To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s12041-018-0914-z Byline: Firoz Hossain (1), Vignesh Muthusamy (1), Neha Pandey (1), Ashish K. Vishwakarma (1), Aanchal Baveja (1), Rajkumar U. Zunjare (1), Nepolean Thirunavukkarasu (1), Supradip Saha (1), Kanchikeri M. Manjaiah (1), Boddupalli M. Prasanna (1,2), Hari S. Gupta (1) Keywords: biofortification; essential amino acids; opaque2; quality protein maize; marker-assisted selection Abstract: Maize is a valuable source of food and feed worldwide. Maize endosperm protein is, however nutritionally poor due to the reduced levels of two essential amino acids, lysine and tryptophan. In this study, recessive opaque2 (o2) allele that confers enhanced endosperm lysine and tryptophan, was introgressed using marker-assisted backcross breeding into three normal inbred lines (HKI323, HKI1105 and HKI1128). These are the parental lines of three popular medium-maturing single cross hybrids (HM4, HM8 and HM9) in India. Gene-based simple sequence repeat (SSR) markers (umc1066 and phi057) were successfully deployed for introgression of o2 allele. Background selection using genome-based SSRs helped in recovering 96\% 96% of recurrent parent genome. The newly developed quality protein maize (QPM) inbreds showed modified kernels (25--50% opaqueness) coupled with high degree of phenotypic resemblance to the respective recipient lines, including grain yield. In addition, endosperm protein quality showed increased lysine and tryptophan in the inbreds to the range of 52--95% and 47--118%, respectively. The reconstituted QPM hybrids recorded significant enhancement of endosperm lysine (48--74%) and tryptophan (55--100%) in the endosperm. The QPM hybrids exhibited high phenotypic similarity with the original hybrids for morphological and yield contributing traits along with responses to some major diseases like turcicum leaf blight and maydis leaf blight. The grain yield of QPM hybrids was at par with their original versions under multilocation testing. These elite, high-yielding QPM hybrids with improved protein quality have been released and notified for commercial cultivation, and hold significant promise for improving nutritional security. Author Affiliation: (1) 0000 0001 2172 0814, grid.418196.3, ICAR-Indian Agricultural Research Institute (IARI), New Delhi, 110 012, India (2) International Maize and Wheat Improvement Centre (CIMMYT), 1041-00621, , Nairobi, Kenya Article History: Registration Date: 16/02/2018 Received Date: 29/12/2016 Accepted Date: 23/08/2017 Online Date: 15/03/2018 Article note: Corresponding editor: Arun Joshi Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12041-018-0914-z) contains supplementary material, which is available to authorized users.