Functional evaluation of culture filtrates of Bacillus subtilis and Pseudomonas fluorescens on the mortality and hatching of Meloidogyne javanica

Abstract

Rhizospheric bacteria Bacillus subtilis and Pseudomonas fluorescens are two widely tested biological control agents against root-knot nematodes (RKN) of different crops. However, their performance as bio-control agents varies with their place of origin. Culture filtrates of rhizospheric bacteria contain some intermediary metabolites that have nematicidal activity. An in vitro experiment was undertaken to evaluate the functionality of culture filtrates of B. subtilis (MN252542.1) and P. fluorescens (MN256394.1) at different concentrations (1.0%, 2.5%, 5.0%, 7.0%, 10.0% and 25.0%) on the hatching and mortality of Meloidogyne javanica at different time span. Bacterial strains were isolated from rhizospheric soils of Bangladesh. At three days after incubation (DAI), 25.0% concentration of culture filtrates of both B. subtilis and P. fluorescens showed 100.0% mortality of second stage juveniles (J 2 ) of M. javanica . Additionally, 25.0% concentration of culture filtrates of both bacteria showed 100.0% inhibition of hatching at one week after incubation (WAI). A decreasing trend in hatching of M. javanica was observed with the increment of the concentration of culture filtrates and progression of incubation time. The findings of this experiment reveal that culture filtrates of these accessions of B. subtilis and P. fluorescens are effective for controlling M. javanica and would be potential candidates for developing bio-nematicides.

Biorational management of root-knot of brinjal (Solanum melongena L.) caused by Meloidogyne javanica

“…In several preliminary in vitro experiments, it was found that B. subtilis and P. fluorescens strongly influenced the mortality and hatching of M . javanica , however, the pattern of influence of two organic amendments (vermicompost and BD) on the nematode was inconsistent ( Das et al., 2021a ; 2021b ). On the basis of these findings, organic amendments were integrated with the two bacteria in these trials.…”

“…The use of biocontrol agents like fungi and bacteria is of growing interest for controlling PPN non-chemically ( Crawford and Clardy, 2011 ). Two rhizosphere bacteria Bacillus subtilis and Pseudomonas fluorescens have been reported to inhibit RKN reproduction, egg hatch, and juvenile survival by producing different enzymes and toxins ( Siddiqui and Mahmood, 1999 ; Das et al., 2021a ). As bio-nematicides are formulated based on living systems, there has always been a gap between laboratory and field performance of those ( Abu-Elgawad and Askary, 2015 ).…”

“…Various concentrations of culture filtrates of B. subtilis and P. fluorescens have been reported to strongly influence mortality and hatching of M . javanica ( Das et al., 2021a ). In an in vitro experiment, the effect of vermicompost, BD, and botanical extracts of marigold and cabbage was evaluated on the hatching and mortality of M. javanica ( Das et al., 2021b ).…”

Biocontrol efficacy of Bacillus velezensis strain YS-AT-DS1 against the root-knot nematode Meloidogyne incognita in tomato plants

“…Rhizosphere bacteria belonging to the Bacillus genus have been widely described to effectively reduce RKNs in both greenhouse and field experiments, such as B. firmus ( Terefe et al, 2009 ), B. pumilus ( Lee and Kim, 2016 ), B. amyloliquefaciens ( Jamal et al, 2017 ), B. subtilis ( Cao et al, 2019 ; Das et al, 2021 ), B. atrophaeus ( Ayaz et al, 2021 ), B. cereus ( Yin et al, 2021b ) and B. altitudinis ( Ye et al, 2022 ). As Bacillus species can rapidly colonise and reproduce in the plant rhizosphere and exhibit strong resistance to various environmental stresses, biocontrol agents based on Bacillus have shown greater advantages in production, storage, and reliability of RKN biocontrol efficiency compared with other bacterial antagonists of RKN ( Lalloo et al, 2010 ).…”