Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/20/2012
Publication Date: 10/4/2012
Citation: Sreerekha, M.V., Sanchez, P.L., Eizenga, G.C. 2012. Dissecting the genetic diversity in African rice. Rice Technical Working Group Meeting Proceedings. 34th Rice Technical Working Group. Hot Springs, AR Feb. 27 - Mar. 1, 2012. pg. 50-51. Interpretive Summary:
Technical Abstract: African cultivated rice, Oryza glaberrima, and its progenitor, O. barthii are excellent sources of important genes for rice improvement because they exhibit tolerance to several abiotic and biotic stresses. Development of advance backcross (ABC) populations between an unadapted donor parent and adapted recurrent parent facilitate the introgression of agronomically important traits from the donor parents into the recurrent parent background. Subsequent development of backcross inbred line (BIL) sets from ABC populations provides genetic stocks for translational genomics studies. The objectives of this study were to determine the genetic diversity in a collection of O. barthii and O. glaberrima accessions, evaluate the collection for reaction to sheath blight disease, and develop a set of founder lines for developing sets of BILs with O. barthii and O. glaberrima genetic backgrounds. A collection of 107 O. glaberrima and 57 O. barthii accessions was assembled that originated from sixteen different African countries and genotyped using 36 genome-wide SSR (simple sequence repeat) markers. Four population groups were identified from the STRUCTURE analysis: "population 1" composed of mostly O. glaberrima and some O. barthii accessions; "population 2" composed of a genetically diverse set of O. barthii accessions; "population 3" composed mostly of O. glaberrima accessions with a few O. barthii accessions; and "population 4" composed of the control O. sativa accessions and some O. glaberrima accessions which were genetically similar to O. sativa. PCA analysis confirmed populations 2 and 4 but grouped populations 1 and 3 together using the first three components. These results agree with the most distinct clusters observed in the cluster analyses. All analyses confirmed the genetic distinctiveness of African rice from Asian rice (O. sativa). Also, we observed greater genetic diversity in O. barthii accessions as compared to the O. glaberrima accessions. This African rice collection was evaluated for reaction to sheath blight disease caused by the Rhizoctonia solani fungus using the micro-chamber method. Preliminary data indicated five O. glaberrima accessions and three O. barthii accessions exhibited resistance to sheath blight disease. To develop founder lines for the BILs, O. glaberrima and O. barthii accessions that were genetically distinct were selected as donor parents, and two U.S. rice (O. sativa) cultivars, M-202, a California medium grain temperate japonica, and LaGrue, an Arkansas long grain tropical japonica, were selected as recurrent parents. Due to the extreme sterility observed in the F1 hybrids, the popular O. glaberrima cultivar, CG14, which has genome sequence information, was added as a recurrent parent. To date, BC1F1 seeds have been produced from crosses with 12 O. barthii accessions and three O. glaberrima accessions as donor parents and at least one of the O. sativa recurrent parents. Crosses with CG-14 are currently being made with the O. barthii and O. glaberrima accessions that were successfully crossed with the O. sativa parents and are genetically distinct.