Changes in heterosis of maize (Zea mays L.) varietal cross hybrids after four cycles of reciprocal recurrent selection

Abstract

Two improved tropical maize composites, TZL COMP3 and TZL COMP4; representing complementary heterotic pools have been subjected to four cycles of reciprocal recurrent selection (RRS) for two decades to enhance varietal cross performance. The objectives of this study were to evaluate the effect of selection on genetic gain in heterosis for grain yield and other agronomic traits of these composites. Ten parental populations representing the C 0 to C 4 of each composite and their crosses plus a varietal check were evaluated in a trial at eight environments in Nigeria. Grain yield of the varietal crosses increased with selection by 3.1% cycle -1 . Mean grain yields of the C 4 × C 4 varietal cross exceeded that of a popular improved reference variety by 23%. Selection also reduced anthesis-silking interval, improved ear characteristics, phenotypic appeal and resistance to foliar diseases. Mid-parent heterosis (MPH) increased from 4% at C 0 × C 0 to 24% at C 4 × C 4 . The average rate of genetic gain in heterosis for grain yield in population crosses was 3.1% possibly because of presence of non-additive gene effects. The results of our study present the potential usefulness of the advanced selection cycle as sources of diverse inbred lines with improved combining ability as well as improved varietal crosses that can be multiplied and deployed in areas with limited market access.

Cyclical response of maize populations versus base population and standard genotypes across environments

“…However, origional population -C 0 showed least mean values and unproductive recital for yield related parameters with optimum and delayed plantings at both sites. Past studies also authenticated that improved populations revealed best performance and the highest grain yield than base population, which confirmed that might the feasible genes accumulated in the particular versions of the maize populations (Khamkoh et al, 2019;Kolawole et al, 2019). Significant impact of the recurrent selection cycles was observed on cob traits and grain yield, and the improved populations C 1 and C 2 executed better performance than maize base population (Ayiga-Aluba et al, 2015;Sohail et al, 2018;Sajjad et al, 2020a, b).…”

“…Sin embargo, la población original -C 0 mostró los valores medios más bajos y un comportamiento improductivo para los parámetros de rendimiento relacionados con las siembras óptimas y tardías en ambos lugares. Estudios anteriores también demostraron que las poblaciones mejoradas revelaron el mejor rendimiento y la mayor producción de grano que la población base, lo que confirmó que los genes deseables pueden ser acumulados en versiones particulares de poblaciones de maíz (Khamkoh et al, 2019;Kolawole et al, 2019). Se observó un impacto significativo de los ciclos de selección recurrente en los rasgos de la mazorca y de rendimiento de grano, y las poblaciones mejoradas C 1 y C 2 demostraron un mejor rendimiento que la población base de maíz (Ayiga-Aluba et al, 2015;Sohail et al, 2018;Sajjad et al, 2020a, b).…”

“…On recurrent selection in maize, extensive studies were conducted and varied estimates were recorded due to different breeding material used, environments, and their interactions (Udo et al, 2017;Chen et al, 2019;Khamkoh et al, 2019). In recurrent selection methods, two aims stay common i.e., to improve the genetic potential of origional population, and sustainable genetic variation in the population to assist in enduring maize breeding program (Guimaraes et al, 2018;Kolawole et al, 2019).…”

“…En la selección recurrente en maíz, se llevaron a cabo estudios exhaustivos y se registraron estimaciones variadas debido a los diferentes materiales de reproducción utilizados, los ambientes y sus interacciones (Udo et al, 2017;Chen et al, 2019;Khamkoh et al, 2019). En los métodos de selección recurrente, dos objetivos siguen siendo comunes: mejorar el potencial genético de la población original, y la variación genética sostenible en la población para ayudar en el programa de reproducción de maíz perdurable (Guimaraes et al, 2018;Kolawole et al, 2019 an array of sites and crop seasons to determine the influence of environment on their recital. The genotype with less magnification by the existing climatic conditions is considered most desirable (Annor et al, 2019).…”

Combining ability for morphological and nutritional traits in a diallel cross of tomato (Solanum lycopersicum L.)

“…Least square mean were computed and separated using Fisher's least significant difference (LSD) test (p < 0.05). Mid-parent heterosis was calculated for all measured traits using the formula of Mather & Jinks (1971) and the student t-statistics was used to determine the statistical difference of F 1 hybrid means and the mid-parent according to Wynne et al (1970) and Kolawole et al (2019). Potence ratio was calculated according to Smith (1952) to determine the degree of dominance.…”