African rice gall midge (AfRGM), Orseolia oryzivora Harris and Gagné, is one of the most destructive pests of irrigated and lowland ecologies across 19 African countries. It is indigenous to Africa and morphologically distinct from Asian rice gall midge (AsRGM), Orseolia oryzae Wood-Mason. Crop damage is caused by the larvae, which infest rice tillers at the vegetative growth stage and destroy the growing primordia. Such larval infestation results in the formation of galls in the plants and prevent tillers from developing more leaves or panicles. The insect pest causes 20 to 100% yield losses depending on several factors, including climatic conditions (high rainfall, excessive cloud cover and high humidity), ecosystem (rainfed lowland, hydromorphic, upland and mangrove ecologies), planting season, type of germplasm (landraces vs. improved varieties), planting method (direct seeding vs. transplanting), plant population density, and cultural practices.

Host-plant resistance is the most effective, durable, and farmer-friendly control measure against this pest. In one study, the responses of 273 O. glaberrima accessions to African rice gall midge was screened under screenhouse conditions in Nigeria, which was followed by rescreening of the best 20 accessions (2 moderately resistant, 5 resistant and 13 highly resistant accessions) under natural infestation in a gall midge-endemic field conditions. Two, five, and thirteen accessions were found to be moderately resistant, resistant and highly resistant, respectively, with an overall percentage of infested tillers ranging from 0 to 4%, which was over ten-fold smaller than the susceptible check that had 40% infestation (Ukwungwu et al. 1998). In another study, the responses of 20 rice accessions to African rice gall midge was evaluated at five locations in four West African countries (Ogidiga and Gadza in Nigeria, Karfiguea la in Burkina Faso, Balancera in Sierra Leone, and Longorola in Mali) of which a few genotypes showed both stable and acceptable levels of resistance to the pest (Nwilene et al. 2010). Although none of the accessions showed a consistent level of resistance across all five locations, one O. sativa and five O. glaberrima accessions showed stable and acceptable levels of resistance to AfRGM. Here, we compiled a list of the most promising O. glaberrima landraces (accessions). which could be used as donors in developing African rice gall midge resistant rice germplasm in Africa.

• 10.1017/S1742758400007827
• 10.1080/09670870110103890