Levels of Tolerance and Antibiosis in Rice Varieties Having Moderate Resistance to the Brown Planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

Rice varieties having a moderate level of resistance to the brown planthopper, Nilaparvata lugens, were evaluated to determine the mechanisms of resistance. The host plant-insect interactions were studied in the greenhouse and insectary to determine the levels of antibiosis and tolerance in the moderately resistant varieties. Parameters measured as the tolerance indicator were plant damage, plant weight loss, and yield reduction due to insect feeding. The insect biomass production, growth index, and population growth rate on the test varieties were used as antibiosis indicators. A regression of plant weight loss, due to N. lugens feeding, on N. lugens weight for five varieties indicated that the variety ‘Utri Rajapan’ has a high level of tolerance and no antibiosis. The resistance in ‘IR46,’ ‘Kencana,’ and ‘Triveni’ is due to a combination of antibiosis and tolerance. The relative amount of each of the two resistance components was measured by using the tolerance-antibiosis index. Field studies confirmed results obtained in the greenhouse and insectary studies. Although ‘Utri Rajapan’ had field populations of N. lugens equal to that of the susceptible check, yield reduction was only 25%, compared with 100% in the susceptible check.