ChileanJAR

Field studies were conducted between 1999 and 2002, in Angol, Chile (37º45 ' S, 72º44 ' W) to determine the phenology of the system Orobanche ramosa – tomato (Lycopersicon esculentum Mill.), to characterize the influence of holoparasitism on the growth and development of the host and the productive response at three planting dates (early, normal and delayed). The O. ramosa phenology includes underground and aerial phases, defining a total of six development stages: “a”: nodule; “b”: nodule with initial crown roots; “c”: shoot bud already visible; “d”: shoot bud and crown root developed; “e”: shoot development; and “f”: shoot emerged from soil surface. The underground phase began with the establishment of the parasite, the first phenological event (stage "a") being detected between 120 to 250 degree-days (DG), and the aerial phase (stage "f") began when 550 DG of thermal requirements was surpassed. These phases occurred at flowering and fruit set of the host, respectively. The mean life cycle of the system O. ramosa - tomato was completed with 1,180 DG or 132 days after planting (DDT). Parasitism of O. ramosa altered morphological parameters and the distribution of dry matter in the host before the emergence of O. ramosa, the aerial components being most effected. It translated into important losses of production at the planting dates, which varied between 77 and 81%. Therefore, advancing or delaying the planting date does not constitute an efficient cultural practice for tomato fields to escape O. ramosa parasitism.