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Optimization of Scleroderma spore inoculum for Eucalyptus nurseries in China

Chen, Yinglong (2006) Optimization of Scleroderma spore inoculum for Eucalyptus nurseries in China. PhD thesis, Murdoch University.

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      Abstract

      Scleroderma, a genus of ectomycorrhizal (ECM) fungi, is often associated with trees in disturbed habitats and is therefore considered to be suitable for use in plantation forestry. This study investigated aspects of Scleroderma and its mycorrhizas with the view to its future use in plantation forestry in south China. Spores were chosen as inoculum as they are preferred by nursery managers in south China, due to the lack of on-site fermentation and storage facilities.

      To determine the need for inoculation, Eucalyptus plantations in south China were sampled for sporocarps and mycorrhizas over two years. This study revealed a low diversity of ECM fungi consisting of 15 taxa fruiting beneath Eucalyptus plantations. The most common genera were Scleroderma and Pisolithus, but they were infrequent and the extent of root colonization was poor. Bioassay trials with E. urophylla as a bait host, using soils collected from 8 eucalypt plantations, confirmed low levels of inoculum in field soil. It was concluded that introduction of suitable ECM symbionts into eucalypt nurseries in south China is desirable in the future. As the Scleroderma genus has not been well studied in Australasia or SE Asia, over 140 collections gathered mainly from eucalypt plantations in south China and south-western Australia were described using sporocarp and spore morphology.

      Twelve Scleroderma taxa were recognized from collections made from under eucalypt plantations in south-western Australia and 6 of these were collected from under eucalypt plantations in south China. In conjunction with classical taxonomy, 30 collections, including those used in inoculation trials, were further characterized by phylogenetic analyses of ITS or LSU rDNA sequences. These studies supported classical delineation of some Scleroderma species but not all. Although a limited number of collections were amplified, phylogenetic results showed that most collections in this study were distinct from the European and Malaysian taxa extracted from GenBank (89% bootstrap support for both LSU and ITS regions). In order to optimise spore germination and root colonization, two glasshouse trials were established to examine suitable spore density and spore storage conditions on E. globulus and E. urophylla. A spore density of 105 spores seedling-1 was identified as a suitable dose for promoting root colonization. Spores stored for 5 years at low temperate (4 0C) were almost as effective as freshly collected spores in forming mycorrhizas.

      As the compatibility of Scleroderma fungi with plantation trees is unknown, a glasshouse experiment examined the ability of 15 collections of Scleroderma to form mycorrhizas with seedlings of six plantation trees (Acacia mangium, A. mearnsii, E. globulus, E. urophylla, Pinus elliottii and P. radiata) in a nursery potting mix. Most collections were able to aggressively colonize eucalypts and pines, while roots of acacias were poorly colonized. As the Australian collections were more effective in colonizing short roots on eucalypts than the Chinese collections, it was concluded Scleroderma should be sourced from outside China for inoculating eucalypts in Chinese nurseries.

      To optimize nursery practices to meet the demand for high quality seedlings and clonal lines of E. urophylla and hybrids, for outplanting in south China, effects of rooting medium and inoculation with 6 Scleroderma collections on the growth of E. urophylla were examined in a nursery in south China. Four types of soil taken from eucalypt plantations in south China were compared to a potting mix composed of vermiculite, peat and sand. The inoculant Scleroderma fungi were able to out-compete indigenous mycorrhizal fungi in the rooting media. However, the potting mix was superior to soils both for plant growth and ECM development under nursery conditions.

      This research should facilitate the use of Scleroderma spores in eucalypt nurseries in south China. Spore orchards could be set up in China using Australian Scleroderma spp. from under eucalypts. Spores could be stored dry at 4 0C until they are required for inoculation in potting mixes in containerized nurseries. However, before commercial application, further work on persistence of Scleroderma in the nursery and field, and responses of trees in the field to inoculation, needs to be undertaken.

      Publication Type: Thesis (PhD)
      Murdoch Affiliation: School of Biological Sciences and Biotechnology
      Supervisor: Dell, Bernard
      URI: http://researchrepository.murdoch.edu.au/id/eprint/665
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