Compatibility relations between the edible carrot Daucus carota and D. pusillus, a related wild species from the Argentinian Pampas

Abstract

To establish the feasibility of hybridization between the wild carrot species Daucus pusillus Michx. (2n = 2x = 22; 2n = 2x = 22 and 20), collected in the pampas grasslands of Argentina, and the edible carrot, Daucus carota L. (2n = 2x = 18), controlled pollinations were attempted on the plant. Due to the difficulties encountered, flowers of 12 accesions and three commercial cultivars were excised from individual plants and pollinated in Petri dishes following an incomplete diallel design. After processing, the pollinated pistils (four to six per genotypic combination) were observed under a microscope with UV light. Pollen tubes reaching the ovaries and/or the ovules (compatible relation) were observed in six out of nine D. pusillus × D. pusillus and seven out of 18 D. pusillus × D. carota genotypic combinations. In the eight D. carota × D. pusillus genotypic combinations, only ungerminated pollen, pollen not adhered to the stigmas or pollen tubes overlapping the stylar tissue were observed. Additional flowers were pollinated in a sample of compatible genotypic combinations and the pollinated pistils were in vitro culture to study embryo and endosperm development. Eight out of nine pistils from the intraspecific and nine out of 13 from the interspecific crosses enlarged to form apparently normal schizocarps. Histological analyses revealed normal development of embryo and endosperm. The breeding barriers between the two species are incomplete, making feasible the obtainment of interspecific hybrids by conventional techniques.