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Technical annual report 2000-01



Technical annual report 2000-01


Dept. of Regional Development, Primary Industry, Fisheries and Resources technical annual report; Department of Regional Development, Primary Industry, Fisheries and Resources technical and annual report; Reports; PublicationNT; Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295




Made available via the Publications (Legal Deposit) Act 2004 (NT).






Agriculture -- Northern Territory -- Periodicals; Fisheries -- Northern Territory -- Periodicals

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Dept. of Primary Industry and Fisheries

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Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295



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Department of Primary Industry and Fisheries 176 are being added to pots to test the hypothesis that fresh, young manure may burn the roots or introduce pathogens to the soil. Various levels of chemical fertiliser are being added to pots to test the theory that high levels of fertiliser either burn or weaken roots which then increases the incidence of Phytophthora disease. Various levels of irrigation through different application strategies are being used to test the theory that extreme cycles or levels of soil water status increase the incidence of Phytophthora disease. There are no results to report. Efforts to inoculate the pots with Phytophthora have been unsuccessful. Alterations to the methodology have been identified and will be trialled. The other problem with the trial is the crowding which is encouraging leaf disease and causes a large degree of competition for light. There has also been a large amount of longicorn damage, which is killing the stressed trees. Screening, marcotting and grafting trials The aim of this trial is to identify possible resistant varieties of durian and to test their compatibility as rootstocks with popular commercial scions. This is being done through two processes. The first process involves testing as many as possible durian varieties (and other Durio species) with a number of P. palmivora isolates, from orchards in the Darwin rural area. The most resistant varieties or trees are then being vegetatively propagated to allow rootstock compatibility testing. Alongside that process is a rootstock trial using current commercial material. This trial will allow the identification of rootstock-scion interactions. While a number of possibly resistant varieties/trees have been identified, more testing has to be done. The testing to date has been unsuccessful. The leaf bioassays being conducted have shown very little difference in either varietal resistance or isolate pathogenicity. This is due to poor cultures that, while producing sporangia, do not appear to effectively infect the plant tissue. There has also been little success at vegetatively propagating the varieties/trees selected. Most success has come from work in north Queensland. The climate there appears to be better suited to marcotting though the number of live marcotts in the greenhouse is less than 10% of all the marcotts attempted. The total success rate from marcott-attempt to alive-in-pot is less that 3%. This low level of success has also been found in the major durian growing regions in SE Asia where grafting is the typical method of plant multiplication. Antagonists of Phytophthora: The aim of this trial is too identify and field-test fungi and bacteria that may inhibit (antagonise) Phytophthora. A large number of laboratory tests resulted in the identification of one fungus that inhibits the growth of Phytophthora on Petrie dishes. This fungus is yet to be tested in the field. This research has already identified a useful management practice for growing durian. The large majority of growers do not use living mulch. The benefits are obvious to growers even with the death of young plants. The results of this project will provide growers with some clear direction on the management of orchard durian to control Phytophthora related disease. This is a high priority outcome identified by the Australian Durian Growers Group in the business plan.