Reaction of rice genotypes to brown plant hopper (Nilaparvata lugens (stål) (Hemiptera: delphacidae)) populations and biochemical basis of resistance

Biochemical basis of resistance to BPH was studied by quantifying phenols, sugars, proteins, proline and enzymes such as peroxidise and phenylalanine lyase in healthy and infested plants of 15 selected rice genotypes with varying levels of resistance. The increase in phenol content following BPH feeding was significantly high in the resistant check, PTB 33 followed by other resistant genotypes viz., CE 260, CR Ac 34997, OR 1924-4, IR 64 Sub 1, KAUM 95-1 and RP 4656-IR73678-6-9-B compared to the susceptible check (TN 1). In the case of total sugar content, the susceptible genotypes had higher sugar content than the highly resistant and resistant genotypes. After infestation, the depletion of sugars was observed in both the susceptible and resistant genotypes, but the reduction was more in the susceptible genotypes compared to resistant ones. Similarly, there was reduction in protein levels after feeding in all the genotypes ranging from 23.52 to 67.56 per cent. Though, higher reduction was seen in the susceptible Jaya variety, the reduction in protein content in other genotypes could not be correlated to the level of resistance to BPH. The proline content increased in all the genotypes after feeding ranging from 13.22 to 76.25 per cent and it was highest in the susceptible checks, Jaya and TN 1. The feeding by BPH induced peroxidise and phenylalanine lyase activity in all the rice genotypes. However, the highest peroxidase activity was recorded in the highly resistant genotypes, CR Ac34997 (9999 units/gm) followed by PTB 33 (8800 units/gm) and CE 260 (8099 units/gm). The phenylalanine lyase activity also increased in the infested plants by 15.50 to 52.34 per cent, the resistant genotypes showing the highest increase.