A novel sexual tetraploid plant induced from a diploid cytotype of Paspalum chaseanum (Poaceae)

GALDEANO F; ESPINOZA F; NOVO P.; QUARIN CL; CARRIZO M; WAGNER AW

Foz do Iguazu

Congreso; International Congress of Genetics; 2018

Soc Brasilera de Genetica

The Southamerican grass, Paspalum chaseanum, is a multiploid species with a sexual selfincompatible diploid (2n=2x=20) cytotype and a tetraploid (2n=4x=40) cytotype which reproduces by apomixis, speudogamy and self-compatibility. Sexual plants have never been found in the tetraploid cytotype. The induction of autoploidy from diploid seedlings was aimed at obtaining sexual tetraploid plants that can be used as female parents in crosses with plants of the tetraploid cytotype, or other apomictic, tetraploid, close related congeneric species. A total of 230 diploid seedlings were soaked in a solution of colchicine (0.2%) and dimethyl sulfoxide (2%) during 2, 4 and 6 hours. Flow cytometry analysis was performed in 135 surviving plants. Only one induced 4xplant was recovered, which arose from the treatment of 6 hours with colchicine. The result was confirmed by traditional chromosome counts in root-tip cells. Embryological analysis of 120 mature ovaries, conducted by differential interferential contrast (DIC) microcopy showed the typical structure of the meiotic embryo sac revealing that this induced tetraploid individualreproduced sexually. The induced 4x plant failed to set seed following self-pollination, maintaining the self-incompatibility system of the diploids. However, the plant produced seed after crosses with pollen of the wild apomictic tetraploid cytotype. The sexual self-incompatible 4x plant constitutes a novel suitable female parent in crosses with plants of the apomictic tetraploidcytotype or other apomictic tetraploids from related species. The results suggest that it is possible to break apomixis in natural tetraploids opening the possibility for using their genes in a plant improvement program.