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First Report of Clubroot of Eruca sativa Caused by Plasmodiophora brassicae in Brazil

Eruca sativa Mill. (family Brassicaceae), with its origin in western Asia, is a culinary and pharmacological species cultivated in Europe, Brazil, and other countries. In the United States, it is a minor crop known as arugula or roquette. Clubroot on E. sativa has not been reported in Brazil and has been reported once in the United States in 1914 (1,2,3). On several occasions since 2000, stunted and wilted plants (cv. Rúcula Cultivada) were collected from growers' fields and greenhouses that had been direct-seeded in Vargem Bonita, DF (two fields and one greenhouse) and Quatro Barras, PR (two fields). The infected arugula crops were found in areas where other plants from the genus Brassica were traditionally cultivated. Disease incidence in individual fields varied from 20 to 80%. Diseased plants were severely affected with hypertrophic, malformed roots, and root galls resembling Woronin's description (4). Plasmodia and resting spores in thin sections prepared from root galls were observed with compound and electron microscopes. Pathogenicity tests were conducted on arugula and Brassica pekinensis (Lour.) Rupr. (universal host) with inoculum from naturally infected arugula. The soil of potted test plants at the four-to-five-leaf stage was drenched with a suspension of resting spores. Symptoms identical to those observed on the original plants were produced on all inoculated plants 2 to 3 weeks after inoculation. Control plants remained symptomless. The pathogen was positively identified as Plasmodiophora brassicae Wor. with the combination of macroscopic and microscopic symptoms and signs of the disease and pathogen. P. brassicae was first reported in Brazil in 1965 in the state of São Paulo and in the 1980s in Distrito Federal on several members of the Brassicae. To our knowledge, this is the first report of P. brassicae infecting E. sativa in Brazil. Arugula is a susceptible host and should not be planted on P. brassicae-infested land.

References: (1) D. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN. 1989. (2) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory, On-line publication. ARS, USDA, 2003. (3) J. S. Karling. The Plasmodiophorales. Published by J. S. karling, NY. 1942. (4) M. S. Woronin. Plasmodiophora brassicae the Cause of Cabbage Hernia. Phytopathological Classics 4. The American Phytopathological Society, Ithaca, NY, 1934.