Marker-assisted backcrossing (MABC) for improved salinity tolerance in rice (Oryza sativa L.) to cope with climate change in Vietnam Hien Thi Thu Vu1, Duc Duy Le1, Abdelbagi M. Ismail2, Ham Huy Le1,* 1
Department of Molecular Biology, Agricultural Genetics Institute (AGI), Pham Van Dong Street, Tuliem, Hanoi, Vietnam 2
Crop and Environmental Sciences Division, IRRI, Los Baños, Laguna, Philippines Corresponding author: email@example.com, firstname.lastname@example.org
Abstract Salinity is the most common abiotic stresses leading to the reduction of rice yield in many rice-growing areas of the world. Improvement in salt tolerance of rice for target stress regions is one of the important objectives of many breeding programs. In this study, we are currently applying a MABC (marker-assisted backcrossing) system on foreground selection, recombinant selection followed by background selection for development of Vietnamese rice variety that can tolerate salinity of rised sea water. The highly salt tolerant FL478 was used as a donor to transfer Saltol QTL into Bacthom 7 recipient rice cultivar. A total of 368 SSR markers were conducted to identify 8 markers in Saltol locus and 81 markers in other loci with total of 89 (24%) polymophic markers between the parents, out of which 88 markers were then applied to analyze genotyping of each backross generation with three steps of selection. The results showed that, the best plants of BC3F1 generation carry segments of the donor (11.16 - 12.6 Mb), which had 96.8% - 100 % of the recipient genome. This study revealed that the introgression lines can be directly developed into the salinity tolerance variety, which suitable for cultivating in coastal areas of Vietnamese Deltas. The MABC aids in the transfer of target chromosome segments and may improve the recovery of the recipient genome if background selection is employed. Keywords: marker-assisted backcrossing (MABC); rice (Oryza sativa L); salt tolerance; Saltol QTL; SSR markers. Abbreviations: AGI- Agricultural Genetics Institute; CLRRI- Cuu Long Rice Research Institute; IRRI- International Rice Research Institute; MABC- marker-assisted backcrossing; QTL- quantitative trait loci; SSR- simple sequence repeats (microsatellites). Introduction Vietnam is located in the sub-climatic regions will suffer the negative impacts of climate change to agricultural production. Rice production is affected by global climate change through various pathways. Sea level rise and storm surge, which result from climate change, adversely impact rice production in deltaic regions in Vietnam. Rice (Oryza sativa L.) is a key staple food crop and also a valuable cash crop in Vietnam. Although rice is the major provision for half of the world population, it is more sensitive to salt stress than other cereals (Greenland, 1984; Shannon et al., 1998). Rice production is severely affected by the deposition of soluble salts in the soils of arid and semi arid climates of the world (Ashraf et al., 2008). In Vietnam, the Mekong River Delta (MRD) and Red River Delta (RRD) areas where rice is the main cereal crop and soil salinity is a major constraint to the sustainability and expansion of rice cultivation. These regions will be affected by salinity heavily, which is one of most causes of serious reduction to rice production and economy of Vietnam. To ensure food security as well as maintain and develop the rice sector in the context of climate change, sea level rise and increasing populations are big challenges of the whole nation. Therefore, the great urgency task for rice breeders is to research and improve the rice varieties that can resist to adverse harsh conditions such as salt tolerance. Generally, most rice varieties are sensitive to salinity (Grover and Pental, 2003), however, some traditional indica rice varieties such as Pokkali, Nona Bokra and Kala-rata are fairly tolerant to salinity (Yeo et al., 1990). Salinity...