MEIOSIS AND POLLEN VIABILITY IN HELIANTHUS-TUBEROSUS L AND ITS HYBRIDS WITH CULTIVATED SUNFLOWER

The hexaploid species of Helianthus tuberosus is a potential source of resistance to several sunflower pathogens. Bur crossed with cultivated sunflower, it produces F-1 hybrids which have low values of fertility or even full sterility. Pollen viability and meiotic features were studied in 17 populations of the species H. tuberosus and in F-1 hybrids. Significant differences in pollen viability existed between populations (47.1-98.8 %). In the 15 F-1 hybrids, plant fertility ranged from 0 to 100 % per combination, while pollen viability ranged from 12.4 to 57.1 %. Meiosis was almost normal in the analyzed species, and irregular in the F-1 hybrids. The highest percentage of meiocytes was with bivalents (85.9), but univalents (0.3 %) and multivalents (13.8 %) occurred as well. In metaphase and anaphase, the percentage of meiocytes with fast and lagging chromosomes was high. In anaphase, chromosome bridges were detected in 9.9 % of the meiocytes.