Controlling root-knot nematode (Meloidogyne javanica) by the nematophagous fungus Arthrobotrys oligospora and salicylic acid and study of some plant defense responses

In this study، the ability of nematode-trapping fungus Arthrobotrys oligospora and salicylic acid (SA) were examined to control root-knot nematode، Meloidogyne javanica، in the laboratory and greenhouse conditions. Also changes of polyphenol oxidase (PPO) and peroxidase (POX) enzymes and total phenolic compounds accumulation in different treatments were studied. In greenhouse studies، we used leaf spraying of SA (5 mM) and soil drenching of A. oligospora (106 spore/ml) at six-leaf stage of the plants، separately and in combination. After 50 days of inoculation، diameter of the galls، number of galls and number of egg masses per individual plant، number of eggs per individual egg mass، root and foliage fresh weights were recorded. The data were analyzed in completely randomized design and subjected to analysis of Duncan’s multiple range test (p≤0. 05). The results showed that combined application of A. oligospora and SA were more effective compared to individual application of them. Study of changes in PPO، POX enzymes activities and total phenolic compounds accumulation showed that treatment with these factors caused increase in enzyme activities and also accumulation of total phenolics which shows induction of plant defense system.