ARS | Publication request: Variation in DNA content of Florida paspalum accessions

Submitted to: American Society of Agronomy Branch Meeting
Publication Type: Abstract
Publication Acceptance Date: December 18, 2006
Publication Date: January 17, 2007
Citation: Burson, B.L., Jessup, R.W. 2006. Variation in DNA content of Florida paspalum accessions [abstract]. Southern Branch American Society of Agronomy. Paper No. 1.

Technical Abstract: Florida paspalum (Paspalum floridanum Michx.) is a perennial native grass that grows in the southeastern United States. It is readily grazed by cattle, and its seed are a source of food for wildlife. Efforts to improve the species through breeding have not been attempted because of its complex cytology and unknown reproductive behavior. It has a high number of chromosomes, ranging from 2n=120 to 180. Meiosis is irregular with as many as 80 chromosomes lagging on the metaphase plate during anaphase I, and most of these appear not to be incorporated into the gametes. Even with the loss of this many chromosomes, most plants are highly fertile. High seed set in a meiotically irregular plant is a strong indicator that the species reproduces by apomixis. However, megasporogenesis and megagametogenesis in Florida paspalum appear normal which indicates the species is sexual. If it is sexual, there should be a wide range of chromosomes in plants occurring in nature, but if apomixis is involved, the plants should have a similar chromosome number. To obtain insight into which reproductive process is occurring in this grass, the DNA content of 20 different accessions was determined using flow cytometry to predict their ploidy levels. These accessions were from different geographical regions in Arkansas, Louisiana, Oklahoma, and Texas. There was not a large range in DNA content among accessions. The mean DNA content of the individual accessions ranged from 11.91 pg to 13.95 pg with an overall mean of 12.72 pg (SD=0.29). Because of the meiotic irregularities in this species, more variation in DNA content would be expected if the species reproduced sexually. This suggests that either some unique chromosome restoring mechanism or a form of apomixis is involved.