Stanley E. Bellgard

The arbuscular mycorrhizal fungi colonising roots and root nodules of New Zealand kauri Agathis australis

As the only endemic member in New Zealand of the ancient conifer family, Araucariaceae, Agathis australis is an ideal species to study putatively long-evolved mycorrhizal symbioses. However, little is known about A. australis root and nodular arbuscular mycorrhizal fungi (AMF), and how mycorrhizal colonisation occurs. We used light, scanning and transmission electron microscopy to characterise colonisation, and 454-sequencing to identify the AMF associated with A. australis roots and nodules. We interpreted the results in terms of the edaphic characteristics of the A. australis-influenced ecosystem. Representatives of five families of Glomeromycota were identified via high-throughput pyrosequencing. Imaging studies showed that there is abundant, but not ubiquitous, colonisation of nodules, which suggests that nodules are mostly colonised by horizontal transmission. Roots were also found to harbour AMF. This study is the first to demonstrate the multiple Glomeromycota lineages associated with A. australis including some that may not have been previously detected.

Shoot transcriptome of the giant reed, Arundo donax.

The giant reed, Arundo donax, is a perennial grass species that has become an invasive plant in many countries. Expansive stands of A. donax have significant negative impacts on available water resources and efforts are underway to identify biological control agents against this species. The giant reed grows under adverse environmental conditions, displaying insensitivity to drought stress, flooding, heavy metals, salinity and herbaceous competition, thus hampering control programs. To establish a foundational molecular dataset, we used an llumina Hi-Seq protocol to sequence the transcriptome of actively growing shoots from an invasive genotype collected along the Rio Grande River, bordering Texas and Mexico. We report the assembly of 27,491 high confidence transcripts (≥200 bp) with at least 70% coverage of known genes in other Poaceae species. Of these 13,080 (47.58%), 6165 (22.43%) and 8246 (30.0%) transcripts have sequence similarity to known, domain-containing and conserved hypothetical proteins, respectively. We also report 75,590 low confidence transcripts supported by both trans-ABBySS and Velvet-Oases de novo assembly pipelines. Within the low confidence subset of transcripts we identified partial hits to known (19,021; 25.16%), domain-containing (7093; 9.38%) and conserved hypothetical (16,647; 22.02%) proteins. Additionally 32,829 (43.43%) transcripts encode putative hypothetical proteins unique to A. donax. Functional annotation resulted in 5,550 and 6,070 transcripts with assigned Gene Ontology and KEGG pathway information, respectively. The most abundant KEGG pathways are spliceosome, ribosome, ubiquitin mediated proteolysis, plant–pathogen interaction, RNA degradation and oxidative phosphorylation metabolic pathway. Furthermore, we also found 12, 9, and 4 transcripts annotated as stress-related, heat stress, and water stress proteins, respectively. We envisage that these resources will promote and facilitate studies of the abiotic stress capabilities of this exotic plant species, which facilitates its invasive capacity.

Use of the silverleaf fungus Chondrostereum purpureum for biological control of stump-sprouting, riparian weedy tree species in New Zealand

Conventional willow control in wetland and riparian areas of New Zealand is undertaken using cut-stump and/or drill and injection application of glyphosate. The presence of herbicide residues in catchment water supplies has seen the investigation of non-chemical alternatives to poplar and willow control in Auckland water catchment areas. We have demonstrated, in glasshouse trials, the efficacy of an aqueous, gel-based formulation of Chondrostereum purpureum to control the regrowth of crack and grey willow (Salix fragilis and S. cinerea). Chondrostereum purpureum isolate ICMP 16392 (isolated from a Prunus sp.) produced the fastest biomass accumulation in liquid culture. Crack willow was significantly more susceptible to cut-stump infection by C. purpureum than grey willow in the glasshouse trial at the end of the 23-week period. Two different formulations were tested; at the end of the trial, there was no significant difference between them with respect to monthly biomass accumulation. Successful field applications of C. purpureum through cut and paste and drill and injection were confirmed by the presence of fruiting bodies on both treated species. Resprouting ability as measured by shoot number was significantly lower on C. purpureum inoculated stumps.