Disease Note.

Fusarium Wilt of Common Bean in the Castilla y Leon Region of Spain. J. M. Diaz-Minguez, Area de Genetica, Departamento de Microbiologia y Genetica, Universidad de Salamanca, Avda Campo Charro s/n, 37007 Salamanca, Spain. F. M. Alves-Santos, E. P. Benito, and A.P. Eslava, Area de Genetica, Departamento de Microbiologia y Genetica, Universidad de Salamanca, Avda Campo Charro s/n, 37007 Salamanca, Spain. Plant Dis. 80:600. Accepted for publication 14 March 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0600B.

High quality common bean (Phaseolus vulgaris L.) cultivars have been grown in the area of Barco de Avila (Castilla y Leon, west-central Spain) for many years. Dry bean yield in this area is known to be affected by infections from Fusarium spp. Losses vary from year to year, depending on environmental conditions, but may amount to a 50% reduction in yield. The most popular cultivars (Riojana and Blanca Redonda) are also the most susceptible. Over the past 3 years we have examined common bean plots grown in the Barco de Avila area and sampled diseased plants. Symptoms observed corresponded to a vascular disease of beans (1) called bean yellows or Fusarium yellows, caused by Fusarium oxysporum Schlechtend.:Fr. f. sp. phaseoli J. B. Kendrick & W. C. Sny-der. Similar symptoms have been observed in common bean fields in the southeast of Spain (3). F. oxysporum was consistently recovered from sections of stems showing vascular discoloration (identification was confirmed by Javier Tello Marquina, Instituto Nacional de Semillas y Plantas de Vivero, Madrid, Spain). Monoconidial cultures of isolates were prepared and used to inoculate bean plants (cultivar Blanca Redonda) using a standard root-dip inoculation technique (2). The concentration of spores in the inoculum was adjusted to 1 million spores/ml. The tests were carried out in a controlled environment chamber at 22 to 24°C. Several isolates reproduced the yellowing and willing symptoms observed in the field within 2 lo 3 weeks after inoculation. Mycelia and conidia were evident on the surface of stems of dying plants. F. oxysporum was recovered from stems and petioles of wilted plants, thus fulfilling Koch's postulates. To our knowledge, this is Ihe first report of bean yellows in the Castilla y Leon region of Spain.