Use of a dietary exposure system for screening of insecticidal compounds for their toxicity to the planthopper Laodelphax striatellus

Abstract

We developed a dietary exposure assay for screening insecticidal compounds for their toxicity and for assessing the side effects of insecticidal proteins produced by genetically engineered (GE) plants on the planthopper Laodelphax striatellus Fallén. The fitness bioassay confirmed that the diet fulfills the requirements to be used in the dietary exposure system. To validate the efficacy of the dietary exposure system, nymphs of L. striatellus were fed diets treated with different concentrations of an inorganic stomach poison, potassium arsenate (PA), or a cysteine protease inhibitor, E-64. The results showed that with increasing concentrations of E-64, the larval development time was prolonged, the adult weight was reduced and the survival rate of L. striatellus was decreased. Similarly the survival rates of L. striatellus consistently decreased with increasing PA content in the diet. The data indicate that the dietary exposure assay is able to detect the effects of insecticidal compounds on L. striatellus. Subsequently, this assay was successfully used for assessing the potential toxicity of Cry2Aa. The results showed that L. striatellus larvae were not negatively affected when fed the artificial diet containing purified Cry2Aa at 300 μg/g diet. In the assay, the stability and bioactivity of crystal (Cry) proteins in the food sources were confirmed by enzyme-linked immunosorbent assay and sensitive-insect bioassays. These results show that L. striatellus is not sensitive to Cry2Aa. We conclude that the dietary exposure system is valid and useful for assessing the toxicity of insecticidal compounds produced by GE plants on planthoppers.

Consumption of Bt rice pollen containing Cry1C or Cry2A does not pose a risk to Propylea japonica (Thunberg) (Coleoptera: Coccinellidae)

“…Larvae and adults of the green lacewing, C. sinica , were not affected by feeding on Cry1C or Cry2A proteins or on Cry1C- or Cry2A-containing Bt rice pollen 10 11 12 36 . The planthopper, Laodelphax striatellus (Homoptera: Delphacidae), was not adversely affected when fed an artificial diet containing Cry2A at 300 μg/g diet 37 . Larvae of the silkworm, B. mori , were fed Cry1C- or Cry2A rice pollen 13 .…”

Transgenic cry1C or cry2A rice has no adverse impacts on the life‐table parameters and population dynamics of the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)

“…For example, Yang et al showed that Bt rice (T1C‐19 or T2A‐1) did not affect the ecological fitness parameters, including nymphal survival rate and duration, sex ratio and female adult weight, and nor the detoxification enzyme activities of BPH compared with non‐ Bt rice (MH63); however, the key parameters for population growth, namely the fecundity and population dynamics in the field, were not evaluated. In addition, an artificial diet study with the small brown planthopper, Laodelphax striatellus Fallén (Hemiptera: Delphacidae), has revealed no sensitivity to high doses of purified Cry2Aa …”

Cry78Ba1, One Novel Crystal Protein from Bacillus thuringiensis with High Insecticidal Activity against Rice Planthopper

“…Each treatment was repeated three times. Using the method reported by Liu et al, 18 the insecticidal activity of the protein against three hemipteran pests was determined with a double parafilm membrane feeding system. Twenty-one individuals were used on one replication.…”