Abstract

Dwarf maize (Zea mays L.) hybrids grown in Zimbabwe have limited resistance to maize streak virus disease (MSD). Combining ability studies are important in revealing a genotype’s utility in hybrid combinations. We investigated combining abilities and mode of inheritance of resistance to MSD in dwarf maize germplasm. A six-parent half diallel cross was conducted to generate fifteen F₁ hybrids, which were evaluated in a replicated field trial under an artificial epidemic of MSD. Scoring for MSD, development was done two weeks after inoculation and at flowering. Significant differences (p<0.05) for resistance to MSD were observed among the F₁ progeny. These differences were attributed to both general combining ability (GCA) and specific combining ability (SCA), which were both significant (p<0.05). GCA was more important than SCA as suggested by the large ratio (2.51) of GCA and SCA variance components. Additive gene effects were therefore predominant in the inheritance of resistance to MSD. Heritability of resistance to MSD was high (71%), suggesting that only a few major genes were involved.  We believe that this is the first time that genetic analysis of resistance to MSD has been reported for dwarf maize germplasm.

Key words: Dwarf maize varieties, maize streak virus disease (MSD), general combining ability   (GCA), specific combining ability (SCA), gene action.