Combining ability amongst CIMMYT’s early maturing maize (Zea mays L.) germplasm under stress and non-stress conditions and identification of testers

Abstract

CIMMYT (International Maize and Wheat Research Institute) Zimbabwe's early maturing maize program, which aims to supply seed to approximately 4 million hectares of maize area in eastern and southern Africa, lacks adequate information on heterotic relationships among early maturing germplasm and has no early maturing testers for hybrid development. Open-pollinated varieties (OPVs) and hybrids are the products targeted for this region. Among the hybrids, three-way and doublecross hybrids are desired. Thus the use of single crosses as testers would be an appropriate choice for such a breeding program as one could potentially identify three-way combinations during the early generation test. A twelve-parent diallel was formed and crosses evaluated to identify heterotic groups and single-cross testers. Crosses were evaluated under four diVerent environments in Zimbabwe, two optimal, one low nitrogen stress and one drought stress. P5 (an early maturing line from heterotic group A) and CML 395 (a late maturing inbred line from heterotic group B) were used as reference parents to establish heterotic groupings of germplasm used in the diallel. The single cross (P7/P8) was identiWed as a potential group A tester because of: (a) co-classiWcation of inbred lines into heterotic group A, (b) good yields-9.8 t/ha (optimal), 3.4 t/ha (low nitrogen) and 2.1 t/ha (drought); and (c) good GCA eVects for grain yield (0.49 t/ha) of line P7 while line P8 contributed to reduced height and anthesis-silking interval.

Evaluation of Maize Top Cross Hybrids for Grain Yield and Associated Traits in Three Agro-Ecological Zones in Ghana

“…The cause of low productivity has been ascribed partly to the use of traditional low yielding open-pollinated varieties (MOFA-SRID, 2006). At present, there is a growing demand for use of hybrid seeds especially early and extraearly drought resistant materials with high grain yield potential that can provide early harvest to bridge the hunger gap before the harvest of a full-season crop (Pswarayi and Vivek, 2007), ideal for off-season planting and suitable for minor rainfall season production which tend to be very short. Regrettably, the National Maize Program does not 2.2 Maize varieties and inbred lines used for the study Twenty-seven genotypes including three open-pollinated varieties (normal OPV parents), three check varieties and 21 inbred lines (donor parents) were used for the study.…”

Combining Ability and Gene Action of Tropical Maize (Zea mays L.) Inbred Lines under Low and High Nitrogen Conditions

“…Genetic studies have been conducted on maize genotypes under low N using different sources of genetic material (Badu-Apraku et al, 2013;Betràn et al, 2003;De Souza et al, 2008;Makumbi et al, 2011;Meseka et al, 2006;Meseka et al, 2013;Miti, 2007;Pswarayi & Vivek, 2008). However, information on gene action conditioning grain yield under low N has been contradictory.…”

Combining Ability for Grain Yield Performance among CIMMYT Germplasm Adapted to the Mid-Altitude Conditions

“…GCA is a very important factor when making these decisions (Pswarayi & Vivek, 2008;Singh et al, 2013). Hence, the identification of those many lines with positive GCA effects for GY across sites, under optimum, managed drought, low-N and random stress sites random stress sites are important.…”