Bacteria as Biocontrol Tool against Phytoparasitic Nematodes

Abstract

Phytoparasitic nematodes cause severe damage and yield losses to numerous agricultural crops. Considering the revision of the EU legislation on the use of pesticides on agricultural crops, control strategies with low environmental impact are required. The approach based on the use of bacteria seems particularly promising as it also helps to reduce the applied amounts of chemicals and stabilize ecological changes. This paper gives an overview of the main types of bacteria that can be used as biological control agents against plant parasitic nematodes and their interrelationships with plants and other organisms. Many experiments have given positive results of phytoparasitic nematode control by bacteria, showing possible prospects for their application. In vitro, greenhouse and field experiments have shown that bacteria can regulate the development of ecto- and endoparasitic nematodes by different modes of action. Triggering the induction of plant defense mechanisms by bacteria is seen as the optimum tool because the efficacy of bacterial treatment can be higher than that of chemical pesticides or at least close to it. Moreover, bacterial application produces additional positive effects on growth stimulation, raises yields and suppresses other pathogenic microorganisms. Commercial formulations, both as single bacterial strains and bacterial complexes, are examined.

On the potential of Bacillus aryabhattai KMT-4 against Meloidogyne javanica

“…This can be correlated to the nematicidal activity exhibited by the bacterium against M. javanica. A vast variety of PGPR has been investigated and explored for their ability of being used as effective biological control agents against phyto-pathogenic nematodes (Migunova and Sasanelli, 2021). The application of rhizospheric microorganisms (Azotobacter chroococcum, Bacillus subtilis, and Trichoderma harzianum) and their combinations reduced the average no.…”

Photorhabdus spp.: An Overview of the Beneficial Aspects of Mutualistic Bacteria of Insecticidal Nematodes

“…Detecting the ability of Photorhabdus bacteria to survive in soil and in fresh water for 1 week, has probably fixed a time frame for their additional biocontrol applications, independent of their mutualistic EPNs [ 50 ]. Hence, various formulations ( Figure 1 ), mainly based on just the bacteria and/or bacterial metabolites, have been recorded [ 2 , 4 , 12 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ]. In this regard, increased pathogenicity islands of the Photorhabdus chromosome, with many genes encoding various insecticidal protein toxins, antibiotics, bacteriocins, and enzymes, were reviewed [ 5 , 58 , 59 ], but more have still been further identified, e.g., [ 55 , 56 , 60 , 61 ].…”

“…They decreased its reproduction factor (RF) (55–62%), egg masses (48–68%), and number of galls (51–67%). Likewise, the cell-free supernatant of these bacteria reduced the number of egg masses (72–83%), galls (51–74%), and RF (62–72%) of the false root-knot nematode, Nacobbus aberrans [ 4 , 109 ]. Interestingly, on many economically important crops, the costs of controlling plant parasitic nematodes with these inexpensively produced bacteria [ 90 ] would generally be more economical than using common chemical nematicides, such as Cadusafos and Oxamyl.…”

“…Recently, the importance of using beneficial bacteria in integrated pest and pathogen management programs has been emphasized. These bacteria can reduce the chemical inputs used for plant protection, and stabilize ecological changes [ 4 ]. Conceivably, entomopathogenic bacterial species of the genus Photorhabdus (Enterobacteriales: Morganellaceae) may be a favorable alternative for expanding the biocontrol of many plant pests and pathogens, via their secretion of various arrays comprising effective bioactive metabolites [ 2 , 5 , 6 , 7 , 8 , 9 ].…”

Selection of Bacterial Strains for Control of Root-Knot Disease Caused by Meloidogyne incognita

“…Most of available commercial products are formulations of Bacillus subtilis and B. amyloliquefaciens [ 23 ]. Moreover, Bacillus firmus I-1582 (Bf I-1582) and B. amyloliquefaciens FZB42 (now reclassified as a strain of B. velezensis [ 24 ]) have been approved for use against RKNs on vegetable crops in Europe [ 25 ]. Mechanisms of suppressiveness of these species to RKNs are related to egg colonization and degradation, as well as to the induction of a plant systemic resistance [ 26 ].…”