Elucidating the Diversity of Aquatic Microdochium and Trichoderma Species and Their Activity against the Fish Pathogen Saprolegnia diclina

Abstract

Animals and plants are increasingly threatened by emerging fungal and oomycete diseases. Amongst oomycetes, Saprolegnia species cause population declines in aquatic animals, especially fish and amphibians, resulting in significant perturbation in biodiversity, ecological balance and food security. Due to the prohibition of several chemical control agents, novel sustainable measures are required to control Saprolegnia infections in aquaculture. Previously, fungal community analysis by terminal restriction fragment length polymorphism (T-RFLP) revealed that the Ascomycota, specifically the genus Microdochium, was an abundant fungal phylum associated with salmon eggs from a commercial fish farm. Here, phylogenetic analyses showed that most fungal isolates obtained from salmon eggs were closely related to Microdochium lycopodinum/Microdochium phragmitis and Trichoderma viride species. Phylogenetic and quantitative PCR analyses showed both a quantitative and qualitative difference in Trichoderma population between diseased and healthy salmon eggs, which was not the case for the Microdochium population. In vitro antagonistic activity of the fungi against Saprolegnia diclina was isolate-dependent; for most Trichoderma isolates, the typical mycoparasitic coiling around and/or formation of papilla-like structures on S. diclina hyphae were observed. These results suggest that among the fungal community associated with salmon eggs, Trichoderma species may play a role in Saprolegnia suppression in aquaculture.

Fungal Colonization on Body Surfaces of Dead South American Sea Lions on Sandy Beaches, and an Evaluation of Risk of Contamination to Humans at Southern Brazil

“…may originate from the tidal washes on the carcasses, since this genus is often found in the marine environment [48] and reports of pathologies in pinnipeds and cetaceans associated to this genus have not been reported [9,27]. The exclusive presence in O. flavescens carcasses, taking into account the differences observed in the composition of fungal communities in the sandy sediment it is suggestive of a possible suppressive action by other genera in the same substrate, as observed previously with other mycotic colonizations [49]. The genera Rhizopus spp, Alternalia spp and Paecilomyces, are considered to be cosmopolites, and in this study were identified only in the control samples, suggesting that there presence is not related to the presence of the carcasses in the sand.…”

Molecular and Morphological Characterization of Two Novel Species Collected from Soil in Korea

“…Some of the species of Microdochium are terrestrial cause economic damage to important plants [38,39], nonpathogenic, and also sometimes endophytes [40]. Many species of Microdochium were also identified in the aquatic (marine) environment after evaluating diseased as well as healthy salmon eggs and have been reported as M. lycopodinum and M. phragmitis [41]. The root necrosis and decay of grasses caused by M. bolleyi [42] and M. paspali is responsible for the seashore paspalum disease of Paspalum vaginatum [39].…”

Potential of marine sponge-derived fungi in the aquaculture system

“…A study by Assem et al (2014) showed that fungi T. reesei-degraded date pits (FDDP) have the potential to reduce the density of bacterial population in the intestines of Oreochromis niloticus fish without impacting the fish weight or health welfare condition. A previous study by Liu et al (2016) Enzymatic index (EI) is the semi-quantitative approach to measure enzyme activities. The results showed that T. reesei has higher protease activity than other enzyme activity.…”