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Florida Lawn Turfgrass Breeding at the University of Florida: 2011 Update By Kevin E. Kenworthy, Ph.D., University of Florida / IFAS, Gainesville, Florida

The turfgrass breeding program at the University of Florida has remained active in the past year propagating advanced lines for further evaluation, development of new material and collaborating with several other scientists. The following summary will provide a snapshot our most recent efforts and future objectives. During the past three years the turfgrass breeding program has placed a greater effort on under- standing drought responses in warm-season turfgrass. Recently a graduate student’s projects were completed that identified differential base transpiration rates

between St. Augustinegrass, bermudagrass and zoysiagrass. This study also showed that these species and different cultivars and experimental entries within a species require variable drydown periods before they reduce their base transpiration rate. Rooting depth potential and root volumes were also measured in this study. In brief, we now know which plants have a high base transpiration rate and will respond to a drydown by quickly reducing transpiration or maintain their base rate for a longer period of time. Similarly, we also know which plants have an initial lower transpiration rate and the same differential changes in transpiration depend- ing on the length of the drydown period. This knowledge combined with the rooting information has provided a focus for the breeding program in terms of which parameters to select for in order to decrease supplemental irrigation at the home- owner level. The limitation of the above work is that all studies were

conducted in a greenhouse or artificial conditions and may not accurately reflect a natural stand of turf. To help address the- se deficiencies additional graduate student projects are in pro- gress. One project is examining the field drydown response of 60 zoysiagrass lines. Those lines with the best and worst drydown responses have been selected for evaluation of root parameters so that variable root parameters can be associated with extended (maintenance of green color) or short drydown responses. This research is ongoing. Two additional graduate students are re-examining the lines

identified above with variable base transpiration rates and vari- able transpirational changes in response to extended drought


periods. These plants have now been planted in the field and one student will study the root architecture of these plants and one student will study the shoot architecture and transpiration rates. This data will be collected before, during and following periods of drought. This study will be mimicked in the greenhouse by growing the plants in plastic four foot deep tubes. One of our objectives is to gain an understanding of how confident the turfgrass breeding program can be by screening and selecting plants for their rooting characteristics using data from plants grown in tubes in a controlled green- house environment. Collaborating scientists helping to direct these projects include Dr. Bryan Unruh, Dr. Diane Rowland and Dr. John Erickson. In 2010, a unique five-year collaborative effort between

several university turfgrass breeding programs was created with an objective of identifying and releasing cultivars of four warm-season turfgrass species that have improved drought responses across a wide range of environments. The collaborating turfgrass breeding programs (and associated species) are the University of Florida (zoysiagrass), Texas A&M University (zoysiagrass and St. Augustinegrass), Oklahoma State University (bermudagrass), the University of Georgia (bermudagrass and seashore paspalum), and North Carolina State University (St. Augustinegrass). This project requires that each program share 80 lines of their respective species with all other locations. As an example, the University of Florida sent or planted 80 zoysiagrass lines to two locations in Texas, two locations in Georgia and one location each in Oklahoma, North Carolina and Florida. In 2011, all plants were shipped and planted. In 2012, irrigation will be withheld and data will be collected at all locations for drydown responses. Following the drydown, five lines from each institution and spe- cies will be selected for further study by each university’s turfgrass extension specialist (e.g. Dr. Bryan Unruh at the Uni- versity of Florida). At the end of the five year period it is antici- pated that cultivars of each species will be jointly released that are widely adapted and exhibit better drought responses than currently used cultivars. In addition to breeding for improved drought responses pro-

jects continue (with collaborators) that involve screening for insect responses (Dr. Eileen Buss and Dr. Rob Meaghar), dis- ease responses (Dr. Phil Harmon), and nematode responses (Dr. Billy Crow); and multi-location trials of zoysiagrass, St. Augustinegrass, centipedegrass and bahiagrass are planned or have been established in 2011. Dr. Crow recently graduat- ed a student that focused a tremendous amount of time to- wards a project jointly funded by FTGA, FGCSA and the

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