Mutant crtRB1 gene negates the unfavourable effects of opaque2 gene on germination and seed vigour among shrunken2-based biofortified sweet corn genotypes

Sweet corn is one of the most popular vegetables worldwide. However, traditional shrunken2 (sh2)-based sweet corn varieties are poor in nutritional quality. Here, we analysed the effect of (1) beta-carotene hydroxylase1 (crtRB1), (2) opaque2 (o2) and (3) o2 + crtRB1 genes on nutritional quality, germination, seed vigour and physico-biochemical traits in a set of 27 biofortified sh2-based sweet corn inbreds. The biofortified sweet corn inbreds recorded significantly higher concentrations of proA (16.47 mu g g(-1)), lysine (0.36%) and tryptophan (0.09%) over original inbreds (proA: 3.14 mu g g(-1), lysine: 0.18%, tryptophan: 0.04%). The crtRB1-based inbreds had the lowest electrical conductivity (EC), whereas o2-based inbreds possessed the highest EC. The o2 + crtRB1-based inbreds showed similar EC to the original inbreds. Interestingly, o2-based inbreds also had the lowest germination and seed vigour compared to original inbreds, whereas crtRB1 and o2 + crtRB1 introgressed sweet corn inbreds showed similar germination and seed vigour traits to their original versions. This suggested that the negative effect of o2 on germination, seed vigour and EC is nullified by crtRB1 in the double mutant sweet corn. Overall, o2 + crtRB1-based sweet corn inbreds were found the most desirable over crtRB1- and o2-based inbreds alone.