ارزیابی برخی جدایه‌های باکتریایی مرتبط با ریشه بر نماتد Meloidogyne javanica در شرایط آزمایشگاه

Root-knot nematodes (Meloidogyne spp.) are the most widespread parasitic nematodes, causing damage of numerous crops. Due to environmental restrictions on nematicidal use for their controlling, biological control has recently gained increasing interest. Certain root-associated bacteria produce and excrete metabolites that are inhibitory to plant pathogenic nematodes (direct effect) or decrease the effect of plant pathogenic nematodes indirectly through increase in plant-resistance. In the present study, the effect of root-associated bacteria was studied on the egg hatching and the second stage juvenile (J2s) mortality of M. javanica under laboratory condition. For this purpose, 35 strains of bacteria were extracted and purified from rhizosphere of healthy tomato, eggplant, bell pepper and watermelon plants, as well as eggplant and pistachio infected with root-knot nematodes. Then 100 eggs or J2s of M. javanica were separately added to petri dishes containing 10 ml of bacterial suspension with a concentration of 107 cells and kept under controlled conditions at 27 °C. Sterile distilled water was used in the control treatment. After 120 hours, the number of hatched eggs was counted. Also, after 48 hours, immobile J2s were concentrated in small volumes of sterilized water. The suspension was filtered using a petri dish containing filter paper (Whatman no. 1) for recovering alive nematodes. Immobile (dead) nematodes were counted after 24 hours. Both experiments were performed in a completely randomized design with three replications. The results showed that after 120 hours, Pseudomonas sp. I01, Pseudomonas sp. I02 and Bacillus sp. reduced egg hatching by 79.5, 77.8 and 69.4 percent, respectively, as compared to the control. Also, Pseudomonas sp. I01, Bacillus sp. and Clostridium sp. were determined to be the most effective strains on J2s mortality of M. javanica by increasing 149, 131 and 120 percent, respectively, as compared to the control. It should be noted that molecular and phenotypic identification of effective isolates are under determination.