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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.

Open access

Dong Sub Kim, Steven B. Kim, Mike Stanghellini, Melody Meyer-Jertberg, and Steven A. Fennimore

Soil disinfestation with steam has been evaluated in strawberry fruiting fields as a nonchemical method of soil disinfestation; however, little is known about the use of steam for field production of strawberry daughter plants. The objective of this study was to compare daughter plant production in soils previously treated with steam compared to those treated with standard methyl bromide (MB) and chloropicrin (Pic) treatments. A prototype field steam applicator and a self-propelled diesel-fueled steam generator and applicator were tested at two high-elevation nurseries near Macdoel, CA, in Sept. 2018 and Aug. 2020, respectively. The steam application heated the soil above 60 °C for ≈60 minutes to a depth of 25 cm at both nurseries. The pest control efficacy of the steam applications against weeds, Verticillium spp., Tylenchulus semipenetrans, and Pythium ultimum were similar to that of MB:Pic. The stolons and daughter plants densities in fields with steam treatment were similar to those in fields with MB:Pic treatment. Therefore, we suggest that soil disinfestation with steam may be a viable method of producing healthy strawberry plants. However, more research is needed to verify plant sanitation and quality.

Open access

Zhanao Deng, Natalia A. Peres, and Johan Desaeger

Caladiums (Caladium ×hortulanum Birdsey, Araceae Juss.) are ornamental aroids often used as container or landscape plants (Evans et al., 1992). They are valued for their variably shaped, bright foliage. Most commercial caladium plants are produced by forcing tubers in containers. Florida growers produce essentially all the caladium tubers used in the United States and in the world for pot plant production and tuber sales (Bell et al., 1998; Deng et al., 2008b). Roughly, two-thirds of Florida-produced caladium tubers are used to produce pot plants, and one-third are used for direct planting in the landscape.