Abstract:

The maize weevil (Sitophilus zeamais Motschulsky) is one of the most destructive storage insect pest of maize (Zea mays L.) in tropical Africa and worldwide, especially when susceptible varieties are grown. Therefore, grain resistance against the maize weevil should be part of a major component of an integrated maize weevil management strategy. The specific objectives of this study were to: i) determine farmers’ perceptions about weevil resistance in maize cultivars; ii) determine the genotypic variation for maize weevil resistance in eastern and southern Africa maize germplasm lines; iii) study the gene action conditioning weevil resistance in the inbred line populations from eastern and southern Africa maize germplasm and to measure their combining ability for yield and weevil resistance; iv) determine the effectiveness of two cycles of modified S, recurrent selection in improving a tropical maize population “Longe5” for weevil resistance and agronomic superiority and v) evaluate the effectiveness of the "weevil warehouse techniques" compared to the “laboratory bioassay technique" as methods of maize screening against the maize weevil. A participatory rural appraisal (PRA) was conducted in three districts between December 2010 and January 2011, to gather information on the maize weevil pest status in Uganda and farmers’ perceptions about improved maize varieties and the major attributes desired in new maize varieties. Over 95% of farmers knew the maize weevil and its pest status, and were reportedly controlling the maize weevil using wood ashes, red pepper and Cupressus sempervirens. The estimated postharvest weight losses attributed to weevil damage was over 20% within a storage period of four months. The most highly ranked attributes desired in the new maize varieties included high grain yield, tolerance to drought and low nitrogen stresses, resistance to field pests and diseases, good storability and resistance to storage pests. In the search for new sources of weevil resistance, a total of 180 inbred lines from three different geographical areas were screened for weevil resistance using the laboratory bioassay technique. Eight inbred lines (MV21, MV23, MV75, MV102, MV142, MV154, MV157, and MV170) were consistently grouped in the resistant class, and therefore selected as potential donors for weevil resistance in the maize improvement programs. Large significant genetic variations for weevil resistance, and high levels of heritability (89 - 96%) were observed. The results revealed that there was no significant association between maize weevil resistance and grain yield; suggesting that breeding for maize weevil resistance can be achieved without compromising grain yield.