Bacillus thuringiensis (Bt) produces a variety of insecticidal crystal proteins and widely used as one of the most successful biological control agents. Recently, studies that introduce cry genes into crops to create pest resistance have made much progress, and the total area of land planted with Bt crops has increased substantially. In this study, pest resistance of 8 transgenic Bt rice events with a synthetic cry1Ac gene linked to rice rbcS-tp sequence were assessed under laboratory conditions. Bioassays were performed against Cnaphalocrocis medinalis, which is a significant pest of rice in Asia. C. medinalis larvae were shown to be susceptible to all eight events, even though there were differences between the causes of death. The results differed between developmental stages of the larvae, despite the fact that all 8 events led to high mortalities. These results may be a significant foundation for the evaluation of improved transgenic Bt rice.

Streptomyces is the largest genus of Actinobacteria that forms fungus-like branched networks of hyphae. Streptomyces has been clinically important because they produce various secondary metabolites with antibacterial, antifungal, and nematocidal activities. In order to explore novel insecticidal compounds, extracts from 363 strains of Actinobacteria were screened for their juvenoid and anti-juvenoid activities using yeast-two hybrid system. Among them, extract of Streptomyces spp. showed high anti-juvenoid activity. This extract also showed high level of insecticidal activities against larvae of Aedes albopictus, Laodelphax striatellus, and Ostrinia furnacalis. These results suggested that the secondary metabolites of Streptomyces could be natural sources of novel insecticidal compounds.

Entomopathogenic fungi have been widely studied for their potential as the effective biological control agents. They produce variety of secondary metabolites with insecticidal activities, and it is reasonable to assume that entomopathogenic fungi might produce secondary metabolites modulating juvenile hormone for their survival against defense mechanisms of host insect. In this study, Beauveria spp. and Lecanicillium spp. strains cultured on unpolished rice medium were extracted with acetone. Both extracts showed juvenile hormone antagonist (JHAN) activities in the yeast-two hybrid β-galactosidase assay. In addition, they showed high insecticidal activities against Aedes albopictus, Plutella xylostella, and Ostrinia furnacalis. These results suggested that secondary metabolites of entomopathogenic fungi could be useful for development of novel IGR insecticides.

Insect growth regulators (IGRs) are insecticides that disrupt the normal development of target insects by inducing symptoms such as premature molting or supernumerary larval stages. IGRs are categorized into three types based on their mode of action. One of the them is classified as juvenile hormone agonists (JHAs). In recent studies, we identified juvenile hormone antagonists (JHANs) from plant extracts. In order to identify a novel juvenile hormone agonists and antagonists, we tested 2,354 chemical compounds using the yeast-two hybrid system. Among them, 2 JHAs and 4 JHANs were selected and their insecticidal activities were evaluated against Aedes albopictus larvae. These results may be useful for development of novel IGR insecticides.

This japonica cultivar was developed from a cross between two F₁ hybrids of YR13168 (Milyang 95/Iri390) and YR13198 (Milyang101/Iri390) using anther culture. It has about 104 days of growing duration from seeding to heading and relatively short

Areumbyeo', a second generation Tongil-type rice variety (Oryza sativa L.), has been developed at National Yeongnam Agricultural Experiment Station (NYAES) from 1983 to 1999 and released in 2000. A single cross between YR3299-34-2-2 and Suweon 318 (was co