Rice backcross population assessment for iron tolerance through phenotypic and genotypic analyses

Iron toxicity has become a serious issue affecting rice (Oryza sativa L.) production in many irrigated lowland areas. The selection of Fe2+-tolerant rice cultivars under iron toxicity conditions and the identification of molecular markers are good approaches to obtaining tangible results. This study aimed to identify simple sequence repeat (SSR) markers that were associated with iron tolerance traits in a rice backcross population. A total of 117 seedlings from the backcross (BC3F2) of ‘OM6830’/‘AS996’//‘AS996’ were phenotyped at the 4-week-seedling stage at Ton Duc Thang University, Ho Chi Minh City, Vietnam. The rice population was screened in Yoshida nutrient medium supplemented with FeCl2 at a concentration of 150 mg L−1 under greenhouse conditions. Phenotypic analysis was conducted by scoring two parameters, namely, root length and leaf bronzing. Genotypic analysis was carried out on the BC3F2 population by using four markers, i.e., RM6, RM240, RM252, and RM451, for association analysis with iron tolerance. A total of 23 BC3F2 lines were selected on the basis of their higher tolerance (score 1) for Fe2+ compared with the tolerant parental line ‘AS996’. The markers RM6 and RM240 were highly polymorphic and identified different Fe2+-tolerant lines in the BC3F2 population. Among the BC3F3 progeny derived from the selected 23 BC3F2 lines, BC3F3-7 was identified as the most Fe2+-tolerant line. BC3F3-15 was also found to be Fe2+ tolerant. Both lines showed good development capability and provided high yields under stress conditions. These tolerant BC3F3 lines could be further screened with additional SSR markers in future breeding programs aiming to increase rice production in iron-contaminated areas of the Mekong Delta, Vietnam.