Phytophthora cinnamomi is a devastating pathogen worldwide and phosphite (Phi), an analogue of phosphate (Pi) is highly effective in the control of this pathogen. Phi also interferes with Pi starvation responses (PSR), of which auxin signalling is an integral component. In the current study, the involvement of Pi and the auxin signalling pathways in host and Phi-mediated resistance to P. cinnamomi was investigated by screening the Arabidopsis thaliana ecotype Col-0 and several mutants defective in PSR and the auxin response pathway for their susceptibility to this pathogen. The response to Phi treatment was also studied by monitoring its effect on Pi- and the auxin response pathways.

More Phytophthora species are detected from environmental samples through DNA metabarcoding than are isolated by baiting. We investigated whether bulking soil samples and baiting ~ 300 g samples in standard 1 L tubs resulted in the isolation of fewer Phytophthora and Phytophythium species compared with using 15 – 20 g samples of non-bulked soil in individual 200 ml tubs. At each of four sites with dying vegetation, 50 soil samples were collected and baited separately in small tubs, followed by plating of lesioned baits over 7 days. The number of Phytophthora species obtained was compared with those obtained from bulking the 50 samples and baiting subsamples in large tubs. Half of the asymptomatic baits were plated on day 7 and the remaining were assessed for the presence of Phytophthora using metabarcoding. Root samples with rhizosphere soil from the bulked soil in each site were also assessed using metabarcoding. A higher number of Phytophthora species was recovered from each site from baiting small volumes of non-bulked soil than large volumes of bulked soils. Metabarcoding of the asymptomatic baits revealed species not isolated from lesioned baits. More species were detected from the roots using metabarcoding than were isolated from baits. Metabarcoding did not reveal any species from the rhizosphere soil and roots that were not also detected from metabarcoding of the asymptomatic baits and/or plating. The numbers of Phytopythium species detected using the different methods followed the same trend as for Phytophthora. It was concluded that baiting small samples from across a site in separate small tubs results in the isolation of a higher number of Phytophthora species than the standard technique of baiting large samples of bulked soils, and that this, together with metabarcoding of asymptomatic baits, detects the highest total number of species.

Trees of Eucalyptus camaldulensis × E. globulus subsp. globulus hybrids growing at Pinjarra, Western Australia, were harvested for assessment of wood fibre and wood properties of sawn timber. Trees were 5-y-old at the time of felling. Wood density was in the medium range: mean green density was 980 kg m⁻³, basic density was 507 kg m⁻³ and air-dry density was 653 kg m⁻³. Green moisture content was 94%. Tangential shrinkage before reconditioning was greater than the shrinkage of mature E. camaldulensis or 13-y-old E. globulus. Radial shrinkage of the hybrid wood at 4.9% was similar to that of mature E. camaldulensis but less than that reported from 13-y-old E. globulus. The wood of E. camaldulensis × E. globulus has potential for value-added purposes; no problems were identified with sawmilling, drying and sanding.

Endophytes were investigated for their potential to protect Cinnamomum cassia (cinnamon) from Phytophthora root rot. From healthy cinnamon trees in diseased plantations, 134 bacterial and fungal endophytes were isolated and screened in vitro for their ability to antagonise the root rot pathogens Phytophthora cinnamomi, P. multibullata and P. × vanyenensis. Seventeen endophytes exhibiting high levels of antagonism in vitro (more than 45%) were then tested in a glasshouse study for their ability to reduce the impact of Phytophthora infection in cinnamon seedlings. Trials using cinnamon seeds or seedlings inoculated with an endophyte and then infested with Phytophthora identified three endophytes expressing high levels of disease suppression (based on root damage reduction) and plant growth promotion. These were Penicillium citrinum, Xylaria curta and Clonostachys rosea. These endophytes can potentially be used in the biological control of root rot in cinnamon, but this must be explored further under field conditions.