ACTIVITY OF SERRATIA SPP. AND BACILLUS SPP. AS BIOCONTROL AGENTS AGAINST MELOIDOGYNE INCOGNITA INFECTING TOMATO

Abstract

Background: Tomato )Solanum lycopersicum( is one of the most popular vegetable crops in Egypt. It is affected by a wide range of pests; prominent among them is root-knot nematode (RKN) (Meloidogyne spp.) which is considered as one of the major limiting factors affecting tomato productions worldwide, especially in Egypt. Aim of study: The present study was performed to evaluate the quantitative and qualitative chitionolytic potentials of Serratia, Bacillus megaterium and B. subtilis as well as their nematicidal effect against Meloidogyne incognita under both in vitro and in vivo conditions. Methodology: Qualitative and quantitative assays of bacterial chitinase of the applied bacteria were determined using Chitinase assay agar and liquid media, as well as the nelson-somogyi method. Nematicidal and ovicidal activities of bacterial treatments were evaluated by Test Tube Bio-assay technique. A greenhouse experiment was conducted for in vivo evaluation of bacterial treatments on nematode parameters. The most effective bacterial isolate was molecular identified based on the nucleotide sequencing of its 16S rRNA gene. Results: Serratia sp. (S2) showed the highest total and specific chitinase activities (0.620 U/mL and 0.079 U/mg), respectively, followed by S1 (0.560 U/mL and 0.061 U/mg) and S3 (0.434 U/mL and 0.057 U/mg). B. megaterium appeared the minimum total and specific chitinase activities (0.320 U/mL and 0.042 U/mg), and no chitinase activities was shown for B. subtilis. Serratia sp. (S2) recorded the highest ovicidal activity (53.61%) even when applied at low concentration (1%). Among greenhouse experiment, Serratia sp. (S2) recorded the minimum number of galls and egg masses. The nucleotide sequence analysis of 16S rRNA gene of Serratia sp. (S2) proved that this isolate could be a strain related to S. marcescens, therefore, it was documented in GenBank as S. marcescens strain ARC3 under the accession number MN533708. Conclusion: The results indicated that S. marcescens strain ARC3 showed the maximum nematicidal potentiality against M. incognita and its significant chitinolytic activity play an essential role in such bio-control effect. Recommendation: Chitonlytic bacteria could be suggested as effective and eco-friendly alternative approach for controlling the M. incognita.