Assessment of host plant resistance in Oryza sativa to the African rice gall midge, Orseolia oryzivora Harris and Gagné (Dipt., Cecidomyiidae), with a description of a new method for screening under artificial infestation

Abstract

A new method is described for screening rice germplasm for resistance to the African rice gall midge (AfRGM), Orseolia oryzivora, year‐round under conditions similar to a severe natural outbreak, using an AfRGM culture to start infestation in a tunnel screenhouse over an irrigated rice field. During 1996 and 1997, 907 test entries of Oryza sativa were screened. Eighteen entries, 17 of which were traditional African lines, had infestation levels at least 50% below those on the partially resistant check variety NHTA 8 at 63–70 days after transplanting, though none showed very strong resistance. When traditional African lines and improved lines were screened together, the latter were on average markedly more susceptible. A field trial using caged plots indicated that even under no‐choice conditions the varieties NHTA 8 and Eguazankpa maintained their partial resistance relative to the susceptible variety ITA 306. A comparison of the new screenhouse screening method with one using seedlings in insect cages suggested that the latter was less suitable for detecting partial resistance. An experiment in which NHTA 8 and ITA 306 were infested with one to four neonate AfRGM larvae per seedling showed that the difference in resistance between these varieties decreased with increasing infestation pressure. The potential role of partial resistance in the management of AfRGM, and methods for detecting it, are discussed.

Biology of the African rice gall midge Orseolia oryzivora (Diptera: Cecidomyiidae) and its incidence on wet-season rice in Nigeria

“…Consumption of rice, Oryza sativa L. (Poaceae), is growing rapidly in sub-Saharan Africa (WARDA, 2005), with consumption outstripping production in many countries (Williams et al, 2001;Kormawa et al, 2004;Mohapatra, 2006;Omoloye and Vidal, 2007;WARDA, 2008). The rice production deficit in Nigeria is attributed mainly to low rice yields due to insect pest infestation (WARDA, 2007).…”

Female reproductive biology of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (Hymenoptera: Eulophidae), two parasitoids associated with the African Rice Gall Midge, Orseolia oryzivora (Diptera: Cecidomyiidae)

“…Nacro et al. 1996 and Williams et al. 2001 showed that an increase of 1% in the percentage of tillers with galls at stem‐elongation reduced yield by 2–3%.…”

“…For example, tolerant varieties such as Cisadane experience a lower level of yield loss than more susceptible varieties. Nacro et al 1996 andWilliams et al 2001 showed that an increase of 1% in the percentage of tillers with galls at stem-elongation reduced yield by 2-3%. In addition to reducing grain yield, AfRGM attack also results in delayed and uneven grain maturation, which makes harvesting difficult.…”

Comparative Study of the Morphology of the Ovipositor ofPlatygaster diplosisae(Hymenoptera: Platygasteridae) andAprostocetus procerae(Hymenoptera: Eulophidae) Two Parasitoids Associated with the African Rice Gall Midge,Orseolia oryzivora(Diptera: Cecidomyiidae)

“…The amount of yield loss caused by the gall midge larva varies among rice varieties. Nacro et al [2], and Williams et al [3] showed that an increase in 1% in the percentage of tillers with galls at the stem-elongation stage reduced yield by 2 to 3%.…”