![Sample our Bioscience journals, sign in here to start your access, Latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5925/TOC-Subject-Sample-2021-Bioscience.jpg"})
Abstract
Interspecific crosses between two species of the Turnera ulmifolia complex with yellow flowers have been carried out. As a result, two hybrids were obtained: T. krapovickasii (K4) x T. ulmifolia (U), 2n = 4x=20 and T. ulmifolia (U) x T. krapovickasii (K5), 2n = 5x=25. The hybrids were cytologically studied in order to determine their genomic relationships. The chromosome pairing data of hybrids indicates that T. ulmifolia is a segmental allopolyploid and, on the basis of the results obtained, the genomic constitution AuAuBaBaBuBu is proposed for this species. The cytological analysis of the tetraploid hybrid has also revealed the presence of PMCs with 2n = 40 that should have been formed by pre-meiotic chromosome doublings and would give rise to the formation of fertile 2n gametes. From this finding, it is suggested that, in the genus Turnera, unreduced gametes may result from at least two mechanisms: (1) premeiotic doubling and (2) meiotic nuclear restitution.