Location: Crop Germplasm ResearchTitle: Genetic diversity among pentaploid buffelgrass accessions
|Renganayaki, K - Texas A&M University|
|Dowling, C - Texas A&M University|
|Jessup, Russell - Texas A&M University|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2015
Publication Date: 6/9/2015
Citation: Burson, B.L., Renganayaki, K., Dowling, C.D., Hinze, L.L., Jessup, R.W. 2015. Genetic diversity among pentaploid buffelgrass accessions. Crop Science. 55:1637-1645.
Interpretive Summary: Buffelgrass is an important range and pasture grass primarily grown for cattle production in many of the drier regions of the tropics and sub-tropics throughout the world. The grass is easy to establish and can survive long periods without rainfall. It will persist and produce quality forage in areas receiving only 12 to 15 inches of rainfall a year. Its drought tolerance is a desirable trait to have in pasture and range grasses. Unfortunately, buffelgrass has some undesirable traits and the most limiting of these is its lack of cold tolerance. Most buffelgrass plants will not survive temperatures below 25 deg F which limits where the grass will grow. The only known buffelgrass plants that survive colder winters have 45 chromosomes rather than the more common number of 36 chromosomes. It is assumed the extra nine chromosomes in these plants are responsible for the increased cold tolerance. However, there are other 45 chromosome buffelgrass plants that will not survive colder winters but these were collected from different geographical areas than the cold tolerant types. Because of this, the genetic makeup of these plants should be different. This study was undertaken to determine the genetic differences among 128 plants in the USDA buffelgrass collection that have the extra nine chromosomes. Using molecular markers, it was determined that there are genetic differences among these different plants. Most of those with winter hardiness are more similar to one another than to those lacking cold tolerance. These plants have different genetic backgrounds and there is a great deal of genetic diversity in the collection. This information is of value to plant breeders working with the species.
Technical Abstract: Buffelgrass (Pennisetum ciliare) is an important range and pasture grass that grows in the arid tropics and semi-tropics. It has excellent drought tolerance but lacks winter hardiness. Even though the grass reproduces primarily by apomixis, it is highly polymorphic. A range of chromosome numbers have been reported for the species but 2n=4x=36 is the most common number. Eighty-five buffelgrass accessions that were collected in the Republic of South Africa in 1976 had 45 chromosomes. These were significantly more winter hardy than regular buffelgrass and it was assumed this was from the extra nine chromosomes. Thirty-one additional 45-chromosome plants have since been identified in the USDA National Germplasm System (NPGS) buffelgrass collection and these were in the NPGS prior to 1976; however, they lack cold tolerance. This study was conducted to determine the genetic diversity among all of the pentaploid buffelgrass accessions in the NPGS, and specifically to determine if the winter hardy and non-winter hardy genotypes can be separated. AFLP markers were used to determine the genetic diversity and phylogenetic relationships among the 131 accessions. Ten primer combinations generated 862 polymorphic bands, and the number of bands identified by each primer ranged from 74 to 117, with a mean of 93.4. UPGMA cluster analysis and principle coordinate analysis revealed two major groups with one group separating into four sub-groups. Genetic similarity coefficients among the accessions ranged from 0.39 to 0.98 with an average of 0.74. These findings indicate there is considerable genetic diversity among the pentaploid accessions. Most of the cold and non-cold-tolerant genotypes separated by individual sub-groups but not by group. It appears the different pentaploid genotypes have polyphylogenetic origins.