Biosystematics and biosecurity
A: Symptoms on New Zealand avocado,
misdiagnosed as avocado scab (PDD 58048).
B: Authentic avocado scab symptoms, from
Florida, USA (PDD 10774).
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"Biosecurity is reliant on the expertise of systematists to underpin the identification of harmful organisms. Correct identification is essential to enable sound analysis and prediction of pest behaviour, which in turn governs decision making on appropriate management measures."
Barney Stephenson, Biosecurity New Zealand
The science of biosystematics involves discovery, description and differentiation of all forms of life, and is fundamental to other fields of biological science. Biosystematists are aligned with national biological collections and databases that, together, provide reference material to substantiate the presence (or absence) of species in New Zealand, and accurate records of their distribution and relationships with other organisms. The combination of national expertise in biosystematics research and comprehensive, databased biological collections provides the foundation for sound and effective biosecurity practice.
Although biosystematics skills are not widely taught in New Zealand universities, there are opportunities for graduate students who are interested in taxonomy to gain higher degrees under co-supervision by Landcare Research biosystematists and their colleagues in university biological sciences departments. Suitably qualified local applicants have competed successfully against overseas applicants in several recent biosystematics appointments in Landcare Research.
Nationally significant collections
Central to biosystematics research in New Zealand are four nationally significant biological collections that Landcare Research curates on behalf of the nation:
- Allan Herbarium (CHR: more than 500,000 dried specimens of plants)
- New Zealand Arthropod Collection (NZAC: about 6 million specimens of insects and other arthropods)
- New Zealand Fungal Herbarium (PDD: more than 75,000 dried collections of fungi)
- International Collection of Micro-organisms from Plants (ICMP: more than 15,000 living strains of fungi and bacteria).
The collections have a two-fold role. First, they house the biosystematists' tools: authenticated reference specimens with which newly collected or intercepted material can be compared critically to determine its identity. Is it something already recorded here, something new to New Zealand, or even something new to science? Second, they are repositories of 'vouchers', or material evidence that allows identifications made by non-biosystematists to be validated. This also supports historical records and allows their accuracy to be revisited in the future, to be confirmed, revised, or refuted – none of this is possible with 'records' that consist of nothing more than a printed report or database entry.
Both of these functions of biological collections have been powerfully enhanced in this modern age of molecular analysis techniques; curation of living cultures and of extracted nucleic acid is increasingly becoming standard practice.
Case of mistaken identity solved
A recent case illustrates the power of the combination of biosystematic expertise, authenticated material, vouchers and molecular techniques.
New Zealand avocado growers recently experienced special pre-export conditions imposed on their exports to Australia because of a 15-year-old published record of avocado scab in New Zealand. Growers and scientists were aware that the distinctive symptoms were nowhere in evidence in the New Zealand crop, but how do you refute a published record? Fortunately, the New Zealand avocado scab record had been vouchered with dried herbarium specimens and a living culture; PDD also had several authenticated herbarium specimens that had been prepared from diseased avocado trees in the Americas by the scientist who first described the pathogen, Sphaceloma perseae. Very quickly, it was established that the New Zealand 'record' was misidentified:
- the amorphous New Zealand 'symptoms' (resembling windrub) did not resemble the symptoms on authenticated specimens (see photograph)
- the vouchered culture grew much too quickly to equate with the biosystematists' experience of other related pathogens (such as lemon scab)
- the living culture was soon identified, by morphological and molecular techniques, as a saprophyte (a plant or bacterium that lives off dead or decaying organic material) with no known pathogenic potential on avocado (or any other host).
This evidence has been presented to the Australian biosecurity authorities, and New Zealand avocado growers are looking forward to the resumption of their normal trans-Tasman trade. The corollary is that the biostatus of Sphaceloma perseae should now be listed as 'Absent from New Zealand; recorded in error'. Like the Australians, we should be vigilant to prevent its arrival from overseas.
Solving problems, providing advice
There have been other cases, too, where biosystematics expertise has solved biosecurity problems or provided advice and assistance. These include:
- resumption of carrot exports to Australia after infestations of mites were identified as a species common to both countries
- demonstration that a suspected new exotic whitefly had been recorded decades earlier from native bush and specimens preserved in NZAC, eliminating the need for further investigation of management options
- provision of technical advice to the National Pest Plant Accord on the gazetting of plant species as Unwanted Organisms prohibited from propagation, sale, or distribution
- organisation of weed identification workshops which enhance the skills of biosecurity officers and develop a framework for closer working relationships between botanical systematists and biosecurity staff
- web-accessible database of names, host relationships, distribution, images, keys, and literature for all fungi recorded from New Zealand: http://nzfungi.landcareresearch.co.nz
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Page last updated: 30 April 2008