The hexaploid species of Helianthus tuberosus is a potential source of resistance to several sunflower pathogens. But crossed with cultivated sunflower, it produces F, 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 F1 hybrids. Significant differences in pollen viability existed between populations (47.1–98.8%). In the 15 FI 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, 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.

Three diploid perennial sunflower species are useful for variety improvement : Helianthus mollis, because of sessile leaves, H. salicifolius, because of a high oil concentration, and H. maximiliani, a potential source of resistance to Sclerotinia sclerotiorum . The crossability of these species to cultivated sunflower was examined .Hybrids were obtained from eight combinations, with 3-15 Fl plants per combination . The 171's exhibited the dominant phenotype of the wild species . Pollen viability varied between 32 .1 and 69 .9% . Meiosis was irregular in the Fl hybrids . At diakinesis, bivalents (62 .7-97 .9% of meiocytes), univalents (0-31 .23%), and multivalents (3 .84-7 .68%) were detected . At anaphase I, chromosome bridges were detected in 6 .77 to 11 .44% of meiocytes . Fast chromosomes in metaphase I, and lagging chromosomes in anaphase I and telophase II were evidenced in a high percentage of meiocytes .

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