DNA finger printing of gall midge
Genetics of resistance in rice against gall midge biotype2 lead to identification of a new resistance gene in the rice cultivar T1477. The rice root-knot nematode resistance was found to be controlled by quantitative genes. DNA diagnostic tools to identify rice gall midge biotypes 1,2,3,4, and 5 have been developed. A 69bp transposon was identified in African rice gall midge, which is deleted in the Asian rice gall midge signifying possible evolution of the Asian rice gall midge from African rice gall midge. Work on molecular aspects of virulence in the pest revealed that a 170bp locus is linked to the avirulence gene in bioyupe1 and biotype2 of rice gall midge. Cytogenetics studies showed that rice gall midge males have 6 and females have 8 somatic chromosomes. But the germ line cells have chromosomes more than the somatic number. The cytoplasmic incompatibility causing endosymbiotic bacterium Wolbachia was found to be present in both males and females of the rice gall midge biotype2. Contrary to the earlier finding that gall midge females produce monogeny progeny, it was found that very low proportions of gall midge females produce bisexual progenies.
Further works are under progress to develop tightly linked markers for the gall midge resistance genes, Gm2 and Gm4. Recombinant inbred lines are being developed to map the root-knot nematode resistance gene in rice. The role of Wolbachia in sex determination and sex-ratio distortion of the rice gall midge is being investigated.