Evaluation of resistance and tolerance of rice genotypes from crosses of Oryza glaberrima and O. sativa to the rice root-knot nematode, Meloidogyne graminicola

Resistance and tolerance to Meloidogyne graminicola infection of introgressed rice genotypes derived from crosses between M. graminicola -resistant Oryza glaberrima genotype CG14 and -susceptible O. sativa genotype IR64 were evaluated in an indoor growth chamber and outdoor raised beds. None of the 44 introgressed genotypes: 24 first backcross F 2 generation (BC 1 F 2 ) and 20 first backcross F 3 generation (BC 1 F 3 ) evaluated did express the same level of resistance as the resistant O. glaberrima reference genotypes included in the experiments for comparison. Lower nematode multiplication factor on the BC 1 F 3 genotypes suggests that M. graminicola resistance trait segregated among the 3 rd generation progeny of the backcross population. The majority of the introgressed genotypes were susceptible and sensitive to M. graminicola infection, some genotypes were susceptible but tolerant and few were both resistant and tolerant to nematode infection. Several genotypes with resistance and/or tolerance to M. graminicola were identified that could either be further developed into advanced breeding lines to produce resistant and/or tolerant cultivars or in the short-term developed into M. graminicola -resistant and/or –tolerant cultivars for use by resource-poor farmers.