Abstract
BackgroundMicrobial cultures are extensively used as environment friendly ways for biological control of parasitic pests, including the root-knot nematodes, alternative to the use of chemical nematicides. The present study was conducted to isolate some lytic rhizobacteria and examine their nematicidal activity against Meloidogyne incognita J2 mortality and egg hatching in in vitro test.ResultsLytic Rhizobacteria were isolated from soil samples adhering to tomato plant roots from different localities at Giza governorate, Egypt. Six bacterial isolates, exhibited high efficacy against root-knot nematodes, were identified based on the analysis of the 16S rRNA gene sequence as Pseudomonas aeruginosa, Paenibacillus polymyxa, Lysinibacillus sphaericus, Bacillus cereus, Bacillus subtilis, and Achromobacter xylosoxidans. These strains showed high production of chitinase, chitosanase, and protease using colloidal chitin and soluble chitosan as carbon sources. Two strains, Paenibacillus polymyxa and Bacillus subtilis, produced the highest levels of chitinase in the media. Except for Pseudomonas aeruginosa, all the bacterial strains produced high levels of chitosanase.ConclusionThe results revealed that high amounts of protease were, however, secreted by Pseudomonas aeruginosa as compared to the other strains. In in vitro tests, all the bacterial culture filtrates potentially displayed nematicidal effect in M. incognita egg hatching and an obvious increase in J2 mortality as compared to control. Paenibacillus polymyxa caused 100% juvenile mortality followed by Bacillus subtilis 97.25%, Bacillus cereus 94%, Achromobacter xylosoxidans 93%, Lysinibacillus sphaericus 92%, and Pseudomonas aeruginosa 84.29% after 48 h of exposure, as compared to control.
Highlights
The word sustainable agriculture has been resounded among international organizations over the past decades
The present study aims to (a) isolate and identify some lytic bacterial strains from soil adhering to tomato plant roots, (b) evaluate their production of chitinase, chitosanase and protease, and (c) investigate the nematicidal potential of the isolated strains against Meloidogyne incognita and egg hatchability under in vitro conditions
These isolates were identified by analysis of the sequence similarity of 16S rDNA gene sequence with that on Genbank database as Pseudomonas aeruginosa, Paenibacillus polymyxa, Lysinibacillus sphaericus, Bacillus cereus, Bacillus subtilis, and Achromobacter xylosoxidans, respectively
Summary
The word sustainable agriculture has been resounded among international organizations over the past decades. Meloidogyne spp., the most extensively studied nematode genera attack plants, have been economically reported as root-knot nematodes. The potential negative impacts of synthetic nematicides have created the need to discover alternative safe and ecofriendly control methods. Biological control using plant-growth–promoting rhizobacteria (PGPR) is a promising tool and safe alternative approach for controlling plant-parasitic nematodes (Lee and Kim 2016; Rika et al 2017; Priyank et al 2018; Sidhu 2018). Microbial cultures are extensively used as environment friendly ways for biological control of parasitic pests, including the root-knot nematodes, alternative to the use of chemical nematicides. The present study was conducted to isolate some lytic rhizobacteria and examine their nematicidal activity against Meloidogyne incognita J2 mortality and egg hatching in in vitro test
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