Introgression of opaque2 allele into sweetcorn composite through marker-assisted selection

Corn (Zea mays L.) is the third most important staple cereal crop after wheat and rice, which is used for human consumption, biofuels, livestock feed and also as raw material in industry. It provides over 20% of total calories in human diet. The sh2 mutant in supersweet corn composites and hybrids leads to enhanced sugar and vitamin B3 content in developing grains and reduction of starch content in mature grains. The deficiency of essential amino acids lysine and tryptophan in maize proteins has been significantly improved with the use of opaque2 (o2) allele leading to the development of quality protein maize (QPM). In this study, the opaque2 allele was pyramided in a sweet corn composite with Shrunken 2 (sh2) allele to develop a sweet and quality protein maize composite with higher content of essential amino acids and vitamins. QPM inbred line VQL-2 was used as the donor parent for o2 allele having higher value of lysine (3.64 ± 0.1 g/100 g), tryptophan (1.91 ± 0.01 g/100 g) and vitamin B3 (1.97 ± 0.02 mg/100 g) and the Punjab sweetcorn-1 as the recurrent parent having higher values of vitamin B1 (0.1 ± 0.01 mg/100 g) and C (6.58 ± 0.82 mg/100 g). The EU-Sweetcorn QP composite was developed through marker-assisted backcross breeding using umc1066 marker linked to o2 mutant and selection of homozygous sh2sh2 plants was done phenotypically at maturity. The EU-Sweetcorn QP composite developed for the first time in India has superior nutritional quality, e.g., high essential amino acids lysine and tryptophan and vitamins B1, B3 and C as estimated using RP-HPLC–PDA.