Abstract
BackgroundThe brown planthopper (BPH) Nilaparvata lugens (Stal) is a serious pest of rice in Asia. Development of novel control strategies can be facilitated by comparison of BPH feeding behaviour on varieties exhibiting natural genetic variation, and then elucidation of the underlying mechanisms of resistance.Methodology/Principal FindingsBPH feeding behaviour was compared on 12 rice varieties over a 12 h period using the electrical penetration graph (EPG) and honeydew clocks. Seven feeding behaviours (waveforms) were identified and could be classified into two phases. The first phase involved patterns of sieve element location including non penetration (NP), pathway (N1+N2+N3), xylem (N5) [21] and two new feeding waveforms, derailed stylet mechanics (N6) and cell penetration (N7). The second feeding phase consisted of salivation into the sieve element (N4-a) and sieve element sap ingestion (N4-b). Production of honeydew drops correlated with N4-b waveform patterns providing independent confirmation of this feeding behaviour.Conclusions/SignificanceOverall variation in feeding behaviour was highly correlated with previously published field resistance or susceptibility of the different rice varieties: BPH produced lower numbers of honeydew drops and had a shorter period of phloem feeding on resistant rice varieties, but there was no significant difference in the time to the first salivation (N4-b). These qualitative differences in behaviour suggest that resistance is caused by differences in sustained phloem ingestion, not by phloem location. Cluster analysis of the feeding and honeydew data split the 12 rice varieties into three groups: susceptible, moderately resistant and highly resistant. The screening methods that we have described uncover novel aspects of the resistance mechanism (or mechanisms) of rice to BPH and will in combination with molecular approaches allow identification and development of new control strategies.
Highlights
Rice, one of the world’s most important food crops is attacked by insect pests totalling around 800 species, in both field and storage [1]
brown planthopper (BPH) feeding on Azucaena, IR694 and Nipponbare were similar to TN1
BPH took more than 8 h to produce honeydew on IR64, Babawee, F1 and MR232
Summary
One of the world’s most important food crops is attacked by insect pests totalling around 800 species, in both field and storage [1]. Extensive chemical control of BPH on rice can cause serious problems including toxicity to natural enemies of BPH such as Anagrus nilaparvatae [5], increased total production cost, and possible long term agro-ecosystem and human health damage [6,7]. Breeding programmes to develop rice varieties resistant to insect pests should complement or replace conventional control strategies. The brown planthopper (BPH) Nilaparvata lugens (Stal) is a serious pest of rice in Asia. Development of novel control strategies can be facilitated by comparison of BPH feeding behaviour on varieties exhibiting natural genetic variation, and elucidation of the underlying mechanisms of resistance
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