Submitted to: American Society of Agronomy Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/17/2001
Publication Date: 2/3/2002
Technical Abstract: Florida paspalum, Paspalum floridanum Michx., is a native, warm-season grass that is distributed from southern New Jersey to Florida and west to Illinois, eastern Kansas and central Texas. It is palatable and is grazed by cattle but forage production is limited. Florida paspalum has larger seed than most Paspalum species and there is interest in its use as a food source for game birds. There are several traits that need improvement in this species. Before improvement programs are initiated, there is a need to learn more about the reproductive biology of this grass. This investigation was undertaken to determine the cytology, reproductive behavior, and fertility of Florida paspalum. The species has approximately 160 chromosomes with irregular meiosis in both the pollen mother cells (PMC) and megaspore mother cells(MMC). In the PMCs, the chromosomes associated as univalents, bivalents, and multivalents, and during anaphase I, approximately 60 univalents lagged behind to form a large micronucleus. Pollen stainability of 19 accessions ranged from 26.3 to 61.9% with a mean of 42.2%, and all produced viable seed. Even though lagging chromosomes and large micronuclei were observed during meiosis in the MMCs, linear tetrads of megaspores were produced and the chalazal member of each tetrad developed into the functional megaspore which developed into an 8-nucleated embryo sac. These observations suggest that Florida paspalum reproduces sexually, but its irregular meiotic behavior should cause the plants to be sterile. A system may have evolved where the micronucleus is incorporated into one of the micro- or megaspores that has a competitive advantage over aneuploid gametes. Upon fertilization, the original chromosome number is restored and the off-spring are fertile. Another possibility is that a unique form of apomixis is occurring and it was not detected. Additional research is needed to resolve this problem.