Zhao Kuijun

Source area of spring population of meadow moth, Loxostege sticticalis L. (Lepidoptera: Pyralidae), in Northeast China

The meadow moth, Loxostege sticticalis L., is an important outbreak pest in Northeast China. The spring population in Northeast China was considered as immigrants from North China; however, the population dynamics during 1996–2007 was not consistent with this traditional theory. In this study, the source area of the spring population of the meadow moth in Northeast China was identified by trajectory analysis using the wind field simulated by mesoscale numerical forecast model MM5. The results indicated that the population of the meadow moth in North China was able to migrate into Northeast China, but had not made a crucial contribution to the outbreaks there since the weather systems were generally adverse for such a long range migration in most of the years. On the other hand, high density cocoons of L. sticticalis have frequently been found in autumn in Northeast China since 1996. The trajectory analyses indicated that most of L. sticticalis in Northeast China in spring emerged from the cocoons that had overwintered either locally or in neighboring countries, i.e. Mongolia and Russia. The development of overwintering areas at higher latitudes coincides with the increased frequency of second-generation larvae; both phenomena might be attributed to the regional climate change associated with global warming.

Cloning, Expression and Activity of cry1Ia Gene from Bacillus thuringiensis Isolate

A Full-length cry1Ia gene fragment, which obtained by PCR amplification with a pair of primers designed according to cryIa-type gene sequences and DNA from Bacillus thuringiensis Btc008 as template, was introduced into expression vector pET-21b and transformed into Escherichia coli BL21(DE3). Molecular weight of the induced express product was 81 kD. The encoded protein was composed of 719 amino acid residues and the predicted MW was 81.2 kD. The amino acid sequence of the Cry1Ia was very different from those of 12 known Cry1Ia-type proteins. This gene with accession number AF373207 was designated as cry1Ia8 by International Bt Insecticidal Gene Nomenclature Committee. The bioassay results indicated that the Cry1Ia toxin protein showed distinctly insecticidal activity against Ostrinia furnacalis and Plutella xylostella with LC50 of 0.268 μg/g and 2.227 μg/mL, respectively, while it also had insecticidal activity against Leguminivora glycinivorella,but no activity against Pyrrhalta aenescens. The novel cry1Ia8 gene will be new resource for the construction of genetically engineered bacterium and transgenic plant for biocontrol of insect pests. It is also available for screening gene stacks to delay the resistance produce of the pests.

Expression of Cry1Ac protein in cry1Ac/CpTI transgenic rice and its resistance in different developmental stages to Chilo suppressalis

The expression patterns of Cry1Ac protein and the resistance to striped stem borer Chilo suppressalis (Walker) of cry1Ac / CpTI transgenic rice ( Oryza sativa L.) were investigated by ELISA and laboratory bioassay. ELISA results showed that Cry1Ac protein could be detected in all organs during the development process of cry1Ac / CpTI transgenic rice. The content of Cry1Ac protein varied markedly in different tissues at different stages: it was higher in the earlier stage than in the later stage. The highest level of Cry1Ac protein in terminal leaves of the main stem was found at the jointing stage. Thereafter, it decreased at the booting stage, and a gradual reduction to the lowest level was recorded from the flowering to the filling stage, before a slight increase was shown at the maturing stage. In addition, higher concentrations of this protein were detected in the main stem at the seedling, jointing and flowering stages than at other stages. Relatively lower levels of Cry1Ac protein were found in seeds. The results from laboratory bioassay showed high resistance of terminal leaves of the main stem in all developmental stages to C. suppressalis larvae. Corrected mortality values of C. suppressalis at 4 days after feeding on the detached leaves of cry1Ac / CpTI transgenic rice reached 90% before the filling stage and decreased to nearly 60% after the filling stage. Interestingly, results of whole plant bioassay coincided with those obtained in the detached leaf bioassay. The tendency of larval morality in the detached leaf bioassay and whole plant bioassay was consistent with that of Cry1Ac protein content in the different growing periods and organs.

Studies on Occurrence Ecological Factors and Management Strategies of Ambrostoma quadriimpressum in Harbin City

This paper investigated effects of four ecological variables on the damage levels of elm leaf beetle (different effects of minimum and maximum values, relations between each two variables were also explored) and discussed current management measures. The results showed that among these factors, interval between elm trees significantly affected damage level by this leaf beetle species, and perimeter of elm trunk could change this effect. On the other side, while middle values for each index were deleted, effects comparison between minimum and maximum parts showed that good root soil as overwintering was related with more damage; more severe damages on elm tree would result in more control measures used; on elm tree with bigger trunk, more damages were observed; and if other elm tree was closer, more damages would occur. Secondly, good root soil was related with more measures used; good root soil was correlated with smaller perimeter; good root soil was associated with bigger interval. Thirdly, more measures were correlated with bigger perimeter; more measures were also correlated with good root soil. Fourthly, bigger perimeter was correlated with worse root soil. Current dominant control measures included chemical pesticide application preventing adult insects from descending or climbing up along trunk before and after overwintering. These results suggested that we should focus on elm leaf beetle management on all the elm trees instead of only on bigger elm trees at proper period simultaneously because occurrence on these elm trees were related intensively although this adult elm leaf beetle species could not fly and had limited movement ability.

Genetic Differentiation Analyses Based on mtDNA CO II Gene Sequences Among Different Geographic Populations of Aphis glycines (Hemiptera: Aphididae) in Northeast China

Abstract Aphis glycines (Hemiptera: Aphididae) is considered as a cosmopolitan pest of cultivated soybean, major difficulties in its control measures may be due to its higher genetic diversity; however, the knowledge about population genetic diversity of this species is limited. This study aimed to represent the genetic differentiation among different geographic populations of soybean aphid in Northeast China. In order to investigate and assess the genetic diversity, genetic differentiation, molecular variance, population structure, ecological importance and evolutionary history of A. glycines, we sequenced a fragment of one protein-coding gene, the cytochrome c oxidase II of mitochondrial DNA gene. The results showed that four haplotypes were defined among CO II gene of 180 sequences of soybean aphid in Northeast China including H1 shared by all the populations. Lower haplotype diversity (Hd=0.3590± 0.0420) and nucleotide diversity (Pi=0.0012±0.0002) were observed and high gene flow was detected in every two populations, while most of the variation (80.81%) arose from variability within A. glycines from individuals. Low genetic differentiation and high gene flow (Nm=2.106) indicated a high migration rate between the populations, which might reveal that gene flow in different geographic populations did not affect by geographical distance. The phylogenetic tree and the haplotype network of A. glycines were obtained based on sequences of CO II gene, there were no significant genealogical branches or clusters recognized in NJ tree, and no clear distribution, delineation of haplotypes were demonstrated in the haplotype network according to geographical location. This study rejected the vicariance hypothesis: geographic isolation could be a barrier and it restricted A. glycines gene flow among 10 populations.