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Disease Note.

Phytophthora megasperma var. sojae on Asparagus officinalis in France. A. Baudry, DRAF/SRPV/ GRISP, Domaine de la Grande-Ferrade, BP 81, 33883 Villenave d'Ornon Cedex, France. J. P. Morzieres, and Ch. Lafaurie. DRAF/SRPV/ GRISP, Domaine de la Grande-Ferrade, BP 81, 33883 Villenave d'Ornon Cedex, France. Plant Dis. 79:1188. Accepted for publication 3 October 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1188B.

In 1989, 1991, and 1993, significant losses resulting from a slimy rot in the production of white asparagas spears were observed in several fields in southwest France (1). The symptoms included pinkish, slimy, and elliptical necrotic lesions that were localized on the apical and/or pleural sections of the spears. Symptoms appeared in the early spring under wet and cold conditions. In 1989, the first symptoms were observed beginning on 5 April and no additional losses were noted after 20 April. During this period, air temperatures ranged between 8 and 17C, and rainfall totaled 240 mm. Samples were collected from asparagus fields in Landes, Pyrenees-Atlantiques (SW France) and Aude (SE France). A Phytophthora sp. was isolated from symptomatic tissues of affected spears. Morphological features were evaluated on malt-agar medium, tryptophan-agar medium, and tap water. Pathogenicity of isolates was assessed on wounded and nonwounded surviving white spears at 15C and on 4-month-old seedlings, cv. Steline, in the growth chamber at 15 plus or minus 1C. Each isolate produced nonpapillate, obpyiform sporangia (56.1 to 69 ? 33.6 to 39.3 μm), oogonia (30.3 to 35.5 μm) with smooth walls, and mainly paragynous antheridia (2). The minimum, optimum, and maximum temperatures for growth were 5 to 9, 21 to 26, and 30C, respectively. These isolates were identified as Phytophthora megasperma Drechs, var. sojae A. A. Hildebrand. All isolates caused soft necrotic lesions on wounded spears, but not on nonwounded spears. Areas of soft, whitish necrosis were observed along young spears and roots of asparagus seedlings 2 weeks after inoculation. No symptoms were observed on the noninoculated plants. The fungus was reisolated from necrotic tissue of surviving spears.

References: (1) A. Baudry et al. Phytoma Defense des Cultures. Sept./Oct. 432:51, 1991. (2) P. G. Falloon and R. G. Grogan. Plant Dis. 72:495, 1988.