Genetic Advance in Grain Yield and Other Traits in Two Tropical Maize Composites Developed via Reciprocal Recurrent Selection

Abstract

Assessment of genetic gain in two tropical maize (Zea mays L.) composites improved across years is critical in determining their future improvement and use as sources of inbred lines. Two genetically complementary tropical maize composites were subjected to four cycles of reciprocal recurrent selection (RRS) for grain yield, resistance to foliar diseases, and other desirable agronomic traits using a reciprocal S1 testcross evaluation scheme. The objectives of this study were to evaluate the effects of this selection scheme on: (i) the rate of genetic gain in grain yield and other traits, (ii) the changes in variance and heritability estimates, and (iii) changes in correlations between grain yield and other traits in the two tropical maize composites. One hundred S1 lines, each derived from the original (C0) and advanced (C4) cycles of the two composites, were crossed in pairs to form 100 C0 × C0 and 100 C4 × C4 testcrosses, which were evaluated along with 10 commercial hybrid checks in a replicated trial across eight environments in Nigeria. The observed genetic gain was 3.60% cycle−1 for grain yield. On average, the top 10 C4 × C4 testcrosses outyielded the commercial hybrids by 29% and had desirable agronomic traits and improved resistance to foliar diseases. The genetic variance estimates for C0 and C4 of each composite were significantly larger than zero for most traits. These results indicated that the RRS was effective in improving grain yield and other desirable agronomic traits without diminishing genetic variability that can be exploited for further improvement of the two tropical maize composites.

Association studies between grain yield and agronomic traits of a MARS maize (Zea mays L.) population under drought and non-stress condition

“…The Delta method was used to compute the standard errors as proposed by Holland (2006). The genotypic correlation greater than twice the value of its standard error was considered to be significant statistically (Kolawole et al, 2018)…”

Phenotypic performance of new pro-vitamin A maize (Zea mays L.) hybrids using three selection indices

“…Maize (Zea mays l.) is a staple cereal crop in Africa (Musundire et al 2021) with increasing demand as food, animal feed and industrial products in nigeria (Olaniyan 2015;kolawole et al 2018). the ever-increasing human population and demand led farmers in diverse agro-ecological zones of nigeria to the cultivation of various maize genotypes with yield increase over open-pollinated varieties viz., synthetics, composites, non-conventional maize hybrids (top-cross, double top-cross, and va-rietal cross), and conventional maize hybrids (single, three-way and double-cross).…”

Reciprocal Recurrent Genomic Selection Is Impacted by Genotype-by-Environment Interactions

“…In an RGS breeding program in wheat for the less complex trait grain fructans compared to grain yield, significant genotype-by-environment interactions were observed with little effects on prediction accuracies (Veenstra et al, 2020). In contrast, in an RRS program in tropical maize focusing on grain yield, Kolawole et al (2018) also observed that genotype-by-environment interactions negatively affected the observed response to selection.…”

“…Recurrent selection cycles are applied to further manifest this tendency. The success of RRS has been demonstrated in outcrossing species such as maize (Eyherabide and Hallauer, 1991;Tardin et al, 2007;Souza et al, 2010;Kolawole et al, 2018) and sugar beet (Doney and Theurer, 1978;Hecker, 1985). To the authors knowledge, no studies were published that investigate the potentials and limits of RRS in autogamous cereals such as wheat.…”