No abstract

A LUCID TM multi-access computer-based key for identifying 175 genera of plant pathogenic fungi of temperate crops is described. The key takes a pragmatic, rather than a taxonomic approach to identification, enabling a non-specialist to key out many suspected plant pathogens based on microscopic examination of the fungal structures, and plant disease symptoms. Taxonomic jargon is kept to a minimum and images of morphological characteristics are used frequently. Fact sheets on the diseases caused by common pathogens are also included in the programme.The key is available in the public domain, and should be useful to anyone with a microscope wishing to identify a common fungal disease.

Alternaria tenuissima causes a leaf spot disorder of Pseudopanax 'Gold Splash', a New Zealand native shrub with export potential. A range of fungicides viz., bitertanol, captafol, chlorothalonil, dichlofluanid, iprodione, mancozeb, prochloraz, procymidone, propineb, and vinclozolin were tested for efficacy against the pathogen. Three techniques were used based on growth on: (1) fungicide amended media; (2) leaf disc; and (3) intact plants. The efficacy of fungicides in agar was not directly related to their effectiveness on leaf discs or on intact plants. In contrast, all fungicides effective on leaf discs were also effective on intact plants. The leaf disc technique showed that bitertanol, chlorothalonil, iprodione, prochloraz, and vinclozolin became less effective 4 weeks following application. In contrast, captafol, dichlofluanid, and propineb were effective inhibitors throughout the 4 weeks tested by the leaf disc H95004Received 12 January 1995; accepted 12 July 1996 technique. On pot plants in a greenhouse, mancozeb was the most effective protectant followed by propineb, prochloraz, dichlofluanid, and captafol.

Camellia flowerblight, caused by Ciborinia camelliae was found in a Wellington garden in August 1993. Mycological features ofthe fungus isolated matched published descriptions and infectivity tests on fresh camellia blooms confirmed pathogenicity. A survey by MAFQUAL soon after the discovery, showed the pathogen was widespread in the Wellington area. There have been no reports of the disease in other regions. The pathogen attacks only flower tissue. Symptoms first appear as small, irregular brown specks. These soon enlarge and coalesce to form extensive lesions which eventually cover entire petals and finally complete flowers, a process which can happen within 3 days. Infective conidia are not produced on blossoms but sclerotia develop on fallen blooms. These sclerotia give rise to apothecia during the next flowering season, hence there are no secondary infection cycles. There appear to be no resistant varieties of Camellia japonica. Control of this pathogen is primarily by cultural means and by exclusion, although biological control measures are being explored. Public education is required to prevent the disease spreading to other parts of New Zealand.

The reliability of random amplified polymorphic DNA (RAPD) techniques to amplify polymorphisms in the asparagus (Asparagus officinallis L.) genome was investigated. DNA fragments generated by 10-base primers were separated on 1.5% agarose or 8% polyacrylamide gels, and the sensitivity of ethidium bromide and silver staining of amplified DNA products analysed on these gels was compared. Resolution of DNA bands on polyacrylamide gels was superior to that on agarose gels. Silver staining was more sensitive than ethidium bromide staining. The gel type used to separate DNA bands, and the staining technique used influenced the number of bands visualised for each DNA profile generated. The six asparagus cultivars used in this study were distinguished by unique banding patterns generated by each primer. OPC-12 for example generated polymorphic markers unique to three of the cultivars investigated. These markers were: ASP (500, 400, and 300 bp), TU (700 bp), and (PC 550 bp). Our investigation indicates that RAPD markers can be used to characterise asparagus cultivars, and that the technique is sensitive enough to reveal differences within seed-raised commercial cultivars. RAPD technology has the potential to detect somaclonal variation occurring during micropropagation.