Characterization of Plant Growth–Promoting Traits of Bacteria Isolated from Larval Guts of Diamondback Moth Plutella xylostella (Lepidoptera: Plutellidae)

Abstract

Eight bacterial isolates from the larval guts of Diamondback moths (Plutella xylostella) were tested for their plant growth-promoting (PGP) traits and effects on early plant growth. All of the strains tested positive for nitrogen fixation and indole 3-acetic acid (IAA) and salicylic acid production but negative for hydrogen cyanide and pectinase production. In addition, five of the isolates exhibited significant levels of tricalcium phosphate and zinc oxide solubilization; six isolates were able to oxidize sulfur in growth media; and four isolates tested positive for chitinase and beta-1,3-glucanase activities. Based on their IAA production, six strains including four that were 1-aminocyclopropane-1-carboxylate (ACC) deaminase positive and two that were ACC deaminase negative were tested for PGP activity on the early growth of canola and tomato seeds under gnotobiotic conditions. Acinetobacter sp. PSGB04 significantly increased root length (41%), seedling vigor, and dry biomass (30%) of the canola test plants, whereas Pseudomonas sp. PRGB06 inhibited the mycelial growth of Botrytis cinerea, Colletotrichum coccodes, C. gleospoiroides, Rhizoctonia solani, and Sclerotia sclerotiorum under in vitro conditions. A significant increase, greater than that of the control, was also noted for growth parameters of the tomato test plants when the seeds were treated with PRGB06. Therefore, the results of the present study suggest that bacteria associated with insect larval guts possess PGP traits and positively influence plant growth. Therefore, insect gut bacteria as effective PGP agents represent an unexplored niche and may broaden the spectrum of beneficial bacteria available for crop production.

The Role of Soil Beneficial Bacteria in Wheat Production: A Review

“…These results were consistent with earlier report on the P and Zn solubilizing properties of Acinetobacter sp. [44]. Nearly all the Acinetobacter species isolated from rhizosphere soil of the three wheat varieties in the present study were efficient phosphate and zinc solubilizers and produced iron chelating siderophores [45].…”

Interactions between Indole-3-acetic Acid Producing Acinetobacter sp. SW5 and Growth of Tomato Plant

“…SW5 Acinetobacter spp. are widely distributed in soil and water, and some of them have been reported to enhance the growth of many plants (Indiragandhi et al, 2008;Gulati et al, 2009;Shi et al, 2011). In this study Acinetobacter sp.…”

“…(Huddedar et al, 2002;Chaiharn et al, 2008;Rokhbakhsh-Zamin et al, 2011). Although many species of Acinetobacter are reported as PGPR (Indiragandhi et al, 2008;Gulati et al, 2009;Kang et al, 2009;Shi et al, 2011), this SW5 strain showed a high plant growth promoting capability. SW5 strain has a 97.875% of sequence homology of 16S rRNA gene compared with the type strain A. guillouiae ATCC 11171 T reported recently by Nemec et al (2010), and some general characteristics of SW5 strain were coincided with those of other Acinetobacter spp.…”

“…This is much higher than 15 µg/ml of IAA at 2 days incubation by A. rhizosphaerae BIHB723 in 0.1% tryptophan added nutrient broth (Gulati et al, 2009), and 7.9-8.2 µg/ml of IAA by other strains of Acinetobacter spp. (Indiragandhi et al, 2008). Acinetobacter sp.…”

Penicillium citrinum VFI-51 as biocontrol agent to control charcoal rot of sorghum (Sorghum bicolor (L.) Moench)

“…helps in disease suppression (Indiragandhi et al, 2008). IAA helps the host plants to stimulate seed germination, root formation and root elongation (Ahemad and Kibret, 2014) whereas HCN was also reported to help in disease suppression (Haas et al, 1991).…”