Effect of a Trichoderma bio-inoculant on ectomycorrhizal colonisation of Pinus radiata seedlings

• Main Author: Minchin, Rhys F
• Format: Dissertation
• Language: English

Content Partner: Lincoln University. Ectomycorrhizal colonisation potential of Pinus radiata seedlings inoculated with the commercially available Trichoderma species bio-inoculant, Arbor-Guard™, was investigated in a commercial containerised nursery setting and in a separate glasshouse experiment, which included the co-inoculation of specific ectomycorrhizal fungi. Application of Arbor-Guard™ to Pinus radiata seedlings in a containerised commercial nursery had no significant effect on the ability of the naturally occurring ectomycorrhizal (ECM) fungi to colonise the seedlings. Thelephora terrestris was the dominant ectomycorrhizal species colonising the P. radiata root tips and has been described as a species able to rapidly outcompete other ECM species colonisation, particularly in high organic matter media like that used at the containerised commercial nursery investigated. In a similar experiment run to augment the commercial experiment, specific ECM fungi identified as Rhizopogon roseolus, Suillus luteus, and Rhizopogon villosulus were co-inoculated with Arbor-Guard™ to investigate the effect on the colonisation potential of the respective ECM species in combination with Trichoderma. The treatment effect of the addition of Arbor-Guard™ did not negatively impinge on the ECM species found, or the abundance of ECM root tips colonising the P. radiata seedlings. Ectomycorrhizal species in the Thelephoraceae family were the dominant species found colonising the P. radiata root tips. Of the inoculated ECM, S. luteus was the only detected species colonising the P. radiata root tips but was only found in low abundance. Non-conducive abiotic factors for optimum ECM colonisation were considered the most likely reason for the low colonisation of the inoculated ECM species. Any effect of the unintentional co-inoculation of the wood decaying fungi Hypholoma fasciculare and Lentinula edodes, due to misidentification, with the inoculated ECM species was unable to be resolved in this study. However, it was speculated that H. fasciculare may have had a negative effect on the inoculated ECM species colonisation. In vitro dual culture assays were initiated to investigate the specific interactions between each of the candidate ECM fungi inoculated in the glasshouse experiment when challenged with each of the six Trichoderma isolates in Arbor-Guard™. Both competition for nutrients and/ or space were concluded to be the main antagonistic mechanisms potentially used by five o