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Title: ISOLATION AND CHARACTERIZATION OF MICROSATELLITE LOCI FOR THE ENTOMOPATHOGENIC FUNGUS BEAUVERIA BASSIANA (ASCOMYCOTA: HYPOCREALES)

Author
item SMAGGHE, GUY - GHENT U., GHENT BELGIUM
item LOEB, MARCIA
item TIRRY, L - GHENT U., GHENT, BELGIUM

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2003
Publication Date: 9/9/2003
Citation: Smagghe, G., Loeb, M.J., Tirry, L. 2003. Isolation and characterization of microsatellite loci for the entomopathogenic fungus beauveria bassiana (ascomycota: hypocreales). Molecular Ecology.

Interpretive Summary: Spodoptera littoralis, the cotton leafworm, is a polyphagous pest of world wide importance for growers of cotton, vegetables, and ornamentals. Insecticide-resistant populations cause severe problems in various countries. Therefore, it is important to find natural products that can kill this pest. The extract of fat body tissue from another moth, Manduca sexta, is used to induce development of genital tissues and midgut cells in tissue culture. However, when this material was fed to larvae of the cotton leafworm at high concentrations, it was found to inhibit their metamorphosis, and to cause severe damage to the midguts of the larvae. This substance may have compounds in it which can be useful for insect control. However, more work is needed to separate out the active ingredients from the fat body extract in order to use it effectively as a pesticide. At this time, scientists would benefit most from this knowledge, although it is hoped that in the future, agriculturalists may be able to use the active ingredient as a substitute for conventional insecticides.

Technical Abstract: An extract prepared from fat body tissue from Manduca sexta pupae (FBX) is known to induce development of Lepidopteran genital tracts as well as promote mitosis in midgut cells cultured in vitro. When FBX was incubated with pupal imaginal wing discs from Spodoptera littoralis in vitro, it induced development of this tissue. FBX at 25 ul/ml clearly promoted wing development., but at 1.0 ul/ml, 58% of cultured wing discs evaginated. In the presence of the hormone, 20-hydroxyecdysone, 100% of all wing discs evaginated at both concentrations of FBX. Thus, FBX reinforced by 20-hydroxyecdysone, was able to promote development of the wing discs of this Lepidopteran species in vitro. Feeding FBX to larvae of Spodoptera littoralis at 10% dilution induced 92% inhibition of pupation compared to controls, and induced 52% mortality when used at 1%. At lower concentrations (0.1 and 0.01%), toxicity was lost. Autopsy of killed animals showed severe effects on the midgut; tissue was thin and flacid. Therefore, high doses of FBX administered in vivo disrupted a tissue targeted in vitro. Further research is needed to elucidate its mode of action and the nature of the active ingredient in the extract.