espanolDos especies de girasol silvestre originarias de America del Norte se han naturalizado en la Argentina: Helianthus annuus L. y H. petiolaris Nutt., anuales, diploides (x=17) y autoincompatibles. La primera no ha sido descripta anteriormente en el pais y corresponderia a H. annuus ssp. annuus. Se encontraron poblaciones establecidas en las provincias de Cordoba, La Pampa, Buenos Aires, Entre Rios, Mendoza y San Juan. Otras plantas, que corresponderian a descendencias de H. annuus var. macrocarpus, el girasol cultivado, se encontraron creciendo en forma adventicia en toda la region de cultivo, incluyendo Santa Fe y Chaco. H. petiolaris esta mas difundida, principalmente en La Pampa, San Luis y oeste de Buenos Aires, en suelos arenosos y continua su expansion. Excepto en Entre Rios, Mendoza y San Juan, las dos especies silvestres son simpatricas en diversas localidades. Ambas pueden cruzarse con el girasol cultivado y se hallaron plantas morfologicamente intermedias en 15 departamentos provinciales, lo que indicaria la formacion de enjambres hibridos como en su centro de origen. Se estima que estas especies se han establecido en un 50% de la region de cultivo del girasol, con importantes implicaciones para el mejoramiento genetico y la bioseguridad, en el caso de liberacion de cultivares transgenicos. EnglishTwo wild sunflower species native to North America have been naturalized in Argentina: Helianthus annuus L. and H. petiolaris Nutt., are annuals, diploid (x=17) and selfincompatibles. The former was not previously described in this country and would correspond to H. annuus ssp. annuus. Populations were found in Cordoba, La Pampa, Buenos Aires, Entre Rios, Mendoza and San Juan provinces. Other plants matching progenies of cultivated sunflower, H. annuus var. macrocarpus, were found as adventitious within the cultivated region, including Santa Fe and Chaco. H. petiolaris is much more pervasive, mainly in La Pampa, San Luis and Western Buenos Aires, on sandy soils, and continues spreading. Both species can hybridize with the cultivated sunflower and morphologically intermediate plants were found in 15 counties, which would point to hybrid swarms formation, such as in their center of origin. It was estimated that these wild species have established over 50% of the sunflower cultivated area, which has important implications for genetic breeding and biosafety, in the case of release of transgenic cultivars.
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