Phylogenetic characteristics of novel Bacillus weihenstephanensis and Pseudomonas sp. to desert locust, Schistocerca gregaria Forsk\xe5l (Orthoptera: Acrididae)

Tamer A Mashtoly,Ashraf A Marzouk,Gamal M Abdelatef,Mohamed Reda,Assem Abolmaaty,Mohamed S El-Zemaity

doi:10.1186/s41938-019-0188-7

Abstract

Thirty bacterial isolates were isolated from the gut contents of diseased/dead locust. Their pathogenicity was tested against 4th instar nymphs of desert locust, Schistocerca gregaria Forskål (Orthoptera: Acrididae). Two isolates, designated DL2 and DL6, out of thirty showed the highest insecticidal activities against locust nymphs in preliminary bracketing. They were bioassayed via leaf dip and per os techniques and toxicity was determined using SAS program. The insecticidal activity of DL6 was more than DL2, whereas LC50’s values of 35 × 106 and 13 × 106 cfu’s/ml were determined for DL2 and DL6, respectively, after 48 h of leaf-dip treatment. However, LD50’s value of 53 × 106 and 26 × 106 cfu’s/ml was determined for DL2 and DL6, respectively, after 24 h of per os treatment. The relative potencies of DL6 to DL2 were (2.6 and 2.03) folds in leaf-dip and per os treatments, respectively. Biochemical characterization was conducted, using GEN III MicroPlate™ Biolog identification system and confirmed with molecular identification via 16S rDNA gene sequencing. Nucleotide sequencing of each was submitted to a gene bank and an accession number was generated for each isolate. Obtained bacterial strains DL2 and DL6 were identified as Bacillus weihenstephanensis (KY630645) and Pseudomonas sp. (KY630649), with a similarity of 100 and 75% to B. weihenstephanensis strain PHCDB9 (NR_024697) and Pseudomonas sp. strain DSM11821 (KF417541), respectively. The tested strains proved their potential to be bio-pesticide agents involved in controlling desert locust nymphs.Graphical abstract

Highlights

Locust swarms are considered to be a dramatic severe threat to sustainable food production globally (Lecoq, 2001)
Most entomopathogenic bacteria are spore forming which count on Cry toxins to cause insect mortality
Isolation of the entomopathogenic bacteria from the diseased and dead locusts resulted in thirty different purified bacterial strains, isolated from the gut and the dead locust paste

Summary

Introduction

Locust swarms are considered to be a dramatic severe threat to sustainable food production globally (Lecoq, 2001). A lot of environmental concerns have been raised about the adverse impacts of the chemical pesticides used in controlling locusts. These concerns have drawn attention to the importance of developing biocontrol agents against locusts. Entomopathogenic bacteria such as Bacillus spp. possess antagonistic effects as pesticide. Some non-spore forming bacteria such as Pseudomonas spp. exhibited different virulence factors encoded in their excretions. The insecticidal characteristics of non-spore forming bacteria to insects depend on the capability of the entomopathogen to enter, survive, persist in mid-gut physicochemical conditions and immune defenses, and excrete toxic substances that disrupt host physiology (Dieppois, et al 2015)

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Conclusion