BROWN PLANTHOPPER NILAPARVATA-LUGENS STAL (HOMOPTERA, DELPHACIDAE) BIOTYPES CAPABLE OF ATTACKING RESISTANT RICE VARIETIES IN MALAYSIA

Biotypes of brown planthopper populations collected in and around the Muda area in Peninsular Malaysia in 1989 and 1990 were examined by comparing the amount of honeydew excreted by the female adults on 5 standard rice variaties: Mudgo (which has the Bph 1 gene for resistance to the brown planthopper), ASD7 (bph 2), Rathu Heenati (Bph 3), Babawee (bph 4) and TN1 (no resistance genes). Most populations from the Muda area showed similar biotypical properties regardless of the collection sites or crop seasons. Among the 4 resistant varieties used, high mortality was recorded on Rathu Heenati and Babawee. A relatively larger amount of honeydew was discharged on ASD7; this was followed by Mudgo. Little honeydew excretion was recorded on Rathu Heenati and Babawee. A similar trend was also observed in most populations collected from other sites on the west and east coasts of Peninsular Malaysia. Two explanations are considered for this phenomenon, i.e., these biotypes had developed in Malaysia or immigrated from Sumatra, Indonesia.