AFLP Variation in Agamospermous and Dioecious Bluegrasses of Western North America

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Abstract
Native perennial bluegrasses are common and persistent in the understory steppe vegetation of western North America. The agamospermous Poa secunda Presl. complex circumscribes a number of commonly recognized forms including big bluegrass (P. ampla Merr.), canby bluegrass (P. canbyi Scribn.), and sandberg bluegrass (P. sandbergii Vasey). Poa fendleriana (Steudel) Vasey is a dioecious, morphologically distinct bluegrass species that is also native to western North America. The amplified fragment length polymorphism (AFLP) method was used to analyze genetic variation within and among cv. Canbar canby bluegrass, cv. Sherman big bluegrass, two allopatric natural populations of sandberg bluegrass, and one natural germplasm source of P. fendleriana Results indicate that Sherman and Canbar are comprised of one or several fixed genotypes, respectively, that are related to sandberg bluegrass. Although several fixed genotypes were also detected within the two natural sandberg bluegrass populations, high levels of genetic diversity were present in the agamospermous sandberg populations and dioecious P. fendleriana population. Patterns of AFLP variation in P. secunda are consistent with facultative apomixis and outcrossing mode of reproduction. Moreover, population differentiation between the two highly diverse natural sandberg bluegrass populations, collected from sites nearly 600 km apart, is very low (GS = 0.14) and reflect a high degree of gene flow. However, the AFLP profiles of Canbar canby bluegrass and Sherman big bluegrass were distinct from sandberg bluegrass. The P. secunda complex, as a group, was clearly distinguishable from P. fendleriana Thus, DNA fingerprinting was used to characterize naturally diverse bluegrass germplasm sources that may be used for large‐scale revegetation efforts across the western USA.