Developing new flood-tolerant varieties at the international rice research institute (IRRI)
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Submergence is a major abiotic stress causing major yield losses in rainfed and irrigated rice production areas in South and South East Asia, and some parts of Africa. Considerable progress in breeding new tolerant rice varieties has been made during the last decade after the identification of a major quantitative trait locus (QTL) named SUB1. Using marker assisted backcrossing (MABC), this QTL was subsequently incorporated into many popular Asian mega-varieties with a high level of precision and in a much shorter time compared to using conventional methods. Currently the flood-prone breeding program uses a modified-pedigree scheme that is based upon the selection of SUB1 including field screening combined with a late generation marker assisted selection (MAS) step. We propose late-generation MAS to be an alternative scheme to early-generation MAS. This approach may be useful when there are markers for multiple target genes/QTLs available which enables a breeder to discriminate between advanced breeding lines, and select lines for advanced yield trials and subsequently, for use in hybridization in order to develop new breeding populations. This approach may also be suited to breeding programs with a limited capacity for molecular breeding. Looking towards 2025, there is a strong need to develop improved varieties for flood prone areas including enhancing submergence tolerance with additional complementary QTLs, improving tolerances to other types of flooding such as stagnant flooding, flooding after seeding, disease and insect resistances, agronomic traits, and combining multiple abiotic stresses (i.e. salinity and drought, salinity and submergence). Identifying and validating novel QTLs for these traits will provide useful information to develop breeding strategies and for molecular breeding activities. Exploiting new germplasm and the use of new technologies especially DNA markers, improved phenotyping methods and "breeding informatics" will be essential to complement conventional breeding efforts. International collaboration to co-ordinate, evaluate and develop new breeding material suited to key target regions will also be critical. Society for the Advancement of Breeding Research in Asia and Oceania (SABRAO) 2013.
