Genesis and identification of octoploids generated from tetraploid prairie cordgrass

Prairie cordgrass (Spartina pectinata Link) is a warm season (C-4) perennial grass that could be a potential candidate for studying polyploidization and its effects on environmental adaptability. Polyploidy plays an important role in prairie cordgrass's adaptation and distribution on different ecoregions in the North American Prairie. However, the genetic backgrounds of polyploidy prairie cordgrass distributed in the different edaphic regions are different. Thus, to extend our knowledge of the effect of polyploidy on environmental adaptation, it is necessary to have diverse ploidy levels of plants with a similar genetic background. Tetraploid prairie cordgrass, IL-102 (2n = 4x = 40), was used as explant material to generate octoploids. Germinated seeds were treated with 0.00, 0.03, 0.06, 0.1, and 1% colchicine or 0.000, 0.002, 0.003, 0.005, and 0.007% oryzalin solution with 0.5% dimethyl sulfoxide (DMSO) for 6, 12, or 24 h. Ploidy levels of treated seedlings were determined by flow cytometric analysis and their putative ploidy were confirmed by the chromosome count. Our results show that stable octoploid plants (2n = 8x = 80) were obtained directly by treating with antimitotic agents or by propagating cytochimeric plants. Induced octoploid plants showed increased genome size and stomata size compared with tetraploid plants. By obtaining different cytotypes in the same genetic background, sole effects of ploidy variations on agronomic traits can be determined.