A growth-based screening method for entomolopathogenic bacteria against Spodoptera frugiperda

Bioassay data were analyzed using probit analysis with PoloPlus software (LeOra Software 2002, Berkeley, CA, USA). The mortality results obtained from insect bioassays in this paper are values of the adjust mortality, and the calculation formula as follow: adjust mortality (%) = (mortality of treatment － mortality of control) / (1- mortality of control) × 100%.
Statistical analyses were also performed using SPSS statistical software v12.0 (SPSS, Inc., Chicago, IL, USA). Mortality, colony diameter and enzyme activity were analyzed using one-way analysis of variance (ANOVA), followed by Tukey’s HSD tests. Pearson correlation analysis was employed to evaluate the relationship between protease, chitinase activity of different bacteria and their toxicity to S. frugiperda. A strong linear correlation was indicated by a Pearson correlation coefficient R of > 0.6, corresponding to an R2 value exceeding 0.36.
Table 1, Growth and enzyme activity of different bacteria isolates from field S. frugiperda on milk and chitin medium. Means in the same column followed with the same letter are not significantly different at the 5% level (Tukey’s HSD tests). The data represent the mean of replicates with standard error (SE).
Table 2, Insecticidal activity of different bacteria isolates from field S. frugiperda against the pest. The concentration of bacterial suspension for bioassay are 1×1010 cfu/mL. The mortality results obtained from insect bioassays in this paper are values of the adjust mortality. The data represent the mean of replicates with standard error (SE). Means in the same column followed with the same letter are not significantly different at the 5% level (Tukey’s HSD tests).
Fig. 2, Correlation analysis between virulence of pathogenic bacteria to S. frugiperda and bacterial growth rate. The mortality results obtained from insect bioassays in this paper are values of the adjust mortality.
Table S2, Growth characteristics and toxicity of different bacteria strains isolated in the field. The mortality results obtained from insect bioassays in this paper are values of the adjust mortality. The data represent the mean of replicates with standard error (SE). Data of the genera Serratia and Pediococcus are presented in Table 1 and 2.
Fig. S1, Genera level (A) and species level (B) composition of S. frugiperda pathogenic bacteria in different regions of Jiangsu Province.