TITLE:
Performance of Natural Antagonists and Commercial Microbiocides towards in Vitro Suppression of Flower Bed Soil-Borne Fusarium oxysporum
AUTHORS:
David Nelson, Katherine Beattie, Graham McCollum, Trevor Martin, Shekhar Sharma, Juluri R. Rao
KEYWORDS:
Fusarium oxysporum; Cut Flower Wilt Disease; Natural Antagonistic Bacteria; Bacillus subtilis; Natural and Commercial Plant Extracts; Microbiocides
JOURNAL NAME:
Advances in Microbiology,
Vol.4 No.3,
February
12,
2014
ABSTRACT: Fusarium oxysporum is the causal agent for wilt diseases of many major ornamental and
horticultural crops. In this study, we plated a local cut flower grower’s soil, with a persistent history
of Fusarium wilt of scented stock, Matthiola incana but not the lettuce
rotational crop. This yielded culture plates with characteristic pink to carmine
red fungi, together with a mixed bacterial population, a percentage of which was visibly antagonistic to the
Fusarium. Using molecular analyses via Polymerase Chain Reaction (PCR) assays,
we identified that Fusarium oxysporum, Fusarium culmorum, Fusarium equiseti and Fusarium venenatum were prevalent in the
soil. The co-habiting bacterial colonies that exhibited strong antagonistic
activity (zone of clearance) towards the soil fungi corresponded to Bacillus subtilis, Bacillus amyloliquefaciens and Paenibacillus
polymyxa species. Our results arising from an in vitro study involving Kirby-Bauer disc-diffusion agar assays,
coupled with bio-imaging software techniques demonstrated that the three native
soil bacteria were effective inhibitors of all Fusarium species tested,
while Bacillus subtilis exhibited the
highest antagonism towards the Fusarium
oxysporum. Bioassay tests of micro-biocides Prestop (Gliocadium catenulatum), Serenade Max (Bacillus subtilis QST713) and commercial seaweed extract, AlgiVyt
suppressed in vitro growth of Fusarium oxysporum infecting the scented
stock flower to a greater extent, whilst fresh aqueous extracts of garlic (Allium sativum) and meadowsweet (Filipendula ulmaria) flowers were ineffective
towards soil pathogen suppression. This scoping study offers cut flower growers
additional options of tapping into populations of antagonistic bacteria found
in soil persistently infected with the opportunistic soil phytopathogen Fusarium
oxysporum, affecting cut
flower crops, such as M. incana.