PROVIDENCIA VERMICOLA MEDIATED GROWTH ALTERATION AND INHIBITED GALL FORMATION ON TOMATO PLANTS INFECTED WITH THE ROOT KNOT NEMATODE MELOIDOGYNE JAVANCIA Ammar Amgad Aish 1 , Mohammed Mahmood Sulaiman 1 , Sahar A. Youssef 2 * and Samia I. Massoud 2 1 Plant Protection Department, College of Agricultural Engineering Sciences, University of Baghdad, Iraq. 2* Botany Department, Faculty of Agriculture, Suez Canal University, Ismailia, 45122 Egypt. Abstract The root knot nematode (RKN) (Meloidogyne javanica) is a widespread deleterious pathogen affecting plant growth and yields; thus limiting the agricultural activity worldwide. Therefore, an effective safe control method against the pathogen is urgently needed. The objectives of this research were to isolate an effective biocontrol agent against RKN and to examine its effect on tomato growth. In the present study, only 7 bacterial isolates out of 142 exhibited antagonistic activities against RKN and one isolate showed almost 100% egg hatching suppression. The strain was identified as Providencia vermicola using 16s rRNA and was chosen for further study . In dual culture bioassay, examination under the light microscope showed distinguishable intake black egg masses compared to control. Furthermore, when the black-color egg masses were crushed, a similar alteration of the egg color was observed. In addition, the treated egg masses were unable to infect tomato roots in pots. Under the greenhouse conditions, application of P. vermicola at a rate of 50 ml/pot (1x10 8 CFU/ml) significantly reduced disease symptoms and galls number. Moreover, bacterial application enhanced tomato growth related parameters considerably compared to untreated plants. Similarly, the bacterial filtrate exhibited a substantially nematicidal activity against RKN. Further analysis of the bacterial filtrates showed production of an active substance(s) that was heat stable. Determination of the strain characterization revealed a strong ability to solubilize phosphate and production of Indole Acetic Acid (IAA) whereas siderophore and hydrogen cyanide (HCN) production were not detected. The results indicated that P. vermicola represents a novel bacterial strain protecting tomato plants against RKN. Key words: Nematicide; PGPR; Meloidogyne javanica; Providencia vermicola Introduction Tomato (Lycopersicon esculentum Miller) crop is one of the most consumed vegetables worldwide either fresh, cooked or processed. The fruit is rich in nutrients and its health benefits are well documented (Olaniyi et al., 2010; Bhowmik et al., 2012). In general, the crop is infected with a wide range of pathogens such as fungi, bacteria, viruses and nematodes. Of all parasites, the root- knot nematodes (RKNs) are the most economically destructive pathogens (Oka et al., 2000; Trudgill and Blok 2001) especially in sandy soil. In Egypt, tomato is a major crop cultivated in three consecutive cycles per year and severely affected by RKNs (Ibrahim et al., 2000). The main two species that are frequently reported to cause damage in North East, Egypt is Meloidogyne javanica and Meloidogyne incognita (Ibrahim et al ., 2000; Mahgoob and El-Tayeb 2010). Unfortunately, control of RKN is a challenge due to the life cycle of the pathogen, its adaptation capability to the environment, and the limiting availability of effective and environmentally safe chemical nematicides. Therefore, new strategies for RKN management are urgently needed to control the pathogen with emphasizing on alleviating the environmental stresses. Of all the alternatives, biological control using soil microorganisms provide an acceptable method to manage RKN. Soil microbiota is a conventional source for new and effective biocotrol agents. Recently, many promising antagonistic organisms have been reported as efficient Plant Archives Vol. 19 No. 2, 2019 pp. 3865-3873 e-ISSN:2581-6063 (online), ISSN:0972-5210 *Author for correspondence : E-mail : youssefsahar@rocketmail.com