Institute has been involved in the National Wheat Rust Control Program which was introduced in 1975, following a serious outbreak of rust in the southern wheat growing region in 1973.
India and Pakistan also maintain rust surveillance programs. Integrated research would benefit these two countries as well as Australia, but effective collaboration depends on the establishment of a core of standard reference criteria. At present joint studies are confounded by variations in the pathogen populations, lack of homogeneity among wheat cultivars, and different field and greenhouse environments in each country.
This ACIAR project aims to increase the level of understanding between plant breeders in India, Pakistan and Australia. In the initial stage, wheat cultivars from all three countries will be grown in standard conditions at the Plant Breeding Research Institute at Castle Hill, and then subjected to a broad range of rust pathogens. A wider genetic base of wheat varieties will emerge, and each country will profit from new sources of resistance discovered in the course of research. These new resistance types will also be shared with other countries through CIMMYT's international nursery evaluation program.
Pakistan and India will send research workers to study the Institute's unique approach to hostpathogen interaction. Studies will emphasise the pathological action of rusts, the genetic basis of resistance and plant breeding strategies for durable resistance, based on guidelines from the National Wheat Rust Control Program in Australia.
Representative strains of wheat will be grown in greenhouses at the Institute, and then exposed to a range of rust pathogens. Resistant varieties and other selected cultivars will be carried out in the partner countries.
A separate plant breeding program will be used to identify outstanding commercial wheats, and then rust resistance will be added by backcrossing techniques.
A workshop to be held in India at a later stage of the project will bring wheat breeders and rust pathologists of international standing to meet with workers in India's wheat research program, giving more opportunities for dispersal of information to other wheat producing nations.