Biocontrol of Spoilage in Avocado (Percea americana Mill) Using Pseudomonas fluorescens and Bacillus subtilis BT2

Abstract

The avocado (Persea americana Mill.) is a dicotyledonous plant of the Lauraceae family. It is a fruit rich in nutrients, which has many benefits for human health. It is especially appreciated for its taste quality. However, post-harvest diseases of avocados due to fungal attacks are one of the main constraints on conservation and marketing in Côte d’Ivoire. The aim is to achieve biological control of avocado spoilage fungal strains during post-harvest conservation using Pseudomonas fluorescens and Bacillus subtilis BT2. Thus, 200 sampled lawyers were used for this study. Identification of the fruit spoilage fungal flora on PDA (Potato Dextrose Agar) medium, pathogenicity tests, antagonism and biocontrol tests using P. fluorescens and B.subtilis BT2 were carried out. The results obtained made it possible to identify six (6) fungal genera on spoiled avocados including Colletotrichum, Botryodiplodia, Absidia, Rhizopus, Alternaria and Aspergillus. The respective isolation frequencies were 42.03%, 22.70%, 15.46%, 8.21%, 5.8% and 5.8%. Bacillus subtilis and Pseudomonas fluorescens presented inhibition rates of these fungal genera which vary from 38.72±2.21% to 65.17±0.72% for B. subtilis BT2 and from 44.05±3.25% at 66.51±0.71% for P. fluorescens. Also, these two bacteria inhibited the growth of these spoilage fungi in vivo. The protection tests of healthy avocado fruits with the supernatant of P. fluorescens and B.subtilis BT2 made it possible to preserve the avocado fruits for eight days without any alteration of the pulp. The results of this study therefore made it possible to highlight the effectiveness of P. fluorescens and B. subtilis BT2 as good biocontrol agents for the conservation of avocado fruits in Côte d'Ivoire.