Drought tolerance and rooting capacity of Kentucky bluegrass cultivars
As freshwater resources for turfgrass irrigation become more limited, the development of drought-tolerant turf cultivars will be of great value to turf managers. The objective of the following research was to evaluate the field drought tolerance of Kentucky bluegrass (Poa pratensis L.) cultivars and compare their drought tolerance to rooting capacity. Fifty bluegrass entries were established in the field in Albany, OR and evaluated during drought stress (irrigation withheld) events in 2005 and 2006. Drought tolerance was measured, using digital image analysis, as the number of days until a cultivar reached 50% green tissue. In both years, there was a wide range of cultivar responses to drought, with some cultivars losing 50% green tissue 23 d after irrigation was withheld, while others maintained 50% green tissue up to 45 d after irrigation was withheld. Several cultivars, including Mallard, Moonlight, Prosperity, SR2284, Brilliant, and Diva, demonstrated significantly better drought tolerance than other cultivars. Twenty of the cultivars tested under field conditions were also screened for shoot and root growth in a greenhouse study. There was no correlation between shoot growth, root growth, or root:shoot ratios when compared to drought responses in the field. These results demonstrate that there is wide variability in drought tolerance of bluegrasses but factors other than rooting capacity appear to be responsible for those differences.