بررسی امکان القای مقاومت سیستمیک بر علیه Candidatus Phytoplasma phoenicium

Activation of plant defense system using elicitors is one way in controlling of plant pathogens. Phytoplasmas are obligate parasite restricted to plant phloem cells, inducing virescence, yellowing, witches’ broom, decline and plant death symptoms in their plant hosts. In order to investigate effect of resistance inducing compounds on phytoplasma, Candidatus Phytoplasma phoenicium was transferred from infected black locust trees to healthy periwinkle plants using dodder plant. Infection of the inoculated plants was confirmed by PCR using phytoplasma specific primers. Further the infected periwinkle plants were treated with 250 mM salicylic acid or 3mM benzothiadiazole. Effect of these compounds on symptoms and activity of defensive enzymes were determined. The infected Periwinkle plants showed yellowing, phyllody and stunting. Three weeks later, yellowing reduced in the treated plants and new flowers developed on the plants. Total chlorophyll content was increased up to 37% with significant difference from the infected plants in salicylic acid treated plants, but no significant difference was observed in benzothiadiazole treated plants. Phenylalanine ammonia-lyase activity was significantly increased in treated plants compared to control, however there was no difference between the treatments. Moreover, no significant change was observed in activity of catalase and polyphenol oxidase. Phenylalanine ammonia is a key enzyme in phenylpropanoid pathway, which plays an important role in biosynthesis of phenolic compounds. Alteration in activity of this enzyme plays an important role in response to biotic and non-biotic stress in plant. Despite the recovery of symptoms, the phytoplasma was detected in treated plants by nested PCR using specific primer pairs. Results showed that induction of defensive system using exogenic stimulator could suppress phytoplasma symptoms in infected plant.