Cytogenetic study of hexaploid species Helianthus tuberosus and its F1 and BC1F1 hybrids with cultivated sunflower, H. annuus

Helianthus tuberosus is a potential source of resistance to many disease-provoking pathogens. Three accessions of H. tuberosus were used in this research and they were crossed with cultivated sunflower. Six F] and two BC1F1 hybrid combinations were obtained. Analysis of meiosis was performed using aceto-carmine method (GEORGIEVA-TODOROVA, 1976) and pollen viability was determined by staining method of ALEXANDER (1969). Meiosis was regular in cultivated sunflower and the pollen viability was high (96.8-98.9%). Low percent of irregularities was found in the meiosis of H. tuberosus. Pollen viability was high (97.2-98.7%). Chromosome pairing was mostly regular in F1 hybrids (34 bivalents), but some meiocytes contained 28-32 bivalents with uni- and quadrivalents present. The percent of meiocytes with fast chromosomes in metaphase was 24.6-87.2, with lagging chromosomes in anaphase I 10.5-81.0 and in telophase 25.0-33.3. Chromosome bridges were detected in 0-9.9% of meiocytes in anaphase. Pollen viability in F1 hybrids ranged from 27.0 to 47.9%. In BC1F1 hybrids number of bivalents was 16-25, univalent 2-18 and multivalent 0-1. Although a triploid set of chromosomes (51) was expected in BC1F1 hybrids, number of chromosomes was 45-57. Pollen viability varied from 0 to 54.3%.