Padronização da inoculação e controle da antracnose em bananas com película à base de fécula de mandioca e óleos essenciais

Abstract

The banana is one of the most-produced fruits worldwide. Among the limiting factors of its cultivation, are post-harvest diseases, such as the anthracnose caused by Colletotrichum musae. Given the importance of knowing the factors responsible for the anthracnose development and how to control it with natural products, we aimed in this study to evaluate different inoculation methods and wet periods in the development of Colletotrichum musae lesions in bananas, as well as to check the in vitro and in vivo potential control of anthracnose by a film of cassava starch and essential oils. The banana fungal strain was identified by morphological and molecular characters, using genomic regions GAPDH and ACT. Five inoculation methods were used, one hole with mycelium (1 HM), one hole with suspension (1HS), five holes with mycelium (5HM), five holes with suspension (5HS) and cut with suspension (CS), combined with five wetting periods (0, 6, 12, 24, and 48 h). The essential oils of clove, lemon grass, thyme, cinnamon, and oregano were chosen for their potential inhibition of pathogens and were used at 0.1% concentration, selected in a preliminary test. Two experiments were performed in vitro, one to check the mycelial growth and the other to assess the C. musae conidial germination. During the in vivo test, bananas were treated by curative and preventive methods with cassava starch film at 2 and 3% concentrations and with essential oils combined or not, aiming to control the anthracnose. Fragmented samples of damaged fruit skins were collected for analysis in a scanning electron microscope (SEM). The strain showed morphological features of C. musae. The phylogenetic analysis grouped the strain in the 'gloeosporiodes' complex and in the same clade of C. musae. A higher development of lesions with the 5FS inoculation method combined with 48 h of wetness. Regarding the in vitro test, the oregano essential oil at 0.1% completely inhibited the mycelial growth and germination of C. musae. For the curative and preventive in vivo test, films at 2 and 3%, lemon grass essential oil, as well as thyme alone or all combined with films reduced the lesion sizes in bananas. The images from SEM showed the effect of films at 2 and 3% and of essential oils on the pathogen ultrastructure. Thus, these alternative products can be indicated as promising strategies for anthracnose control in bananas.