INTERSPECIFIC TRI-HYBRID AMONG TETRAPLOID SPECIES OF THE PLICATULA GROUP OF PASPALUM

NOVO P.; ESPINOZA, F; QUARIN CL

Buenos Aires

Simposio; 5th International Symposium of Forage Breeding; 2015

Plicatula is an informal taxonomic group of approximately 30 species morphologicaly related to Paspalum plicatulum. Most of these species have forage potential. A few commercial cultivars have been developed directly by selection from natural germplasm of some species. Genetic improvement through breeding had not been used because most Plicatula species are apomictic tetraploids (4xA). A sexual tetraploid cytotype (4xS) was experimentally developed from a diploidcytotype of P. plicatulum which blooms early in summer (Dec-Jan). Crossing between P. plicatulum (p4xS) and P. chaseanum (ch4xA) produced interspecific hybrids which segregated for reproduction mode, vigor and fertility. Some of these sexual hybrids bloomed at early autumn (Apr). This work was performed to obtain tri-hybrids by crossing a sexual hybrid (p4xS x ch4xA) used as mother plant and a ?Cambá FCA? cultivar of apomictic P. atratum (at4xA) used as pollendonor which flowers in April with the aim to explore the possibility of gene exchange between ?Cambá FCA? and different species of Plicatula. Ten tri-hybrids were obtained and only one survived, which was a vigorous plant. Most chromosomes of the tri-hybrid were associated at meiotic metaphase mainly as bivalents and quadrivalents. Approximately 90% of pollen mother cells had regular anaphase chromosome distribution, and showed regular formation of tetrads. Previous works demonstrated that P. chaseanum is an autotetraploid species and that it basic genome is highly homologous with the genome of the induced autotetraploid of P. plicatulum. P. atratum was reported to be a segmental allotetraploid or a highly diploidized autotetraploid. Thetri-hybrid produces seed. The flow cytometric analysis revealed 2C:5C DNA content ratio for the embryo and endosperm, which indicated that the tri-hybrid reproduces by sexual means. Moreover, its progeny is also fertile and reproduce sexually. The meiotic chromosome behavior of the tri-hybrid and its parents suggests that the three species share and homologous or homeologous basic genome. This vigorous, fertile, sexual reproducing and tetraploid tri-hybridmakes up an interesting pivot germplasm on which gene exchange may be achieved for plant improvement programs in the group.