Isolation and Identification of Plant Growth Promoting Rhizobacteria from Cucumber Rhizosphere and Their Effect on Plant Growth Promotion and Disease Suppression

Abstract

Plant growth promoting rhizobacteria (PGPR) are the rhizosphere bacteria that may be utilized to augment plant growth and suppress plant diseases. The objectives of this study were to identify and characterize PGPR indigenous to cucumber rhizosphere in Bangladesh, and to evaluate their ability to suppress Phytophthora crown rot in cucumber. A total of 66 isolates were isolated, out of which 10 (PPB1, PPB2, PPB3, PPB4, PPB5, PPB8, PPB9, PPB10, PPB11, and PPB12) were selected based on their in vitro plant growth promoting attributes and antagonism of phytopathogens. Phylogenetic analysis of 16S rRNA sequences identified these isolates as new strains of Pseudomonas stutzeri, Bacillus subtilis, Stenotrophomonas maltophilia, and Bacillus amyloliquefaciens. The selected isolates produced high levels (26.78–51.28 μg mL-1) of indole-3-acetic acid, while significant acetylene reduction activities (1.79–4.9 μmole C2H4 mg-1 protein h-1) were observed in eight isolates. Cucumber plants grown from seeds that were treated with these PGPR strains displayed significantly higher levels of germination, seedling vigour, growth, and N content in root and shoot tissue compared to non-treated control plants. All selected isolates were able to successfully colonize the cucumber roots. Moreover, treating cucumber seeds with these isolates significantly suppressed Phytophthora crown rot caused by Phytophthora capsici, and characteristic morphological alterations in P. capsici hyphae that grew toward PGPR colonies were observed. Since these PGPR inoculants exhibited multiple traits beneficial to the host plants, they may be applied in the development of new, safe, and effective seed treatments as an alternative to chemical fungicides.

Halotolerant bacteria belonging to operational group Bacillus amyloliquefaciens in biocontrol of the rice brown stripe pathogen Acidovorax oryzae

“…Furthermore, it has been reported that many Bacillus species successfully colonize the roots of plants and contribute to inhibit the wide range of phytopathogens concomitantly (Islam et al . ; Elshakh et al . ).…”

“…; Islam et al . ). PCR amplification was performed in 50 μ l total volumes with 2×TSINGKE Master Mix (TsingKe Biological Technology, Beijing, China) using a Bioer XP Thermal Cycler (Hangzhou Bioer Tech.…”

Strain-specific variation in plant growth promoting volatile organic compounds production by five different Pseudomonas spp. as confirmed by response of Vigna radiata seedlings

“…Statistical analysis was done by using the software Origin Pro7 SRO (Northampton, MA). Data were analysed using one way analysis of variance, with the Tukey post hoc multiple comparison tests to determine the significant difference in various groups at 5% level of significance (Islam et al 2015).…”

Role of ethylene signalling in growth and systemic resistance induction by the plant growth‐promoting fungus Penicillium viridicatum in Arabidopsis

“…These mechanisms are broadly categorized as being either direct or indirect (Glick, 1995). Direct mechanisms of eliciting growth promotion include producing plant hormones and increasing nutrient availability to the host by solubilizing organic phosphate or fixing atmospheric nitrogen (Contreras-Cornejo, Macías-Rodríguez, Cortés-Penagos, & López-Bucio, 2009;Islam, Akanda, Prova, Islam, & Hossain, 2015;Perez, Sulbaran, Ball, & Yarzabal, 2007). Furthermore, in vitro studies have suggested that plant growth-promoting effects can be mediated by the release of volatile organic compounds (Ryu, Hu, Reddy, & Kloepper, 2003).…”

“…PGPF are non-pathogenic, filamentous, saprophytic rhizosphere fungi that significantly enhance the growth of plants (Hyakumachi, 1994). PGPF from the genera of Fusarium, Penicillium, Phoma, Trichoderma and sterile fungi have been the subject of multiple studies because of their high protective abilities against a variety of plant diseases (Hossain & Sultana, 2015;Hossain, Sultana, Kubota, Koyama, & Hyakumachi, 2008;Kojima, Hossain, Kubota, & Hyakumachi, 2013;Shoresh et al, 2005;.…”