Breaking wheat yield barriers requires integrated efforts in developing countries

Most yield progress obtained through the so called "Green Revolution", particularly in the irrigated areas of Asia, has reached a limit, and major resistance genes are quickly overcome by the appearance of new strains of disease causing organisms. New plant stresses due to a changing environment are difficult to breed for as quickly as the changes occur. There is consequently a continual need for new research programs and breeding strategies aimed at improving yield potential, abiotic stress tolerance and resistance to new, major pests and diseases. Recent advances in plant breeding encompass novel methods of expanding genetic variability and selecting for recombinants, including the development of synthetic hexaploid, hybrid and transgenic wheats. In addition, the use of molecular approaches such as quantitative trait locus (QTL) and association mapping may increase the possibility of directly selecting positive chromosomal regions linked with natural variation for grain yield and stress resistance. The present article reviews the potential contribution of these new approaches and tools to the improvement of wheat yield in farmer's fields, with a special emphasis on the Asian countries, which are major wheat producers, and contain the highest concentration of resource-poor wheat farmers.