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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.

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.

Mutual relationships have been studied between seven plant end seed characteristics (plant height, number of leaves per plant, 1000-seed mass, hectoliter mass, kernel content, seed thickness, seed width) and their correlation with oil content in seed. Significant of highly significant correlations have been found between oil content on one side and 1000-seed mass, hectoliter mass, kernel content, and seed thickness on the other. Anon-significant negative correlation was registered for the number of leaves per plant, non-significant positive correlations for plant height and seed width. The path analysis has revealed a highly significant positive direct effect of hectoliter mass and kernel content and a significant negative direct effect of seed width on oil content in seed. The coefficient of determination has shown that 79.5% of the total variability for oil content were controlled by the factors studied.