Bioscience Methods 2024, Vol.15, No.5, 226-236 http://bioscipublisher.com/index.php/bm 231 breeders combined the o2 allele with genetic modifiers to develop QPM genotypes with hard kernels and high nutritional quality (Tripathy et al., 2017). In India, the development of Vivek QPM-9, a hybrid of two QPM introgression lines, has been a notable success. This hybrid, developed through marker-assisted selection (MAS), has been widely adopted for commercial cultivation. Vivek QPM-9 not only retains high lysine and tryptophan content but also exhibits early maturity and high yield, making it suitable for various agro-climatic conditions (Gupta et al., 2009). Similarly, in sub-Saharan Africa, QPM hybrids have played a crucial role in combating malnutrition. The development of early maturing yellow-endosperm QPM inbreds and their evaluation under multiple environments, including Striga-infested and drought conditions, has led to the identification of stable and high-yielding hybrids (Badu‐Apraku et al., 2015). 5.2 Success stories in hybrid development The integration of genetic markers in maize breeding programs has significantly accelerated the development of QPM hybrids. Marker-assisted backcrossing has been employed to rapidly convert normal maize lines to QPM. For instance, a two-generation marker-based backcross breeding program successfully incorporated the o2 gene into an early maturing normal maize inbred line, resulting in QPM lines with enhanced tryptophan concentration and desirable agronomic traits (Babu et al., 2005). Another success story involves the pyramiding of the o2 and novel opaque16 (o16) genes to further enrich lysine and tryptophan content in sub-tropical maize. This approach led to the development of QPM hybrids with significantly higher nutritional quality compared to their original versions. The reconstituted hybrids showed an average enhancement of 49% and 60% in lysine and tryptophan content, respectively, while maintaining similar grain yield and agronomic traits (Sarika t al., 2018). In the Democratic Republic of Congo, a QPM breeding program developed 137 inbred lines adapted to various agro-ecological conditions. These lines exhibited high genetic variability and were selected based on agro-morphometric characteristics and molecular markers. The program is developing QPM varieties with high grain yield and resistance to local diseases and pests, contributing to increased grain production and improved nutritional security (Mbuya et al., 2012). 5.3 Successful practices in different regions and countries The success of QPM breeding programs varies across regions and countries, depending on local agro-climatic conditions and breeding strategies. In India, the use of SSR markers has been effective in differentiating QPM inbred lines and analyzing their genetic relationships. This has facilitated the utilization of elite QPM germplasm in breeding programs, leading to the development of high-yielding and nutritionally enriched hybrids (Bantte and Prasanna, 2003). In southern Africa, the heritability and associations among grain yield and quality traits in QPM and non-QPM hybrids have been studied to inform breeding decisions. The findings suggest that ear aspect, ears per plant, and starch content are major traits contributing to grain yield. However, the negative association between grain yield and tryptophan content poses a challenge in developing hybrids with both high yield and high nutritional quality. Gene pyramiding is recommended to address this challenge (Figure 2) (Amegbor et al., 2022). Despite the successes, the adoption of QPM varieties has been limited in some regions due to challenges such as the need for isolation from normal maize and minimal collaboration between breeders, farmers, and other stakeholders. To enhance adoption, participatory plant breeding (PPB) and participatory variety selection (PVS) approaches are recommended. These approaches involve farmers and other stakeholders in the breeding process, ensuring that the developed varieties meet local needs and preferences (Tandzi et al., 2017). In conclusion, the integration of genetic markers in maize breeding programs has led to significant advancements in the development of QPM hybrids. Success stories from different regions highlight the potential of QPM to address protein malnutrition and improve food security. However, continued efforts are needed to overcome adoption challenges and ensure the widespread cultivation of QPM varieties.
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