Biocontrol of Acanthoscelides obtectus and Sitophilus oryzae with diatomaceous earth and Beauveria bassiana on stored grains

Combined treatment with Beauveria bassiana, and diatomaceous earth (DE) was evaluated against the bean weevil Acanthoscelides obtectus and rice weevil Sitophilus oryzae. DE from Argentina was screened both alone or in combination with water or dry fungal formulations. DE killed 100% of A. obtectus and 68% of S. oryzae showing a significantly higher insecticidal effect than the fungal dust. For A. obtectus, median lethal time (MLT) with the DE-dry fungus was significantly lower than with a fungal aqueous-suspension. In S. oryzae, powder formulations with either of B. bassiana or DE showed a MLT significantly higher than the wet treatments.     

Interactions between a braconid,Microplitis croceipes,and a fungus,Nomuraea rileyi,in laboratory-reared bollworm larvae

The parasite Microplitis croceipes required 1.1 days longer at 26°C to complete development in Heliothis zea larvae than was required for the fungus Nomuraea rileyi to kill the host larvae and sporulate. Host larvae parasitized by M. croceipes or infected with N. rileyi failed to complete a fifth larval molt or pupate. Of the remaining healthy larvae, one-half completed six larval stadia before popation. Larvae parasitized by M. croceipes were predisposed to infection by N. rileyi, but the fungus inhibited development of M. croceipes if host larvae were infected with N. rileyi within 1 day after parasitization.     

Cloning and phylogenetic analysis of the chitinase gene from the facultative pathogen Paecilomyces lilacinus

AIMS: To PCR-amplify the full-length genomic-encoding sequence for one chitinase from the facultative fungal pathogen Paecilomyces lilacinus, analyse the DNA and deduced amino acid sequences and compare the amino acid sequence with chitinases reported from mycopathogens, entomopathogens and nematopathogens. METHODS AND RESULTS: The encoding gene (designated as PLC) was isolated using the degenerate PCR primers and the DNA-Walking method. The gene is 1458 bp in length and contains three putative introns. A number of sequence motifs that might play a role in its regulation and function had also been found. Alignment of the translation product (designated as Plc, molecular mass of 45.783 kDa and pI of 5.65) with homologous sequences from other species showed that Plc belongs to Class V chitinase within the glycosyl hydrolase family 18. The phylogenetic and molecular evolutionary analysis using mega (Molecular Evolutionary Genetics Analysis) indicated that these chitinases from mycopathogens, entomopathogens and nematopathogens, the majority of which belong to glycosyl hydrolase family 18, were clustered into two well-supported subgroups corresponding to ascomycetes fungal and nonfungal chitinases (bacteria, baculoviruses). CONCLUSIONS: Our study showed that chitinases from mycoparasitic, entomopathogenic and nematophagous fungi are closely related to each other and reaffirmed the hypothesis that baculovirus chitinase is most likely to be of a bacterial origin - acquired by gene transfer. Bacterial and baculoviral chitinases in our study are potential pathogenicity factors; however, we still cannot ascribe any specific function to those chitinases from the fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report describing the chitinase gene and its translation product from Paecilomyces lilacinus, which constitutes the largest number of formulated biological nematicides reported so far, this is also the first study to analyse and resolve the phylogenetic and molecular evolutionary relationships among the chitinases produced by mycopathogens, entomopathogens and nematopathogens.     

Genotypic analysis of Nomuraea rileyi collected from various noctuid hosts

The genetic diversity of 79 Nomuraea rileyi isolates from various lepidopteran hosts in Asia, North America, and South America was evaluated using amplified fragment length polymorphism (AFLP) analysis. Cluster analysis separated the N. rileyi isolates into two major groups and seven subgroups. The resulting dendrogram generally classified the N. rileyi isolates based on insect host and geographical region. The haplotypic diversity index of N. rileyi subpopulations from each location and host origin was ranging from 0.8788 to 1.000. However, analysis of molecular variance (AMOVA) demonstrated no significant differences (p =0.3421) among N. rileyi isolates from different continents. Whereas the genetic variation among the N. rileyi populations from the different host insects within each continent was significantly different (p <0.0001).