USING SOWING DATE MODIFICATION AND GENETIC RESISTANCE TO MANAGE SUNFLOWER BROOMRAPE (Orobanche cumana Wallr.) / UTILIZACIÓN DE LA MODIFICACIÓN DE LA FECHA DE SIEMBRA Y LA RESISTENCIA GENÉTICA EN EL MANEJO DEL JOPO DE GIRASOL (Orobanche cumana Wallr.)

The parasitic weed Orobanche cumana Wallr. (broomrape) constraints sunflower production in eastern and southern Europe and in the Middle East. Resistance of sunflower hybrids to O. cumana race F, which is widespread in the main sunflower growing countries including Spain, is not complete. The infection of six populations of O. cumana (races B and F) in four sunflower genotypes in greenhouse (10 to 32ºC) and in growth chamber (20 to 25ºC) was studied. Also the effect of four sowing dates (SD) on the intensity of the attack of sunflower genotypes by O. cumana race F at three inoculum densities was investigated in an irrigated field in 2000 and 2001. Greenhouse was more favorable than growth chamber for O. cumana infection, which was highest by race F populations. In the field experiment, the reduction of the attack in the moderately resistant hybrid was significant at all SD and higher at late SD as compared to early sowings in both growing seasons. Late sowings (from the end of March until the beginning of April) favor an enhanced expression of the resistance of sunflower to O. cumana race F irrespective of seedbank, and can be therefore recommended, under irrigation and together with the use of moderately resistant sunflower hybrids, as part of an efficient strategy on the control of this parasitic weed. [ABSTRACT FROM AUTHOR]