Combining ability of tropical × temperate maize inducers for haploid induction rate, R1-nj seed set, and agronomic traits

Abstract

In vivo maternal haploid induction in isolation fields is proposed to bypass the workload and resource constraints existing in haploid induction nurseries. A better understanding of combining ability and gene action conditioning traits related to hybrid inducers is necessary to set the breeding strategy including to what extent parent-based hybrid prediction is feasible. This study aimed to evaluate the following in tropical savanna in the rainy and dry seasons for haploid induction rate (HIR), R1-nj seed set, and agronomic traits: 1) combining ability, line per se, and hybrid performance of three genetic pools; 2) genetic parameters, the modes of gene action, and heterosis; and 3) the relationships of inbred–general combining ability (GCA) and inbred–hybrid performance. Fifty-six diallel crosses derived from eight maize genotypes were evaluated in the rainy season of 2021 and the dry season of 2021/2022. Reciprocal cross effects including the maternal effect barely contributed to the genotypic variance for each trait observed. HIR, R1-nj seed set, flowering dates, and ear position were highly heritable and additive inherited, while ear length showed dominant inheritance. The equal importance of additive and dominance effects was found for yield-related traits. Temperate inducer BHI306 was the best general combiner for the HIR and R1-nj seed set, followed by two tropical inducers, KHI47 and KHI54. The ranges of heterosis were trait-dependent and slightly influenced by the environment, where hybrids in the rainy season consistently had higher heterosis than those in the dry season for each trait observed. Both hybrid groups derived from tropical × tropical and tropical × temperate inducers showed taller plants, larger ear size, and higher seed sets than the corresponding parents. However, their HIRs were still below the standard check of BHI306. The implications of genetic information, combining ability, and inbred–GCA and inbred–hybrid relationships on breeding strategies are discussed.

Reciprocal cross effect over seasons on agronomic and yield traits in waxy corn under tropical savanna

“…Besides, reciprocal cross effects significantly impacted heterosis for yields; thus, superior sweet and waxy corn hybrids could be obtained when reciprocal crosses were included (Dermail et al 2018). In contrast, other similar studies using three gene pools of field corn (temperate inducers, tropical inducers, tropical noninducers) under different growing seasons concluded that reciprocal effects, including maternal and non-maternal were significant, but it could be negligible for anthesis date, silking date, plant height, ear height, yield components, and final seed set (Dermail et al 2023).…”

“…Meanwhile, the two-way interaction between genotype and location in tropical rainforest Indonesia was important for flowering times, plant architecture, yield components, and grain yield in field corn (Azrai et al 2022). In tropical savanna Thailand, however, the common G × E variation for agronomic traits and yields in field corn and vegetable corn was two-way interaction between genotype and season (Dermail et al 2020;Fuengtee et al 2020;Dermail et al 2022;Ja et al 2022;Dermail et al 2023). Under a tropical savanna climate, the dry season was more suitable for corn growth and development to obtain a better seed set than the rainy season (Sintanaparadee et al 2022).…”

“…Moreover, the inclusions of reciprocal crosses were important in the yield of waxy corn (Dermail et al 2018). On the other hand, the effects were negligible for the anthesis date, silking date, plant height, ear height, and yield components in field corn (Dermail et al 2023). However, none of the above studies reported on the impact of reciprocal crosses in waxy genetic background, focusing on yields, yield components, and agronomic traits.…”

New liguleless (lg2) maize stocks: Genetic resources for leaf architectural and haploid induction rate assessment studies

“…Temperate maize stocks typically perform poorly under tropical/sub-tropical conditions and are often difficult to maintain and use. For example, temperate haploid inducers exhibit short stature, poor pollen production and seed set and susceptibility to diseases when grown in the tropics (Dermail et al, 2023;Prasanna, 2012;Prigge, Schipprack, et al, 2012).…”

“…Temperate maize stocks typically perform poorly under tropical/sub‐tropical conditions and are often difficult to maintain and use. For example, temperate haploid inducers exhibit short stature, poor pollen production and seed set and susceptibility to diseases when grown in the tropics (Dermail et al, 2023; Prasanna, 2012; Prigge, Schipprack, et al, 2012). These constraints have been overcome with the development of first‐generation tropically adapted inducer lines (TAILs) and second‐generation inducer lines (CIM2GTAILs), which have better agronomic performance compared to temperature inducers (CIMMYT, 2017).…”