Effects of nitrogen on egg-laying inhibition and ovicidal response in planthopper-resistant rice varieties.
A series of experiments was set up to examine the effects of nitrogen on rice (Oryza sativaL.) resistance againstNilaparvata lugens(Stål) andSogatella furcifera(Horváth). Egg laying byN. lugenswas reduced on theindicavariety IR60. Nymph biomass (N. lugensandS. furcifera) was also lower on IR60: this was associated with low honeydew production and a high proportion of xylem-derived honeydew inN. lugensbut not inS. furcifera. Nitrogen increased egg-laying byS. furciferaand increasedN. lugensnymph biomass on all varieties tested. Oviposition and egg mortality in both planthopper species were examined on plants at 15, 30 and 45 days after sowing (DAS).Sogatella furciferalaid more eggs on plants at 15 DAS, but laid few eggs during darkness;N. lugenscontinued to lay eggs on older rice plants (30 DAS) and during darkness. Egg mortality was high on cv. Asiminori, highest at 45 DAS, and higher forS. furciferathan forN. lugens. Mortality ofS. furciferaeggs was associated with lesions around the egg clusters. These were more common around clusters laid during the day and suggested induction by Asiminori of an ovicidal response. Egg mortality declined under higher soil nitrogen levels. Results are discussed in the light of improving rice resistance against planthoppers and reducing rates of planthopper adaptation to resistance genes.
International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines; Centre for Compassionate Conservation, University of Technology Sydney, 15 Broadway, Ultimo, Sydney, NSW 2007, Australia.
Finbarr G
FG
Horgan
International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines; Centre for Plant Molecular Biology and Biotechnology, Tamil Nadu Agricultural University, Coimbatore, 641 003, Tamil Nadu, India.
Thanga Suja
TS
Srinivasan
Directorate of Rice Research, Rajendranagar, Hyderabad, 500 030, Andhra Pradesh, India.
Bhaskar S
BS
Naik
International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines.
Angelee Fame
AF
Ramal
International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines.
Carmencita C
CC
Bernal
International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines.
Maria Liberty P
ML
Almazan
Brown planthopper; Honeydew; Host plant resistance; Nilaparvata lugens; Sogatella furcifera; White-backed planthopper