Diversity and Genetic Population Structure of Fungal Pathogens Infecting White Grub Larvae in Agricultural Soils

Abstract

White grub larvae are important soil-dwelling pests in many regions of Mexico as they attack many important crops such as maize. The use of synthetic chemicals is currently the main control strategy, but they are not always effective; thus, other alternatives are needed. Microbial control using entomopathogenic fungi represents an important alternative strategy, and species within the genera Beauveria and Metarhizium are considered amongst the most promising candidates. Seventeen Beauveria spp. and two Metarhizium spp. isolates were obtained in surveys of white grub larvae from different regions of Guanajuato, Mexico. All isolates were capable of infecting healthy larvae of the white grub Phyllophaga polyphilla in laboratory assays, but mortality never exceeded 50 %. Isolates were identified using morphological and molecular methods. Based on elongation factor1-α and ITS partial gene sequence data, all Beauveria isolates were identified as Beauveria pseudobassiana. Elongation factor1-α and β-tubulin sequence data identified the Metarhizium isolates to be Metarhizium pingshaense. In contrast, three additional Metarhizium isolates obtained the previous year in the same region were identified as M. pingshaense, Metarhizium anisopliae and Metarhizium robertsii. Microsatellite genotyping showed that all B. pseudobassiana isolates were the same haplotype. Enterobacterial Repetitive Intergenic Consensus fingerprinting information confirmed no significant variation amongst the B. pseudobassiana isolates. The ecological role of these isolates and their impact on white grub larvae populations are discussed.

Interaction of Beauveria bassiana and Metarhizium anisopliae with chlorpyrifos ethyl and spinosad in Spodoptera frugiperda larvae

“…The selected insecticides were those that had the smallest negative impact on fungal spore germination. The fungal strains had already been characterized in our Laboratory of Insect Pathology …”

Metarhizium pingshaense applied as a seed treatment induces fungal infection in larvae of the white grub Anomala cincta

“…Infectivity of M. pingshaense to A. cincta when applied as a seed treatment or by direct inoculation Third instar A. cincta larvae were collected from maize crops near San Lorenzo, Guanajuato, Mexico (August-November 2012), transported to the laboratory and identified as described by Guzmán-Franco et al (2012). Conidial suspensions of M. pingshaense isolate MGC02 (from an infected white grub (Carrillo-Benítez et al, 2013)) were prepared as described by Guzmán-Franco et al (2012). We used this isolate because the susceptibility of A. cincta larvae to this isolate, when inoculated directly onto the larvae, had been previously evaluated .…”

“…In addition, another M. pingshaense isolate (MG06) also isolated from an infected white grub (Carrillo-Benítez et al, 2013) was included for comparison and to detect any potential isolate-related differences. Maize seeds were treated with either isolate MG02, isolate MG06 or a Tween 80 solution (control) and sown in 1L plastic containers, only two seeds per pot, but otherwise as described previously (n = 20 for each treatment).…”

Diversidade filogenética e expressão de genes de virulência de Metarhizium com ênfase em isolados brasileiros associados a cultura da cana-de-açúcar

“…A integração de ferramentas moleculares e análises filogenéticas robustas têm auxiliado a taxonomia e o processo de identificação de espécies acelerando e unificando os estudos de caracterização da diversidade e distribuição de fungos entomopatogênicos no controle biológico (STEINWENDER et al, 2011, NISHI et al, 2011, FISHER et al, 2011, CARRILLO-BENÍTEZ et al, 2013, ROCHA et al, 2012, LOPES et al, 2013.…”