Author
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Goldman, Jason |
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Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/17/2015 Publication Date: 4/1/2015 Publication URL: http://handle.nal.usda.gov/10113/60957 Citation: Goldman, J.J. 2015. DNA contents in Texas bluegrass (Poa arachnifera) selected in Texas and Oklahoma determined by flow cytometry. Genetic Resources and Crop Evolution. 62(5):643-647. Interpretive Summary: Genome size is the total amount of DNA packaged in the chromosomes in a single cell of an individual. Genome size can be expressed as a weight in picograms (pg) and there is tremendous variation in genome size depending on the species. Some examples of genome size include rice (1.08 pg), human male (6.36 pg), human female (6.55 pg), barley (11.13 pg), and onion (32.97 pg). The genome size can be detected quickly using flow cytometry with fresh leaf tissue. Knowledge of genome size has many applications ranging from taxonomy and population biology to breeding and quality control in seed production. Texas bluegrass (Poa arachnifera Torr.) is a dioecious (separate male and female plants), perennial, cool-season grass native to southern Kansas, Oklahoma, western Arkansas and most of Texas. Its major use has been for forage on rangelands in Texas and Oklahoma. Hybrids with Kentucky bluegrass (P. pratensis L.) have been developed for use as turfgrass. Currently, the genome size of Texas bluegrass is unknown, therefore, flow cytometry was performed on an assortment of male and female Texas bluegrass plants (n=28), Kentucky bluegrass (n=11), and hybrids (n=18) to estimate genome size in picograms (pg). The Texas bluegrass genome size fell into two groups based on 13 collections sites. Plants collected from northwest Oklahoma (4 locations) and five other locations west of 33.75, -98.39 (latitude, longitude) ranged from 9.64 to 10.07 pg. Plants collected from four sites in Texas, east of 33.20, -98.16 contained a genome size that ranged from 14.02 to 14.75 pg. Kentucky bluegrass had three distinct groups, ranging from 6.38 to 8.85 (n=8), 10.87 to 11.07 (n=2), and 12.5 pg. The hybrids ranged from 8.86 - 16.61 pg. These results will aid Texas bluegrass breeders to rapidly identify hybrids, pure Texas bluegrass with different genome sizes (ca. 9.95 and 14.5 pg), and in some cases specific hybrids, based on genome size estimates. Technical Abstract: Texas bluegrass (Poa arachnifera Torr.) is a dioecious, perennial, cool-season grass native to southern Kansas, Oklahoma, western Arkansas and most of Texas. Its major use has been for forage on rangelands in Texas and Oklahoma. More recently, interspecific hybrids between Texas bluegrass and Kentucky bluegrass (P. pratensis L.) have been developed and commercially released as heat tolerant turfgrass. Currently, the 2C nuclear DNA content of Texas bluegrass is unknown. Therefore, flow cytometry was performed on an assortment of male and female Texas bluegrass genotypes (n = 24) collected from fourteen locations in Texas and Oklahoma to estimate DNA content in picograms (pg). The DNA content of Texas bluegrass fell into two groups based on collection location. Plants collected from northwest Oklahoma and five other locations west of 33.75, -98.39 (latitude, longitude) ranged from 9.64 ± 0.04 to 10.07 ± 0.09 pg. Plants collected from four sites in Texas, east of 33.20, -98.16 contained a DNA content that ranged from 14.02 ± 0.04 to 14.75 ± 0.13 pg. Based on a root tip chromosome count, a male Texas bluegrass plant estimated to be 9.96 pg, appeared to contain 56 chromosomes, indicating the smaller DNA content plants may be octaploids (2n = 8x = 56). Significant differences were not detected between male and female plants based on DNA content. Knowledge of the DNA content in Texas bluegrass should be useful in a breeding program for characterizing germplasm and identifying desired DNA content levels among parental genotypes. |
