Relative Salt Tolerance of 22 Pomegranate (Punica Granatum) Cultivars
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HORTSCIENCE 53(10):1513–1519. 2018. https://doi.org/10.21273/HORTSCI13362-18 Mediterranean countries, and the southwestern United States. Saline brackish groundwater, treated municipal or industrial effluents, and Relative Salt Tolerance of 22 recycled agricultural runoff water are the major alternative water sources for crop irrigation in Pomegranate (Punica granatum) many regions of the world, including those growing pomegranate (Qadir et al., 2008). These Cultivars water sources often contain high salt levels that are detrimental to many species. Salt damage Youping Sun depends on the levels of salts and the degree of Department of Plants, Soils and Climate, Utah State University, 4820 Old salt tolerance of crops. Therefore, the use of Main Hill, Logan, UT 84322 alternative waters for irrigation requires an adequate understanding of how salts impact Genhua Niu1 plant performance and soil characteristics. Department of Horticultural Sciences, Texas A&M AgriLife Research Center Limited literature shows that pomegran- ate is relatively tolerant to salt stress, with at El Paso, Texas A&M University System, 1380 A&M Circle, El Paso, TX variations among cultivars (Bhantana and 79927 Lazarovitch, 2010; El-Khawaga et al., 2013; Okhovatian-Ardakani et al., 2010). ‘Malas- Joseph G. Masabni Saveh’ pomegranate is less tolerant than Department of Horticultural Sciences, Texas A&M AgriLife Extension, Texas ‘Shishe-Kab’ (Khayyat et al., 2014). Irriga- A&M University System, 1710 FM 3053 N, Overton, TX 75684 tion with saline groundwater at 6.0 dS·m–1 increased Na and Cl accumulation in leaves; Girisha Ganjegunte reduced growth, flowering, and yield; and Department of Soil and Crop Sciences, Texas A&M AgriLife Research Center increased incidence of fruit cracking but did at El Paso, Texas A&M University System, 1380 A&M Circle, El Paso, TX not change the total sugar and acidity per- 79927 centages of fruit in 7-year-old ‘Manfalouty’, ‘Wonderful’, and ‘Nab-Elgamal’ pomegran- Additional index words. chloride, mineral nutrition, sodium exclusion, salinity ates, with different responses to saline water irrigation among cultivars (El-Khawaga Abstract. A greenhouse experiment was conducted to determine the relative salt tolerance et al., 2013). ‘Malas Shirin’ pomegranate of pomegranate (Punica granatum) cultivars. Twenty-two pomegranate cultivars were was tolerant up to 40 mM sodium chloride · –1 irrigated weekly with a saline solution at an electrical conductivity (EC) of 10.0 dS m for (NaCl) in 1:1 sand–perlite medium irrigated · –1 4 weeks and subsequently with a saline solution at an EC of 15.0 dS m for another 3 with complete Hoagland’s solution (Naeini weeks (salt treatment). Another group of uniform plants was watered with a nutrient et al., 2006). Okhovatian-Ardakani et al. · –1 solution without additional salts at an EC of 1.2 dS m (control). No visual foliar salt (2010) compared 10 Iranian commercial damage (leaf burn, necrosis, or discoloration) was observed during the entire experi- cultivars in a pot experiment irrigated with mental period; however, salt treatment impacted pomegranate growth negatively, with saline water at three levels of salinity (4, 7, or a large variation among cultivars. Salt treatment reduced shoot length by 25% and dry 10 dS·m–1) and found that salt tolerance is weight (DW) by 32% on average for all cultivars. Cluster analysis classified the 22 tested cultivar dependent, based on vegetative pomegranate cultivars in two groups. The group consisting of ‘Arturo Ivey’, ‘DeAnda’, growth and tissue Na and Cl concentrations. ‘Kazake’, ‘Russian 8’, ‘Apseronski’, ‘Purple Heart’, ‘Carolina Vernum’, ‘Chiva’, However, salt tolerance of many existing ‘Kunduzski’, ‘Larry Ceballos 1’, ‘ML’, ‘Salavatski’, ‘Spanish Sweet’, and ‘Wonderful’ cultivars in the United States is unknown. was more salt tolerant than the group including ‘Al-Sirin-Nar’, ‘Kandahar’, ‘Surh- Identifying salt-tolerant cultivars is of great Anor’, ‘Early Wonderful’, ‘Angel Red’, ‘Ben Ivey’, ‘Utah Sweet’, and ‘Mollar’. The importance in pomegranate production. The sodium (Na) concentration in the leaf tissue of all 22 pomegranate cultivars was less than aim of this study was to determine the relative · –1 1mgg on a DW basis. All pomegranate cultivars in the salt treatment had an average salt tolerance of 22 pomegranate cultivars · –1 leaf chloride (Cl) content of 10.03 mg g DW—an increase of 17% from the control. and their morphologic and physiologic re- These results indicate that pomegranate plants have a strong capability to exclude Na and sponses to saline water irrigation in green- Cl accumulation in leaf tissue. In conclusion, the pomegranate plant is very tolerant to house conditions. 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. Materials and Methods Plant materials. On 12 Mar. 2014, hard- wood cuttings (15 cm) in RL98 Ray Leach Pomegranate (Punica granatum, Lythra- a prominent increase in its consumption. In the Cone-tainers (SC10 Super, Stuewe and Sons., ceae) is a bushy shrub or small tree native to United States, California produces more than Inc., Tangent, OR; diameter, 3.8 cm; depth, Iran to the Himalayas in northern India. It has 90% of U.S. pomegranates, with 26,935 acres, 21 cm; volume, 164 mL) were received from been cultivated since ancient times throughout yielding 10.5 tons/acre according to the Cal- Marcelino’s Nursery (Tornillo, TX). On 5 the Mediterranean regions of Asia, Africa, and ifornia Department of Food and Agriculture May 2014, rooted cuttings were transplanted Europe. The fruit is rich in nutrition, with (Marzolo, 2015). in 5-L treepots (CP512CH, Stuewe and a unique flavor and taste, and medicinal Pomegranate plants adapt to a wide range Sons., Inc.; width, 12.7 cm; height, 30.5 properties. Recent scientific findings corrobo- of environmental and soil conditions, but cm) containing commercial substrate rate the traditional use of the pomegranate as perform best in areas with long, hot, and dry Metro-Mix 902 (50% to 60% composted a medical remedy for its antimicrobial prop- summers (Castle et al., 2011; Holland et al., bark, Canadian sphagnum peatmoss, vermicu- erties and for its health benefits, such as the 2009). Although it is an ancient crop, pome- lite and coarse perlite, starter nutrient charge ability to reduce blood pressure and to act granate has not been studied systematically with with gypsum and slow-release nitrogen, and against serious diseases such as diabetes and regard to cultural practices, fertilization require- dolomitic limestone; SunGroÒ,Agawam, cancer (Holland et al., 2009). Increased public ments, and salinity and drought tolerance. Sa- MA). All plants were grown in a greenhouse awareness of the benefit of the pomegranate, linity is a major environmental constraint in in El Paso, TX (lat. 31°41’45"N, long. particularly in the western world, has led to many pomegranate-growing areas such as India, 106°16’54"W; elevation, 1139 m) for 3 months HORTSCIENCE VOL. 53(10) OCTOBER 2018 1513 –2 –1 andirrigatedwithanutrientsolutionatanEC integral was 16.3 ± 3.2 mol·m ·d , and the state was calculated as Fv/Fm =(Fm –F0)/Fm. of 1.2 ± 0.1 dS·m–1 (mean and SD). The nutrient average relative humidity was 41.4 ± 17.2%. PI was calculated as follows (Strasser et al., solution was prepared by adding 15N–2.2P– Leachate EC. Leachate EC was deter- 2000; Ziv cak et al., 2008): 12.5K (Peters 15-5-15 Ca-Mg Special; Scotts, mined using the pour-through method 1 À ðÞF =F F À F 1 À V Marysville, OH) to reverse osmosis water at according to Cavins et al. (2008). In brief, PI ¼ 0 m · m 0 · j : –1 a nitrogen concentration of 150 mg·L . a saucer was placed under the container that M0=Vj F0 Vj Treatments. On 5 Aug. 2014, all plants had drained for at least 30 min right after were pruned to 30 cm tall. One week later treatment solution was applied. A total of Gas exchange. Leaf net photosynthesis (i.e., 11 Aug.), uniform plants were chosen 100 mL distilled water was poured on the (Pn), stomatal conductance (gS), and transpi- and assigned to two groups, and treatment surface of the substrate to get leachate in the ration (E) of three plants per treatment per was initiated. One group of plants was saucer. The leachate solution was collected cultivar were measured 1 week before har- irrigated weekly with a saline solution at an and tested using an EC meter. One plant per vest using a CIRAS-2 portable photosynthe- EC of 10.0 dS·m–1 (actual EC is 9.9 ± 0.4 treatment per cultivar was chosen for mea- sis system (PP Systems, Amesbury, MA) dS·m–1) for 4 weeks and subsequently with surement each time after treatment solutions with an automatic universal PLC6 broadleaf a saline solution at EC 15.0 dS·m–1 (actual EC were applied. Leachate EC readings were cuvette. A fully expanded leaf at the top of is 14.9 ± 0.6 dS·m–1) for 3 more weeks (salt averaged across cultivars. the plant was chosen for measurement. The treatment). This was because plants irrigated Growth parameters. At the end of the environmental conditions within the cuvette with saline solution did not show any dam- experiment, plant height (measured in centi- were maintained at a leaf temperature of ° age. A greater salinity treatment was needed meters) was recorded from the pot rim to the 25 C, a photosynthetic photon flux of m –2 –1 to distinguish the differences among the 22 top growing point. New growth of shoots 1000 mol·m ·s , and a carbon dioxide m –1 cultivars.