Water stress and disease development in Eucalyptus marginata (jarrah) infected with Phytophthora cinnamomi

摘要: The south-west of Western Australia has a Mediterranean climate and flora endemic to this area, including the keystone species, jarrah (Eucalyptus marginata), have adapted droughted summer conditions. introduction an exotic soil borne pathogen, Phytophthora cinnamomi, challenged survival many other species. expectation might be that plants stressed by drought are more susceptible disease study examined development caused P. cinnamomi in E. marginata significance water status development. Seedlings marginata, clonal resistant were subjected different watering regimes number field glasshouse experiments. To determine level stress could imposed on container-grown seedlings without killing them, preliminary experiment progressively lowered moisture levels substrate their containers, until reached wilting point, at which time was restored predetermined process repeated. With each subsequent droughting point lower it found survive when only 5% lost from container capacity restored. No deaths had occurred after been maintained low for 14 days (Chapter 2). Based these findings, all experiments conducted under controlled conditions 10% restoration. After testing appropriateness underbark inoculation, zoospore inoculation method no wounding necessary, new, non-invasive stem technique developed. Stems moistened pre-treatment, then agar plugs colonized with mycelium held against wads wet cotton wool bound place tape. This resulted high proportion infection 4) need or use zoospores 3). It successfully used large trial rehabilitated bauxite mine site 2-year-old plants, 5). Inoculation late spring winter rainfall. timing allow comparison normal compared itsdevelopment non-stressed, irrigated plants. However, two months area deluged unseasonal abnormally heavy rainfall, negating any difference treatments causing outbreak adjacent infested site. death some noninoculated control clones. Monitoring continued twelve advance mapped. test effect expression conditions, series set up simulated possible conditions; followed These utilised cinnamomi. Plants inoculated prior droughting. Results those not experienced deficit. In both greatest extent colonization results indicated played role inhibiting planta genotypes 8). finding consistent clones, Most recoveries made non-stressed 6) 7), than recorded plants. The showed recovered stems, obvious lesions, segments plated onto selective agar. led intensive vitro investigation into improved methods recovery. Dark brown exudates stems stained surrounding they plated, suggesting presence phenolic compounds. Recovery pathogen increased about first soaked distilled leach out compounds, replated Other recovery also tested, (1) baiting Pimelea ferruginea leaves floated surface filtrate, infected immersed (2) application light temperature regimes. clearly shown grown inhibited outgrowth counter toxic oxidized phenolics growth antioxidant added media whichincorporated concentrations ascorbic acid, adjusted pH levels. There pronounced effect, less significant increase acid concentration 9). The inhibitory possibility that, if planted rehabilitation pre-treated compounds render them resistant, may advantage establishing areas where there potential threat seeds germinated hydroponically constant room. Different synthetic catechol, compound naturally occurring nutrient solution. Roots remained catechol solutions three days, before being root tip higher concentrations, indicating resistance 10). Further work is required treated threatened greater survival, how long protection persists. The important accurate assessment spread implementation management strategies containment control. An can impact revegetation sites aetiology needs fully understood. interaction plant defences invasive range environments field, glasshouse, hydroponics system vitro. indicate increases understand mechanisms involved. indicates clones selected as environmental interactions should further investigated. Lastly, effective implemented critical confidently isolated hosts inhibit overcome required. findings invite research complexity host-pathogen relationships.