New Disease Reports (2006) 14, 26.

First record of Alternaria petroselini sensu lato causing leaf blight on parsley in Australia

J.H. Cunnington 1*, E.J. Minchinton 1, D.P.F. Auer 1 and H.L. Martin 2

*james.cunnington@dpi.vic.gov.au

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Accepted: 03 Oct 2006

During 2005 surveys for parsley diseases in Australia, an Alternaria was isolated from leaf blighted plants in Chambers Flat, Queensland and Clyde, Victoria. Symptoms included chlorotic and necrotic lesions on the leaves that spread down the stems in badly affected plants. The Alternaria sporulated abundantly on moist incubated leaves and was transferred directly to V8 agar and grown under lights. The fungus produced abundant alternarioid conidia that were borne singly, subspherical to oval and 40-80 x 20-25 μm (Fig. 1).

Alternaria petroselini and A. selini are similar species that cause leaf blight of parsley. They are distinguished by whether the conidia are predominantly subsphaerical or oval (Simmons, 1995). However, it has been suggested that these two species could be synonyms based on molecular evidence (Pryor, 2002; Pryor & Bigelow, 2003). The conidia in our cultures were very variable, and although they favoured A. selini, given the inability to be totally confident in a precise identification, this fungus was identified as A. petroselini sensu lato. Neither A. petroselini, nor A. selini have been previously recorded in Australia. Cultures have been lodged in herbarium VPRI.

Pathogenicity experiments were conducted. The fungus was grown on V8 agar at room temperature under lights for one week. The agar plate was flooded with sterile deionised water supplemented with Tween 80 (1 drop Tween 80 per 100 mL deionised water). A conidial suspension (105 conidia per mL) was sprayed onto curly-leaf parsley plants (Petroselini crispum ‘Afro’) until runoff. Control plants were sprayed with sterile deionised water supplemented with Tween 80. Plants were covered in plastic bags and placed in a growth chamber with a 16/8 light cycle, day temperature set at 25°C and a night temperature of 15°C. After 7 days typical leaf blight symptoms could be seen. Plants were heavily blighted 18 days after inoculation (Fig. 2). The fungus was reisolated by directly removing conidia from the leaf surface.

This disease has been recorded in England, the USA and Saudi Arabia (Farr et al., No Date). It is probably widespread in eastern Australia, but has gone unnoticed until these surveys. Economic losses were observed on the Queensland property, but in Victoria the damage was very minor.

Figure1+
Figure 1: Conidia of A. petroselini sensu lato on V8 agar after 1 week
Figure 1: Conidia of A. petroselini sensu lato on V8 agar after 1 week
Figure2+
Figure 2: Parsley plants 18 days after inoculation with conidial suspension. Control plant on far left.
Figure 2: Parsley plants 18 days after inoculation with conidial suspension. Control plant on far left.

References

  1. Farr DF, Rossman AY, Palm ME, McCray EB, No Date. Fungal Databases, Systematic Botany & Mycology Laboratory, ARS, USDA. Retrieved September 20, 2006, from http://nt.ars-grin.gov/fungaldatabases/
  2. Pryor BM, 2002. Alternaria leaf blight of parsley. In: Davis M, Datnov LW, eds. Compendium of Diseases of Carrot, Celery and other Umbelliferous Crops. St. Paul, MN, USA: APS Press, 17.
  3. Pryor BM, Bigelow DM, 2003. Molecular characterization of Embellisia and Nimyba species and their relationship to Alternaria, Ulocladium and Stemphylium. Mycologia 95, 1141-1154.
  4. Simmons EG, 1995. Alternaria themes and variations (112-144). Mycotaxon 55, 55-163.

This report was formally published in Plant Pathology

©2006 The Authors