Genetic analysis and heterotic grouping of quality protein maize (Zea mays L.) inbred lines and derived hybrids under conditions of low soil nitrogen and drought stress

Abstract

Quality Protein Maize (QPM) varieties are rich in lysine and tryptophan, but suffer reduced grain yield (GY) in West and Central Africa (WCA) due to low soil nitrogen (low-N) and intermittent drought stress (DS). Development of stress tolerant QPM hybrids will enhance sustainable maize production and improve nutritional health in WCA. Knowledge of combining ability, gene action and heterotic grouping of QPM inbred lines are crucial to successful breeding strategies for the development of superior hybrids with enhanced nutritional values. The objectives of this study were to: (i) determine the combining ability for GY and other yield traits among 13 newly developed QPM inbred lines, (ii) assign the QPM inbred lines to distinct heterotic groups based on general combining ability effects of multiple traits (HGCAMT) (iii) assess GY performance and yield stability of the single-cross hybrids generated from the inbred lines and (iv) examine the interrelationships among traits contributing to variation in GY of the QPM hybrids under low-N and DS conditions. Seventy-eight single cross hybrids were generated through half-diallel mating of 13 QPM inbred lines and evaluated along with three commercial checks for grain yield and its related traits under low-N and DS conditions. Signi cant general combining ability (GCA) and speci c combining ability (SCA) effects were obtained for grain yield (GY) and yield-related traits. Both additive and non-additive gene effects were involved in the inheritance of GY and other traits under low-N and DS conditions. However, for GY additive gene effect was twice as large as non-additive gene effect. Three heterotic groups were each delineated under low-N and DS. Inbred lines, CRIZEQ-44 and CRIZEQ-77 belonging to different heterotic groups were identi ed as testers for development of superior hybrids for low-N and DS environments. The GY of hybrids ranged from 1092 to 4373 kg/ha and 2543 to 7711 kg/ha, respectively under low-N and high-N conditions, and from 1072 to 4020 kg/ha and 2313 to 7404 kg/ha, under DS and WW condition, respectively. Grain yield reduction due to DS and low-N were 49.5 and 48.3%, respectively. Hybrids CRIZEQ-44 × CRIZEQ-77 was the highest yielding and most stable hybrid across all the growing conditions and should be further evaluated on-farm for release and commercialisation. Number of ears per plant, silking date and plant aspect had positive direct effects on GY and should be included in the selection criteria for improved GY under low-N and DS conditions. IntroductionMaize (Zea mays L.) is one of the world's most important cereal crops, serving multiple applications as food, feed and industrial crop. It is an important crop sub-Saharan Africa (SSA), where its cultivation cut across a wide range of agro-ecological zones including the savannas, which are the main production areas in SSA (Badu-Apraku et al., 2011). The savannas are characterised by low night temperatures, high solar radiation during the day, and low disease incidences which are ideal conditions for m...

Molecular Diversity and Combining Ability in Newly Developed Maize Inbred Lines under Low-Nitrogen Conditions

“…The GCA/SCA ratio exceeded one for all traits measured, indicating that additive gene action plays a crucial role in governing the inheritance of these traits. This finding aligns with the research by Owusu et al [67], Ribeiro et al [38], Badu-Apraku et al [68], and Okunlola et al [14], who also observed additive genetic variance to be predominant in the expression of grain yield across different nitrogen levels. However, this stands in contrast to the studies of Betran et al [69], Worku et al [70], and Makinde et al [71], which highlighted the dominance of non-additive gene action in the genetic control of grain yield under similar conditions.…”

The combining ability of extra-early maturing quality protein maize (Zea mays) inbred lines and the performance of their hybrids in Striga-infested and low-nitrogen environments

“…This suggested that recurrent selection and hybridization can be employed for the genetic improvement of these traits. Similar findings were reported by Wegary et al (2013) and Owusu et al (2023) using the diallel mating method, where both additive and non-additive gene actions were found to be important for the inheritance of grain yield among QPM inbreds under low-N conditions. Meseka et al (2006), Afolabi et al (2019), Abu et al (2021), and Makinde et al (2023) also observed the significance of both additive and non-additive gene actions in the expression of grain yield under low-N conditions.…”