The role of triploids in the origin and evolution of polyploids of Turnera sidoides L. complex (Passifloraceae, Turneroideae)

KOVALSKY, I. EVELIN; ROGGERO LUQUE, JUAN M.; ELÍAS, GABRIELA; FERNÁNDEZ, SILVIA A; SOLÍS NEFFA, VIVIANA G.

JOURNAL OF PLANT RESEARCH

SPRINGER TOKYO

Lugar: Tokyo; Año: 2017

0918-9440

Triploids can play an important role in polyploid evolution. However, their frequent sterility is an obstacle for the origin and establishment of neotetraploids. Here we analyzed the microsporogenesis of triploids (x=7) and the crossabilty among cytotypes of Turnera sidoides, to test the impact of triploids in the origin and demographic establishment of tetraploids in natural populations. Triploids of T. sidoides exhibit irregular meiotic behavior. The high frequency of monovalents and of trivalents with non-convergent orientations results in unbalanced and/or non-viable male gametes. In spite of abnormal chromosome pairing and unbalanced chromosome segregation, triploids are not completely sterile and yield up to 67% of viable pollen. Triploids that originated by fusion of 2n × n gametes of the same taxon showed more regular meiotic behavior and higher fertility than triploids from the contact zone of diploids and tetraploids or triploids of hybrid origin. The reproductive isolation of T. sidoides cytotypes of different ploidy level is not strict and the ?triploid block? may be overcome occasionally. Triploids of T. sidoides produce diploid and triploid progeny suggesting that new generations of polyploids could originate from by crosses between triploids or from backcrosses with diploids. The capability of T. sidoides to multiply asexually via rhizomes enhances the maintenance of neopolyploids at a low frequency in natural populations.