No 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.

No abstract

No abstract

No abstract

In vitro Kirby-Bauer disc-diffusion assays coupled with bio-imaging software techniques were used to assess native forest dwelling "fairy ring" forming fungi (Clitocybe nebularis) and co-habitant forest tree-root colonising non pathogenic, antibiotic producing bacteria (Bacillus licheniformis, Bacillus pumilis) for their antagonism towards Japanese larch dieback oomycetes phytopathogens which also affects ornamental alternative hosts. The aqueous extracts of C. nebularis exhibited the highest clearance (inhibitory) zone of 21.4 × 10 5 pixels = 573%) against Phytophthora ramorum than growth/clear zone Cartesian integrates recorded in untreated (control) disc (3.7 × 10 5 pixels = 100%) over 3-day incubation. The fairy ring fungal extracts also exhibited substantive antagonism against P. kernoviae (147%), P. lateralis (347%) and a solanaceous crop infecting P. infestans (86%). Quite encouragingly, the soil oomycete phytopathogen P. ramorum was inhibited strongly (mean ~ 177%) by both forest bacilli. Aqueous extracts of non-forest antifungal herbaceous plants (garlic and elderberry) expressed similar inhibitory effects (mean ~ 70%). A seaweed fungal elicitor component fucoidan showed moderate levels (mean ~ 85%) of antagonism against P. ramorum, P. kernoviae, P. lateralis and P. infestans. The results in this in vitro study highlight the intensity and vigor of antagonistic forest microflora and non-forest herbaceous antifungal agents such as garlic and other plant extracts as serious candidates for suppression of the oomycete Phytophthora pathogenic fungi in forest soils. This study calls for urgent scoping and impact assessment studies in pot experiments and mini-plot forest trials to gauge the fitness of these natural resources for field level potential biotechnological applications to combat the devastating dieback disease in the native woodlands and horticulture.