Abstract
Micraspis discolor (Fabricius) (Coleoptera: Coccinellidae) is a widely distributed coleoptera predator in southern Asia in rice ecosystem, and adult M. discolor feed on both rice pollen and soft-bodied arthropods. Bitrophic bioassay and tritrophic bioassay were conducted to evaluate the potential impact of Cry1Ac/Cry1Ab-expressing rice Huahui 1 and its non-transgenic counterpart Minghui 63 on fitness parameters of adult M. discolor. The results showed that the survival, and fecundity of this beetle’ adults were not different when they fed on Bt rice or non-Bt rice pollen or Nilaparvata lugens (Stål) reared on Bt rice or non-Bt rice. Toxicity assessment to ensure M. discolor adults were not sensitive to Cry1Ab or Cry1Ac protein independent from the pollen background, M. discolor adults were fed with an artificial diet containing Cry1Ac, Cry1Ab or both protein approximately 10 times higher concentration than in Huahui 1 rice pollen. No difference was detected for any of the life-table parameters tested between Cry protein-containing and pure diet. Artificial diet containing E-64 (N-(trans-Epoxysuccinyl)-L-leucine 4-guanidinobutylamide) was included as a positive control. In contrast, the pre-oviposition and fecundity of M. discolor were significantly adversely affected by feeding on E-64-containing diet. In both bioassays, the uptakes of Cry protein by adult M. discolor were tested by ELISA measurements. These results indicated that adults of M. discolor are not affected by Cry1Ab- or Cry1Ac-expressing rice pollen and are not sensitive to Cry protein at concentrations exceeding the levels in rice pollen in Huahui1. This suggests that M. discolor adults would not be harmed by Cry1Ac/Cry1Ab rice if Bt rice Huahui 1 were commercialized.
Highlights
Rice, Oryza sativa L., is a main food crop for 3.5 billion people in the world [1]
Pesticides and nitrogen fertilizers have doubled the production of many crops including rice [21,22]
The inputs of insecticides and fertilizers have resulted in some negative effects on environments [23,24,25]
Summary
Oryza sativa L., is a main food crop for 3.5 billion people in the world [1] Leaffolders such as Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae) and Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) are three of the most serious pests of rice in temperate to tropical Asia [2,3,4]. Micraspis discolor is distributed from Southern China to Southern Asia [10,11,12,13] It feeds on plants’ pollen, such as pollen of Triticeae Dumort, Oryza sativa L., as well as on a wide range of soft-bodied arthropods and eggs. It has been reported as both phytophagous and entomophagous. Adult M. discolor feed on rice pollen and Nilaparvata lugens (Stål) (BPH), Sogatella furcifera (Horváth) (WBPH), aphids and eggs or larvae of C. suppressalis and T. incertulas etc
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