Plant biotechnology for wheat germplasm improvement

• Punjab Agricultural University, India

Wheat consumption has grown at the unprecedented rate of 2.3% per annum in nearly all developing countries since 1961. This has led to an increasing demand to expand the genetic base of wheat, to enable its adaptation to non-traditional wheat-growing environments. Moreover, in India and other developing countries where deployment of high-yielding varieties and associated agronomy has already dramatically increased wheat production, new diseases have emerged as serious threats to the maintenance of high wheat yields.

This project is designed to broaden the genetic base of bread wheat by introgressing alien genes for new and desirable traits from related wild grasses, to permit continued response to selection. The starting material will come from a unique set of addition lines developed in Mexico, in CIMMYT's wide-crossing program, following intergeneric hybridisation of bread wheat with Elymus, Agropyron, Aegilops and other wild relatives. These alien species carry genetic resistance to the new wheat diseases such as the leaf blight complex (Helminthosporium sativum, Alternaria alternata), head scab (Fusarium graminearum) and karnal bunt (Neovossia indica) and also can tolerate aluminium toxicity and heat stress.

Regenerating tissue cultures will be established from specific addition lines. Scientists in the project will use the relatively high rate of genome re-arrangement that occurs during culture (somaclonal variation) to rapidly introgress traits from the wild species into bread wheat. After evaluating somaclone progeny for disease resistance or stress tolerance and cytogenetic constitution, they will identify wheat genotypes in which alien gene introgression has occurred. As well as using available rapid screening procedures - for example, for aluminium tolerance - the team will develop new ones for traits such as leaf blight resistance and heat tolerance. Conventional screening for tolerance to karnal bunt and head scab will be conducted in India and/or by CIMMYT.

Molecular genetic techniques will be utilised to produce specific DNA probes from among libraries of DNA of the alien species cloned in bacteriophage. These DNA probed will provide means of analysing the chromosomes of those somachonal variants that apparently carry alien genes, using in situ hybridisation and restriction endonuclease analysis. This research will establish a unique method of characterising introduced alien genes or chromosome segments within the wheat genome.

The project has a global perspective and, if successful, could contribute to expanding wheat cultivation into areas previously considered unsuitable for the crop. Specific benefits include: bread wheat genotypes with disease resistance and tolerance of environments stress; a battery of DNA probed to monitor alien gene segregation in breeding programs; effective transfer of plant biotechnology to complement Indian and CIMMY plant breeding programs; and a greater understanding of the genetic and molecular consequences of somaclonal variation.

The links to plant breeders in India and to CIMMY's International Wheat Nursery Program will provide opportunities to evaluate new strains on a global scale and to make them available to wheat breeders in all developing countries.