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Although the wild sunflower species Helianthus laevigatus has not been extensively studied, it may be considered for sunflower breeding as a potential source of desirable genes for Sclerotinia stalk rot resistance and high contents of proteins and linoleic acid in the seed. A set of six H. laevigatus populations was crossed to cultivated sunflower lines and produced nine F 1 (2-14 plants) and 66 BC 1 F 1 hybrid combinations (1-13 plants). Male sterility occurred in F 1 and BC 1 F 1 hybrid combinations and pollen viability was lower in the progenies than in the parents (51.6-77.2% in F 1 and 4.8-34.0% in BC 1 F 1 ). Meiosis was normal in the H. laevigatus populations. It was found that this tetraploid species also occurred in a hexaploid form. Numerous irregularities were observed in the meiosis of the F 1 interspecific hybrids. During diakinesis, quadrivalents and hexavalents were recorded in addition to bivalents. Dislocated chromosomes and chromosome bridges were present in the other phases. The chromosome number in F 1 was 68 (tetraploid). Irregularities in chromosome pairing were observed in the interspecific hybrids at BC 1 F 1 . There were many univalents, and trivalents, quadrivalents and hexavalents were also present. The chromosome number in the BC 1 F 1 generation ranged from 34 to 60. The occurrence of meiotic irregularities in the F 1 and BC 1 F 1 interspecific hybrids indicates that H. laevigatus and the cultivated sunflower differ in genome constitution.

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.