The strange case of a biofilm-forming strain ofPichia fermentans, which controlsMoniliniabrown rot on apple but is pathogenic on peach fruit

Abstract

A biofilm-forming strain of Pichia fermentans proved to be most effective in controlling brown rot on apple fruit when coinoculated into artificial wounds with a phytopathogenic isolate of Monilinia fructicola. Culture filtrates and autoclaved cells had no significant influence on the disease. When sprayed onto the apple fruit surface, this yeast formed a thin biofilm but failed to colonize the underlying tissues. When inoculated into wounds artificially inflicted to peach fruit or when sprayed onto the surface of peach fruit, the same strain showed an unexpected pathogenic behaviour, causing rapid decay of fruit tissues even in the absence of M. fructicola. Both optical and scanning electron microscopy were used to evaluate the pattern of fruit tissue colonization by P. fermentans. While on apple surface and within the apple wound the antagonist retained its yeast-like shape, colonization of peach fruit tissue was always characterized by a transition from budding growth to pseudohyphal growth. These results suggest that pseudohyphal growth plays a major role in governing the potential pathogenicity of P. fermentans, further emphasizing the importance of a thorough risk assessment for the safe use of any novel biocontrol agent.

Use of a marine yeast as a biocontrol agent of the novel pathogen Penicillium citrinum on Persian lime

“…The EPS substances provide protection to microorganisms by concentrating nutrients, enhancing resistance to stresses and preventing desiccation (Chmielewski and Frank, 2003;Prakash et al, 2003;Droby et al, 2009;Elias and Banin, 2012). The ability to form biofilms on the inner surface of wounds was indicated as a possible mechanism of biocontrol (Giobbe et al, 2007). However, little is known about the role of biofilms in the biocontrol activity of antagonistic yeast used to manage postharvest diseases and mechanisms involved in its formation (Droby et al, 2009).…”

“…However, little is known about the role of biofilms in the biocontrol activity of antagonistic yeast used to manage postharvest diseases and mechanisms involved in its formation (Droby et al, 2009). Giobbe et al (2007) observed that the biocontrol efficiency of Pichia fermentans (Lodder, Zentralblatt) against M. fructicola ((G. Winter) Honey) could therefore be due to the ability of yeast cells to remain adhered one to the other and to create a mechanical barrier (biofilm) interposing between the wound surface and the pathogen spore and germ tube, thus hampering infection by M. fructicola.…”

Peach Brown Rot: Still in Search of an Ideal Management Option

“…However, there are several issues to consider before marketing the bio-pesticides. For example, Giobbe et al [129] found that a biofilm-forming strain of Pichia fermentans proved to be most effective in controlling brown rot on apple fruit but pathogenic on peach fruit when co-inoculated into artificial wounds with a phytopathogenic isolate of M. fructicola. The authors, therefore, emphasized the need for a thorough risk assessment before allowing any deliberate release of bio-control agents, considering the associated potential effects, such as displacement of nontarget organisms, allergenicity to humans and other animals, toxicity, pathogenicity, and genetic stability.…”

“…The authors, therefore, emphasized the need for a thorough risk assessment before allowing any deliberate release of bio-control agents, considering the associated potential effects, such as displacement of nontarget organisms, allergenicity to humans and other animals, toxicity, pathogenicity, and genetic stability. Hence, any minimal potential biohazard is inherent to the application of any bio-control agents [129] in peach commodity.…”

“…Because of the increasing concern about the effects of biochemical fungicides (BCAs and conventional fungicides) on the environment [129] and human health [106] and about strain fungicide resistance [131], there is still a need for alternative treatments, based for instance on host resistance, which is considered one of the most cost-effective and environmentally safe strategies for disease control. Breeding for host resistance is a preventive decision measures in crop protection management.…”