Title: Oryza rufipogon as a source of yield improvement in cultivated rice Authors
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 27, 2012
Publication Date: February 27, 2012
Citation: Imai, I., Mcclung, A.M., Yeater, K., Mccouch, S. 2012. Oryza rufipogon as a source of yield improvement in cultivated rice. Rice Technical Working Group Meeting Proceedings. Feb. 27 - Mar. 1, 2012. Hot Spring, AR. pg. 54-55. Technical Abstract: Oryza rufipogon is a wild relative of the cultivated species, Oryza sativa, and has been found to possess genes associated with yield improvement and resistance to biotic and abiotic stresses. We have been exploring the use of O. rufipogon as a genetic resource for yield improvement in the USA rice gene pool. The aus-like O. rufipogon accession, IRGC 105491, which has no apparent agronomic traits of interest, was crossed with the tropical japonica cultivar, Jefferson, which had been released in 1998. Backcrossed progeny (BC2F2) were evaluated in a yield trial (Thomson, et.al. 2003) and six yield enhancing QTL’s were identified on chromosome 1 (1.2), 2 (2.1), 3 (3.2), 6 (6.1), 8 (8.1) and 9 (9.1). Marker assisted selection was used to backcross to Jefferson in an effort to reduce the size of the targeted introgressions and eliminate the presence of any other background introgressions. In 2007 and 2008, BC3 progeny were evaluated at four flooded field locations, and in 2008, two additional aerobic locations were included. Fifty introgressed lines containing the targeted QTLs (4 to 12 lines per QTL) and 20 controls (sib-lines lacking the targeted QTL) were tested along with Jefferson, Cocodrie, Trenasse, and XL723. Under flooded conditions, at least two introgression lines from each QTL were observed to have significantly higher yield than Jefferson. Although under aerobic conditions the introgressed lines were not significantly different than Jefferson, the highest ranking lines were similar across the two irrigation methods. Lines derived from QTL 2.1 and 6.1 averaged 25% higher yield than Jefferson and lines from QTL 1.1, 2.1, 6.1, and 8.1 had significantly greater resistance to sheath blight disease as determined using an inoculated micro-chamber method. One line from QTL 2.1 (43-2-1) and 6.1 (219-2-9) were tested in the 2009 Uniform Regional Rice Nursery and the QTL 2.1 family was confirmed to have yield potential comparable to cultivars Cocodrie, Trenasse, and Templeton. This demonstrates that O. rufipogon improved the yield potential of Jefferson to the level of varieties that were released some 10 years after Jefferson was released. Additional, marker assisted selection and backcrossing was performed using introgressions lines possessing QTL 2.1 and 6.1. In 2010, eighteen BC4F4’s of these QTLs, seven of their original BC3F8 sources, Jefferson and three check cultivars were evaluated in replicated yield trials at two locations. All but five of the BC4 families had significantly higher yield than Jefferson with lines derived from QTL 2.1 being ranked the highest. However, the BC3F8 line (43-2-1) had the highest yield potential indicating that the background introgressions that were eliminated with subsequent backcrossing (BC4) may have actually contributed to enhanced yield. A set of introgression lines from this study are being made available to the public through the Genetics Stocks Oryza collection. In addition, genetic markers linked to the targeted QTLs as well as other O. rufipogon background introgressions will be published. These genetic resources can be used by the USA rice breeding community to increase yield of new cultivars through the incorporation of novel genes derived from this wild related species of rice using marker assisted selection.