Accumulation of Phytoalexins Scoparone and Scopoletin in Citrus Fruits Subjected to Various Postharvest Treatments

Effect of various decay-controlling postharvest treatments on the accumulation of phytoalexins in citrus peel was studied. Ultraviolet illumination and yeast biocontrol agent Pichia guilliermondii elicit the production of phytoalexin scoparone and scopoletin even in the absence of the pathogen. Heat treatment (36°C, 72 hr) alone does not induce scoparone but enhances its production in pathogen-challenged fruit. Elicitation of Endogenous defensive mechanisms of the fruit is involved in the mode of action of these treatments. Effect of antibiotic-producing bacterial biocontrol agent, Bacillus subtilis (strain 160), is not related to the induction of these phytoalexins.