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Open access

Asmita Paudel, Youping Sun, Larry A. Rupp, and Richard Anderson

Open access

Triston Hooks, Genhua Niu, Joe Masabni, Youping Sun, and Girisha Ganjegunte

Pomegranate is a drought-tolerant and salt-tolerant crop. Its fruits contain high levels of phytochemicals that have many health benefits. Pomegranate has the potential to be an alternative crop in areas where water availability is limited, such as west Texas. However, more than 500 pomegranate varieties are estimated to exist worldwide, and little is known about which varieties are suitable for growing in the west Texas region. Therefore, the objective of this study was to evaluate the field performance of 22 pomegranate varieties, specifically based on phenology, resistance to sunburn, fruit split, fruit rot (resistance was calculated by subtracting the percent incidence by 100), yield, fruit phytochemicals, and Brix over the course of 3 years from 2016 to 2018. Cold damage, caused by below-freezing temperatures encountered from Nov. 2018 to Feb. 2019, was also evaluated in Apr. 2019. Our results showed significant varietal differences in nearly all response variables measured, indicating that varietal selection is important for pomegranate production for specific regions, such as west Texas. Leaf budding ranged from 47 to 62 days in 2016, 41 to 54 days in 2017, and 49 to 60 days in 2018. Anthesis ranged from 87 to 119 days in 2016, 80 to 94 days in 2017, and 92 to 114 days in 2018. Fruit resistance to split was broad and ranged from 7.3% to 79.1% in 2017 and from 14.2% to 99.7% in 2018. Fruit sunburn resistance ranged from 14.0% to 64.6% in 2017 and from 28.3% to 90.0% in 2018. Fruit heart rot incidence was nominal for all varieties. Total phenolic compound contents of the pomegranate fruit juice ranged from 0.81 to 1.52 mg GAE/mL, and the total antioxidant capacity ranged from 3.44 to 6.81 mg TE/mL. The yield per tree ranged from 1.00 to 7.96 kg in 2017 and from 0.81 to 10.26 kg in 2018. Brix ranged from 12.5% to 17.4% in 2017 and from 13.9% to 18.4% in 2018. Early winter below-freezing temperatures caused different degrees of cold damage; however, 5 of 22 varieties that originated from Russia did not show any cold damage. Results of a hierarchical cluster analysis based on the means of the key response variables of yield and Brix indicated that four varieties (Al-Sirin-Nar, Russian 8, Ben Ivey, and Salavatski) were notable for having both high yield and high Brix.

Open access

Shannon Rauter, Youping Sun, and Melanie Stock

In response to the growing demand for specialty cut flowers, floral crops are increasingly produced in semiarid areas where soil salinity can impact crop timing, reduce stem length, and decrease yield. The goal of this study was to investigate the salinity sensitivity of ‘Carmel’ and ‘Galilee’ anemone (Anemone coronaria), and ‘Amandine’ and ‘LaBelle’ ranunculus (Ranunculus asiaticus) with respect to physiological characteristics and marketable yield. Nine plants were irrigated weekly for 8 weeks with a nutrient (control) solution with an electrical conductivity (EC) of 0.5 dS⋅m–1 or saline solutions prepared by adding sodium chloride and calcium chloride dihydrate to a nutrient solution to obtain an EC of 1.5, 2.5, 3.5, 4.5, or 5.5 dS⋅m–1. Yield was evaluated by dividing stems into marketable and cull grades based on length and bloom quality. At the end of the study, the visual quality of the plants was scored, and gas exchange data were collected using a portable photosynthesis system. Cultivars of each species responded similarly, and marketable yields were low across all treatments, with average marketable yields (mean ± sd) of 1.7 ± 0.6 stems/plant for anemone and 1.2 ± 0.1 stems/plant for ranunculus. Visual quality (0–5 scale, with 0 = dead and 5 = excellent) decreased from 3 to 1 for anemone and 3 to 2 for ranunculus as EC increased from 0.5 to 4.5 dS⋅m–1 and 0.5 to 5.5 dS⋅m–1, respectively. Anemone leaf greenness decreased by 48%, stomatal conductance (g S) decreased by 79%, transpiration (E) decreased by 75%, and net photosynthesis (Pn) decreased by 92% when irrigation solution EC increased from 0.5 to 4.5 dS⋅m–1. The ranunculus growth index decreased by 17%, leaf greenness decreased by 45%, and E decreased by 23% as irrigation solution EC increased from 0.5 to 5.5 dS⋅m–1. Both anemone and ranunculus can be considered sensitive to salinity, indicating the importance of careful soil management in cut flower production systems in semiarid areas that are at risk for elevated soil salinity.

Free access

Youping Sun, Sarah A. White, David Mann, and Jeffrey Adelberg

Veratrum californicum, a native of the western United States, has long been used in herbal medicine and now also has potential pharmaceutical uses. As a result of a projected increasing demand for V. californicum biomass for pharmaceutical purposes, the development of a chilling protocol for enhanced cultivation efficiency is needed. To study the effects of chilling on the growth of V. californicum, field-collected rhizomes with attached bulbs and roots were potted, stored at 10 °C for 2 weeks, and subsequently chilled at 5 °C for 30 to 180 days before transfer to a greenhouse or growth room. Twenty plants were transferred to the greenhouse every 30 days to observe growth. Ten plants were harvested at shoot emergence and the remaining 10 when leaves were fully expanded. In addition, 10 plants were transferred from 5 °C to a growth room every 30 days where net photosynthetic rates were measured. Longer chilling duration correlated with a reduction in days to shoot emergence and leaf expansion. The net photosynthetic rates of V. californicum plants chilled for 120, 150, or 180 days were higher than those of plants chilled for only 30, 60, or 90 days. Plants exposed to longer chilling durations were taller and had larger, more numerous leaves. Interestingly, V. californicum shoot emergence was also observed in the dark at 5 °C after the bulbs had been stored for 210 days. Growth of the root systems of plants was also observed during chilling. In conclusion, chilling was necessary at 5 °C for a minimum of 120 days to force early emergence and vigorous growth of V. californicum.

Open access

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

Tatarian dogwood (Cornus alba) is an ornamental shrub with white fruits, creamy-white flowers, and red stems in fall through late winter and is widely used in residential landscape, public parks, and botanical gardens. Two greenhouse experiments were conducted to characterize the survival, morphological, aesthetic, and physiological responses of tatarian dogwood seedlings to salinity and drought stresses. In Expt. 1, tatarian dogwood seedlings grown in three soilless growing substrates (Metro-Mix 360, 560, and 902) were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solution (by adding calculated amount of sodium chloride and calcium chloride) at an EC of 5.0 or 10.0 dS·m−1 once per week for 8 weeks. Results showed that substrate did not influence the growth of tatarian dogwood seedling. All plants irrigated with saline solutions at an EC of 10.0 dS·m−1 died, whereas those irrigated with saline solutions at an EC of 5.0 dS·m−1 exhibited severe foliar salt damage with an average visual score of 1.0 (on a scale of 0 to 5, with 0 = dead and 5 = excellent without foliar salt damage). Compared with the control, saline solutions at an EC of 5.0 dS·m−1 reduced plant height and shoot dry weight (DW) by 50.8% and 55.2%, respectively. Relative chlorophyll content [soil plant analysis development (SPAD) reading], chlorophyll fluorescence (Fv/Fm), and net photosynthesis rate (Pn) also decreased when plants were irrigated with saline solutions at an EC of 5.0 and 10.0 dS·m−1. Leaf sodium (Na+) concentration of tatarian dogwood seedlings irrigated with saline solutions at an EC of 5.0 and 10.0 dS·m−1 increased 11 and 40 times, respectively, compared with the control, whereas chloride (Cl-) concentration increased 25 and 33 times, respectively. In Expt. 2, tatarian dogwood seedlings were irrigated at a substrate volumetric water contents (volume of water/volume of substrate, VWC) of 15%, 20%, 25%, 30%, 35%, 40%, or 45% using a sensor-based automated irrigation system for 60 days. Results showed that drought stress decreased plant growth of tatarian dogwood seedlings with a reduction of 71%, 85%, and 87% in plant height, leaf area, and shoot DW, respectively, when VWC decreased from 45% to 15%, but all plants survived at all VWC treatments. Significant reductions of photosynthesis (Pn), stomatal conductance (g S), transpiration rate (E), and water potential were also found in plants at a VWC of 15%, compared with other VWCs. However, SPAD readings and Fv/Fm of tatarian dogwood seedlings were similar among the VWCs. In conclusion, tatarian dogwood seedlings were sensitive to the salinity levels tested in this study but could survive at all tested substrate volumetric water contents and exhibited resistance to drought conditions.

Open access

Youping Sun, Genhua Niu, Haijie Dou, Christina Perez, and Lisa Alexander

Hydrangeas are popular landscape plants that are widely grown in many parts of the world. The objective of this study was to evaluate the salinity tolerance of three novel Dichroa ×hydrangea hybrids [Dichroa febrifuga ‘Yamaguchi Hardy’ × Hydrangea macrophylla ‘Hamburg’ (YH × Hamburg), Dichroa febrifuga ‘Yellow Wings’ ×Hydrangea macrophylla ‘Nigra’ (YW × Nigra), and Dichroa febrifuga ‘Yellow Wings’ ×Hydrangea macrophylla ‘Oakhill’ (YW × Oakhill)]. A 52-day greenhouse study was conducted by irrigating container-grown plants with nutrient solution at an electrical conductivity (EC) of 1.1 dS·m−1 (control) or saline solution at an EC of 5.0 dS·m−1 (EC 5) or 10.0 dS·m−1 (EC 10). At harvest, YH × Hamburg and YW × Nigra in EC 5 and EC 10 still exhibited good quality with average visual scores greater than 4.1 (0 = dead; 5 = excellent). For YW × Oakhill, moderate foliar salt damage was observed with an average visual score of 2.9 in EC 5 and 2.2 in EC 10. Compared with control, the shoot dry weight of YH × Hamburg, YW × Nigra, and YW × Oakhill in EC 5 reduced by 35%, 35%, and 55%, respectively, whereas that in EC 10 decreased by 58%, 58%, and 67%, respectively. Elevated salinity also decreased plant height, leaf area, and leaf greenness [Soil Plant Analysis Development (SPAD) readings]; chlorophyll fluorescence (Fv/Fm); performance index (PI); and net photosynthetic rate (Pn). All these responses might result from excess accumulation of sodium (Na+) and chloride (Cl) ions in hydrangea leaves. In this study, compared with control, leaf Na+ concentration of YH × Hamburg, YW × Nigra, and YW × Oakhill increased 11, 36, and 14 times, respectively, in EC 5, and 31, 53, and 18 times, respectively, in EC 10. Compared with control, leaf Cl concentration increased 4, 9, and 7 times in EC 5, and 10, 11, and 8 times in EC 10 for YH × Hamburg, YW × Nigra, and YW × Oakhill, respectively. Leaf nitrogen (N), phosphorous (P), potassium (K+), and iron (Fe3+) concentrations decreased at elevated salinity levels but did not cause any nutrient deficiency. In summary, the three Dichroa ×hydrangea hybrids exhibited different salinity tolerance: YH × Hamburg and YW × Nigra were more tolerant than YW × Oakhill. Salt-tolerant hydrangea hybrids should be chosen for landscape use if soil and/or irrigation water are salty.

Free access

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.

Full access

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.

Full access

Joseph Masabni, Youping Sun, Genhua Niu, and Priscilla Del Valle

Southern U.S. states such as Texas experience high temperatures and intense solar radiation during the summer production season. Use of shadecloth is common in Spain and other Mediterranean countries and is becoming popular with homeowners or small-acreage farmers in Texas. Little information is available on the applicability of using shadecloth on tomato (Solanum lycopersicum) and chili pepper (Capsicum annuum) in the warm climate of Texas. The effects of two shade nets differing in shading intensity on growth, chlorophyll fluorescence, and photosynthesis of ‘Celebrity’ tomato and ‘Sweet Banana’ chili pepper was investigated from May to Aug. 2014. Plants were grown in 50% shade, 70% shade, or full sun. Compared with the unshaded control, tomato grown in 50% shade had similar yield and shoot fresh and dry weight and less photochemical stress. The 50% shade reduced number and weight of unmarketable tomato fruit. Similar results were obtained with chili pepper except for lower numbers of marketable fruit. The 70% shade significantly reduced yield parameters of both tomato and chili pepper. Both 50% and 70% shadecloth reduced leaf temperatures of tomato and chili pepper with variable results in June and July. Growth index [(height + width 1 + width 2) ÷ 3] of tomato and chili pepper was the highest with 50% shade, the lowest with full sun, and intermediate with 70% shade. The maximum net photosynthetic rates (Pn) of tomato determined from a Pn to light response curve supported the results on growth and yield. However, the maximum Pn of chili pepper was higher in full sun treatment compared with 50% or 70% shade. The latter two were almost identical. This one growing season study indicated that shading at 50% benefits tomato and chili pepper production in west Texas by reducing heat stress; however, a shading percentage below 50% may be better.

Open access

Tingting Tong, Lili Shao, Zhonghua Peng, and Youping Sun