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The role of soil moisture, light and pH on imidacloprid dissipation was investigated. A high performance liquid chromatography (HPLC) based method was developed to quantify imidacloprid present in soil with a recovery of more than 82%. Rate of dissipation of imidacloprid from soil was faster in submerged condition compared to field capacity and air dried condition. Imidacloprid dissipated non-significantly between sterile and non-sterile soils, but at field capacity, the dissipation was faster in non-sterile soil compared to sterile soil after 60 days of incubation. Similarly, under submergence, the dissipation of imidacloprid was 66.2% and 79.8% of the initial in sterile and non-sterile soils, respectively. Imidacloprid was rather stable in acidic and neutral water but was prone to photo-degradation. Therefore, imidacloprid degradation will be faster under direct sunlight and at higher soil moisture.

Studies were undertaken to evaluate the rice genotypes of Sikkim and Tripura for their resistance against brown planthopper (BPH) under glasshouse conditions. Among 74 rice genotypes phenotyped, a genotype (AC-39843) was considered as resistant and two other genotype (AC-39842 and AC-39877) of Tripura were categorized as moderately resistant to BPH. To understand their mechanism of resistance, resistant genotypes were evaluated for different parameter of antixenosis and antibiosis. The antixenosis and antibiosis studies in terms of nymphal setting preference, per cent unhatchability of eggs, nymphal survival and development, honeydew excretion, probing mark test, plant dry weight loss and defence enzymes (Peroxidase, polyphenol oxidaseand catalase) indicated that these genotypes showed confirmation of resistance to BPH compared to susceptible check TN 1. Among resistant genotypes, AC-39843 recorded lowest sugar content followed by AC-39842 and AC-39877 compared to TN1. Total phenol content in AC-39843 was highest followed by AC-39877 and AC-39842. Resistant genotypes found in the study could be used as new resistant donors and utilized in resistance breeding programme against brown planthopper in rice.

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