Inheritance and combining ability studies on grain yield and resistance to maize weevil (Sitophilus Zeamais, Motschulsky) among extra early quality protein maize inbred lines.

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November, 2016
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The maize weevil is one of the most important storage pests of maize in Ghana and Africa as a whole. It causes damage from as low as 20% to as high as 100% in untreated varieties. Developing resistant varieties has been identified as an important and environmentally friendly aspect of the integrated pest management system. However, little is known about the genetic control of resistance to the maize weevil in Ghana. The main objective of this research was to understand the genetic control and heritability of resistance to the maize weevil. The specific objectives were to identify promising genotypes with resistance to the maize weevil. Five parents were crossed in a complete Diallel mating design to obtain 20 hybrids. The 25 genotypes were planted again with two local checks to obtain their seeds. The seeds obtained from these genotypes were subsequently used in the laboratory evaluation for the identification of resistance of the genotypes to the three regional collections of the maize weevils. The laboratory assessment identified parent TZEEQI 111 as the best parental line for resistance to the maize weevil. It exhibited highly significant and negative GCA effects for weevil progeny emergence, percentage weight loss, percentage grain damage and susceptibility index. It also exhibited a positive and significant GCA effect for Median development period. Hybrids TZEEQI 111 × TZEEQI 139, TZEEQI 111 × TZEEQI 12, TZEEQI 111 × TZEEQI 61 and TZEEQI 12 × TZEEQI 66 exhibited significant SCA effects. Heritability estimates revealed high narrow sense heritability for F1 weevil progeny emergence, percentage grain damage and susceptibility index. These results suggest the presence of additive and non-additive gene action in the control of resistance to the maize weevil. Parental lines TZEEQI 111, TZEEQI 139 and TZEEQI 66 performed very well and as such should be considered when forming base population to initiate breeding programs for resistance to maize weevils.
A Thesis Submitted to the Department of Crop and Soil Sciences, Faculty of Agriculture, College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana in Partial Fulfilment of the Requirements for the Award of Degree of Master of Philosophy in Plant Breeding.