Ethanol on the postharvest control of anthracnose in ‘Kumagai’ guava

Abstract

The aim of this study was to evaluate the effects of ethanol on the control of Colletotrichum spp. in ‘Kumagai’ guava and on the fruit physical-chemical attributes. For this purpose, three assays were carried out. For the first assay, fruit were exposed to ethanol vapor (0, 1, 2, 4, and 8 mL·kg-1), applied in hermetic containers. On the second, ethanol was applied by immersion for 2 minutes in different concentrations (20, 30, 40, and 50%). On the last assay, fruit were immersed in 30, 40, and 50% ethanol for 2, 5, and 10 minutes. Fruit that were not exposed to volatile (first assay) or water treated (second and third assay) were used as control. In all assays, guavas were first inoculated with a conidial suspension of Colletotrichum spp. and after 2 hours, fruit were subject to ethanol. Fruit were stored at 25 °C/ 80% RH for 8 days and assessed for incidence, rot severity and physical-chemical properties. Conidial germination and mycelial growth of Colletotrichum spp. were evaluated on in vitro assays. It was observed that 40 and 50% of ethanol, applied by fruit immersion for 2 min, reduced incidence and anthracnose severity with no changes in the guava physical-chemical attributes, when fruit were stored at 25 °C. Applied as a vapor, ethanol reduced only the incidence, but did not reduce anthracnose severity in guavas stored at 25 °C. Under cold storage, fruit treated with 40% ethanol exhibited a reduction of 19% in anthracnose severity. In vitro, ethanol vapor at 70 and 140 µL·L-1 inhibited Colletotrichum spp. mycelial growth rate and when incorporated in potato-dextrose-agar, ethanol (30, 40 and 50%) inhibited Colletotrichum spp. mycelial growth rate and conidial germination.