Exploring Aus germplasm for breeding high zinc rice varieties
2019
Inabangan-Asilo, M. | Descalsota, G.I.L. | Nha, C.T. | Calayugan, M.I. | Panalog, A. | Sue, Z.M. | Arocena, E.C. | Amparade, A. | Tesoro, F. | Marfori-Wazarea, C.M. | Reinke, R. | Swamy, M.
Rice is one of the major staple cereal crops that feed half of the world's population. However, most of the popular high yielding rice varieties are low in essential micronutrients such as iron and zinc in their polished form. Improving the bioavailable Fe and Zn in the polished rice is a feasible and cost effective approach to address the global problem of micronutrient deficiencies or hidden hunger. Among different subgroups of rice germplasm, Aus accessions showed wider variations for grain micronutrients. Aus is closest to indica varieties but belongs to a distinct genetic group and has many promising traits including biotic, abiotic stress tolerance and grain quality traits. At IRRI [International Rice Research Institute], 224 Aus accessions were evaluated for agronomic and grain nutritional traits for 3 seasons (2017DS, 2017WS and 2018DS). The highest yielding Aus accession has 8.6t/ha while grain Zn was 40ppm. Multi-location trials across the Philippines revealed two promising accessions, Kaliboro and Jamir as the most stable and best performing accessions having yield of 3 tons/ha and Zn levels of 35 ppm based on BLUP estimates. These two accessions were used as donor parents in developing recombinant inbred lines (RIILs) mapping population for detecting QTLs for grain Zn content. Mapping studies using these RILs identified several candidate genes from the ZIP family like OsZIP5, OsZIP9, and OsZIP2 found in chromosomes 5 and 3, which are said to be involved in Zn transport in rice. Large effect QTLs for grain Zn content can be used in marker-assisted breeding (MAB) to develop high Zn rice varieties. Aus accessions are valuable source of novel genes not only for stress tolerance but also biofortification traits in breeding programs.
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