Screening and Assessing Biological Differences Among Oomycete-Parasitic Trichoderma asperellum Isolates for Biological Control Development

Abstract

Trichoderma are ubiquitous soil-inhabiting fungi that produce numerous extracellular proteins critical to saprophytic, mutualistic, and mycoparasitic lifestyles. Trichoderma are effective mycoparasites and produce diverse chitinolytic enzymes, glucanases, and proteases, to actively degrade microbial cell walls. The diversity of extracellular proteins and the unique parasitic features of Trichoderma species has resulted in their development as biocontrol agents for numerous plant pathogens. The objective of this study was to characterize biological features important to the selection and commercialization of promising oomycete-parasitic T. asperellum isolates. Nine globally collected T. asperellum isolates previously evaluated for parasitism against Phytophthora ramorum were screened for morphological and sporulation differences in regard to temperature and pH, and the conservation of the commonly screened mycoparasitism-associated chitinase gene, chi42. Sporulation and growth variability was evident between the diverse T. asperellum isolates, but a single copy of the chi42 gene was conserved between all isolates. Screening numerous biological features is important to the selection and development of promising microbial-based biocontrol agents; however, determining the presence or absence of individual parasitic-associated genes may lead to selective biases if relied upon during the initial screening phase. The described analyses will provide a trialed approach used to select a promising Trichoderma biocontrol agent.