Mode of inheritance of rice resistance to African rice gall midge

Abstract

Development of rice (Oryza sativa) varieties with improved traits, like resistance to both biotic and abiotic stresses, is crucial, particularly for sub-Saharan Africa (SSA). Among the biotic stresses, the African rice gall midge (Orseolia oryzivora) is one of the most devastating pests/insects of rice in the region. The objective of this study was to determine the mode of inheritance of resistance to African rice gall midge (AfRGM) as a basis for developing insect resistant rice varieties in the SSA. Four resistant genotypes and four susceptible locally adapted genotypes of rice were crossed in half diallel crossing design. The F2 segregants and their corresponding parents, were evaluated in the cage experiment, against AfRGM in a 4 by 9 alpha lattice design, in three replications. Results showed a significant variation (P<0.05) in rice AfRGM resistance among genotypes. Significant general and specific combining abilities were observed, indicating that both additive and non-additive gene effects were important in rice AfRGM resistance. However, the non-additive effects predominated at 42 and 63 days after infection (DAI). High coefficients of genetic determination in the broad sense (0.96, 0.97 and 0.98, respectively), and moderate narrow sense (0.55, 0.45 and 0.39) at 21, 42 and 63 DAI, were obtained, with a moderate Baker’s ratio of 0.57, 0.46 and 0.40 in the 21, 42 and 63 DAI, respectively; indicating primarily non-additive inheritance among crosses.