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dc.contributor.authorBourguignon, Emmanuel L. T.en
dc.date.accessioned2008-11-18T02:12:35Z
dc.date.issued2008en
dc.identifier.urihttps://hdl.handle.net/10182/641
dc.description.abstractThe overall aim of this research was to improve the understanding of the ecology and diversity of Trichoderma species within the soil and rhizosphere of onion (Allium cepa L.) and potato (Solanum tuberosum L.) under intensive management in New Zealand. The indigenous Trichoderma population was measured in a field trial at Pukekohe over a three year period under six different crop rotation treatments. The treatments included two continuous onion and potato rotations (intensive), two onion/potato mixed rotation (conventional), and two green manure rotations (sustainable). Results showed that Trichoderma populations were stable in both the rhizosphere and bulk soil (1.5 x 10² to 8.5 x 10³ CFU g⁻¹ ODS). The planting and incorporation of an oat (Avena sativa L.) green manure in the sustainable rotations positively increased Trichoderma colony forming unit (CFU) numbers in the rhizosphere soil from 3.4 x 10² to 2.5 x 10³ g⁻¹ ODS. A Trichoderma species identification method was developed based on colony morphology. Representative isolates were verified using restriction fragment length polymorphism (RFLP) and DNA sequencing. The method allowed for rapid and reliable identification of isolated Trichoderma species. Five species were identified in the Pukekohe soil: T. asperellum, T. atroviride, T. hamatum, T. harzianum and T. koningii. Results showed identical species diversity between the rhizosphere, rhizoplane and bulk soil. The species did not strongly compete between each other for the rhizosphere ecological niche and differences in species proportions seemed to be caused by environmental factors rather than the rotation treatments. The incorporation of oat green manure in pots did not significantly promote the indigenous Trichoderma population size and diversity in the rhizosphere of onion plants up to 4 months old. The identified species were the same as in the field trial. The incorporation of onion scale residues was shown to result in low Trichoderma and high Penicillium CFU numbers and a reduction in plant size. Additionally, the presence of high levels (6.0 x 10⁵ CFU g⁻¹ ODS) of Penicillium CFU was negatively correlated with the presence of Trichoderma CFU. The effect of oat incorporation on Trichoderma saprophytic growth was also investigated in a soil sandwich assay and revealed no significant differences. A series of experiments indicated that onion extract obtained from dry onion scale residues had no antifungal activity against either Trichoderma or Penicillium and instead tended to promote their hyphal growth and sporulation. It also showed that competition between Penicillium and Trichoderma isolates was limited despite the ability of Penicillium to produce a wide range of inhibitory substances. Four indigenous Trichoderma species (T. atroviride, T. hamatum, T. harzianum and T. koningii) were shown to be rhizosphere competent in a split tube experiment over a 6 week period. The results of this experiment revealed that, the Trichoderma species clearly displayed differences in their ability to colonise the rhizosphere of young onion seedlings. Species such as T. koningii had the greatest rhizosphere colonising ability regardless of soil depth while T. harzianum displayed the weakest ability. Results also indicated that when inoculated as a mixture the four species competed with one another to colonise the rhizosphere. Overall, this research indicated that the studied crop rotation treatments and the use of oat as a green manure did not strongly promote indigenous Trichoderma populations. Species diversity was constant throughout the research with T. hamatum and T. koningii being the most frequently isolated species.en
dc.format.extent1-235en
dc.language.isoenen
dc.publisherLincoln Universityen
dc.subjectAllium cepaen
dc.subjectTrichodermaen
dc.subjectrhizosphereen
dc.subjectecologyen
dc.subjectindigenousen
dc.subjectpopulationen
dc.subjectcrop rotationen
dc.subjectSolanum tuberosum L.en
dc.subjectAvena sativa L.en
dc.subjectgreen manureen
dc.subjectamendmentsen
dc.subjectspecies diversityen
dc.subjectidentificationen
dc.subjectRFLPen
dc.subjectPenicilliumen
dc.subjectrhizosphere competenceen
dc.titleEcology and diversity of indigenous Trichoderma species in vegetable cropping systemsen
dc.typeThesis
thesis.degree.grantorLincoln Universityen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen
dc.subject.marsdenFields of Research::300000 Agricultural, Veterinary and Environmental Sciences::300100 Soil and Water Sciences::300102 Soil biologyen
dc.subject.marsdenFields of Research::300000 Agricultural, Veterinary and Environmental Sciences::300300 Horticultureen
dc.subject.marsdenFields of Research::270000 Biological Sciences::270300 Microbiology::270305 Mycologyen
lu.contributor.unitLincoln Universityen
lu.contributor.unitBio-Protection and Ecologyen
pubs.organisational-group/LU
pubs.organisational-group/LU/BPEC
pubs.publication-statusPublisheden
dc.publisher.placeLincoln, Christchurchen


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