Plant growth promoting rhizobacteria (PGPR) as eco-friendly alternatives for management root-knot nematodes, Meloidogyne spp. on tomato plants.

Abstract

Plant Growth Promoting rhizobacteria (PGPR) are a various group of bacteria that could be create in the rhizosphere, at root surfaces and in association with roots. PGPR can be used as bio-control agents. The objective of this study was to assess four different bacterial strains i.e. Pseudomonas fluorescens, Azospirillum brasilense, Azotobacter chroococcum and Bacillus megaterium against Meloidogyne spp at three different incubation times i.e. 24, 48, 72 and 168 hrs under laboratory conditions. Furthermore, the strains were evaluated at different application times i.e. (one week before, at the same time and one week after nematode inoculation) as biocontrol agents against Meloidogyne spp. on tomato plants in pots experiments. In vitro results revealed that the highest inhibition percentage in egg hatching and larvae mortality recorded after 168 hrs with B. megaterium by 17.3% and 92%, respectively. Greenhouse, results cleared that all evaluated bacterial strains at all different application times had the potentiality in Meloidogyne spp. parameters reduction i.e. (number of galls, egg masses, females/root system and juveniles in soil) and the reproduction to a huge extent compared to treated plants with nematode alone. Plants inoculated with B. megaterium achieved also the highest increases in shoot and ISSN 2537_ 0715 IJSRSD (2021): Volume 4, Issue 2, August 2021 International Journal of Scientific Received: June 2021, Accepted: July 2021 Research and Sustainable Development Page 2 of 31 root lengths and weights when applied one week before nematode inoculation by 213.3, 175, 180 & 291.3%, respectively compared to the other application times. Also it the highest values of ch.a, chl.b, total chlorophyll and carotenoids by 1.0, 0.75, 1.75 and 0.78 mg/ g.f.w., respectively recorded with B.megaterium when applied one week before nematode inoculation after 30 days from transplanting. Plants inoculated with A. chroococcum recorded the lowest photosynthetic pigments. Peroxidase (POX) and polyphenol oxidase (PPO) were increased with all bacterial strains treatments. The significant increase of dehydrogenase activity and total count of bacteria of all different bacterial strains observed when applied at all three application times were compared to plants infected with nematode alone.