Selection for freezing tolerance in St. Augustinegrass through somaclonal variation and germplasm evaluation

St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is the least cold-hardy turfgrass species. Development of freezing-tolerant St. Augustinegrass cultivars would greatly benefit home owners in many southern states of the US. Towards this breeding goal, 7800 plants regenerated through tissue culture and 36 germplasm accessions were screened for improved freezing tolerance. Among the conditions tested, 1 week at 13 C followed by another week at 3 C, then freezing at )3 to )5 C for 3 h, was found to be suitable to distinguish genotypes in freezing tests. The experiments revealed that germplasm accession Elm4 was significantly more freezing-tolerant under a controlled environment than Raleigh , the current commercially available, most freezing-tolerant cultivar. In addition, out of 7800 regenerated plants from tissue culture, somaclonal variant SVC3 showed significantly more freezing-tolerant than its parent Raleigh .