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CROP BREEDING, GENETICS & CYTOLOGY

Combining Ability for Resistance to Maize Weevil among 14 Southern African Maize Inbred Lines

^a Dep. of Agronomy, Iowa State Univ., Ames, IA 50011
^b CIMMYT, Apdo Postal 6-641, 06600, Mexico D.F., Mexico
^c Deceased 2004,, Midlands State Univ., Faculty of Natural Resources Management and Agric., P.B. 9055, Gweru, Zimbabwe

^* Corresponding author (k.pixley{at}cgiar.org)

Maize weevil, Sitophilus zeamais Motschulsky, is an important pest of stored maize (Zea mays L.) in the tropics. We used 14 southern African maize inbred lines to assess (i) combining ability for resistance to maize weevil in F₂ and F₂–Syn 1 grain, (ii) the importance of maternal effects for resistance of F₂ and F₂–Syn 1 grain to maize weevil, and (iii) combining ability for grain yield of F₁ hybrids. Maize weevil resistance of F₂ grain was evaluated in 2000 for a 14-parent diallel, and in 2002 for F₂ and F₂–Syn 1 grain of a 10-parent subset diallel. Fifty-gram grain samples of each hybrid were infested with 32 weevils for a 10-d oviposition period, after which the samples were incubated in a laboratory. Grain yield was evaluated for the 14-parent diallel during the summer of 1999–2000 at four locations in Zimbabwe. General combining ability (GCA), specific combining ability (SCA), and reciprocal effects were highly significant (P < 0.01) for number of F₁ weevils emerged from F₂ grain samples for the combined 2000 and 2002 analysis for the 10-parent subset diallel. For weevil resistance of F₂–Syn 1 grain, GCA and SCA effects were significant (P < 0.01), while reciprocal effects were not important. The GCA was more important than SCA for grain yield, indicating that yield was controlled mainly by additive gene action among these lines. There was no significant relationship between grain yield and weevil resistance. Although inheritance of weevil resistance was complex, our results suggest using inbred lines with good GCA for weevil resistance as female parents for hybrids or as components of synthetic (open-pollinated) cultivars for regions where farmers often store maize grain without chemical protection against weevils.

Abbreviations: CIMMYT, International Maize and Wheat Improvement Center • CML, CIMMYT maize line • CTH, controlled temperature and humidity • GCA, general combining ability • masl, meters above sea level • MDP, median development period • SCA, specific combining ability