Development of near-isogenic lines for multiple QTLs associated with salinity tolerance in rice
2009
Zantua, R.E. | Thomson, M.J. | de Ocampo, M.P. | Egdane, J.A. | Concepcion, J.C.T. | Vispo, N.A. | Sajise, A.G. | Singh, R.K. | Ismail, A.M.
The development of near-isogenic lines (NILS) is an important step in the characterization and fine-mapping of quantitative trait loci (QTLs) and for molecular marker-assisted breeding. The purpose of developing these NILs is to isolate salt tolerance QTLs in the background of the recurrent parent to test their individual effects. Previously, several salt tolerance QTLs were mapped at IRRI using a recombinant inbred lines (RIL) population between the salt-tolerant landrace Pokkali and the sensitive variety IR29. A highly tolerant RIL, FL 478 (IR 66946-3R-178-1-1), was backrossed to IR29 for NIL development. A first set of 140 FL 478/IR29 BC3F4 lines was genotyped with 28 simple sequence repeat markers, and 55 selected lines were screened for tolerance in the phytotron. Six promising lines were backrossed two more times to IR29, and subsequently 122 FL 478/IR29 BC5F1 plants were genotyped with 70 SSR markers to define the Pokkali introgressions. Five NILS with a single Pokkali introgression at the major tolerance Saltol QTL in chromosome 1 and a clean IR29 background were identified. In addition, several other NILs were identified with an IR29 background and Pokkali introgression at additional QTLs on chromosomes 2,10,and 12. The BC5F2 progeny will be screened for salinity tolerance at the seedling stage in a salinized nutrient solution to determine the magnitude of each QTL effect. These NILs will be essential for fine-mapping individual QTLs and for future steps to pyramid multiple QTLs to increase the level of salinity tolerance in high-yielding rice varieties.
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