MECHANISMS OF RESISTANCE TO THE BROWN PLANTHOPPER NILAPARVATA-LUGENS IN WILD-RICE (ORYZA SPP) CULTIVARS

Three wild rice species and six cultivated rice varieties were evaluat ed to determine their mechanisms of resistance to Nilaparvata lugens ( Stal.). Wild rice species, Oryza officinalis, O. punctata, and O. lati folia and cultivated rices Rathu Heenati (Bph 3), Babawee (bph 4), ARC 10 550 (bph 5), Swarnalata (Bph 6), Ptb 33 (bph 2 + Bph 3) and the su sceptible Taichung Native (TN 1) (no resistance gene) were included in the study. In a free choice seedbox screening test, wild rice species maintained their high level of resistance through the 48 h exposure t o N. lugens nymphs while plant damage ratings of cultivated rice varie ties increased with time. Wild rices were non preferred and significan tly more individuals settled on susceptible TN 1 followed by cultivate d rices. The quantity of food ingested and assimilated by N. lugens on wild rices was less than on cultivated resistant varieties. N. lugens caged on resistant wild rices had slow nymphal development, reduced l ongevity, low fecundity, and low egg hatchability as compared to N. lu gens on cultivated resistant varieties.