Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2010
Publication Date: 6/1/2010
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2279.pdf
Citation: Poss, J.A., Russell, W.B., Bonos, S.A., Grieve, C.M. 2010. Salt tolerance and canopy reflectance of Kentucky bluegrass cultivars. HortScience. 45(6):952-960. Interpretive Summary: Water resources used for turf grass operations are significant and being increasingly scrutinized. Programs for developing grasses that can withstand water and salinity stress are paramount to efficient irrigated turf operations. Kentucky bluegrass selections (Poa pratensis L.) screened previously for drought tolerance were evaluated for salinity tolerance with leaf spectral reflectance techniques. The ability to monitor or evaluate the efficiency of turf grass systems in saline areas can be dramatically improved by applying remote sensing principles. Remotely-sensed ground-based hyperspectral reflectance of six drought tolerant KBG clones at individual wavelengths ranging from the violet visible to the far infrared portion of the electromagnetic spectrum (350nm to 2500nm) were used to calculate vegetative indices that were significantly related with the salt tolerance rankings of the KBG cultivars. Vegetative indices calculated from grass sward reflectance were significantly sensitive to salinity-induced changes in grass canopies and were able to discriminate significantly between salt tolerant (‘Baron’, ‘Brilliant’, and ‘Eagleton’) and salt sensitive cultivars (‘Cabernet’, ‘Midnight’, and A01-856). Plant leaf reflectance measurements and calculated vegetative indices are able to rapidly estimate subtle changes in important plant growth variables useful to researchers, grass breeders, golf course superintendents, or turf grass managers.
Technical Abstract: Six cultivars or selections of kentucky bluegrass (Poa pratensis L.) were grown outdoors from vegetative clones in a gravelly sand medium from Apr. to Sept. 2005 in Riverside, CA, at soil water salinities ranging from 2 to 22 dS/m. Cultivars Baron, Brilliant, Cabernet, Eagleton, Midnight, and the selection A01-856, a ‘Texas’ x Kentucky bluegrass hybrid (P. arachnifera x P. pratensis), were evaluated for salt tolerance based on relative and absolute cumulative biomass production, growth rates, leaf chloride concentration, and hyperspectral ground-based remote sensing (RS) canopy reflectance measurements. Remotely sensed indices were linearly correlated with absolute biomass production. Three variations of a Normalized Difference Vegetation Index (NDVIred, NDVIprotein, and NDVIinfra) decreased with increasing salinity-induced changes in grass canopies. An index based on the red-edge inflection point increased (became less negative) with increasing salinity. A Floating Water Band Index decreased with decreased leaf moisture content related to increasing salinity but did not discriminate between cultivars. Shoot spreading rate and NDVIinfra were both related to shoot chloride concentration differences among the kentucky bluegrass (Poa pratensis L) (KBG) cultivars or selections. In theory, non-destructive RS monitoring of above-ground turf development, including NDVIinfra, coupled with measurement of leaf chloride concentrations could be useful in turf salt tolerance breeding programs. Salt tolerance rankings among the KBG cultivars varied depending on the evaluation methods and selection criteria used. Based on absolute and relative biomass, growth rate, and RS, cultivars Baron, Brilliant, and Eagleton were rated as more salt-tolerant than ‘Cabernet’, ‘Midnight’, and AO1-856.