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.
Highlights
Maize (Zea mays L.) is the most important staple crop in Southern Africa, accounting for more than 50% of all the calories consumed in these countries (Byerlee and Eicher, 1997)
We investigated combining abilities and mode of inheritance of resistance to maize streak virus disease (MSD) in dwarf maize germplasm
A preponderance of general combining ability (GCA) effects suggested that additive gene effects were more important in the inheritance of resistance to MSD in the materials evaluated
Summary
Maize (Zea mays L.) is the most important staple crop in Southern Africa, accounting for more than 50% of all the calories consumed in these countries (Byerlee and Eicher, 1997). In Zimbabwe, most of the maize is produced by smallholder farmers who have limited access to financial resources, the latest technologies, and land. Maize streak virus disease (MSD) is one of the major diseases that can potentially cause a total crop failure on susceptible varieties during severe epidemics, and is reported to cover an estimated 60% of the total arable area in Africa (DeVries and Toenniessen, 2001). The disease is endemic throughout the maize producing areas in Africa. Use of resistant varieties is recognized as the most effective, economically viable and environmentally benign method of controlling this disease, especially for resource-poor farmers who cannot afford chemical control (Ngwira and Pixley, 2000; Lagat et al, 2008).
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