ABSTRACT
BACKGROUND: Light stimulation at a specific wavelength triggers various responses in insects and can be used for pest control. To develop efficient and ecofriendly photophysical pest control methods, the effects of green light on locomotion, growth (molting and eclosion) and reproduction in Nilaparvata lugens (Stål) (BPH), a major rice pest, were studied. Transcriptomics and transmission electron microscopy (TEM) were used to investigate the mechanisms involved. RESULTS: BPH adults showed disrupted daily locomotion patterns following green light treatment at night and exhibited abnormal locomotion peaks. Total 6-day locomotion of brachypterous adults was significantly greater than in the control group. The durations of growth stages 1-4 were all shorter under green light treatment than in the control, whereas the time from fourth molting to eclosion (stage 5) was significantly longer. When BPH adults under green light treatment began laying eggs, the egg hatching ratio (36.69%) was significantly lower than in the control (47.49%). Moreover, in contrast to the control, BPH molting and eclosion events tended to happen more at night. Transcriptome analysis proved that green light significantly affected the expression of genes involved in cuticular proteins, chitin deacetylase and chitinase, which are related to cuticular development. TEM observations confirmed abnormal cuticular development in nymph and adult BPHs (endocuticle, exocuticle and pore canals) under green light treatment. CONCLUSION: Green light treatment at night notably affected locomotion, growth and reproduction in BPH, thus providing a novel idea for controlling this pest. © 2023 Society of Chemical Industry.
Subject(s)
Hemiptera , Oryza , Animals , Hemiptera/physiology , Nymph , ReproductionABSTRACT
The insecticide emamectin benzoate (EB) was formulated with nanoparticles composed of DSPE-PEG2000-NH2 by the co-solvent method to determine its adverse impacts on the environment and to reinforce its dispersion, adhesion, and biocompatibility. A good encapsulation efficiency (70.5 ± 1.5%) of EB loaded in DSPE-PEG2000-NH2 polymeric liposomes was confirmed. Dynamic light scattering (DLS), transmission electron microscopy (TEM), and contact angle meter measurements revealed that the DSPE-EB nanoparticles had a regular distribution, spherical shape, and good leaf wettability. The contact angle on corn leaves was 47.26°, and the maximum retention was higher than that of the reference product. DSPE-EB nanoparticles had strong adhesion on maize foliage and a good, sustained release property. The efficacy trial showed that the DSPE-EB nanoparticles had a strong control effect on S. frugiperda larvae, with the LC50 of 0.046 mg/L against the third-instar S. furgiperda larve after 48 h treatment. All these results indicate that DSPE-EB nanoparticles can serve as an insecticide carrier with lower environmental impact, sustained release property, and effective control of pests.
ABSTRACT
Pseudoligosita yasumatsui and Anagrus nilaparvatae are both egg parasitoids of the brown planthopper, Nilaparvata lugens (Stål) (BPH). In this study, we obtained a stable strain of P. yasumatsui reproduced via thelytoky through indoor rearing and screening. We assessed the parasitism capacity of this strain on eggs of N. lugens by comparing the parasitism preference and circadian rhythm of this strain to that of A. nilaparvatae, which is proved as the dominant egg parasitoid species of BPH in rice fields. The findings indicated that both egg parasitoids could parasitize fertilized and unfertilized BPH eggs, however, with a significant preference for fertilized eggs. The daily parasitization volume of P. yasumatsui was slightly higher than that of A. nilaparvatae. Both egg parasitoids preferred parasitizing 1-3-day-old BPH eggs, but the parasitism amount of 5-6-day-old BPH eggs by P. yasumatsui is higher than that by A. nilaparvatae. The parasitism events of both species of egg parasitoid wasps occurred primarily from 7:00-15:00 and the parasitism amount at night accounted for less than 15% of the total amount. The results indicate that this strain of P. yasumatsui reproduced via thelytoky could be valuable for rice planthopper control.
ABSTRACT
The brown planthopper (BPH) is one of the main pests endangering rice yields. The development of rice varieties harboring resistance genes is the most economical and effective method of managing BPH. To identify new BPH resistance-related genes, a total of 123 rice varieties were assessed for resistance and durable resistance. Three varieties were immune, and nine were highly resistant to BPH. After whole-genome resequencing of all 123 varieties, 1,897,845 single nucleotide polymorphisms (SNPs) were identified. Linkage disequilibrium (LD) decay analysis showed that the average LD of the SNPs at 20 kb was 0.30 (r2) and attenuated to half value (~0.30) at a distance of about 233 kb. A genome-wide association study (GWAS) of durable resistance to BPH was conducted using the Fast-MLM model. One quantitative trait locus, identified on chromosome 2, included 13 candidate genes. Two candidate genes contained a leucine-rich repeat and CC-NBS-LRR or NB-ARC domains, which might confer resistance to pests or diseases. Interestingly, LOC_Os02g27540 was highly expressed and was induced by BPH; GWAS identified potential rice genes coding for durable resistance to BPH. This study helps to elucidate the mechanism of durable resistance to BPH in rice and provides essential genetic information for breeding and functional verification of resistant varieties.
