Determination of Maize Landraces for Resistance to Maize Weevil (Sitophilus zeamais Motschulsky) and Larger Grain Borer (Prostephanus truncates): A Case Study from Kenya

This chapter evaluate to screen Kenya Local Coastal Maize Landraces for Resistance to Maize Weevil (Sitophilus zeamais Motschulsky) and Larger Grain Borer (Prostephanus truncates). The maize weevil, Sitophilus zeamais, is a ubiquitous pest of maize and other cereal crops worldwide and remains a threat to food security in subsistence communities. Few population genetic studies have been conducted on the maize weevil, but those that exist have shown that there is very little genetic differentiation between geographically dispersed populations and that it is likely the species has experienced a recent range expansion within the last few hundred years. Farmers in the coastal region continue to grow the native coastal maize landraces (LCML) despite the availability of improved maize varieties. In an effort to comprehend why farmers favour growing LCML despite the release of improved maize open pollinated varieties (OPVs) and hybrids, research was conducted to examine LCML. The goal was to test 25 LCML and 5 improved checks for maize weevil and larger grain borer resistance. The screening was carried out at Kenya Agricultural and Livestock Organization (KALRO) Kiboko, Kenya. Complete block design (CBD) was used. Maize grains was disinfected of any field infestation of the LGB pest by heating in ventilated electrical oven a 60-70°C for 2 hours and let the grain cool in the oven overnight (use kilner jars with glass lids). Maize weevil caused 12.2% (Kanjerenjere) - 32.4% (KDV-3) weight losses compared to only 5.0% (Chitweka) - 8.7% (Matsere) caused by the LGB. This implies that, given the same conditions, weevils are more disastrous and priority should be given to controlling them. Among Kenyan local coastal maize landraces, resistance to maize weevil and LGB varied during storage. There was a consistent pattern of LGB resistance among landraces from Kwale, Kilifi, and Lamu. For the maize weevil, where resistance was widespread in the area, no such pattern was seen. Maize weevil exposure has lasted a lot longer than LGB, which was only discovered in the early 1990s. The susceptibility of some improved varieties to storage pests may partly explain why farmers grow local cultivars since PH 4 is the most readily available commercial cultivar. The objectives of various insect resistance breeding programmes in coastal Kenya may use landraces with superior responses to storage pests directly or as sources of resistance.