Epsilon Archive for Student Projects

Abstract

The fungal genus Trichoderma has seen extensive use as a biocontrol agent (BCA) due to its antagonistic properties and adaptation as a plant symbiont. Studies have revealed that enzymes, among which are cellulases, produced by Trichoderma spp. can induce resistance to antibiotic peptides which are excreted by Trichoderma ssp. for defence, which would otherwise damage the host plant. This has led to the idea of an evolved symbiotic relationship between host plant and Trichoderma. Previous research has shown how CIRA, Cellulase Induced Resistance to Alamethicin (a peptaibol), induces resistance in Arabidopsis thaliana, making it a potential target endogenous symbiosis pathway for the biocompatibility of commercial plant species with Trichoderma spp.. Insights into the underlying genetic factors controlling these mechanisms are essential for future BCA progress. Here we perform phenotypic investigations into biocontrol and biostimulation through the inoculation of eight inbred sugar beet (Beta vulgaris ssp. vulgaris) lines with Trichoderma afroharzianum T-22 to investigate the biostimulating effect on plant biomass production. Additionally, the pathogen Aphanomyces cochlioides was used to inoculate sugar beet seedlings to test the biocontrol effect of T. afroharzianum T-22 on our inbred lines. Eight selected lines were grown from seed and inoculated with either Trichoderma or Aphanomyces (or both) with control and grown for 4 weeks, followed by harvesting and data collection. Furthermore, investigation into early plant biostimulation of sugar beet by T. afroharzianum T-22 for a candidate plant gene previously identified in Arabidopsis thaliana in CIRA assays was conducted. DNA extraction and PCR were also used to confirm allele presence in additional inbred lines. Results of phenotypic growth output and resistance scores by ANOVA, followed by post hoc tests showed large phenotypic variation between inbred lines. Biomass production investigated for biocontrol showed a general negative effect of Trichoderma, although there were lines that displayed positive biocontrol, with enhanced biomass and an improved resistance score to A. cochlioides infection compared to control. Like biostimulation, inbred line genetics seems to have a determining effect on biocontrol response. In the investigations into biostimulation we see a general positive effect of T-22 on biomass production, with large variation between inbred lines and little contribution from plant development alone. However, all three factors “line”, “DAT” and “T-22 Application” that were tested showed large effects from interactions. In biocontrol, biomass was negatively affected by Trichoderma application, with large variation between inbred lines and disease progression. This had a large negative effect particularly on lateral root biomass. Investigations into disease resistance showed line variation largely affecting significant results with interactions between Trichoderma application and disease progression. Marker assisted allelotype identification was confirmed by sanger sequencing, which together with plant phenotypic data confirmed positive biostimulation for lines with the wildtype I allele.