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

Abstract

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

Keywords

• Desert locust
• Entomopathogenic bacteria
• Microbial control
• Microbial identification
• 16S rRNA genes sequencing
• Biolog identification system