Creation of Hexaploid and Octaploid Zoysiagrass Using Colchicine and Breeding

Zoysiagrasses (Zoysia Willd.) are a slow-growing, tetraploid (2n = 4x = 40) turfgrass that can be successfully managed with less input than many other warm-season grasses. Despite extensive genetic and morphological variation, genotypes with the ability to recuperate quickly from damage are rare. Therefore, a long-term effort to increase vegetative growth rates was initiated during 2009 by first studying the effectiveness of six colchicine seed treatments and breeding for manipulating the ploidy level of 'Zenith' zoysiagrass. Colchicine-treated seedlings were screened using flow cytometry for genome size changes. Four putative octaploids and one cytochimera were identified. Average stomata length of the four colchicine-induced putative octaploids were 28% larger than that of Zenith, but the cytochimera's stomata length was not altered. Pollen diameter of the four putative octaploids was larger than that of Zenith and the cytochimera. Pollen stainability was relatively unchanged by the colchicine treatments. Further self-and cross-pollination of 09-TZ-103 (putative M-0 octaploid) led to the development and verification of M-1 octaploid and M-1 hexaploid genotypes. These results support that DNA content of the L-I (epidermis), L-II (germ line), and L-III (adventitious roots) histogenic layers of Zoysia can be manipulated with colchicine and breeding. Future evaluation of the turfgrass performance of these polyploids is the next step in determining the value of this breeding procedure for improvement of zoysiagrass.