Effects of nitrogen on egg-laying inhibition and ovicidal response in planthopper-resistant rice varieties

Finbarr G Horgan,Thanga Suja Srinivasan,Bhaskar S Naik,Angelee Fame Ramal,Carmencita C Bernal,Maria Liberty P Almazan

doi:10.1016/j.cropro.2016.07.033

Abstract

A series of experiments was set up to examine the effects of nitrogen on rice (Oryza sativa L.) resistance against Nilaparvata lugens (Stål) and Sogatella furcifera (Horváth). Egg laying by N. lugens was reduced on the indica variety IR60. Nymph biomass (N. lugens and S. furcifera) was also lower on IR60: this was associated with low honeydew production and a high proportion of xylem-derived honeydew in N. lugens but not in S. furcifera. Nitrogen increased egg-laying by S. furcifera and increased N. lugens nymph 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 furcifera laid more eggs on plants at 15 DAS, but laid few eggs during darkness; N. lugens continued 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 for S. furcifera than for N. lugens. Mortality of S. furcifera eggs 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.

Highlights

The brown planthopper, Nilaparvata lugens (Stål), and whitebacked planthopper, Sogatella furcifera (Horvath), are major pests of rice (Oryza sativa L.) in Asia (Cheng, 2009; Bottrell and Schoenly, 2012)
Egg laying and phloem feeding rates of N. lugens were lower on IR60 than on the susceptible standards T65 and IR22 and the proportion of xylem feeding was higher than on the other three varieties (Fig. 1, Table 1)
High nitrogen causes a decline in host plant resistance against nymphs of N. lugens on Asiminori and IR60

Summary

Introduction

The brown planthopper, Nilaparvata lugens (Stål), and whitebacked planthopper, Sogatella furcifera (Horvath), are major pests of rice (Oryza sativa L.) in Asia (Cheng, 2009; Bottrell and Schoenly, 2012). N. lugens is a serious pest under intense rice production in lowland irrigated farms where outbreaks are linked to high nitrogen and pesticide inputs (Gallagher et al, 1994; Heinrichs, 1994; Bottrell and Schoenly, 2012). In contrast to several research papers on the instability of antibiotic defenses against nymphs, there have been few evaluations of stability in antixenotic defenses (but see Lu et al, 2004) and no studies on the stability of the ovicidal response against planthopper eggs under high nitrogen fertilization

Methods

Results

Discussion

Conclusion