Development of β-carotene, lysine, and tryptophan-rich maize (Zea mays) inbreds through marker-assisted gene pyramiding
Neelima Chandrasekharan, Nagalakshmi Ramanathan, Bharathi Pukalenthy, Sarankumar Chandran, Manickam Dhasarathan, Adhimoolam Karthikeyan, Ganesan Kalipatty Nalliappan, Sudha Manickam, Ravikesavan Rajasekaran, S. Vellaikumar, Vignesh Muthusamy, Firoz Hossain, H. S. Gupta, Senthil Natesan
Abstract
Abstract Maize ( Zea mays L.) is the leading cereal crop and staple food in many parts of the world. This study aims to develop nutrient-rich maize genotypes by incorporating crtRB1 and o2 genes associated with increased β-carotene, lysine, and tryptophan levels. UMI1200 and UMI1230, high quality maize inbreds, are well-adapted to tropical and semi-arid regions in India. However, they are deficient in β-carotene, lysine, and tryptophan. We used the concurrent stepwise transfer of genes by marker-assisted backcross breeding (MABB) scheme to introgress crtRB1 and o2 genes. In each generation (from F 1 , BC 1 F 1 –BC 3 F 1 , and ICF 1 –ICF 3 ), foreground and background selections were carried out using gene-linked ( crtRB1 3′TE and umc1066) and genome-wide simple sequence repeats (SSR) markers. Four independent BC 3 F 1 lines of UMI1200 × CE477 (Cross-1), UMI1200 × VQL1 (Cross-2), UMI1230 × CE477 (Cross-3), and UMI1230 × VQL1 (Cross-4) having crtRB1 and o2 genes and 87.45–88.41% of recurrent parent genome recovery (RPGR) were intercrossed to generate the ICF 1 -ICF 3 generations. Further, these gene pyramided lines were examined for agronomic performance and the β-carotene, lysine, and tryptophan contents. Six ICF 3 lines (DBT-IC-β 1 σ 4 -4-8-8, DBT-IC-β 1 σ 4 -9-21-21, DBT-IC-β 1 σ 4 -10-1-1, DBT-IC-β 2 σ 5 -9-51-51, DBT-IC-β 2 σ 5 -9-52-52 and DBT-IC-β 2 σ 5 -9-53-53) possessing crtRB1 and o2 genes showed better agronomic performance (77.78–99.31% for DBT-IC-β 1 σ 4 population and 85.71–99.51% for DBT-IC-β 2 σ 5 population) like the recurrent parents and β-carotene (14.21–14.35 μg/g for DBT-IC-β 1 σ 4 and 13.28–13.62 μg/g for DBT-IC-β 2 σ 5 ), lysine (0.31–0.33% for DBT-IC-β 1 σ 4 and 0.31–0.34% for DBT-IC-β 2 σ 5 ), and tryptophan (0.079–0.082% for DBT-IC-β 1 σ 4 and 0.078–0.083% for DBT-IC-β 2 σ 5 ) levels on par with that of the donor parents. In the future, these improved lines could be developed as a cultivar for various agro-climatic zones and also as good genetic materials for maize nutritional breeding programs.