Instability of the greens-type phenotype in poa annua L

The turfgrass species Poa annua L. is most prevalent as an invasive, annual weed in managed turfs. Conversely, the dwarf perennial greens-type biotype produces a high turf quality with great utility to the golf-course industry. In the past 60 yr, several attempts have been made to breed a commercial cultivar of the greens-type biotype with little sustained success. Here, we characterize the morphological traits of the greens-type phenotype and investigate its inheritance and stability through genetic crosses. The results indicate that the greens-type phenotype links single-branching inflorescences with reductions in culm length, tiller length, leaf length, and panicle length to a single genetic mechanism. However, in advanced-generation progeny, the segregation of the greens-type phenotype does not conform to the disomic single-gene inheritance model. Tetrasomic inheritance, gene complementation, and quantitative inheritance models are also presented. These results, along with the observation of somatic reversions, suggest that the greens-type phenotype is unstable and may be regulated by an epigenetic mechanism.