Characterization of Beauveria bassiana and Metarhizium anisopliae isolates from Cenicafe's collection

Abstract

The efficiency of biological agents de­pends on their knowledge, their biology, the environment, and the mechanism of interaction between them and the host. During this study 76 multiesporic isolates of the entomogenous Beauveria bassiana (Bb) and 19 of the fungus Metarhizium anisopliae (Ma) were characterised through the evaluation of quantitative va­riables such as (PPB) pathogenicity against coffee berry borer-CBB, Hypothenemus hampei (Ferrad); TL₅₀ time in which the probed dose causes 50% of mortality of the population; (E) spore production; (TCD) diametral growth; (TE) spore size, (PG) germination rate; (PE) enzyme reaction; (TRE) starting time of enzyme reaction. In the case of Metarhizium anisopliae (Ma), the evaluated variables were PPB, PG, PE, TRE. The isolates were classified according to PCB, establishing 4 groups: Group 1, PPB <25%; Group 2, PPB between 25% & 50%; Group 3, > than 50% and < than 80%, and Group 4, >80%. For Bb, in Group 1, were most of them registered from H. hampei, Co­lombia. Within the Group 4, 15 isolates from Coleoptera, 5 from Lepidoptera and 1 from Homoptera were found; seventeen of those were isolated in Colombia and 2 from other countries. For Ma, most of them belonged to Group 4, vine from Colombia (Coleoptera). Ma9220, from Australia, (Coleoptera), belonged to Group 3. The analysis of variance of the groups showed the effect of them in the variables PPB, TL₅₀, E, TCD, PG, PE and TRE for Bb and the variables PPB y PG for Ma; the Tukey test (p=0.05) showed that the Bb and Ma groups were different in PPB. A multivariate main component analysis was carried out with a group of 17 isolates of Bb in which the following variables were evaluated (PPB, TL₅₀, PG, PE, TRE, E, TCD, and TE). Likewise, a dendrogram (descriptive grouping) and a cluster statistic analysis were done in order to select groups of isolates according to the evaluated variables, variance analysis of the clusters (p=0,05), and Tukey test (5%) were applied to the groups of isolates. The components that more contributed to the total varíation were: PE, TRE, PPB, and E, in contrast, TRE, TCD, and PG, accounted for the lower degree of variation. The dendrogram and the cluster statistical analysis characterized three groups of isolates. However, according to the initial point of selection of the isolates, a new grouping was made, so that those isolates with PPB upper than 80% were grouped in one cluster. The analysis of variance of the groups showed differences between them in the variables PPB and TCD. The variable pathogenicity to the CBB (PPB) let the separation of groups of isolates in both types of analysis. The characterization of the collection isolates allowed to select those variables that most contributed to the separation of isolates, to identify strains, to establish relationships between them according to their biology and locality, to define their host specificity and their potential to control the CCB and other insect pests of economical importance in Colombia and other countries