Effect of Exogenous Salicylic Acid on Plant Defense Mechanism in Chickpea (Cicer arietinum L.) against infection of Meloidogyne incognita

Salicylic acid (SA) is a major component of phenylpropanoid pathway and is known to induce systemic acquired resistance (SAR) against many pathogens and pests. The current experiment was conducted to study the effect of exogenous SA in inducing resistance to chickpea plants at two inoculum levels of root-knot nematode (Meloidogyne incognita). SA was applied as both seed treatments and foliar sprays at 1000 ppm and 1500 ppm concentrations. All SA treatments were able to alleviate the infection by M. incognita, with seed treatment at 1500 ppm being most effective. However, no significant variation was observed in total phenols and enzyme activities of peroxidase, polyphenoloxidase and phenylalanine ammonia lyase with increase in the inoculum level. The decrease in the root-knot index due to SA treatments was more at lower inoculum level (1000 J2/plant) than at higher inoculum level (10,000 J2/plant). Nevertheless, SA was able to induce defense reactions in both inoculated (roots) and uninoculated (leaves) parts of infected plants that were persistant till the end of the crop growing period. The results support the hypothesis that SA can induce plant defense mechanism in the form of SAR to prevent further attack by pathogens.