Cytogenetic studies in triploid and tetraploid hybrids of Turnera krapovickasii, T. scabra and T. subulata (Passifloraceae, Turneroideae).

Abstract

Cytogenetic studies in triploid and tetraploid hybrids of Turnera krapovickasii, T. scabra and T. subulata (Passifloraceae, Turneroideae). In order to investigate the genomic relationships among species of series Turnera (x= 5), a controlled crossing program was performed and yielded numerous hybrids. Among the yellow flowered species of series Turnera, T. krapovickasii, T. scabra and T. subulata have diploid and autotetraploid cytotypes. So far, the degree of reproductive isolation between diploids and autotetraploids, and the degree of genomic affinity at tetraploid level are unknown. In this study, we present the results of the cytogenetic analysis of triploid (2n=3x=15) intraspecific hybrids of T. krapovickasii and T. scabra and tetraploid (2n=4x=20) (2n=4x=20) T. krapovickasii × T. scabra and T. subulata × T. scabra hybrids. In the triploid hybrids we found cells with 1 to 5 trivalents and the pollen viability was 11.4% - 15.2%. In the tetraploid hybrids we found cells with 1 to 5 quadrivalents and the pollen viability was 76% - 87.97%. The results of this work revealed that the reproductive isolation between diploids and tetraploids is incomplete, and that the triploid hybrids are not completely steriles. Likewise, the cytogenetic analysis of the interspecific hybrids evidenced that the genomes of T. krapovickasii, T. scabra and T. subulata display more affinity at tetraploid level than at diploid level.