In vitro AND in vivo ANTI-FUNGAL EFFECT OF CHITOSAN ON POST-HARVEST STRAWBERRY PATHOGENS

Abstract

Plant diseases with a negative impact on strawberry yield (Fragaria ? ananassa), such as anthracnose and fruit rot, are mainly controlled using pesticides, which can cause harmful effects; thus, new control alternatives for fruit decay are needed. Chitosan is a compound already evaluated for fungal disease control at postharvest. The aim of this study was to evaluate the in vitro and in vivo control activity of chitosan against post-harvest fungal strawberry pathogens, such as Colletotrichum gloeosporioides, Colletotrichum acutatum, Fusarium oxysporum and Phytophthora sp. The experimental design was completely random, with at least three repetitions for each chitosan treatment (5, 7.5, 10 and 15 mg mL?1 ). The data obtained were transformed with the x ?0 5. function. A variance analysis (p?0.05), and a Tukey’s test (p?0.05) were conducted using the SAS software. In vitro bioassays showed the anti-fungal effects of chitosan (5, 7.5, 10 and 15 mg mL?1 ) against all pathogens tested, which are related to the inhibition of mycelial growth and spore germination. The best results were observed in F. oxysporum and Phytophthora sp. with 100% of mycelial growth and spore germination inhibition. In vivo bioassays showed that strawberry fruit inoculated with mycelium or spores, and then immersed in chitosan (7.5, 10 and 15 mg mL?1 ), displayed a significant reduction (p?0.05) in disease severity index after two treatments: 1) exposure for 7 d at 2?2.0 °C, and 2) for 3 d at room temperature (25?2.0 °C). The best results were observed in fruit treated with 15 mg mL?1 chitosan, which showed a disease severity range of 1-1.2 for fruit inoculated with mycelium and 1-1.6 with spores. These findings show that chitosan is a promising alternative in post-harvest disease control in strawberries.