Isolation and identification of entomopathogenic nematodes and their symbiotic bacteria from Kurdistan province in Iran

Abstract

Entomopathogenic nematodes (EPNs) are commonly used as biological agents for control of insect pests. This study was carried out to identify EPNs, determine dominant and frequent species in Kurdistan province, Iran and characterize their symbiotic bacteria. Identification of EPNs was performed based on morphological and morphometrical characters and also rRNA-ITS gene sequences. Two EPNs, Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae) and Steinernema feltiae (Rhabditida: Steinernematidae) were identified. Out of totally 150 soil samples collected mainly from mid-southern parts of the province, 60% were positive for EPNs. Heterorhabditis bacteriphora showed the highest frequency in this region, remarkably 59.3% of soil samples contained this species. Incidences of H. bacteriphora in grasslands, woodlands and alfalfa fields were 57.3, 14.6 and 28.0 percent, respectively. Steinernema feltiae was found only in alfalfa fields with 0.66% frequency. Bacterial symbionts of H. bacteriophora and S. feltiae were also identified based on biochemical characters and recA gene sequencing. In this research, two species of Photorhabdus were isolated from H. bacteriophora namely P. luminescens subsp. kayaii and P. temperata subsp. thracensis. Xenorhabdus bovienii was identified from infective juveniles of S. feltiae.

When Competitors Join Forces: Consortia of Entomopathogenic Microorganisms Increase Killing Speed and Mortality in Leaf- and Root-Feeding Insect Hosts

“…One approach to increase biocontrol efficacy is to combine different biocontrol agents with different modes of action and ecological niches [ 8 ]. Several studies found improved biocontrol success when applying BCA consortia [ 9 – 11 ]. However, other studies have reported antagonistic interactions when applying combinations of microbial BCA [ 12 ].…”

Populations of entomopathogenic nematodes in agricultural lands

“…Seven isolates (4 isolates of Steinernematidae and 3 isolates of Heterorhabditidae) were recovered from pastures and 14 isolates (8 isolates of Steinernematidae and 6 isolates of Heterorhabditidae) were recovered from forest soil samples; vice versa, in some reports, occurrence of EPNs was higher than these values. For example, Abdolmaleki et al (2016) studied 150 soil samples from forest, pastures, and agricultural lands of Kurdistan Province, Iran; and found that 60% of the samples were EPNs-positive. Heterorhabditis bacteriophora was the most isolated species of EPN in this study.…”

Characterization and pathogenicity of symbiotic bacteria associated with entomopathogenic nematode: Steinernema species KALRO

“…In the free-living non-feeding stage of EPNs, the infective juveniles (IJ) infect insects by penetrating through body orifices and cuticles. The EPNs Steinernema and Heterorhabditis species are symbiotically associated with pathogenic bacteria species Xenorhabdus and Photorhabdus respectively (Ferreira & Malan, 2014;Kalia et al, 2014;Abdolmaleki et al, 2016;Salgado-Morales et al, 2019). These bacteria belong to the family Enterobacteriaceae in the gamma subdivision of proteobacteria (Sangeetha et al, 2016;Salgado-Morales et al, 2019).…”

“…The Xenorhabdus bacteria inhabit the bacterial vesicle of Steinernema while Photorhabdus are found in the gut of Heterorhabditis EPNs. Once the IJs invade an insect, the pathogenic bacteria are released from the intestines into the hemocoel of the host insect (Dillman & Sternberg, 2012;Ferreira & Malan, 2014;Abdolmaleki et al, 2016;Aiswarya et al, 2017). The bacteria multiply as the EPNs nourish on them and insect tissue and reproduce killing the insect host within 24-48 h (Shapiro-Ilan et al, 2015;Ulug et al, 2015).…”