Resistance-breaking ability and feeding behavior of the brown planthopper, Nilaparvata lugens, recently collected in Korea

Resistance-breaking ability of wild brown planthopper (BPH), Nilaparvata lugens, on resistant rice varieties has been reported in many Asian countries. To understand the development of this ability of wild BPH in Korea, we conducted a nymphal survivorship test and electrical penetration graph (EPG) study on susceptible and resistant rice varieties with four different BPH populations, which were collected in the early 1980s (S-BPH), 2005, 2006, and 2007. The S-BPH showed low survival rates on resistant rice varieties carrying Bph1 and bph2. However, recent wild BPH populations seemed to have high resistancebreaking ability according to elevated survival rates on most other resistant rice varieties, except Gayabyeo (Bph1 + bph2) and Rathu Heenati (Bph3). In addition, the two 2005-BPH populations selectively reared on ASD7 and Cheongcheongbyeo for three and seven generations, respectively, maintained their resistance-breaking ability against Bph1 and bph2 simultaneously. On the other hand, in stylet penetration behavior monitored with the EPG technique during a 15-h period, recent BPH could not easily feed on the phloem sap of three resistant rice varieties, Cheongcheongbyeo (Bph1), ASD7 (bph2), and Gayabyeo. The average time necessary for reaching the first phloem feeding pattern (Ph) by recent BPH on resistant rice varieties was about 6 hours, three times longer than on susceptible rice varieties (TN1, indica type, and Ilpumbyeo, japonica type). The total Ph duration of wild BPH also decreased significantly on the resistant rice varieties. From these results, we suggest that, though recent wild BPH collected in Korea simultaneously have high resistance-breaking ability on resistant rice varieties carrying Bph1 and bph2 through the increase in the survival rate, they still have to pay some price to feed on the phloem sap of resistant rice varieties.