Broomrapes (Orobanche spp.) are obligate parasites that infect roots of dicotyledonous plants. Orobanche species are particularly important in southern and eastern Europe, the Middle East, and North Africa. O. crenata (crenate broomrape) has been known to threaten legume crops since antiquity. This parasitic weed is mainly restricted to the Mediterranean Basin, southern Europe, and the Middle East and is an important pest in grain and forage legumes as well as in some Apiaceous crops such as carrot and celery (2,3). In Spain, O. crenata is a well-known problem on grain legumes in the south (Andalucía and Extremadura regions) and along the entire east coast north to the border with France. However, it has never been reported as a problem in central Spain. Castilla-León is the major pea-, vetch-, and lentil-producing area of Spain and was believed to be free of O. crenata. However, widespread and heavy infections of O. crenata (as many as 20 broomrapes per m2) were identified in the spring of 2007 on lentil and common vetch growing in several fields in Salamanca Province, between La Vellés, Palencia de Negrilla, and Aldeanueva de Figueroa, covering an area of approximately 80 km2. Infection of lentil and vetch plants was confirmed by digging up the plants to verify the attachment of the broomrape plant to the lentil or vetch roots. Morphology was typical of O. crenata (2), i.e., large erect plants with single, nonbranched spikes that may reach a height of up to 1 m, bearing many flowers of diverse pigmentation from yellow through white to pink and violet. The calyx is 13 to 18 mm with segments free and bidentate. The corolla is 18 to 28 mm, glandular pubescent, the lips often with lilac veins, lips divergent, large, and not ciliate. The anthers are brown, glabrous, or subglabrous. The filaments insert 2 to 3 mm above the base of the corolla and are hairy at the base with glandular hair at the apex. Voucher specimens were deposited at the Herbarium of the Botanic Department of the University of Córdoba. The heavy and widespread level of infection observed in several fields is most likely explained by an inadvertent introduction of O. crenata seed mixed with seed of lentil and vetch. To our knowledge, this is the first report of O. crenata infecting lentil and common vetch in Salamanca Province and is relevant because the area was considered free of the plant. Remarkably, a recent modeling study suggested that O. crenata might become a problem in central and northern Spain (1) since climatic conditions are suitable for its establishment. The spread of this infestation should be monitored because it could represent a major constraint on legume production in this region.
References: (1) J. H. Grenz and J. Sauerborn. Agric. Ecosyst. Environ.122:275, 2007. (2) D. M. Joel et al. Biology and Management of Weedy Root Parasites. Page 267 in: Horticultural Reviews. Vol. 33. John Wiley and Sons, Inc. Hoboken, NJ, 2007. (3) D. Rubiales et al. Euphytica 147:187, 2006.
