Cultivable Bacteria Populations Associated with Leaves of Banana and Plantain Plants and Their Antagonistic Activity Against Mycosphaerella fijiensis

Abstract

Mycosphaerella fijiensis is the etiological agent of Black Sigatoka, a fungal disease that affects production of banana and plantain crops in tropical regions. The sizes of cultivable epiphytic and endophytic bacterial populations, aerobic endospore forming bacteria (AEFB), and antagonist bacteria against M. fijiensis isolated from three Musa spp. cultivars from Urabá (Colombia) were studied, in order to find a suitable screening strategy to isolate antagonistic bacteria. Most of the variability found in the epiphytic and endophytic bacterial community sizes among fruit trees was explained by the cultivar differences. We found population sizes ranging from 1.25 × 10(3) to 9.64 × 10(5) CFU/g of fresh leaf and found that 44 % of total cultivable bacteria belong to the AEFB group. We isolated 648 AEFB from three different cultivars and assessed their antagonistic activity against M. fijiensis using the cell-free supernatant obtained from bacterial liquid cultures in three different in vitro assays. Five percent of those bacteria showed higher percent inhibition than the positive control Bacillus subtilis UA321 has (percent inhibition = 84 ± 5) in the screening phase. Therefore, they were selected as antagonistic bacteria against the pathogen. The strains with the highest percentage of antagonism were found in older leaves for the three cultivars, given support to recommend this group of leaves for future samplings. Some of these isolated bacteria affected the mycelium and ascospores morphology of the fungus. They also presented in vitro characteristics related to a successful colonization of the phylloplane such as indolic compounds, surfactant production, and biofilm formation, which makes them possible, potential candidates as biological control agents.

Comparative analysis of the in vitro and in planta secretomes from Mycosphaerella fijiensis isolates

“…The fact that most of these cultivars are unsuitable for breeding of resistant lines necessitates the extensive use of fungicides as the primary means for disease control (Churchill 2011). However, the increasing use of these compounds has resulted in many economic, health and environmental problems (Ceballos et al 2012). Furthermore, the constant application of fungicides has induced chemical resistance in M. fijiensis (OrozcoSantos 2013), turning this fungus into a serious agronomic problem.…”

Endophytic bacteria from banana cultivars and their antifungal activity

“…Studies of plant/microorganism interactions and the role of these microorganisms in plants have indicated their utility for a large number of applications, such as the biological control of numerous diseases (Zheng et al, 2011;Ceballos et al, 2012), promotion of plant growth Coombs et al, 2004;Montañez et al, 2012), and bioremediation of contaminated environments (Ma et al, 2011).…”

“…Endophytic bacteria isolated from older banana leaves exhibited higher percentages of antagonistic activity against Mycosphaerella fijiensis, which affected the morphology of the mycelia and ascospores (Ceballos et al, 2012).…”

Mecanismos de acción de <i>Bacillus</i> spp. (Bacillaceae) contra microorganismos fitopatógenos durante su interacción con plantas

“…Diferentes tipos de microorganismos, como virus, hongos y bacterias han sido empleados clásicamente para el control biológico de enfermedades (Ceballos et al, 2012;Chowdhury et al, 2015a). Dentro de este último grupo se destacan los géneros Pseudomonas y Bacillus.…”