Screening Methods for Isolation of Biocontrol Epiphytic Yeasts against Penicillium digitatum in Lemons

Abstract

Worldwide, the green rot caused by Penicillium digitatum is one of the most aggressive postharvest diseases of lemons. Searching for sustainable alternatives to chemical fungicides, epiphytic yeasts as potential biocontrol agents were isolated from citrus fruits using a tailor-made selective medium. For disclosing their antagonistic potential against P. digitatum, obtained isolates were subjected to direct screening methods, both in vitro and in vivo. In the course of the primary in vitro screening that comprised dual culture assays, 43 yeast strains displaying antagonistic activities against the pathogen were selected. Subsequently, such strains were subjected to an in vivo screening that consisted of a microscale test, allowing the selection of six yeast strains for further analysis. In the final screening using macroscale in vivo tests, three strains (AcL2, AgL21, and AgL2) displaying the highest efficiencies to control P. digitatum were identified. The protection efficiencies in lemons were 80 (AcL2), 76.7 (AgL21), and 75% (AgL2). Based on sequence analysis of the PCR amplified D1/D2 domains of the 26S rRNA genes, they were identified as representatives of the species Clavispora lusitaniae. Interestingly, the strains exhibited a broad action spectrum among citrus fruits as they were also able to combat the green mold disease in grapefruit and two orange varieties. The direct screening methods applied in this study favored the recovery of efficient candidates for application as biological control agents to combat fungal infestations of citrus fruits.

Native Cultivable Bacteria from the Blueberry Microbiome as Novel Potential Biocontrol Agents

“…In addition to a possible upcoming ban on artificially synthesized fungicides, the extensive use of chemical compounds in agriculture entails a number of disadvantages, such as the increasing public concern of their toxicity along with severe negative environmental impacts, the emergence of resistant phytopathogenic strains, and expectable trade barriers. Thus, emphasis was placed on the development of novel, sustainable, eco-friendly, and safe biocontrol technologies [ 19 , 20 , 21 ].…”

Antifungal activity of non-conventional yeasts against Botrytis cinerea and non-Botrytis grape bunch rot fungi

“…The most frequently reported yeast antagonists include mainly strains belonging to the Metschnikowia pulcherrima , Hanseniaspora spp., Pichia spp. e.g., teleomorph Meyerozyma ( Pichia ) guilliermondii , as well as strains of Wickerhamomyces anomalu s, Aureobasidium pullulans (yeast-like fungus) and Meyerozyma guilliermondii ( Parafati et al, 2015 ; di Francesco et al, 2016 ; Cordero-Bueso et al, 2017 ; Chen et al, 2018 ; Pereyra et al, 2021 ).…”

Biocontrol potential of wine yeasts against four grape phytopathogenic fungi disclosed by time-course monitoring of inhibitory activities

“…The exploration of these epiphytic yeasts as biocontrol agents arises as a valuable option as they have the advantage of not disrupting the local ecological makeup. In addition, while being in their natural ecosystem they can evolve better and easily adjust to the associated environmental conditions, thus being more prone to demonstrate effective and consistent biocontrol activity against grapes phytopathogens ( Parafati et al, 2015 ; Pretscher et al, 2018 ; Pereyra et al, 2021 ). In fact, most of the species represented in our collection include previously reported antagonists of grape phytopathogenic fungi ( Suzzi et al, 1995 ; Bleve et al, 2006 ; Raspor et al, 2010 ; Nally et al, 2012 ; Pantelides et al, 2015 ; Lemos Junior et al, 2016 ; Cordero-Bueso et al, 2017 ; Pretscher et al, 2018 ; Reyes-bravo et al, 2019 ) while the antagonistic potential of Nakazawaea ishiwadae and Yamadazyma mexicana are herein reported for the first time.…”

“…Competition for nutrients and space, antibiosis (production of diffusible or volatile compounds), mycoparasitism, and induction of host resistance have been pointed out as the main modes of action underlying their antagonistic activity (reviewed in Bélanger et al, 2012 ; Spadaro and Droby, 2016 ). Therefore, it is likely that the best sources of antagonistic strains are their own natural environments in which they have developed strategies to colonize, access nutrients and space and, to inhibit other coexisting microorganisms (including epiphytic pathogens), thus ensuring their survival ( Parafati et al, 2015 ; Pretscher et al, 2018 ; Pereyra et al, 2021 ).…”