Hypersensitive response and induced resistance in rice gene differentials against biotype 1 of Asian rice gall midge, Orseolia oryzae at Mandya, Karnataka

Hypersensitive reaction (HR) and induced resistance were noticed in resistant rice genotypes infested by gall midge. Detailed observations on Phalguna (Gm2 gene), Abhaya (Gm4 gene), ARC 5984 (Gm5 gene) infested with gall midge biotype 1 revealed that the infestation triggered HR in the plant, leading to extensive tissue necrosis at the apical meristem and browning of central leaf. This was followed by maggot mortality and premature tillering. In susceptible genotypes this phenomenon was not evident. HR leading to necrosis is fatal to host plant but premature tillering was observed. Further, the secondary tillers were infested subsequently with the gall midge biotype 1 eggs at 7, 14, 21 and 28 days after primary infestation, and maggots failed to establish and cause silver shoot. However, HR was observed 6 days after secondary tiller infestation, when the primary tillers were infested 28 days after. But cent per cent maggot mortality was observed, regardless of the time interval between infesting primary and secondary tillers in all the HR + plants. Thus, the HR is not confined to the tillers of primary infestation but it also triggers systemic acquired resistance in other tillers in Phalguna, Abhaya and ARC 5984, whereas, in W1263 (Gm1 gene), HR+ was not evident but antibiotic effects were observed along with maggot mortality.