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Title: Chromosome Segment Substitution Lines: A Powerful Tool for the Introgression of Valuable Genes from Oryza Wild Species into Cultivated Rice (O. sativa)

item ALI, M. LIAKAT - University Of Arkansas
item SANCHEZ, PAUL - University Of Arizona
item YU, SIBIN - Huazhong Agricultural University
item LORIEUX, MATHIAS - International Institute For Tropical Agriculture
item Eizenga, Georgia

Submitted to: Rice
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2010
Publication Date: 12/23/2010
Citation: Ali, M., Sanchez, P.L., Yu, S., Lorieux, M., Eizenga, G.C. 2010. Chromosome segment substitution lines: A powerful tool for the introgression of valuable genes from wild species of rice (Oryza spp.). Rice. 3:218–234.

Interpretive Summary: In ancient times, cultivated rice was domesticated from wild species of rice (Oryza species) but only about 60% of the variation present in the wild donors was transferred into cultivated rice, resulting in a much reduced “gene pool”. In order to recover the genetic variation in the Oryza species that was lost during the domestication process, crosses have been made to reintroduce traits important to rice improvement like pest resistance, drought tolerance, tolerance to acid soils, larger panicles, more seed per panicle, etc. Re-introduction of useful traits would be expedited by having chromosome segment substitution lines (CSSLs) available. CSSLs have the background of an adapted rice cultivar with a single chromosomal segment from a wild Oryza donor species so that the complete donor genome is represented across a set of approximately 100 CSSLs. Because the CSSLs have most of their genome from the adapted rice cultivar, they are easier for breeders to use to incorporate desirable traits into new rice cultivars, thus broadening the rice gene pool. In addition, CSSLs provide a platform for discovering new genes and a tool for conducting basic studies to dissect the function of genes controlling agronomically important traits. This paper summarizes the useful agronomic traits related to biotic stress, abiotic stress, and yield enhancement that have been identified in the wild Oryza species and in CSSL introgression lines that have been reported in the literature. This information will enable researchers to utilize CSSL populations that are available and capture more of the variation that was lost during rice domestication.

Technical Abstract: Wild species of rice (genus Oryza) contain many useful genes but a vast majority of these genes remain untapped to date because it is often difficult to transfer these genes into cultivated rice (O. sativa L.). Chromosome segment substitution lines (CSSLs) and backcross inbred lines (BILs) are powerful tools for identifying these naturally occurring, favorable alleles in unadapted germplasm. In this paper, we present an overview of the research involving CSSLs and BILs in the introgression of quantitative trait loci (QTLs) associated with the improved performance of rice including resistance to various biotic and abiotic stresses, and even high yield from wild relatives of rice and other unadapted germplasm into the genetic background of adapted rice cultivars. The CSSLs can be used to dissect quantitative traits into the component genetic factors and evaluate gene action as single factors (monogenic loci). CSSLs have the potential to uncover new alleles from the unadapted, non-productive wild rice accessions, develop genome-wide genetic stocks, and clone genes identified in QTL studies for functional genomics research. Recent development of high density SNP (single nucleotide polymorphism) arrays in rice and availability of custom-designed medium and low density SNP arrays will enhance the CSSLs development process with smaller marker-defined segment introgressions from unadapted germplasm.