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Disease Note. Phytophthora megasperma var. sojae on Asparagus in Chile. B. A. Latorre, Facultad de Agronomía, Pontificia Universidad Católica, Casilla 6177, Santiago, Chile. R. Vargas, and S. E. Bartolotti. Facultad de Agronomía, Pontificia Universidad Católica, Casilla 6177, Santiago, Chile. Plant Dis. 76:101. Accepted for publication 1 August 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0101D. In 1987 and 1988, Phytophthora sp. was isolated on amended corn-meal agar (CMA) (2) from decayed samples of roots and spears of Asparagus officinalis L. collected in the Central Valley of Chile. Each of four isolates showed nonpapillate, proliferating, ovoid to obpyri-form sporangia (av. 44 X 27.1 µm). Aplerotic, globose, and smooth-walled oogonia (av. 30.3 ",m) with mainly paragynous antheridia were produced. Mycelia growth was not obtained on CMA after 5 days at either 5 or 30 C, and optimal growth occurred at 18-20 C. On this basis, the isolates were identified as P. megasperma Drechs. var. sojae A.A. Hildebrand (confirmed by CABjIMI, Kew, England). Asparagus spears of cv. UC 157 inoculated with 50 µI of a mycelial suspension (108 propagules per milliliter) prepared from each of four isolates developed water-soaked lesions after 4 days in a moist chamber at 20 C. Seedlings of UC 157 inoculated with 10 ml of a mycelial suspension (106 propagules per milliliter) from two isolates developed leaf chlorosis and necrosis after 30 days under greenhouse conditions and showed necrotic root lesions, significantly fewer spear stalks, and a 76 and 83% reduction of root fresh weight compared with controls. These symptoms agree with those observed in the field or previously described (1). P. m. sojae was reisolated from inoculated roots and spears. |