USE OF DIVERSE GERMPLASM FOR GENETIC IMPROVEMENT OF RICE
Location: Dale Bumpers National Rice Research Center
Title: Enhancement of Yield Using Chromosomal Introgressions from Oryza rufipogon
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 1, 2008
Publication Date: February 15, 2008
Citation: Mcclung, A.M., Moon, A.M., Eizenga, G.C., Mccouch, S.R. 2008. Enhancement of Yield Using Chromosomal Introgressions from Oryza rufipogon. In: Proceedings of the 32nd Rice Technical Working Group Meetings, February 18-21, 2008, San Diego, CA. 2008. CDROM.
Over the past decade, the McCouch lab has developed a network of collaborators to explore the gene space of the wild ancestral species, O. rufipogon, by crossing it with an array of elite O. sativa international cultivars. Advanced backcross populations were constructed in which transgressive variation could be genetically dissected. Using a common set of molecular markers to identify QTLs associated with enhanced performance in wild x cultivated populations in different regions of the world, it was demonstrated that specific O. rufipogon introgressions confer superior performance for an array of agronomic and yield-related traits (flowering time, panicle size, seed size and shape, number of seeds per plant). The superior performance is due to transgressive variation associated with alleles from the low-performing O. rufipogon parent that enhance the performance of the elite O. sativa recurrent parent.
As part of the NSF funded project “GEPR: Exploring the genetic basis of transgressive variation in rice”, we are using near isogenic lines (NILs) to explore what happens when ‘adapted gene complexes’ are disrupted, giving rise to positive transgressive variation. We suggest that the introduction of selected ‘wild QTLs’ into commercial cultivars has the potential to enhance elite varieties. In addition, this may lead to a better understanding of how ‘wild QTLs’ are associated with key regulatory elements, or master switches, located near the top of critical gene networks associated with yield and other aspects of agronomic performance.
In this study, a set of 70 NILs that had been developed from a cross of Jefferson/O. rufipogon and identified to possess QTL associated with yield components were evaluated in replicated field trials in 2007. These studies were conducted at Beaumont and Alvin, Texas and Stuttgart and Jonesboro, Arkansas. The study consisted of six families of introgression lines each family possessing a “yield” QTL located on a different chromosome, either chr 1, chr 2, chr 3, chr 6, chr 8, or chr 9. Each QTL family was represented by 4 to 12 independent introgressions of the targeted QTL and several check NILs, having a common background but lacking the introgression. The NILs were evaluated in standard yield plots, replicated three times at each location. In addition, four commercial cultivars, Jefferson (parent), Cocodrie, Trenasse, and XL723, were included in the evaluation as repeated checks. The materials were evaluated for main crop yield, yield components, agronomic traits, and milling quality.
Early results from this study indicate that some of the QTL introgressions were associated with significantly improved yield and agronomic traits relative to the Jefferson parent. In addition, several individual NILs were ranked high for yield across the four locations indicating that the impact of the introgression was stable across environments. These results indicate that this approach provides a way of selectively introducing components of quantitative trait variation from a wild gene pool into an elite cultivar, without the requirement for whole-genome compatibility. It can serve as the basis for both inbred and hybrid varietal improvement and has the potential to expand the cultivated gene pool of cultivated rice.