Extract of Xanthomonas axonopodis induces resistance in Solanum tuberosum against Pectobacterium atrosepticum

Abstract

Potato (Solanum tuberosum) is affected by many pathogens, such as the necrotrophic bacterium Pectobacterium atrosepticum (Pba), resulting in substantial economic losses. The induction of natural disease resistance in crops using biological and chemical elicitors has received increasing attention in recent years, due to the low environmental toxicity of this method of disease management. We evaluated the ability of the autoclaved suspension of Xanthomonas axonopodis (XTH) to modulate the defense metabolism and retard the disease caused by P. atrosepticum in detached leaves of S. tuberosum. Our results demonstrated that XTH slowed the progression and ameliorated the disease symptoms caused by P. atrosepticum. This effect may be related to the early activation of antioxidant enzymes such as catalase (CAT) at 0.5-h post treatment (hpt), as well as to the activation of the defense-related enzymes, phenylalanine ammonia lyase (PAL) and chitinase at 24 hpt and 12 hpt, respectively. Leaves treated with XTH + Pba also showed increase in polyphenol oxidase activity at 96 hpt. Leaves pretreated with the biotic elicitor did not show increase on free SA level, differing from the those inoculated with Pba. Our results indicated that XTH induces the plant defense metabolism and delays the progression of disease in potato caused by P. atrosepticum.