Zoysiagrass species are cross-fertile and easily interbreed with one another. Tis is somewhat uncommon as the definition of species revolves around being reproductively isolated. While crosses between different zoysiagrass species can occur naturally, they are also often used by plant breeders as a means of mixing traits of interest into new and improved cultivars. Consequently, intermediate types between species are not unusual and a continuous range of variation exists in the Zoysia genus for many morphological traits. A few examples of this include cultivars like Cavalier, Crowne, Zeon, and Zorro. While these cultivars typically have finer texture than Z. japonicas like Zenith or Chinese Common, they don’t have texture as fine as many Z. matrellas such as Diamond or L1F. Te wide range in leaf texture that exists among the zoysiagrasses listed in Figure 1 is an example of not only the variation that exists between various zoysia species, but also the shared traits in which they overlap. Tese intermediate types can be difficult to classify and their relationships with other zoysia species have not always been clearly understood.


In order to investigate this, researchers at North Carolina State University (Raleigh, NC), in collaboration with the University of Florida, USDA-ARS in Tifton, GA, and Blue Moon Farms conducted a study which evaluated 62 zoysiagrass cultivars and collections representing five different zoysia species: Z. japonica, Z. matrella, Z. machrostachya, Z. minima, and Z. sinica. In order to determine the true genetic relationships among these individuals, DNA markers were used to investigate their genetic constitution. Molecular or DNA markers are changes in short sequences that occur at specific locations on an individual’s DNA. When individuals have differences in those sequences, they can be used to distinguish one individual from another. In this case, 55 DNA markers were evaluated and the relationships among the 62 zoysiagrasses included in this study were determined based on differences in their sequences. For example, if Meyer were to have a lot of markers in common with Zenith and just a few markers in common with Diamond, then Meyer would be more genetically similar to Zenith and therefore more closely related to it.


After analyzing the commonalities and differences between each pair of zoysiagrass samples, a tree of relationships was established that reflected not only the relationships among zoysiagrass species, but also the true delineation between them. Tis is useful in determining where commonly used zoysiagrass varieties should be properly classified. Te zoysiagrass tree of relationships presented in Figure 2 indicates that the 62 zoysiagrass samples analyzed fell into four sub-groups, or clusters. Cluster I includes true Z. japonica cultivars, while Cluster III includes true Z. matrella cultivars. Cluster II, consisting of hybrids, is right in the middle of both species.


TPI Turf News May/June 2018 49


More importantly, Cluster II is divided into two sub- groups: Hybrid I which includes Z. japonica x Z. matrella hybrids that have a higher contribution of genetic material from Z. japonica, and Hybrid II which are also hybrids between the two species but have a higher contribution of Z. matrella genetic material. To validate the DNA marker results, information on flowering characteristics from the 62 samples was also collected. Tese included peduncle width, pedicel length, raceme length, number of seeds per raceme, seed length and seed width for a number of flowers per entry. Tis is an important step because these are the characteristics that have been traditionally used by botanists to classify the 350,000+ species of the world’s flowering plants.


Figure 2


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