HORTSCIENCE 51(2):197–201. 2016. Asteraceae is an exceedingly large family of flowering plants widespread in the wild and landscape. Many aster species have been Response of 10 Aster Species to Saline studied for salt tolerance, and their responses to salinity are highly dependent on the Water Irrigation species. Plains zinnia (Zinnia grandiflora) plants all died at an EC of 7.3 dS·m–1, and Shasha Wu chocolate daisy (Berlandiera lyrata) had low College of Landscape Architecture, Fujian Agriculture and Forestry survival percentages and low foliar ratings at University, No. 15 Shangxiadian Road, Cangshan District, Fuzhou, Fujian EC of 5.5 and 7.3 dS·m–1 (Niu et al., 2012a). 350002, China; and Texas A&M AgriLife Research Center at El Paso, Texas Treasure flower (Gazania rigen), known as A&M University System, 1380 A&M Circle, El Paso, TX 79927 coastal gazania and naturalized on coastal dunes and roadsides in Australia, had 52.5% Youping Sun1 and Genhua Niu1 greater reduction of shoot DW at EC of –1 Texas A&M AgriLife Research Center at El Paso, Texas A&M University 12 dS·m compared with nonsalinized controls (EC of 0.8 dS·m–1), but had no other signs of System, 1380 A&M Circle, El Paso, TX 79927 stress or injury (Niu and Rodriguez, 2006). James Altland Seven cultivars of Zinnia marylandica all died when irrigated with EC at 6.0 and USDA-ARS, 1680 Madison Avenue, Wooster, OH 44691 8.2 dS·m–1 for 4 weeks (Niu et al., 2012b). Raul Cabrera Xeriscaping with native plants is promoted to conserve water, concurrent with use of Rutgers Agricultural Research and Extension Center, Rutgers University, reclaimed water (Meyer et al., 2009). 121 Northville Road, Bridgeton, NJ 08302 We investigated the relative salt tolerance of nine aster species and one hybrid, among Additional index words. Asteraceae, physiological response, salt tolerance which damianita (C. mexicana), gregg’s mist- Abstract. Asteraceae is one of the largest plant families with many important garden flower (E. greggii), blackfoot daisy (M. leu- ornamental species. Salt tolerance of 10 aster perennials was evaluated in a greenhouse canthum), aromatic aster (S. oblongifolium), experiment, including the following: damianita (Chrysactinia mexicana), gregg’s mist- four-nerve daisy (T. scaposa), skeleton-leaf flower (Eupatorium greggii), shasta daisy (Leucanthemum 3superbum ‘Becky’), blackfoot goldeneye (V. stenoloba), and zexmenia (W. daisy (Melampodium leucanthum), lavender cotton (Santolina chamaecyparissus), aromatic texana) are native to Texas. Copper canyon aster (Symphyotrichum oblongifolium), copper canyon daisy (Tagetes lemmonii), four- daisy (T. lemmonii) is distributed in the nerve daisy (Tetraneuris scaposa), skeleton-leaf goldeneye (Viguiera stenoloba), and mountains of southern Arizona and adjacent zexmenia (Wedelia texana). Plants were irrigated with nutrient solution at electrical northern Mexico. Like many perennials native conductivity (EC) of 1.2 dS·mL1 (control) or saline solutions at EC of 5.0 or 10.0 dS·mL1 to southwestern United States, especially in (EC 5 or EC 10) for 5 weeks. Upon termination, growth parameters, foliar salt damage, New Mexico or Texas, most of the species relative chlorophyll content [Soil-Plant Analysis Development (SPAD) readings], and aforementioned are considered drought toler- mineral concentration were measured. Gregg’s mistflower, skeleton-leaf goldeneye, and ant (Lady Bird Johnson Wildflower Center, lavender cotton were the most salt-tolerant species with less reductions in shoot dry weight 2015); however, their salt tolerance is un- (DW) in both EC 5 and EC 10. Considering the relatively severe foliar salt damage (visual known. Shasta daisy (Leucanthemum quality score of 3.1 and 2.7 at EC 5; 2.4 and 1.6 at EC 10) and mortality rate (10% and ·superbum ‘Becky’) is perhaps the most 40%) in EC 10, aromatic aster and zexmenia should be avoided where poor quality water popular shasta daisy in the United States may be used for irrigation. Gregg’s mistflower and skeleton-leaf goldeneye had relatively because of its sturdy habit and garden de- lower leaf sodium (Na) concentrations suggesting that both species can selectively exclude pendability (Hawke, 2007). Lavender cotton Na. Damianita and the four daisies, i.e., blackfoot daisy, copper canyon daisy, four-nerve (S. chamaecyparissus) is also a drought- daisy, and shasta daisy, were salt sensitive as evidenced by their greater growth reduction, tolerant border, foundation, rock garden, and foliar salt damage, and high Na and chlorine (Cl) accumulation in leaves, and should be seashore material; however, little is known on avoided in landscapes where poor quality water may be used for irrigation. its response to salinity. There is little research- based knowledge about the responses of the aforementioned aster perennials to salinity. Water shortages and poor water quality climate changes (Cai et al., 2014a). Urban The purposes of this study were to determine are critical challenges to gardening and landscape irrigation with alternative water the relative salt tolerance by quantifying and landscaping in many regions of the world sourcessuchasmunicipalreclaimedwateris comparing the responses of shoot growth, and will continue to be a serious issue due to commoninaridandsemiaridregions number of flowers, DW, visual quality, chlo- (Grieve, 2011). A potential problem of using rophyll content, and mineral concentration of reclaimed water is elevated salt levels, these widely used aster perennials to elevated which adversely affects plant growth, de- salinity in a greenhouse experiment. Received for publication 19 Nov. 2015. Accepted for publication 6 Jan. 2016. velopment, and causes foliar salt injury on This research is supported by a Specific Coopera- sensitive plants (Cai et al., 2014b; Niu et al., Materials and Methods tive Agreement from Department of Agriculture 2012a; Veatch-Blohm et al., 2014). Unlike (USDA), Agricultural Research Service, the fruits and vegetables where maximizing Plant materials and growing conditions. USDA National Institute of Food and Agriculture yield is the ultimate goal, the maintenance Rooted cuttings of the 10 species of Aster- Hatch project TEX090450, and Texas A&M Agri- of good aesthetic appearance and blemish- aceae mentioned above were received from Life Research. free foliar tissue are important for orna- Southwest Perennials (Dallas, TX) on 18 The content is solely the responsibility of the mental plants (Niu and Cabrera, 2010). Sept. 2014. Uniform plants were trans- authors and does not necessarily represent the Therefore, it is important to identify salt- planted into 3.9-L pots with equal amount official views of the funding agencies. Shasha Wu was a visiting scholar at Texas A&M AgriLife tolerant plants for areas where poor quality of Metro-Mix 360 (Sun Gro Horticulture, Research Center at El Paso financed by China water may be used for irrigation to conserve Bellevue, WA) on 6 Oct. and placed in the Scholarship Council, China. high-quality potable water, while maintain- greenhouse in El Paso, TX (31°45#31##N/ 1Corresponding author. E-mail: Youping.sun@ag. ing an aesthetically appealing landscape 106°29#11##W). Two weeks after transplant- tamu.edu or [email protected]. (Niu and Rodriguez, 2006). ing, saline water irrigation treatment was HORTSCIENCE VOL. 51(2) FEBRUARY 2016 197 initiated. Before treatment, all plants were according to their morphological character- and reported on a dry plant basis as described well irrigated with a nutrient solution with an istics (>10 cm for gregg’s mistflower; >5 cm by Isaac and Johnson (1975). EC of 1.2 dS·m–1, which was made by adding for damianita, blackfoot daisy, aromatic as- Statistical analysis. A two-way analysis 1g·L–1 15N–2.2P–12.5K (Peters 15-5-15 Ca- ter, and skeleton-leaf goldeneye; >3 cm for of variance was used to test the effects of soil Mg Special; Scotts, Marysville, OH) to re- lavender cotton; and >2 cm for zexmenia). salinity and species on plant growth. Means verse osmosis water. The average air The first and second branches >5 cm were separation among treatments was conducted temperature in the greenhouse was 26.8 °C/ counted for copper canyon daisy. Flowering using Tukey’s honest significant difference 21.5 °C (day/night). The average daily light characteristics were also quantified by count- multiple comparison. Relative shoot DW was integral was 12.2 mol·m–2·d–1, and the aver- ing the number of flower buds, open flowers, calculated for each plant in EC 5 or EC 10 age relative humidity was 40.4% during the and faded flowers (Niu et al., 2013). Thereafter, treatment as: experiment period. all aboveground parts (including stems, leaves, Relative shoot DW ð%Þ Experimental design and treatments. The and flowers) were harvested and DW was experiment used a split-plot design with the determined after oven-drying at 70 °Cfor4d. ¼ðShoot DW in control salinity treatment as the main plot and 10 Foliar salt damage evaluation. Foliar salt À Shoot DW in salt treatmentÞ species as the subplot with 10 replications per damage was rated by giving a visual score =Shoot DW in control · 100% treatment per species. Saline solutions at EC based on a reference scale from 0 to 5, where of 5.0 dS·m–1 (EC 5) and 10.0 dS·m–1 (EC 10) 0 = dead; 1 = over 90% foliar damage (salt Similarly, relative values for height, were made by adding 1.20 g·L–1 sodium damage: burning, necrosis, and discolor- crown diameter, number of shoots and chloride (NaCl) and 1.16 g·L–1 calcium chlo- ation); 2 = moderate (50% to 90%) foliar flowers, and DW were calculated. These –1 –1 ride (CaCl2), and 2.80 g·L and 2.67 g·L damage; 3 = slight (<50%) foliar damage; 4 = relative values were used as salt tolerance CaCl2, respectively, to the nutrient solution good quality with minimal foliar damage; indexes for hierarchical cluster analysis mentioned above.