Abstract

CARO C, LUISA FERNANDA; VILLAMIZAR R, LAURA FERNANDA; ESPINEL C, CARLOS  and  COTES, ALBA MARINA. Effect of the culture médium in the virulence of nomuraea rileyi on Spodoptera frugiperda (Lepidoptera: Moctuidae). Rev. Colomb. Entomol. [online]. 2005, vol.31, n.1, pp.79-88. ISSN 0120-0488.

Isolate Nm005 of nomuraea rileyi was selected in a previous study by causíng 95% mortality in the fall armyworm Spodoptera frugiperda, the most important pest in maize crops. In order to produce hígh quality conidia for developing an efficient biopesticide, the objective of the present worK was to determine the effect of the culture médium and some potential virulence inductors on the microbiological characteristics and biocontrol activity of the ¡i. rileyi conidia. The fungus was grown on miliet, rice, oat and soybean substrates. After evaluating yield, germination and biocontrol activity of produced conidia on the substrates, the soybean médium was selected because the conidia presented the best characteristics. In addition, the fungus was grown on yeast-malt extract agar médium supplemented with several potential inductors of virulence that consisted of two proteic inductors, a homogenization of larvae, a non specific inductor, an inductor based on a polymer and a control with no inductor. By using a bioassay, the proteic inductor 1 and polymer inductor 1 were selected because they caused an increase in biocontrol activity. Afterwards, the combined effect of the selected substrate for mass production and the selected potential inductor of virulence on the germination and biocontrol activity of the fungus was evaluated. The polymer inductor 1, combined with the culture médium, liad a positive effect on the characteristics evaluated. The results obtained suggest that the type and composition of the culture médium determines the microbiological characteristics and virulence of the biomass produced.

Keywords : Bioassay; Inductors of virulence; Pathogenicity; Mass production.

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