Abstract
Quality protein maize (QPM; Zea mays L.) has effectively enhanced levels of the amino acids, lysine, and tryptophan, over normal maize and provided balanced dietary protein for the health and development of monogastric animals and humans. However, as in normal maize, QPM varieties are low in provitamin A (ProVA), a precursor of vitamin A, which can lead to vitamin A deficiency in humans when maize is a significant part of their diet. In this study, maize inbred Hp321-1 carrying the favorable alleles crtRB1-5′TE-2 and crtRB1-3′TE-1 that can enhance levels of ProVA, was used as donor for improving ProVA in QPM inbred lines CML161 and CML171. Functional markers for identifying the favorable alleles crtRB1-5′TE-2 and crtRB1-3′TE-1 were used in foreground selection, and simple sequence repeat markers were used in background selection for the BC1F1, BC2F1, and BC2F2 generations. The background recovery rates were 77.4 and 84.5 % for CML161 and CML171 populations, respectively, in the BC1F1 generation, and 89.9 and 92.1 % in the BC2F2 generation. With foreground and background selection, the mean ProVA concentration has been improved from 1.60 µg g−1 in the parent of CML161 to 5.25 µg g−1 in its BC2F3 offspring, from 1.80 µg g−1 in the parent of CML171 to 8.14 µg g−1 in its BC2F3 offspring while maintaining similar QPM characteristics of the recurrent parents. The success from this study offers maize breeders a procedure for increasing ProVA in QPM lines, which will greatly mitigate vitamin A deficiency and protein-energy malnutrition in developing countries.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-015-0349-7) contains supplementary material, which is available to authorized users.
Highlights
Maize is the staple food and main source of energy for millions of poor people living in developing countries, including China, India, and many countries in Africa and Latin America (IITA 2009; Nuss and Tanumihardjo 2010; Li et al 2012)
The donor parent Hp321-1 had the favorable allele crtRB1-50TE-2 with a 600-bp band, while unfavorable allele crtRB1-50TE-1 had an 800-bp band corresponding to the recurrent parents CML161 and CML171
The results showed that Quality protein maize (QPM) inbred lines CML161 and CML171 introgressed with the favorable alleles crtRB1-50TE-2 and crtRB1-30TE-1 had 3.28-fold and 4.52-fold increase in the mean provitamin A (ProVA) concentration, which indicated that the marker-assisted backcross (MAB) procedure was effective in transferring the favorable crtRB1 gene and increasing the ProVA level in maize
Summary
Maize is the staple food and main source of energy for millions of poor people living in developing countries, including China (especially Southwestern China), India, and many countries in Africa and Latin America (IITA 2009; Nuss and Tanumihardjo 2010; Li et al 2012). In the summer 2010, seeds of CML161, CML171, and Hp321-1 were sown and crosses were made at the YAAS Baiyi Maize Research Station (BMRS, 25°230N, 102°90E, 1970 MASL), Kunming, Yunnan, China, to generate F1 populations of CML161 and CML171. In the winter 2010, the F1 was used to develop ‘backcross progenies’ (BC1F1 populations) by backcrossing the F1 with their recurrent parents CML161 and CML171 at the YAAS Gasa Maize Research Station (GMRS, 21°950N, 100°80E, 588 MASL), Jinghong, Yunnan, China. In the summer 2011, 597 BC1F1 plants of the CML161 population and 462 BC1F1 plants of the CML171 population were selected via FS and screened with BS for recovering individuals with C80.0 % genetic similarity to the recurrent parent to develop ‘backcross progenies’ BC2F1 populations by backcrossing the BC1F1 with their recurrent parent CML161 and CML171 at the BMRS. The two parallel crossing schemes for CML161 and Hp321-1, and CML171 and Hp321-1 are shown in Supplementary Fig. 1
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