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Open access

Jiaqi Xia and Neil Mattson

Common ice plant (Mesembryanthemum crystallinum L.) is a novel edible succulent plant with savory flavor. It has epidermal bladder cells (EBCs) that store water and sodium chloride (NaCl) located on the epidermis of the leaves and stems. Ice plant is an obligatory halophyte that requires NaCl for optimum growth. The objective of this study was to determine the impact of NaCl on growth of ice plant for hydroponic production as an edible leafy green and to quantify the ability of ice plant to take up NaCl from the environment. Four-week-old seedlings of ice plant were transplanted into hydroponic systems, established for 1 week, and given five NaCl treatments [0 M (control), 0.05 M, 0.10 M, 0.20 M, 0.40 M NaCl]. Sequential destructive harvests to determine plant growth occurred at day 7, 14, and 21 after NaCl treatment. The 0.05 M NaCl had the greatest stimulating effect on biomass, increasing total fresh weight (FW) by 173% and shoot FW by 193% compared with the control plants. The 0.10 M NaCl also had stimulating effect as compared with 0 M, but plants were not as large as those receiving 0.05 M NaCl. The 0.20 M NaCl had little effect on plant growth compared with the control. The 0.40 M NaCl had a strong stunting effect on plant growth. All plants treated with NaCl had less root weight than the control, and higher NaCl concentration resulted in greater reduction in root weight. However, for the 0.05 and 0.10 M treatment, the gain in shoot weight exceeded the loss in root weight. Plants gained or lost water in a faster rate than dry mass, which resulted in larger differences among treatments in FW than in dry weight (DW). Plants treated with higher NaCl concentrations developed fewer, smaller, and thicker leaves but contained more EBCs per unit leaf surface area. There was high Na and Cl accumulation in leaf tissues of all salt-treated plants (e.g., 180,507 mg·kg−1 Na and 125,084 mg·kg−1 Cl in the 0.05 M treatment vs. 13,558 mg·kg−1 Na and 12,991 mg·kg−1 Cl in the 0 M treatment). This indicated potential for bioremediation of saline soil or hydroponic water. Concentrations of macronutrients such as nitrogen (N), phosphorus (P), calcium (Ca), magnesium (Mg), and sulfur (S) were reduced when plants received increasing NaCl treatments. In general, this study showed that growth of ice plant benefited from 0.05 and 0.10 M NaCl additions to the hydroponic nutrient solution. Ice plant deserves further work on its ability to reduce Na and Cl from accumulating in recirculating hydroponic nutrient solution.

Open access

Kaitlin A. Hopkins, Michael A. Arnold, Charles R. Hall, H. Brent Pemberton, and Marco A. Palma

Variation in floral characteristics and growth habits within the native range of the North American wildflower Ratibida columnifera (Nutt.) Wooton & Standl. suggests potential for breeding and selection efforts to develop improved cultivars for commercial and residential landscapes. Experiments in seed propagation were performed to enable perpetuation of unique germplasms. Overnight hydration, storage condition variations, stratification and scarification, and seed maturation effects were assessed to determine impacts on viability and percent germination. Overnight hydration had no impact on percent germination. Germplasm had a significant effect on germination for all remaining experiments. Seed maintained viability at the same rate through 18 months, when slight reductions were noted. Cold storage at 3 °C had no effect on viability or percent germination of dry seed compared with storage at 23 °C. All three germplasms exhibited increased percent germination with some stratification period, and declined significantly in percent germination with all acid scarification treatments. Experiments indicated that most germplasms benefit from between 30 to 60 days of cold, moist stratification. There was a significant interaction effect among germplasms, location on the inflorescences, and maturity stages for R. columnifera. Data suggest that seed should be harvested as close as possible to when natural dispersal would occur for optimum germination. The degree of improvement in viability and percent germination associated with harvesting at various developmental stages, seed pretreatments, and storage conditions suggests that to achieve germination success, pretreatments should be used for propagation of seed from mature inflorescences and that variation can be expected within different genotypes of this species.

Open access

Justin J. Lombardoni, Josh A. Honig, Jennifer N. Vaiciunas, Ronald S. Revord, and Thomas J. Molnar

The perennial stem canker disease eastern filbert blight (EFB), caused by Anisogramma anomala, is devastating to most trees of European hazelnut (Corylus avellana), as genetic resistance is rare in the species. The pathogen is harbored by the wild American hazelnut (Corylus americana) found throughout much of eastern North America. Wild American hazelnut is generally resistant or tolerant to EFB, and is fully cross compatible with C. avellana, the species grown commercially for its nuts, making it a valuable resource for disease resistance breeding. The objective of this study was to identify quantitative trait loci (QTLs) associated with EFB resistance and tolerance in these two species. Three unrelated EFB-resistant C. americana selections [Oregon State University (OSU) 533.069 from Pennsylvania, OSU 403.040 from Nebraska, and OSU 557.122 from Wisconsin] were crossed with C. avellana ‘Tonda di Giffoni’ (TdG), a cultivar from Italy known to be tolerant of EFB. Their progenies, each containing 124 trees, were exposed to A. anomala through field inoculations and natural spread over 7 years, then each tree was evaluated for cumulative disease response. Results showed that disease response of all three populations exhibited a roughly normal distribution, indicating that resistance/tolerance was under multigenic control. An average of 2869 total markers were used to construct each population’s linkage map following genotyping, which included an average of 121 published simple sequence repeat markers to anchor linkage groups (LGs) to those of previous studies. Linkage maps were constructed for each parent of each population and used to map QTLs associated with EFB response. The subsequent analysis resolved five EFB-related QTLs across the three populations, highlighting three genic regions. Unexpectedly, only one QTL was identified from one of the three resistant C. americana parents, located on LG11 of the map of OSU 403.040, whereas three QTLs were found in a similar region on LG10 across the three maps of TdG, and a fifth QTL was found on LG6 of one TdG map. The lack of strong QTLs identified from the three EFB-resistant C. americana parents suggests that their resistance may be highly quantitative and not resolved within the constraints of this study. In contrast, tolerance from TdG appears to be conferred by a limited number of genes with relatively strong effects. Based on prior mapping work in European and American hazelnut where R genes have been located on LG2, LG6, and LG7, the QTLs associated with resistance/tolerance on LG10 and LG11 represent novel resistance regions. These QTLs present new targets for marker aided breeding, especially when pyramiding EFB resistance genes is a goal.

Open access

Kaitlin A. Hopkins, Michael A. Arnold, Charles R. Hall, Brent Pemberton, and Marco A. Palma

Variation in floral characteristics and growth habits within the native range of the North American wildflower Ratibida columnifera (Nutt.) Wooton & Standl. suggest potential for breeding and selection efforts to develop improved cultivars for commercial and residential landscapes. Toward that end, experiments in vegetative propagation were performed to enable perpetuation of unique germplasm. Stem development stage, applications of auxin, genotypic variation, and the effects of bottom heat applications were assessed to determine impacts on rooting percentages and adventitious root system quality measures. Younger apical stem sections rooted more readily and produced better quality root systems than more lignified basal stem cuttings. Optimal rooting percentages and rooted cutting quality ranged from 0.10% to 0.30% IBA (indole-3-butyric acid) quick dips, with 0.30% being optimal for most genotypes. Application of 26 °C bottom heat improved rooting ability in both cool and warm seasons compared with ambient and bottom heat of 32 °C. Bottom heat of 32 °C improved most rooting measures over ambient during the cool season, but not during the warm season. The degree of improvement in adventitious rooting associated with various developmental stage, auxin quick dips, and bottom heating varied among accessions of R. columnifera, suggesting that adventitious rooting characteristics should be evaluated as a selection criterion for cultivar development within this species.

Open access

Sabahudin Hadrović, Filip Jovanović, Sonja Braunović, Tatjana Ćirković Mitrović, Ljubinko Rakonjac, Mersida Jandrić, and Dina Hadrović

To select softwood broadleaves for biomass cropping, a study of the carbon and nitrogen content of the bark and wood of six softwood broadleaves in southwestern Serbia was conducted. Compared with white willow, european aspen, common alder, black poplar, and silver birch, goat willow has a high potential for carbon storage in bark and wood, representing a promising softwood broadleaf for biomass production.

Open access

Suzette P. Galinato, Aidan Kendall, and Carol A. Miles

Growers need reliable information on costs and returns they can expect for a cider apple (Malus ×domestica) orchard suitable for mechanization because specialty cider apples can only be used for making cider, and returns are expected to be lower than for fresh table apples. This study estimates the costs, returns, and net profit that growers may realize by planting cider apples in either a freestanding or tall spindle system that use a mechanical harvester (both systems) and mechanical hedger (tall spindle system only). Results show that both production systems have positive net returns during full production, and their respective break-even returns are lower than the current market price, demonstrating that both systems are potentially profitable investments. Results also show that the tall spindle system is potentially more profitable due to the advantages of earlier start of fruiting and higher crop yield. The estimated net returns of the tall spindle system during full production are nearly 4 times higher than that of a freestanding system. At a discount rate of 10%, the net present value (NPV) of the tall spindle system is positive and payback period is 13 years, whereas the NPV of the freestanding system is negative. The discount rate represents the time value of money and reflects the perception of risk for the investment. The break-even discount rates (i.e., NPV = 0) are ≈6.88% for the freestanding system and 10.78% for the tall spindle system. Sensitivity scenarios found that when all else was constant, profitability increased as market price, crop yield, and production area increase and also when the cost of the harvester decreased. Because mechanical harvesters are expensive, profitability tends to be more favorable for larger farms due to economies of scale. Also, a high picking efficiency is important because fruit that falls on the ground is considered crop yield loss and reduces the gross income from cider apples.

Open access

Rongrong Duan, Deke Xing, Tian Chen, and Yanyou Wu

High- and low-affinity transport systems are the main pathways for the transportation of NO3 and NH4 + across intracellular membranes. NO3 and NH4 + are assimilated through different metabolic pathways in plants. Fifteen ATP molecules are hydrolyzed in the metabolic process of NO3 ; however, only five ATP molecules are hydrolyzed in that of NH4 +. In this research, seedlings of Iris pseudacorus and Iris japonica were used as the experimental materials in the NO3 :NH4 + = 30:0, NO3 :NH4 + = 28:2, NO3 :NH4 + = 27:3, NO3 :NH4 + = 15:15, NO3 :NH4 + = 3:27, and NO3 :NH4 + = 0:30 treatments at the 7.5 mmol·L−1 the total nitrogen content (TN). The intracellular free energy was represented by physiological resistance (R) and physiological impedance (Z) according to the Nernst equation and could conveniently and comprehensively determine the cellular metabolic energy (GB). The maximum absorption rate (Vmax) and Michaelis constant (Km) for NH4 + and NO3 uptake were calculated according to the kinetic equation. The results showed that the cellular metabolic energy (GB) of I. pseudacorus was 1 to 1.5 times lower than that of I. japonica at each treatment on the 10th day. The GB values of I. pseudacorus and I. japonica seedlings increased with increasing NH4 + concentration. However, there was a turning point at the NO3 :NH4 + = 15:15 treatment for the cellular metabolic energy of I. pseudacorus and I. japonica. Correlation analysis showed that the value of cellular metabolic energy was negatively correlated with the Vmax and Km for NO3 uptake, whereas it was positively correlated with that for NH4 + uptake. These results demonstrate that the NO3 :NH4 + = 27:3 treatment level was the most suitable for I. pseudacorus and I. japonica. This indicates that the greater cellular metabolic energy is the most suitable for plant growth when the concentration of ammonium or nitrate had no significant difference at treatment. These results provide a simple and rapid solution for removal of nitrogen by determination of cellular metabolic energy.

Open access

Xiangguang Duan, Wei Liu, Xiaojing Wang, Lixia Zhang, Shuguang Liu, Lili Guo, Dalong Guo, and Xiaogai Hou

Paeonia ostii T. Hong & J. X. Zhang is a perennial oil and medicinal plant with great importance as well as landscaping. P. ostii is being extensively planted in China, but the soil fertility limits the yield and quality. There is little information available on the effects of phosphorus fertilization on productivity, physiological characteristics, and seed yield and quality. This study investigated the influence of different phosphorus levels, 0 kg·hm−2 (CK), 90 c−2 (P1), 135 kg·hm−2 (P2), 180 kg·hm−2 (P3), 225 kg·hm−2 (P4), and 270 kg·hm−2 (P5), on the photosynthesis, morphology, physiological parameters, and yield of P. ostii. The results indicated that the net photosynthetic rate, stomatal conductance (g S), and transpiration rate of P. ostii increased significantly with the application of P4, which increased by 34.77%, 65.72%, and 21.00% compared with CK, respectively. Simultaneously, the contents of soluble sugar, soluble protein, and photosynthetic pigment in P4 were the highest compared with other treatments. In addition, thousand-grain weight (326.4 g) and seed yield per plant (37.33 g) of P4 were significantly higher than the control. However, the total amount of unsaturated fatty acids in P4 was lower compared with other treatments. The indexes of high correlation coefficients with Dim 1 and Dim 2 were g S and superoxide dismutase (SOD), respectively. The results showed that phosphorus levels improved plant photosynthetic capacity and increased antioxidant capacity as well as seed yield. Furthermore, phosphate fertilizer had significant effects on the oil composition. Moreover, the effect of phosphorus application rate on the growth index of P. ostii was greater than that of the physiological index.

Open access

Charles F. Forney, Kristen Cue, and Sherry Fillmore

The protrusion of sprouts is a major cause of loss of dry onions (Allium cepa L.) during extended storage. Sprouting is conventionally suppressed by treating onions with maleic hydrazide (MH) before harvest. More recently, ethylene was reported to inhibit sprout growth in stored onions, but commercial use of ethylene has been limited. Therefore, the objective of this study was to assess the effectiveness of ethylene on sprout suppression of five commercial cultivars of onions during storage and compare its effectiveness with and without MH treatment. Onions treated with MH were stored for up to 9 months at 1 °C in atmospheres with and without ethylene in a series of experiments conducted over six seasons. Differences in sprout elongation and protrusion were observed during storage in air among the five cultivars. Storage in ethylene was effective in inhibiting sprout elongation and root growth of onion bulbs in all cultivars, with concentrations of 7 µL·L−1 ethylene being more effective than 1 µL·L−1 ethylene. Delaying application of ethylene by 4 months was less effective in inhibiting sprout elongation than continuous treatment. Ethylene provided greater sprout suppression than MH treatments alone and could serve as a replacement for MH.

Open access

Phillip A. Wadl, Livy H. Williams III, Matthew I. Horry, and Brian K. Ward

The yield and insect resistance of 12 sweetpotato (Ipomoea batatas) clones grown in two different production systems (organic black plastic mulch and conventional bare ground) were evaluated in 2016 and 2017 in coastal South Carolina. Significant differences in total storage root yield, marketable storage root yield, U.S. No. 1 storage root yield, and percent of U.S. No. 1 storage roots in all trials were found, except for percent of U.S. No. 1 storage roots in 2017 for the organic black plastic mulch trial. In the organic black plastic mulch trials, ‘Bonita’ and USDA-04-136 consistently produced high marketable yields, whereas ‘Ruddy’ and USDA-W388 consistently produced the lowest marketable yields. ‘Averre’, ‘Beauregard’, ‘Covington’, and USDA-09-130 exhibited variable performance, with marketable yields among the highest in a single year. For the conventional trials, USDA-04-136 consistently produced high marketable yields, whereas ‘Ruddy’ and USDA-W-388 consistently produced the lowest marketable yields. ‘Averre’, ‘Bonita’, ‘Covington’, and USDA-09-130 exhibited variable performance, with marketable yields among the highest in a single year. For the organic black plastic mulch, significant differences were detected in the percent of uninjured roots and percent white grub (primarily Plectris aliena) damage in 2016 and in wireworm (Elateridae)-cucumber beetle (Diabrotica)-flea beetle (Systena) severity index (WDS severity index) in 2016 and 2017. USDA-04-136 and USDA-W-388 consistently had the lowest WDS severity index, whereas ‘Covington’ consistently had the highest WDS severity index. For the conventional trials, significant differences were found among clones in both years for all insect rating variables, except for percent sweetpotato weevil (Cylas formicarius elegantulus) damage. ‘Ruddy’, USDA-04-136, and USDA-W-388 consistently yielded the highest percent of uninjured roots, whereas ‘Averre’, ‘Bonita’, SC-1149-19, and USDA-09-130 consistently had the lowest percent of uninjured roots. The research reported here for yield and insect resistance under conventional and organic production systems will be useful for producers in the selection of cultivars suitable for growth in South Carolina.