Phyllosticta Beaumarisii Sp.nov.: A Cause of Leafspot on Muehlenbeckia Adpressa.

Abstract

Muehlenbeckia adpressa (Labill.) Meissn. is a vigorous climber or ground cover which scrambles over other plants. It is a widespread coastal plant endemic to Southern Australia where it is commonly known as "Climbing lignum" or "Macqaurie vine"(2). The species produces rounded leaves, 2 to 6 cm in length, often cordate at the base and crinkled around the margins. Insignificant yellowgreen flowers are borne in short axillary racemes. Plants are grown from seed or can be easily propagated by stem cuttings. M. adpressa grows vigorously during spring and autumn, slowly during winter and is virtually dormant during a hot summer. Because of its rapid growth and hardiness, M. adpressa is useful for fence or embankment cover in coastal situations (5 ) . In July 1984, a patch of badly diseased M. adpressa was observed at Beaumaris, Victoria on a cliff top, adjacent to Port Phillip Bay. Virtually all mature leaves of plants in an area of 10 sq, m. contained distinctive necrotic spots. Spots were roughly circular to elliptical in shape and were tan in colour with a maroon margin. Individual spots reached a diameter of 11 mm but frequently coalesced to form a larger area of necrosis. Spots appeared to be randomly distributed, were visible from both sides of leaves and sometimes contained numerous pycnidia barely visible to the naked eye (Fig. 1). Numerous lesions were excised, washed, surface sterilized and placed on agar media. A variety of fungi developed in culture including species of Epicoccum, Alternaria, Penicillium, Aspergillus, Fusarium and several unidentified yeasts. The only fungi producing pycnidia in culture were Phoma macrostoma Mont. and a slow growing Phyllosticta sp. which had pycnidia similar to those present within the necrotic lesions. Extractions from very tiny lesions, or from pycnidia in diseased leaf tissue, yielded pure cultures of this Phyllosticta sp.. Fig. 1. Pycnidia of Phyllostica beaumarisii sp. nov. and necrotic spots on leaf of Meuhlenbeckia adpressa. (x2)