Octoploid Zoysiagrass: Origin, Stability, Characteristics, And Breeding Behavior

All known species of zoysiagrass are tetraploids (2n = 4x = 40) but octoploids have been reported. This research was conducted to evaluate ploidy variability from a stand of zoysiagrass where an 8x clone (E11) originated, and to characterize progeny from E11 and other ploidy variable clones. Clone ploidy was determined by flow cytometry and clones and progeny were assessed for aboveground and belowground morphological variability. Clone E11 was confirmed as 8x with a G1 peak twice that of 'SS-500' (Empire, Sod Solutions, Inc.). Among 31 clones from the field where E11 originated, 20 were tetraploid, but 11 showed two flow cytometry peaks of similar numbers of events - one at a 4x value like Empire and a second at an 8x value like E11. From the group of 11 clones, three clones (C62, C96, and C107) that initially had double peaks reverted back to the 4x level, two (C92 and C105) stabilized at 8x, and six (C4-1, B10, C13, I31, C87, and C93) continued to show double peaks. Progeny from C62 and C96 were only 4x. Progeny from the E11, C92, and C105 were all 8x except for one 6x plant among eight progeny of C105. Progeny from two clones with double peaks (C4-1 and C93) were only 8x. These results show that, with variable ploidy of histogenic layers, a progeny generation is needed to stabilize 8x lines. Morphology studies showed that E11 generally followed the expected trend of increased size of vegetative and floral parts and root morphology found with chromosome doubling.