Nutritional niche overlap analysis as a method to identify potential biocontrol fungi against trunk pathogens

Authors: Wallis, Christopher

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2021
Publication Date: 5/19/2021
Citation: Wallis, C.M. 2021. Nutritional niche overlap analysis as a method to identify potential biocontrol fungi against trunk pathogens. Biocontrol. 66:559-571. https://doi.org/10.1007/s10526-021-10091-w.
DOI: https://doi.org/10.1007/s10526-021-10091-w

Interpretive Summary: Identifying effective biological control agents involves high-throughput screening on the ability of selected microorganisms to induce host defenses, parasitize pathogens, produce antibiotics, inhibit pathogenicity factors, and outcompete for resources. Although technological improvements have allowed screening for most of these factors to proceed quickly, assays to assess the ability for potential biocontrol agents to outcompete pathogens for resources remains slow and tedious. Therefore, this study utilized phenotype microarrays (PM) to assess the ability of three endophytic fungal species with potential biocontrol activity and six grapevine fungal pathogens to use hundreds of different carbon and nitrogen sources. A measure of competitiveness was calculated based on the ability of the endophytes to use a greater number of sources than the pathogens. Based on this, two fungal endophytes, Trichoderma harzianum and Lecanicillium lecanii, were concluded to equally compete or outcompete all six tested pathogens. Therefore, these two pathogens would be chosen for further biological control screening experiments.

Technical Abstract: Endophytic fungi could possess biological control activity and therefore are often screened for capacity to limit pathogen infections. Biological control agents possess various mechanisms to limit pathogens including the ability to induce host defenses, the capacity to directly parasitize other microorganisms, the ability to produce antibiotics, the ability to interfere with pathogenicity factors, and the ability to outcompete for resources and occupy shared niches. Of these, measuring the competition for resources and niches remains difficult. Therefore, this study utilized phenotype microarrays on three endophytes (Trichoderma atroviridae, Trichoderma harzianum and Lecanicillium lecanii) with potential biological control activity and six grapevine fungal pathogens to assess carbon and nitrogen source utilization. Of the six pathogens, the more aggressive Neofusicoccum parvum and Diplodia seriata utilized a greater number of carbon and nitrogen sources than the relatively less aggressive pathogens Eutypa lata, Lasiodiplodia theobromae, Phaeomoniella chlamydospora, and Togninia minima. All three endophytes had a greater niche overlap of carbon and nitrogen resource use than Eutypa lata and Phaeomoniella chlamydospora. However, only T. harzianum and L. lecanii were determined to be able to equally compete or slightly outcompete N. parvum and D. seriata over carbon or nitrogen sources. Therefore, based on these results involving carbon and nitrogen source niche utilization, T. harzianum and L. lecanii would be advanced to additional biological control agent screening. These results demonstrated the capacity of phenotype microarrays to assess the ability of endophytes to outcompete pathogens as part of ongoing efforts to identify biological control agents.