Evaluation of a newly isolated bacterium,Pseudomonas chitinolyticasp. nov., for controlling the root‐knot nematodeMeloidogynejavanica∗

Abstract

Soils infested with the root‐knot nematode Meloidogyne javanica were treated with Pseudomonas chitinolytica sp. nov. a bacterium isolated from crustacean shell‐amended soil, and planted with tomato seedlings. Tests performed in greenhouses and screenhouses, as well as in microplots, indicated improved growth and yield of nematode‐infected plants exposed to P. chitinolytica, with reduced nematode infection in comparison with infected non‐treated plants. Speed seedling tests showed a significant decrease in second‐stage juveniles (J2) penetrating into the roots; multiwell in vitro tests revealed an increase in the mortality rate of J2 exposed to the microorganism. P. chitinolytica filtrate expressed strong chitinolytic and proteolytic activities. However, nematode eggs pretreated with P. chitinolytica filtrate and then incubated with wheat germ agglutinin conjugated to fluorescein isothiocyanate, exhibited the same labelling pattern as non‐filtrate‐treated eggs. This excluded the possibility of direct chitinolytic involvement of P. chitinolytica filtrate with nematode eggs. Dialyzed or boiled filtrate did not affect J2 mobility or root infection, which excluded the possibility of proteolytic involvement with J2. Although the exact mode of action of P. chitinolytica and the technology of its application for field control of plant parasitic nematodes require further investigation, this potential bionematicide offers promise.