Treatment with chitosan protects habanero pepper against the infection with <i>Phytophthora capsici</i>

Abstract

Similar to most members of the genus Capsicum, the habanero pepper (Capsicum chinense Jacq.) is susceptible to the deadly disease Phytophthora blight caused by the oomycete Phytophthora capsici. Currently, this pathogen is controlled mainly with agrochemicals, a non-effective strategy with undesirable effects on the environment and human health. In this work, we evaluated the protective effect of chitosan against the infection with P. capsici. Cultivation of P. capsici in vitro in the presence of 10 μg · mL-1 chitosan reduced its growth significantly; however, higher concentrations (100 and 500 μg · mL-1) practically blocked its growth (by 90 and 95%, respectively). On the other hand, spraying high concentrations of chitosan (100 and 500 μg · mL-1) on three-month-old habanero pepper plants prevented the spreading of the oomycete, but lower concentrations (1 and 10 μg · mL-1) did not prevent the disease. Interestingly, the application of chitosan did not protect the plants if they were previously wounded; thus, it is possible that the treatment has a direct effect on the oomycte, instead of producing a defense-related response in the plant. Since chitosan is an innocuous food additive, our results suggest it can be used as an environmentally friendly complement to the traditional agronomical practices in the control of Phytophthora blight in peppers.