Influence of hydrogen cyanide-producing rhizobacteria in controlling the crown gall and root-knot nematode, Meloidogyne incognita

Abstract

Out of 39 isolates of rhizobacteria, recovered from economic plants grown in 8 locations in Egypt, 6 isolates were able to produce Hydrogen Cyanide (HCN). 16S rRNA sequence analysis identified these isolates as: Pseudomonas japonica strain NBRC 103040, Bacillus megaterium strain CtST3.5, Pseudomonas sp. strain Gamma-81, P. tolaasii strain ATCC 33618, P. chlororaphis strain Lzh-T5, and P. mosselii strain CV25. These HCN producers were able to inhibit growth of Agrobacterium tumefaciens and affect viability of Meloidogyne incognita juveniles in vitro. The isolates of P. japonica and Pseudomonas sp. Gamma-81 prevented the gall formation on tomato plants by A. tumefaciens, regardless of the presence of M. incognita. The isolates of B. megaterium, P. chlororaphis, P. tolaasii, and P. mosselii decreased the weight and number of galls produced by A. tumefaciens in the presence or absence of M. incognita. The 6 HCN producers decreased the population of M. incognita and the number of nematode galls than the positive control, when used against M. incognita. A similar effect was achieved against mixed infections with M. incognita and A. tumefaciens. The HCN-producing rhizobacteria, in the presence of A. tumefaciens and/or M. incognita, caused obvious increment in all growth parameters of tomato than the negative control and healthy plants. The only exception was found in case of Pseudomonas sp. Gamma-81 against M. incognita and against mixed infection, where growth parameters of tomato were decreased. Although the isolates were naturally isolated from the rhizosphere of economic plants, it must be cautiously considered since the isolate identified as P. japonica has been reported as a human pathogen. Also, P. tolaasii was reported causing a bacterial blotch on cultivated mushrooms under certain environmental conditions. Further investigations are needed.

Bacterial Community Structure Dynamics in Meloidogyne incognita -Infected Roots and Its Role in Worm-Microbiome Interactions

“…The interaction between the virulence of M. incognita and the microbial diversity in the various niches M. incognita occupy has been studied in the context of biological control, revealing complex relationships, which efficacy diminishes with the transfer from lab to field ( 20 ). In this field of research, common themes include the isolation of Meloidogyne pathogens from the cuticles of J2s ( 21 – 23 ) and the identification of soil microbes and bacterial volatile compounds with antagonistic effects ( 24 , 25 ) from key taxa, including Rhizobia ( 26 ), Trichoderma and Pseudomonas ( 27 , 28 ), Pasteuria ( 29 ), Pochonia ( 30 , 31 ), and some mycorrhiza ( 31 – 33 ).…”

Impact of Plant Growth Promoting Rhizobacteria in the Orchestration of Lycopersicon esculentum Mill. Resistance to Plant Parasitic Nematodes: A Metabolomic Approach to Evaluate Defense Responses Under Field Conditions

“…Several PGPR genera that have been used as biocontrol agents include Azospirillum, Azotobacter, Pseudomonas, Gluconacetobacter, Azoarcus, Bradyrhizobium, Burkholderia, Bacillus, Alcaligenes, Paenibacillus, Serratia etc. [26,27,28,29]. Furthermore, PGPR also comes up with the interior functions of the plants such as maintaining the ROS levels generated inside plant through effective scavenging mechanisms [16,30].…”

“…They also trigger the antioxidant levels in plants (enzymatic and non-enzymatic) during nematode infection, a prerequisite for triggering defense responses within them [31]. The PGPR have also been significantly known to modulate the levels of plant metabolites by up-regulating the enzymatic activities of secondary metabolites such as phenols, sugars, amino acids and organic acids [23,26]. In addition, PGPR were found to induce ISR in tomato plants infested with nematodes through modulating the biochemical profiles of plants [26].…”

Identification and characterization of Vietnamese coffee bacterial endophytes displaying in vitro antifungal and nematicidal activities

“…isolate was positive for the HCN production. This volatile compound has already been demonstrated to control the development in vitro and in planta of the fungal pathogen Sclerotinia sclerotiorum (Nandi et al, 2017), the bacterial pathogen Agrobacterium tumefaciens and the parasitic nematode M. incognita (Abd El-Rahman et al, 2019). In the literature, several bacteria from the rhizosphere were described as HCN producers (Ahmad et al, 2008;Ghodsalavi et al, 2013).…”