Combining Ability and Heterotic Grouping of Selected Yellow Maize (Zea Mays L.) Inbred Lines for Resistance to Maize Streak Virus Disease

Abstract

Maize streak virus disease (MSVD) is a major constraint to maize production in sub-Saharan Africa. Developing nutritious and high-yielding yellow maize hybrids to complement white maize is an important step in achieving food and nutrition security in the face of MSVD for sustainable food systems in Ghana. The objectives of this study were to (i) determine the combining ability effects of yellow maize inbred lines for grain yield and other yield-related components, (ii) classify the inbred lines into heterotic groups, and (iii) assess the performance of the resultant single cross hybrids and inbred lines across maize streak infested environments. Eight yellow maize inbred lines were used to develop 28 F1 hybrids in a half diallel mating design. The hybrids, plus four standard checks were evaluated using a 8 × 4 alpha lattice design with two replications in the field. The inbred lines were evaluated adjacent to the hybrids using a randomized complete block design whilst in the greenhouse, evaluation was done using a completely randomized design with two replications. Both hybrids and inbred lines were screened under artificial MSV inoculation, natural MSV inoculation, and controlled environments. General combining ability (GCA) effects were not significant for most traits including grain yield whereas specific combining ability effects were significant for most traits. This suggested that the inheritance of these traits was conditioned by non-additive gene action. Inbred lines were grouped into two distinct heterotic groups based on significant SCA values. WYML 6 × WYML 8, 9450 × WYML 10, PIONEER, and WYML 12 × WYML 9 were the best-performing hybrids for grain yield across environments, indicating tolerance of resistance to MSV. However, grain yield in the naturally-infested environment was lower than in the artificially-infested environment. This suggested that there could be mixed infections or that the strain of MSV present in the natural environment could differ from that used for artificial inoculation. The area under the disease progress curve showed that MSV infested less than 50% of all fields in the study. Keywords: Zea mays, combining ability, heterosis, heterotic groupings, maize streak virus.