The slowing of gains in maximum genetic yield potential is a matter of considerable concern. Continued genetic improvement of food crops — using both conventional as well as biotechnology research tools — is needed to shift the yield frontier higher and to increase stability of yield. In rice, wheat, and maize research, three distinct, but interrelated strategies are being pursued to increase genetic maximum yield potential: changes in plant architecture, hybridization, and wider genetic resource utilization. Significant progress has been made in all three areas. IRRI remains optimistic that it will be successful in developing the new "super rice," with fewer — but highly productive — tillers. IRRI claims that this new plant type, in association with direct seeding, could increase rice yield potential by 20% to 25%, although it is still probably 10 to 12 years away from widespread impact on farmers' fields (Khush, 1995). New wheat plants with an architecture similar to the "super rices," including larger heads, more grains, and fewer tillers, could lead to an increase in yield potential of 10% to 15% above the best current germ plasm (Rajaram and Borlaug, 1997). Introducing genes from related wild species into cultivated wheat can introduce important sources of resistance to several biotic and abiotic stresses, and perhaps permit higher yield potential as well, especially if the synthetic wheat is used as parent material in hybrid wheat production.
The success of hybrid rice in China, which now covers more than 50% of irrigated area, has led to a renewed interest in hybrid wheat. Recent improvements in chemical hybridization agents, advances in biotechnology, and the emergence of the new wheat plant type have made a reassessment of hybrids worthwhile. With better heterosis and increased grain filling, the yield frontier of the new plant material could be 25% to 30% above the current germ plasm base.
In maize, yield increases have been achieved by breeding plants that can withstand higher planting densities, as well as the shift to single cross hybrids.
Maize production has really begun to take off in many Asian countries, especially China. It now has the highest average yield of all cereals in Asia, with much of the genetic yield potential yet to be exploited. Recent developments with high-yielding quality protein maize (QPM) varieties and hybrids will also improve the nutritional quality of the grain without sacrificing yields. This achievement offers important nutritional benefits for livestock and humans.
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