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Youping Sun and Alyssa Lanae Palmer

Ornamental grasses are popular in urban landscapes in Utah and the Intermountain West United States, one of the driest and fastest growing regions in the United States. This experiment evaluated the responses of five ornamental grass species [blue grama (Bouteloua gracilis), indian sea oats (Chasmanthium latifolium), ‘Blue Dune’ sand ryegrass (Leymus arenarius), pink muhly grass (Muhlenbergia capillaris), ‘Foxtrot’ fountain grass (Pennisetum alopecuroides)] and two ornamental grasslike species [fox sedge (Carex vulpinoidea), common rush (Juncus effusus)] to saline irrigation water in a greenhouse. Plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m–1 (control) or saline solutions at an EC of 5.0 or 10.0 dS·m–1. At the first harvest (9 weeks after the initiation of treatment), sand ryegrass, pink muhly grass, and fountain grass irrigated with solutions at an EC of 5.0 and 10 dS·m–1 had good visual quality with no or minimal foliar salt damage; however, the remaining species exhibited slight or moderate foliar salt damage. There were no significant differences in shoot dry weight (DW) among treatments within any species, except fox sedge and fountain grass. At the second harvest (18 weeks after the initiation of treatment), sand ryegrass, pink muhly grass, and fountain grass still had no or minimal foliar salt damage, and indian sea oats and fox sedge exhibited slight or moderate foliar salt damage. Compared with the control, all species irrigated with solutions at an EC of 10.0 dS·m–1 had reduced shoot DWs with the exception of blue grama. However, only common rush and pink muhly grass irrigated with solutions at an EC of 5.0 dS·m–1 had lower shoot DWs than the control. These results demonstrated that seven ornamental grass or grasslike species had a very strong tolerance to the salinity levels used in the 4-month experiment. Although plant growth was inhibited as a result of saline irrigation, plant visual quality of sand ryegrass, pink muhly grass, and fountain grass was still acceptable. These three species appear to be more suitable for landscapes in which saline irrigation water is used. Further research is needed to evaluate more ornamental grasses for landscapes in salt-prone areas and nearby coastal regions.

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Youping Sun, Genhua Niu, and Christina Perez

Salt tolerance of seven Texas Superstar® perennials [Malvaviscus arboreus var. drummondii (Turk’s cap), Phlox paniculata ‘John Fanick’ (‘John Fanick’ phlox), Phlox paniculata ‘Texas Pink’ (‘Texas Pink’ phlox), Ruellia brittoniana ‘Katie Blue’ (‘Katie Blue’ ruellia), Salvia farinacea ‘Henry Duelberg’ (‘Henry Duelberg’ salvia), Salvia leucantha (mexican bush sage), and Verbena ×hybrida ‘Blue Princess’ (‘Blue Princess’ verbena)] was evaluated in a greenhouse experiment. Plants were irrigated with a nutrient solution at electrical conductivity (EC) of 1.1 dS·m−1 (control) or a salt solution at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) for 8 weeks. ‘John Fanick’ and ‘Texas Pink’ phlox plants in EC 5 had severe salt foliage damage, while those in EC 10 were died. Mexican bush sage in EC 10 had severe salt foliage damage. Turk’s cap, ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and ‘Blue Princess’ verbena had minor foliar damage regardless of treatment. EC 5 reduced the shoot dry weight (DW) by 45% in ‘Texas Pink’ phlox and 11% to 18% in ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and mexican bush sage, but did not impact the shoot DW of Turk’s cap and ‘John Fanick’ phlox. EC 10 further decreased the shoot DW of ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and mexican bush sage plants by 32%, 29%, and 56%, respectively. EC 5 decreased leaf net photosynthesis (Pn) of ‘Texas Pink’ phlox and mexican bush sage, while EC 10 reduced Pn of all species except ‘Henry Duelberg’ salvia and ‘Blue Princess’ verbena. ‘Katie Blue’ ruellia and ‘Blue Princess’ verbena had relatively lower leaf Na concentration and ‘John Fanick’ phlox, ‘Texas Pink’phlox, and mexican bush sage had higher leaf Cl concentrations. In summary, Turk’s cap, ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and ‘Blue Princess’ verbena were the most tolerant perennials, and ‘John Fanick’ phlox, ‘Texas Pink’ phlox, and mexican bush sage were the least tolerant to salinity.

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Youping Sun, Donglin Zhang, and John Smagula

Nodal segments containing one axillary bud (1 to 1.5 cm) were disinfected using 10% bleach and were established on a Murashige and Skoog (MS) medium without hormones at 27 °C and with a 16-h photoperiod. The sprouted shoots (≈1.0 cm) were cultured on a MS medium supplemented with 6-benzylaminopurine (BAP), kinetin (KIN), or zeatin (ZT) at 2.3, 4.5, 9.1, or 18.2 μM. After 38 d, ZT and BAP significantly induced multiple shoot formation with multiplication rates of 4 to 6, whereas the multiplication rate of KIN was less than 2. Shoots cultured on ZT grew significantly taller than those on BAP and KIN. The height of the longest shoots treated with ZT was 4.6 cm, which was 1.6 to 2.2 times greater than those treated with BAP or KIN. To induce rooting, shoots (≈2 cm) were subcultured on one-fourth strength MS (1/4 MS) medium containing either 3-indolebutyric acid (IBA) or 1-naphthylacetic acid (NAA) at 2.6, 5.1, or 10.3 μM. Adventitious roots formed in vitro after 2 to 4 weeks. IBA at 10.3 μM produced the best rooting (100%) compared with other treatments after 38 d of culture. The average number of roots per shoot for IBA was ≈15, which was 1.6 to 3.1 times as many as that of other treatments. All rooted plantlets were then transplanted into a mix of peatmoss and perlite (1:1 v/v) and acclimatized in a mist system. Average plantlet survival was 73.6% after 35 d. After acclimatization, they were grown in a pot with Metro-mix under greenhouse conditions for 10 weeks where 95% of plants survived and grew up to 6.8 cm high. The micropropagation procedure, i.e., nodal segments containing one axillary bud proliferated on MS with 4.5 μM ZT followed by in vitro rooting on 1/4 MS plus 10.3 μM IBA, could be used for commercial mass production of new inkberry cultivars.

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Youping Sun, Joseph Masabni, and Genhua Niu

Excessive salinity in soil and irrigation water in combination with waterlogging in coastal regions can significantly reduce the productivity of many agricultural crops. To evaluate the plant growth responses to simulated seawater (SSW) flooding, seedlings of 10 vegetables (broccoli, chinese cabbage, chinese greens, cucumber, eggplant, kale, radish, ‘Red Crunchy’ radish, spinach, and tomato) were flooded with SSW at electrical conductivity (EC) of 44.0 ± 1.3 dS·m−1 or tap water at EC of 0.8 ± 0.1 dS·m−1 for 24 hours and grown subsequently for 2 weeks in a greenhouse. Chinese greens and cucumber plants died shortly after flooding with SSW, whereas other vegetables exhibited various degrees of visible salt damage. Chinese cabbage suffered the strongest reduction, whereas spinach, tomato, and eggplant exhibited the least decrease in dry weight (DW) due to SSW flooding in comparison with their perspective control. Two weeks after flooding treatment with SSW, net photosynthetic rate of broccoli, kale, spinach, and tomato was reduced by 43% to 67%, transpiration rate by 35% to 66%, and stomatal conductance (g S) by 51% to 82%. In summary, spinach, eggplant, and tomato were the most tolerant, whereas chinese cabbage, chinese greens, and cucumber were the least tolerant to SSW flooding.

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Shasha Wu, Youping Sun, and Genhua Niu

To provide more species for landscapes where poor-quality irrigation water is used, salt tolerance of commonly used landscape plants should be characterized. Nine ornamental species, including six herbaceous and three woody, were irrigated with nutrient solution at electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solution at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) for 8 weeks and their growth and physiological responses were determined. Although growth was reduced in orange peel jessamine (Cestrum ‘Orange Peel’) and mexican hummingbird bush (Dicliptera suberecta) as salinity increased, no obvious signs of stress or injury were observed, indicating that orange peel jessamine and mexican hummingbird bush were the most salt tolerant. Flame acanthus (Anisacanthus quadrifidus var. wrightii), rock rose (Pavonia lasiopetala), and ‘Dark knight’ bluebeard (Caryopteris ×clandonensis ‘Dark Knight’) had more growth reduction than that of orange peel jessamine and mexican hummingbird bush with minimal or no foliar damage in EC 5 and slight foliar damage in EC 10. Cardinal flower (Lobelia cardinalis) and mexican false heather (Cuphea hyssopifolia) exhibited mortality rates of 30% and 20%, severe foliar damage, and greater than 70% reduction in leaf area and dry weight in EC 10 compared with their respective controls. Although the growth reductions in butterfly blue (Scabiosa columbaria) were not as great as cardinal flower and mexican false heather, 40% of butterfly blue plants were dead with moderate foliar damage in EC 10. Therefore, cardinal flower, mexican false heather, and butterfly blue plants were considered as moderately salt sensitive. Eastern red columbine (Aquilegia canadensis) was the most salt sensitive among the species investigated with moderate foliar damage in EC 5 and all plants died in EC 10. Four out of the nine species tested had significant differences in net photosynthetic rate (Pn), stomatal conductance (g s), and/or relative chlorophyll content between the control and EC 10, and the difference varied with species. Shoot ion concentrations of the nine ornamentals were also affected by salinity levels and varied among species.

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Youping Sun, Guihong Bi, Genhua Niu, and Christina Perez

The goal of this experiment was to evaluate the efficiency of foliar application of dikegulac sodium on increasing the lateral branching of ‘Merritt’s Supreme’ bigleaf hydrangea (Hydrangea macrophylla). Plants were grown in greenhouses at two locations including El Paso, TX and Kosciusko, MS. Two weeks before application of dikegulac sodium, half of plants were hand-pinched leaving two nodes. Foliar spray of dikegulac sodium at 400, 800, or 1600 mg·L−1 was then applied to pinched and unpinched plants. There were two additional control treatments: pinched or unpinched without application of dikegulac sodium. Data were collected at 2 weeks, 6 weeks, 80 days, and 10 months after treatments. Bigleaf hydrangea plants exhibited severe phytotoxicity including interveinal chlorosis or bleaching of new growth at 2 weeks after application of dikegulac sodium with more pronounced symptoms at higher dikegulac sodium concentrations. The severity of phytotoxicity symptoms became less significant at 6 weeks after treatment. The effect of dikegulac sodium on bigleaf hydrangea plant growth, number of branches, and number of flowers depended on both locations and dosages. In El Paso, TX, dikegulac sodium at 800 or 1600 mg·L−1 inhibited bigleaf hydrangea plant growth at 6 weeks and 80 days after treatment, and this effect disappeared at 10 months after treatment. Dikegulac sodium at all tested dosages doubled or tripled the number of branches of pinched or unpinched bigleaf hydrangea, respectively, at 80 days after treatment. At 10 months after treatment, the number of branches and flowers of bigleaf hydrangea plants tended to increase, but was insignificant. In Kosciusko, MS, dikegulac sodium at 1600 mg·L−1 reduced the plant growth at 6 weeks after treatment. This treatment increased the number of branches and flowers of unpinched plants by 196% and 95% and pinched plants by 53% and 31%, respectively, at 10 months after treatment. Dikegulac sodium application could be used to increase number of branches and flowers and produce compact ‘Merritt’s Supreme’ bigleaf hydrangea. However, the efficacy varied with environmental conditions.

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Youping Sun, Genhua Niu, Joseph G. Masabni, and Girisha Ganjegunte

A greenhouse experiment was conducted to determine the relative salt tolerance of pomegranate (Punica granatum) cultivars. Twenty-two pomegranate cultivars were irrigated weekly with a saline solution at an electrical conductivity (EC) of 10.0 dS·m–1 for 4 weeks and subsequently with a saline solution at an EC of 15.0 dS·m–1 for another 3 weeks (salt treatment). Another group of uniform plants was watered with a nutrient solution without additional salts at an EC of 1.2 dS·m–1 (control). No visual foliar salt damage (leaf burn, necrosis, or discoloration) was observed during the entire experimental period; however, salt treatment impacted pomegranate growth negatively, with a large variation among cultivars. Salt treatment reduced shoot length by 25% and dry weight (DW) by 32% on average for all cultivars. Cluster analysis classified the 22 tested pomegranate cultivars in two groups. The group consisting of ‘Arturo Ivey’, ‘DeAnda’, ‘Kazake’, ‘Russian 8’, ‘Apseronski’, ‘Purple Heart’, ‘Carolina Vernum’, ‘Chiva’, ‘Kunduzski’, ‘Larry Ceballos 1’, ‘ML’, ‘Salavatski’, ‘Spanish Sweet’, and ‘Wonderful’ was more salt tolerant than the group including ‘Al-Sirin-Nar’, ‘Kandahar’, ‘Surh-Anor’, ‘Early Wonderful’, ‘Angel Red’, ‘Ben Ivey’, ‘Utah Sweet’, and ‘Mollar’. The sodium (Na) concentration in the leaf tissue of all 22 pomegranate cultivars was less than 1 mg·g–1 on a DW basis. All pomegranate cultivars in the salt treatment had an average leaf chloride (Cl) content of 10.03 mg·g–1 DW—an increase of 17% from the control. These results indicate that pomegranate plants have a strong capability to exclude Na and Cl accumulation in leaf tissue. In conclusion, the pomegranate plant is very tolerant to saline water irrigation up to an EC of 15 dS·m–1 with little foliar salt damage and a slight growth reduction. Investigation is needed to determine the effects of saline water on the fruit yield and nutritional quality of pomegranate.

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Lifei Chen, Youping Sun, Genhua Niu, Qiang Liu, and James Altland

Relative salt tolerance of eight Berberis thunbergii (japanese barberry) cultivars (B. thunbergii ‘Celeste’, ‘Kasia’, ‘Maria’, ‘Mini’, and ‘Talago’; B. thunbergii var. atropurpurea ‘Concorde’, ‘Helmond Pillar’, and ‘Rose Glow’) was evaluated in a greenhouse experiment. Plants were irrigated with nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions at an EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) once a week for 8 weeks. At 4 weeks after treatment, all barberry cultivars in EC 5 had minimal foliar damage with visual scores of 4 or greater (visual score 0: dead, 5: excellent). At 8 weeks after treatment, in EC 5, ‘Helmond Pillar’, ‘Maria’, ‘Mini’, and ‘Rose Glow’ plants exhibited slight foliar salt damage with an average visual score of 3.5, whereas ‘Celeste’, ‘Concorde’, ‘Kasia’, and ‘Talago’ had minimal foliar salt damage with an averaged visual score of 4.4. However, most barberry plants in EC 10 exhibited severe foliar salt damage 4 weeks after treatment with the exception of ‘Concorde’ and were dead 8 weeks after treatment. Compared with control, at the end of the experiment (8 weeks of treatments), shoot dry weight (DW) of ‘Celeste’, ‘Helmond Pillar’, ‘Maria’, and ‘Rose Glow’ in EC 5 was reduced by 47%, 47%, 50%, and 42%, respectively, whereas shoot DW of ‘Concorde’, ‘Kasia’, ‘Mini’, and ‘Talago’ in EC 5 did not change. In EC 10, shoot DW of ‘Celeste’, ‘Concorde’, ‘Kasia’, and ‘Talago’ was reduced by 75%, 35%, 55%, and 46%, respectively. The averaged sodium (Na) concentration of all barberry cultivars in EC 5 and EC 10 was 34 and 87 times, respectively, higher than the control, whereas leaf chloride (Cl) concentration of all barberry cultivars in EC 5 and EC 10 was 14–60 and 29–106 times, respectively, higher than the control. Growth, visual quality, and performance index (PI) were all negatively correlated with leaf Na and Cl content in all cultivars, suggesting that excessive Na and Cl accumulation in the leaf tissue led to growth reduction, salt damage, and death. In summary, ‘Concorde’, ‘Kasia’, and ‘Talago’ were relatively salt tolerant; ‘Helmond Pillar’, ‘Maria’, ‘Mini’, and ‘Rose Glow’ were relatively salt sensitive; and ‘Celeste’ was in between the two groups. Generally, barberry plants had moderate salt tolerance and can be irrigated with marginal water at an EC of 5 dS·m−1 or lower with slight foliar damage.

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Genhua Niu, Pedro Osuna, Youping Sun, and Denise S. Rodriguez

Ornamental chile peppers are popular bedding plants. As high-quality water supply becomes limited in many parts of the world, alternative waters such as municipal reclaimed water is encouraged to be used for landscape irrigation. The purpose of this study was to assess the relative salt tolerance of 10 cultivars of ornamental chile peppers by irrigating the mature plants with saline solutions and germinating seeds in saline substrate in a greenhouse. In the mature plant salt tolerance experiment, plants were irrigated with nutrient solution (no addition of salts, control) or saline solution at electrical conductance (EC) of 4.1 dS·m−1 or 8.1 dS·m−1 for 8 weeks. Plants in the EC of 4.1 dS·m−1 treatment did not have any foliar salt damage regardless of cultivar. At EC of 8.1 dS·m−1, ‘NuMex Memorial Day’ had the most severe foliar salt damage, whereas ‘NuMex April Fool’s Day’, ‘NuMex Cinco de Mayo’, ‘NuMex Thanksgiving’, and ‘NuMex Twilight’ had little or no foliar damage. Shoot dry weight (DW) reduction at EC of 8.1 dS·m−1 compared with control was smallest in ‘NuMex Thanksgiving’ (15%), whereas ‘NuMex Memorial Day’ had the greatest reduction of 74% followed by ‘NuMex Christmas’ of 61%. The highest shoot DW reduction in ‘NuMex Memorial Day’ coincided with lowest visual score, indicating that this cultivar was the least tolerant to salinity. The leaf Na+ and Cl concentrations increased dramatically with increasing EC of the irrigation water in all cultivars. The highest Na+ concentration of 10.9 mg·g−1 DW at EC of 8.1 dS·m−1 was observed in ‘NuMex Christmas’. The highest Cl concentration at EC of 8.1 dS·m−1 was found in ‘NuMex Memorial Day’ with 64.8 mg·g−1 DW, which was four times higher than the control. In the seedling emergence experiment, seeds of the 10 cultivars were germinated in substrate either moistened with reverse osmosis water (EC ≈0) or saline solution at EC of 17.1 dS·m−1. ‘NuMex Christmas’ and ‘NuMex Memorial Day’ had the lowest relative seedling emergence index, indicating that these two cultivars were the least tolerant to salinity during the seedling emergence stage. ‘NuMex Thanksgiving’ and ‘NuMex Cinco de Mayo’ had the highest relative seedling emergence index. Combining the results from both experiments, we concluded that ‘NuMex Cinco de Mayo’ and ‘NuMex Thanksgiving’ were the most tolerant cultivars, whereas ‘NuMex Christmas’ and ‘NuMex Memorial Day’ were the least tolerant ones.

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Xiaoya Cai, Youping Sun, Terri Starman, Charles Hall, and Genhua Niu

Earth-Kind® is a special designation given to select rose cultivars with superior stress tolerance (heat, drought, and pest tolerance) and outstanding landscape performance. The responses of Earth-Kind® roses to high salinity stress are unknown. A greenhouse study was conducted to evaluate 18 Earth-Kind® rose cultivars (Belinda’s Dream, Cecile Brunner, Climbing Pinkie, Ducher, Duchesse de Brabant, Else Poulsen, Georgetown Tea, La Marne, Madame Antoine Mari, Marie Daly, Monsieur Tillier, Mrs. Dudley Cross, Mutabilis, Perle d’Or, Reve d’Or, Sea Foam, Souvenir de St. Anne’s, and Spice) in College Station and 10 of the same 18 cultivars in El Paso in response to two salinity levels at electrical conductivity (EC) of 1.2 (control, nutrient solution) and 10.0 dS·m−1 (EC 10). In both locations, ‘Belinda’s Dream’ and ‘Climbing Pinkie’ in EC 10 had no or little reduction in shoot growth, flower number, and leaf SPAD readings. The net photosynthetic rate (Pn), stomatal conductance (g S), and transpiration (E) did not decrease in these two cultivars at EC 10 in El Paso. In College Station, ‘Mrs. Dudley Cross’, ‘Reve d’Or’, and ‘Sea Foam’ in EC 10 also had no or little reduction in shoot growth, flower number, and leaf SPAD readings. In both locations, ‘Cecile Brunner’ and ‘Else Poulsen’ in EC 10 had severe visual foliar salt damage, and they had the greatest reductions in shoot growth and flower number. In addition to these two cultivars, the lowest relative shoot dry weight (DW) and flower number was observed in ‘Madame Antoine Mari’, ‘Perle d’Or’, ‘Spice’, and ‘Souvenir de St. Anne’s’ in College Station. In summary, ‘Belinda’s Dream’, ‘Climbing Pinkie’, ‘ Mrs. Dudley Cross’, ‘Reve d’Or’, and ‘Sea Foam’ were the most salt-tolerant cultivars, whereas ‘Cecile Brunner’, ‘Else Poulsen’, ‘Madame Antoine Mari’, ‘Perle d’Or’, ‘Spice’, and ‘Souvenir de St. Anne’s’ were the least salt-tolerant among the cultivars investigated.