Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/21/2000
Publication Date: 4/5/2001
Citation: McCouch, S. R., M.J. Thomsom, E.M. Septiningsih, P. Moncada, J. Li, J. Xiao, S.N. Ahn, T. Tai, C. Martinez, A. M. McClung, X.H. Lai, S. Moelpojawiro, L.P. Yuan, H.P. Moon, E. Guimaraes, and J. Tohme. 2001. Wild QTLs for Rice Improvement. pp 151-169. In: Rice Research and Production in the 21st Century, Symposium Honoring Robert F. Chandler, Jr., Rockwood, W.G. (ed.), Los Banos, Philippines. International Rice Research Institution. 224 pp. Interpretive Summary: Rice is grown around the world in diverse environments and provides daily sustenance for over half of the world's population. Most current day rice varieties were orginally domesticated from wild species of rice that were found near the Himalayas and in South China. Through thousands of years of selection and, more recently, cross breeding efforts, thousands of rice varieties have been developed and grown. There are over 120,000 rice varieties stored in seed respositiories around the world. However it is believed that through this selection process, useful genes in the wild species of rice may have been inadvertantly lost and are not present in current varieties. Thus, at study was conducted to determine if wild weedy species of rice could be used to enhance the yield potential of current high yielding rice varieties. Breeding programs in China, Indonesia, Korea, Colombia, Brazil, the Ivory Coast, and USA used a local rice variety that was then crossed with a wild species of rice. The material was backcrossed to the local variety so that only small amounts of the wild species genome would be incorporated and the offspring of the cross would be well adapted to local growing conditions like the local variety. Offspring from the crosses were evaluated for agronomic traits and yield potential in field trials conducted in the participating country. Genomic analysis was conducted to determine chromosomal regions that contained DNA from the wild species. More than half of the regions derived from the wild species resulted in a positive impact on agronomic traits or yield. These results indicate that wild species of rice are important genetic resources that can be used for continued improvement of rice varieties by breeding programs.
Technical Abstract: Domestication of plants for agricultural use has brought about profound genetic change in ancestral plant species. Intensive, scientific breeding of crop varieties by modern plant breeders over the last century hs narrowed the gene pool in many crops. Many wild ancestors of modern crop plants can still be found in their natural habitats and have been collected and maintained in national and international germplasm collections. These collections offer the possibility of abundant genetic variation that may be useful in breeding programs. A new advanced backcross breeding strategy that utilizes molecular linkage map data has been developed as a means of incorporating useful genes from wild ancestors. Rice breeding programs located in China, Indonesia, Korea, Colombia, Brazil, Ivory Coast and the USA participated with researchers at Cornell University to test this new breeding method. A crossing program was initiated using high yielding local varieties and three wild ancestors of rice. Segregating progeny from backcross populations (BC2) were evaluated in the country of origin for various yield and agronomic traits and quantitative trait loci (QTL) were determined at Cornell for each breeding population. More than half of the QTLs from crosses made with Oryza rufipogon species exhibited a positive effect. In particular, genes located on chromosome one were found to positively influence height, grains per plant, and grain weight across several of the rice populations. Although results from the other two wild species are still pending, these observations indicate that wild ancestors may contribute genes that will be commonly useful to breeding programs around the world.