Agrobacterium-Mediated Transformation of Zoysia Matrella (L.) Merr.Using Embryogenic Callus Cultures.

Most warm-season turfgrasses are released as vegetative cultivars and are highly heterozygous.  Propagation of many commercial cultivars of zoysiagrass is by clonal methods (e.g. sod, sprigs, etc.) rather than by seed.  A vegetative cultivar already possesses desirable and specific characteristics; therefore, the direct manipulation of elite clones (cultivars) by molecular genetic techniques should be an easy and efficient way to improve existing cultivars.  Even though there are a few reports of transformation in the genus with Zoysia japonica Steud and Z. sinica Hance, the transformation frequency is low, the protocols are far from routine and efficiency is genotype dependent. Agrobacterium-mediated transformation protocols reported thus far for Zoysia species have used either highly embryogenic callus or stolon nodes.  Here we show results describing the tissue culture systems and efficiency of Agrobacterium-mediated transformation of Zoysia matrella (L.) Merr. cvs. ‘Diamond’, ‘Cavalier’, ‘Zorro’ and ‘DALZ 0501’. High quality, embryogenic calli were induced from 10 to 25% of shoot explants using a modified MS medium.  Sonication-assisted Agrobacterium-mediated transformation (SAAT) was employed to produce large numbers of transgenic Zoysia plants with low cost and short time. The putative transgenic lines were identified by PCR, and transformation efficiency reached more than 20%. The PCR (+) transgenic  lines are being test crossed to determine the inheritance pattern of the transgenes.