To help stave off global hunger, Cornell University plant breeders -- on a treasure hunt armed with genome maps -- have discovered genes in wild rice species that may help boost production of some of the world's major agricultural crops.
"We've gone back and found wild species that contain genes that may help us boost production," said Steven D. Tanksley, Cornell's Liberty Hyde Bailey Professor of Plant Breeding and Biometry. "The world is only so big, the population is growing and we need to continue feeding that population." Tanksley and Susan R. McCouch, Cornell assistant professor of plant breeding, along with other Cornell researchers are announcing their research in the journal Nature, (Nov. 21, 1996) in an article, "Genes from the wild boost rice yields." The research was done by Tanksley and McCouch, as well as Cornell post-doctoral fellows Jinhua Xiao, Silvana Grandillo and Sang Nag Ahn. Jiming Li and Longping Yuan, of the China National Hybrid Rice Engineering Technology and Research Center in Hunan, People's Republic of China, also contributed to the research. The Cornell researchers used grants from the U.S. Department of Agriculture and the Rockefeller Foundation.
"Land mass is actually shrinking in Asia and as a society we've increased rice yields per acre about as much as we could. We can't increase the land, so we have to do something," said McCouch. "Fertilization is no longer an effective way to boost yield -- it's plateaued. So, instead of boosting land mass -- which we can't do -- we're manipulating the plant's genetics."
In the case of rice, there has not been a significant yield increase in two decades. Yet the world's agriculturists are using only 25 percent of the genetic diversity available. In other words, the same types of rice have been cultivated over and over again, effectively reducing rice's natural diversity. With so much homogeneity, the researchers explain, rice has reached a genetic bottleneck. Using genes from the wild versions of crops, such as rice, means the scientists are re-introducing the crop's natural diversity -- and increasing the yield.
From 1965 to 1995, the world's population doubled to reach its current size of 5.7 billion people. With global estimates of 8.9 billion people to feed by the year 2030, the Cornell scientists are looking for ways to improve production of staple food crops.
"We've been breeding rice for 70 years, with the same set of rice types," McCouch said.
While examining wild rice, McCouch and her colleagues have been systematically mapping genes of rice varieties and looking for the specific loci or genes -- known as the Quanitative Trait Locus, or QTL -- that would tend to boost production. Before molecular genetics breeders had no way of finding the genes from the wild species, because there was no way of identifying the functions of the genes in the wild species.
Not only is rice being genetically mapped, but other researchers throughout the world can tap into a Cornell information Web site and use that mapping data to boost rice production in their parts of the world. McCouch said that although the wild species are generally useless for crop production -- since they do not produce much rice, have very small grains, and the plant tends to shatter -- there is some useful genetic treasure.
Specifically, McCouch and Tanksley used the domesticated Oryza sativa rice. Through gene-mapping activities, they deduced that the wild rice O. rufipogon contained two production-boosting QTLs: simply named YLD1 and YLD2. By recombining the QTL of the wild variety with the domesticated one, the researchers obtained between a 15 percent and 17 percent improvement in production.
China produces 40 percent of the world's rice. The Cornell scientists collaborated with the Hunan Hybrid Rice Institute, in the People's Republic of China and provided the Chinese agricultural field station with recombined and introgressed rice.
"Essentially, we are mining the wild species for previously undiscovered genes," Tanksley said. "There is no way to effectively identify these genes through traditional methods, so we have turned to recently developed genetic techniques. We hope to reverse the genetic erosion and selectively enrich the genetic base of crop plants. Results from this research demonstrates that genes in wild rice and other wild relatives of crop plants can do spectacular things. All we're doing is using modern techniques to find those genes and harness them for human food production."