Abstract
Vitamin A deficiency is a severe public health problem among children and pregnant women in underdeveloped countries like Bangladesh who largely depend on rice for most of their required vitamins and minerals. However, vitamin A or its precursor does not exist in the endosperm of traditional rice. Japonica type transgenic Golden Rice (GR) has carotenoids biosynthetic pathways conferring B-carotene (precursor of vitamin A) accumulation in the endosperm. Therefore, this study was undertaken primarily to introgress transgene locus conferring B-carotene biosynthesis from four different events, namely, GR1-309, GR2-G, GR2-E and GR2-R into BRRI dhan29, a mega rice variety of irrigated (Boro) ecosystem through marker assisted backcrossing (MAB). One event specific sequence tagged site (STS) and 102-105 SSR markers were used for foreground and background selection during early generation backcross in each population. Background recovery in the advanced backcross introgression lines (BILs) was confirmed using a 384-plex GoldenGate SNP (single nucleotide polymorphism) genotyping assay. Background recovery, phenotypic resemblance to BR29 and total carotenoids (TC) content in polished grains of self pollinated seeds were considered for progeny selection in all generations. A set of 8 backcross introgression lines (BILs) from BR29XGR1-309, 7 BILS from BR2XGR2-G, 11 BILS from BR29XGR2-E and 15 BILS from BR29XGR2-R populations have been identified as promising materials for further evaluation in target environment. The recovery of recurrent parental background among the BILS quantified using both SSR (97% to 99%) and SNP (91.4% to 96.2%) marker loci reflected in the expression of yield and its components traits and grain quality parameters showing no significant difference from BR29 in all the populations with a few exceptions. The total carotenoids contents in polished grains in the selected BILS were found to have up to 12 μg/g after 2 months of storage at ambient temperature. This level of TC is enough to meet at least 50% of the estimated average requirement (EAR) for young children and pregnant women, based on bioconversion rate of golden rice B-carotene to vitamin A and per capita daily consumption of rice in Bangladesh.