Genetics of resistance to rice gall midge (Orseolia oryzae)

A representative set of donor parents of rice with consistently high level of resistance to different biotypes of rice gall midge, Orseolia oryzae (Wood Mason) (Diptera: Cecidomyiidae), was crossed to T(N)1, the susceptible check and the F₁'s F₂'s and F₃'s along with parents were screened under glasshouse as well as field conditions against the biotypes 1, 2 and 4 to understand the mode of inheritance of biotype-specific resistance. Crosses were also made among the parents resistant to different biotypes and the F₁, F₂ and F₃ plants were screened to study the allelic relationships of the biotype-spedfic resistance genes. The inheritance studies revealed a simple mode of inheritance with resistance being dominant over susceptibility. Reciprocal combinations in selected crosses revealed no maternal influence in the manifestation of resistance in respect of all the biotypes studied. Allelic relationship studies revealed that the dominant gene governing resistance against biotype 1 in Eswarakora, W 1263 and NHTA 8, designated as Gm1, was non-allelic and independent of the gene Gm3 conferring resistance in Bhumansan, Banglei and T 1432. Against biotype 2, the gene Gm4 conferring resistance in Bhumansan is, nonallelic to the resistance gene Gm5, which is allelic in NHTA 8, Banglei and T 102. The dominant resistance gene Gm6 against biotype 4 in NHTA 8 is nonallelic to the resistance gene Gm7 in Banglei, T 1432 and T 1477, which is allelic in them.