Genetic gains in three breeding eras of maize hybrids under low and optimum nitrogen fertilization

Abstract

A comparative study on the response of six maize hybrids: two hybrids each from the 1980s (8321-21 and 8425-8), 1990s (9801-11 and 9803-2) and 2000s (0103-11 and 0103-15) to sub-optimal and optimal nitrogen fertilization was conducted in Oke-Oyi, Nigeria. The trials were set up in a split plot with three nitrogen levels (0, 30 and 90 kg N ha -1 ) as a main plot and six hybrids as sub-plots. Significant interactions were observed between hybrid and N level for all characters, with increasing in variation as the level of N decreased. Mean grain yield reductions across eras were 73.8% at no-N and 32.6% at low-N, and those of optimal-N fertilization were 34.3% and 15.7% for 1980s and 1990s genotypes respectively. Depending on N treatment, grain yield varied from 0.67 to 4.89 t ha -1 . Kernel number was most severely reduced by N stress, but had positive and highly significant (p≤0.01) correlation with grain yield at all N levels. Genetic gains in grain yield were 42% (between 1980 and 2000 eras) and 9% (between 1990 and 2000 eras) under optimal-N fertilization. The two modern hybrids of 2000 era (0103-11 and 0103-15) were outstanding for all the agronomic traits and leaf chlorophyll concentration at all N levels. Improving traits associated with fertilizer N response could accelerate rate of genetic gains in maize yields.

Gains in Grain Yield of Extra‐Early Maize during Three Breeding Periods under Drought and Rainfed Conditions

“…It was therefore expected that the inbred lines would withstand the drought stress occurring during flowering and grain filling in the savannas of WCA, as had been observed in cultivars of other maturity groups. Results revealed that mean grain yield increased by 48.4 and 62.4%, as N increased from 0 to 30 kg ha −1 and from 30 to 90 kg ha −1 , respectively (Bello et al, 2014). We recognized at the very early stages of the IITA extra-early maize improvement program that several genes governed the expression of drought tolerance in maize.…”

“…Several extra-early inbred lines in the IITA Maize Program possessed drought escape mechanism(s) and drought tolerance genes. Bello et al (2014) conducted a comparative study on the response of six maize hybrids, two each from the 1980, 1990, and 2000 eras under three N levels (0, 30, and 90 kg N ha −1 ); the N levels were used as main plots and the six hybrids as subplots. Thus, a tremendous opportunity existed for improvement of the performance of the cultivars in the program by introgressing genes for improved tolerance to drought and Striga resistance.…”

“…The trials were also evaluated under optimal conditions at Mokwa and Zaria (high-yield attributed to higher total biomass production and kernel weight, accompanied by reduction in days to flowering and plant height (PHT). Bello et al (2014) conducted a comparative study on the response of six maize hybrids, two each from the 1980, 1990, and 2000 eras under three N levels (0, 30, and 90 kg N ha −1 ); the N levels were used as main plots and the six hybrids as subplots. Results revealed that mean grain yield increased by 48.4 and 62.4%, as N increased from 0 to 30 kg ha −1 and from 30 to 90 kg ha −1 , respectively (Bello et al, 2014).…”

“…Bello et al (2014) conducted a comparative study on the response of six maize hybrids, two each from the 1980, 1990, and 2000 eras under three N levels (0, 30, and 90 kg N ha −1 ); the N levels were used as main plots and the six hybrids as subplots. Results revealed that mean grain yield increased by 48.4 and 62.4%, as N increased from 0 to 30 kg ha −1 and from 30 to 90 kg ha −1 , respectively (Bello et al, 2014). The genetic gains in grain yield of 42% (between 1980 and 2000) and of 9% (between 1990 and 2000) were obtained under optimal N fertilization (90 kg of N ha −1 ).…”

Indeks Toleran dan Evaluasi Karakter Seleksi Jagung Hibrida terhadap Pemupukan N Rendah

“…Salah satu upaya untuk mengatasi ketersediaan N yang rendah di tanah yaitu menggunakan varietas jagung toleran N rendah (Bello et al 2014;Syafruddin et al 2013;Efendi et al 2014). Jagung hibrida yang toleran terhadap N rendah mampu mengurangi risiko kegagalan panen dan dapat meningkatkan efisiensi pemupukan pada lahan suboptimal (Wegary et al 2014).…”