Composition of lysine and tryptophan among biofortified-maize possessing novel combination of opaque2 and opaque16 genes

Abstract

Traditional maize possesses low lysine (0.150−0.250%) and tryptophan (0.030−0.040%) essential for human growth and development. So far, no maize hybrid with recessive opaque2 (o2) and opaque16 (o16) genes that significantly enhance lysine and tryptophan is released for commercial cultivation. Here, we introgressed both o2 and o16 genes in the parental lines of two popular white hybrids viz., HM5 (HKI1344 × HKI1348−6-2) and HM12 (HKI1344 × HKI1378) through molecular breeding. Gene-specific simple sequence repeat (SSRs) markers (umc1066 and phi057) for o2 and gene-linked SSRs (umc1149 and umc1141) for o16 were utilized for genotyping BC1F1, BC2F1 and BC2F2 populations. Use of >100 SSRs led to 90–95 % recovery of recurrent parent genome. The mean lysine and tryptophan among introgressed progenies was 0.520 % and 0.132 %, respectively compared to original lines (lysine: 0.212 % and tryptophan: 0.039 %). The reconstituted hybrids recorded 152 % and 332 % higher lysine and tryptophan, respectively over original hybrids. The o2o2/o16o16-based hybrids also possessed 51 % and 43 % higher lysine and tryptophan, respectively over o2-based checks. The grain yield of improved versions of HM5 (7203 kg/ha) and HM12 (6247 kg/ha) was at par with original versions (HM5: 7282 kg/ha; HM12: 6482 kg/ha). These newly developed maize hybrids hold immense promise to alleviate malnutrition.