Phytohormone-Induced Resistance against <i>Xanthomonas axonopodis</i> PV. <i>citri</i> in <i>Citrus aurantifolia</i>

Abstract

Citrus canker is a perilous disease caused by Xanthomonas axonopodis pv. citri (Xac) which is hardly manageable. Till now, chemicals used against Xac either proved less effective against the disease or hazardous for environment. In this study, we investigated how phytohormones such as Salicylic acid (SA, 3 mM), Jasmonic acid (JA, 0.3 mM), 3-indolacetonitrile (IAN, 0.6 mM), Nicotinic acid (NA, 5 mM), Folic acid (FA, 0.5 mM) influenced canker disease. Disease severity and lesion diameter were significantly mitigated by exogenous application of these phytohormones compared with water (control) accompanied by the increase of latent period. However, these phytohormones did not show any in vitro antimicrobial properties against Xac. Concomitant with boosted resistance, phytohormones treated leaves showed the higher level of phenyl ammonia lyase (PAL) activity. Besides, total phenolic compounds (TPC) and potassium contents were also higher in phytohormone treated plants compared with control. Phytohormones showed the significant and better performance on disease mitigation than control among which, SA showed the highest performance while JA and INA showed the moderate performance. However, NA and FA showed the lowest performance. This result recommended that application of some phytohormones had elicited some biochemical and physiological events which induced the resistance against Xac.

Untitled

“…Elicitors are natural or synthetic compounds that activate chemical defense in the plant (Garcia-Brugger et al, 2006). However, IR against citrus canker through the application of different elicitors was investigated previously (Wang and Liu, 2012;Li and Wang, 2013;Nayem et al, 2017). Quality citrus production is being hindered by Xanthomonas axonopodis pv.citri that is influencing world citrus industry.…”