bluuebunny/crossref_metadata_2025 huggingface dataset:
Luther Burbank’s Plums
Authors: Karp David
Published: February 2019

The 113 named varieties of plums introduced by Luther Burbank (1849–1926) were by far the most numerous and arguably the most significant of his horticultural accomplishments. He began by importing 12 seedlings from Japan in 1885, including ‘Abundance’ and ‘Satsuma’ (Prunus salicina). The cultivars he released in the late 19th and early 20th centuries played a crucial role in developing commercial cultivation of Asian-type plums in California, the United States, and much of the world; they also served as founding clones for later breeders. His crowning achievement was ‘Santa Rosa’ (introduced 1906), which in 1945, ‘Santa Rosa’ accounted for 36% of the California plum harvest. Many of Burbank’s other cultivars of primarily P. salicina ancestry were extensively cultivated in California in the early and middle 1900s, including ‘Beauty’ (introduced 1911), ‘Burbank’ (1888), ‘Duarte’ (1911), ‘Eldorado’ (1904), ‘Formosa’ (1907), and ‘Wickson’ (1895). His most important introductions of European plum (P. domestica) were ‘Improved French’ prune (1898), ‘Sugar’ prune (1899) and ‘Standard’ prune (1911). Some of Burbank’s more obscure introductions never received general distribution and have disappeared; others such as ‘Santa Rosa’, ‘Shiro’ (1899), and ‘Elephant Heart’ (released posthumously in 1929) still are commonly cultivated today in home gardens and for sale at local markets.
Luther Burbank’s Best Berries
Authors: Hummer Kim E. , Finn Chad E. , Dossett Michael
Published: February 2019

Luther Burbank, the quintessential nurseryman of the early 20th century, remarked that small fruit was the “Cinderella of the pomological family.” He stated that although tree fruits had been improved to the point of an almost uncountable number of cultivars, it was the time and responsibility of his generation and those to follow to develop the small fruit for human consumption. Burbank had a penchant for detecting potential qualities of unusual plants and his broad association with plant explorers at the U.S. Department of Agriculture and elsewhere allowed him to examine diverse wild berry species. He obtained seeds of many small fruit species from throughout the world. He made wide crosses within and between these genera and species. Burbank selected and named many cultivars to be introduced through his nursery and elsewhere. He named and released ≈40 blackberries, raspberries (Rubus L.), and strawberries (Fragaria L.); four grapes (Vitis L.); and a hybrid Solanum that he named ‘Sunberry’. He sometimes exaggerated their descriptions for promotion or public recognition. For example, Rubus ×loganobaccus ‘Phenomenal’ was, he stated, “far superior in size, quality, color, and productivity…” to ‘Loganberry’. Unfortunately, this cultivar was not a commercial success. Burbank made a few crosses and sold what he considered to be improved species, e.g., ‘Himalaya Giant’ blackberry (R. armeniacus). He created new common names for foreign species, e.g., balloon berry (R. illecebrosus) and Mayberry (R. palmatus), to better market them. However, his amazingly keen observations of thornlessness, pigment diversity, and recognition of repeat flowering and fruiting in blackberries, raspberries, and strawberries, were insightful of the needs of future industry. Burbank was a disciple of Darwin and his theory of natural selection. Burbank’s classic breeding approach, to make wide crosses, produce large numbers of hybrid seedlings, choose significant seedlings with his traits of choice, and backcross to the desired parent for several generations, was successful, although he did not know of ploidy or gene recombination. Unfortunately, the ‘Himalaya blackberry’, now ubiquitous in hedgerows and fields throughout the Pacific Northwest in the United States, is designated as a federal noxious weed. Although not presently in commercial production, three of his Rubus cultivars (‘Burbank Thornless’, ‘Snowbank’, and ‘Phenomenal’) are preserved in the U.S. Department of Agriculture, National Clonal Germplasm Repository, in Corvallis, OR.
Use of Controlled Water Deficit to Regulate Poinsettia Stem Elongation
Authors: Alem Peter , Thomas Paul A. , van Iersel Marc W.
Published: February 2019

Height regulation is crucial in poinsettia (Euphorbia pulcherrima) production for both aesthetics and postharvest handling. Controlled water deficit (WD) offers a potential alternative to plant growth retardants (PGRs) for poinsettia height regulation. We have previously shown that WD can be used to regulate poinsettia stem elongation. However, it is not clear how WD can be used to achieve different plant heights and how it affects aesthetic qualities such as bract size. Our objectives were to determine whether a range of plant heights can be achieved using controlled WD and to investigate possible adverse effects of WD on shoot morphology. Rooted cuttings of poinsettia ‘Classic Red’ were transplanted into 15-cm pots filled with 80% peat:20% perlite (v/v) substrate. Three target heights (43.2, 39.4, and 35.6 cm) were set at pinching (Day 27) and height tracking curves were used to monitor plants throughout the production cycle (77 days from pinching to finish). Substrate volumetric water content (θ) was maintained at 0.40 m3·m−3 (a matric potential of ≈–5 kPa) during well-watered conditions and reduced to 0.20 m3·m−3 (≈–75 kPa) when plants were taller than desired based on the height tracking curves. Control plants were maintained at a θ of 0.40 m3·m−3 throughout the study and had a final height of 51.2 cm. Plants with the 35.6-cm target height exceeded the upper limits of the height tracking curve despite being kept at a θ of 0.20 m3·m−3 for 70 days and had a final height of 39.8 cm. The final plant heights in the 39.4- and 43.2-cm target height treatments were 41.3 and 43.5 cm, respectively, within the 2.5-cm margin of error of their respective target heights. Relative to control plants, bract area was reduced by 53%, 47%, and 31% in the 35.6-, 39.4-, and 43.2-cm target height treatments, respectively. Our results indicate that WD can be an effective method of height control, but WD may also decrease bract size.
Biofumigation Performance of Four Brassica Crops in a Green Chile Pepper (Capsicum annuum) Rotation System in Southern New Mexico
Authors: Rudolph Rachel E. , Sams Carl , Steiner Robert , Thomas Stephen H. , Walker Stephanie , Uchanski Mark E.
Published: February 2019

Biofumigation is a sustainable method of soil management in cash crop rotations that can increase soil organic matter (SOM), moderate soil pH, suppress weeds and soilborne pathogens through glucosinolates (GSL), and increase water infiltration. This 2-year (2011–13) field study evaluated four different Brassica crops for their biofumigant potential in a chile pepper rotation system in southern New Mexico. The four cultivars included: three mustards (Brassica juncea ‘Caliente 61’, ‘Caliente 199’, and ‘Pacific Gold’) and one broccoli (Brassica oleracea var. botrytis ‘Arcadia’). As a result of concerns that these mustards could be hosts for nematodes, a greenhouse study was conducted in the second year to evaluate the biofumigant crops for their southern root-knot nematode (Meloidogyne incognita, RKN) host suitability and their seedling establishment in the presence of RKN. In Year 1 (2011), conditions were ideal, which resulted in high mustard biomass production and, consequently, significantly higher SOM and lower pH than the bare soil control plots. However, there were no chile pepper yield differences among treatments. Conditions were much less favorable in Year 2 and the resultant poor biomass production did not cause an increase in SOM as seen in Year 1. In the RKN greenhouse study, broccoli was the least susceptible biofumigant crop. After one nematode generation (683 cumulative heat units), RKN populations were less than half of the original inoculum level on the broccoli. However, RKN populations increased in the presence of ‘Caliente 61’, ‘Caliente 199’, and ‘Pacific Gold’. Overall, broccoli produced lower biomass and lower GSL concentrations than the mustard treatments but may be a valuable crop for growers with nematode issues because RKN populations decreased in its presence. Based on high biomass production and high GSL concentration, ‘Caliente 199’ showed the most potential as a biofumigant crop for southern New Mexico.
Apical Dominance and Planting Density Effects on Weed Suppression by Sunn Hemp (Crotalaria juncea L.)
Authors: Cho Alyssa H. , Chase Carlene A. , Treadwell Danielle D. , Koenig Rosalie L. , Morris John Bradley , Morales-Payan Jose Pablo
Published: February 2019

A field study was conducted in 2008 and 2009 in Citra, FL, to evaluate the effects of seeding rate and removal of apical dominance of sunn hemp (Crotalaria juncea L.) on weed suppression and seed production by sunn hemp. Three seeding rates of sunn hemp were used: a representative seed production rate of 11 kg·ha−1, an intermediate seeding rate of 28 kg·ha−1, and a cover crop seeding rate of 45 kg·ha−1. Cutting the main stem at 3, 4, or 5 weeks after planting to break apical dominance was compared with an uncut treatment. Cutting had no significant effect on shoot biomass, photosynthetically active radiation (PAR) penetrating the canopy, and nondestructive leaf area index (LAI). As a result, cutting also had no effect on weed density and biomass in 2008 and very little effect in 2009. Increase in seeding rate resulted in linear decrease in PAR and increase in LAI in both years. Seeding rate had a greater effect on suppression of weed biomass than on suppression of weed density. There was a linear decline in sunn hemp branching with increased seeding rate in 2009 and, averaged across years, flower number decreased linearly with increased seeding rate. Cutting to break apical dominance induced branching but had no effect on flower number. No seed pod production occurred and we postulate that the lack of seed production may be the result of the absence of effective pollinators in fall when short-day varieties of sunn hemp flower in Florida.
Ripening Quality of ‘Bartlett’ Pears (Pyrus communis L.) Subjected to Phytosanitary X-ray Irradiation Treatment Followed by Simulated Retail Display
Authors: Sea Sokrith , Rakovski Cyril , Prakash Anuradha
Published: February 2019

The objective of this study was to determine the effect of phytosanitary X-ray irradiation on the physicochemical properties and sensory attributes of early- and late-harvest ‘Bartlett’ pears (Pyrus communis L.) during ripening under simulated commercial conditions. Irradiation delayed ripening, which in turn affected respiration rate, ethylene production, and firmness. Irradiation decreased ethylene production in early- and late-harvest pears and maintained firmness as compared with the control pears. In the early-harvest pears, irradiation did not affect respiration rate, weight loss, or total soluble solids. However, in the late-harvest pears, irradiation resulted in an increase in respiration rate and weight loss and a decrease in total soluble solids. The appearance for irradiated early-harvest pears was rated lower by consumers, but there were no significant differences in the rest of the attributes. Consumers rated the irradiated late-harvest pears lower (P < 0.05) than the non-treated pears for overall liking, texture, and flavor on a 9-point hedonic scale. Consumers perceived the late-harvest irradiated pears to be less sweet than the control (P < 0.05), which correlated with total soluble solids of 12.4% for treated pears vs. 13.2% for the control. Our results show that there were significant differences between the early- and late-harvest pears in their responses to irradiation. Although some sensory attributes were negatively affected, the delay in ripening helped reduce bruising and mold development in irradiated pears during the retail display simulation.
Genetic Characterization of Pitahaya Accessions Based on Amplified Fragment Length Polymorphism Analysis
Authors: Pagliaccia Deborah , Vidalakis Georgios , Douhan Greg W. , Lobo Ramiro , Tanizaki Gary
Published: February 2019

Hylocereus (Berger) Britton and Rose and Selenicereus (Berger) Britton and Rose are two genera of vine cacti, commonly named pitahaya, that produce fruit that are gaining in popularity as an exotic fruit in many countries. There has also been an increasing interest in these fruits because they can be grown in areas that are prone to drought and heat where other fruit production is not possible. However, there is significant taxonomic confusion regarding species within these genera as well as some uncertainty among named varieties. Amplified fragment length polymorphism (AFLP) was used to genotype a large pitahaya collection to determine if there was redundancy in some of the commonly named varieties as well as to assess the overall diversity of the collection. A total of 51 markers were scored from 230 accessions. Seven distinct clades were found with 126 putative clones but only three clades had high bootstrap (greater than 80%) support and one had moderate support (60%). Some of the differently named varieties were identical based on our analysis, but there was also genotypic diversity within putatively named varieties. The results of this study will help growers and researchers to choose genetically distinct accessions from the germplasm collection to investigate how different accessions perform in their growing regions.
Screening Carrot Germplasm for Resistance to Xanthomonas hortorum pv. carotae
Authors: Christianson Charles E. , Jones Stephen S. , du Toit Lindsey J.
Published: February 2019

Xanthomonas hortorum pv. carotae (Xhc) causes bacterial blight of carrot (Daucus carota L.), is endemic in the primary regions of carrot seed production, and is readily seed-transmitted. Genetic resistance to Xhc is not well documented in commercially available carrot cultivars, and there has been little public research on screening for resistance. Carrot PI lines (n = 66), public inbred lines (n = 2), and commercial cultivars (n = 17) were assessed for response to Xhc in a greenhouse in 2012 based on the incidence and severity of bacterial blight symptoms after inoculation as well as Xhc population [colony-forming units (CFU)/g dry foliage] detected by dilution plating onto XCS agar, a semiselective medium for Xhc. Severity of bacterial blight averaged 8.8% ± 0.4% (mean ± se) with a range of 0% to 50%, and size of the Xhc population detected on the foliage averaged 8.16 × 109 ± 1.07 × 109 CFU/g (range, 1.38 × 104 to 3.28 × 1011 CFU/g) for individual plants. Eight putative resistant PI lines and five highly susceptible PI lines selected from the 2012 screening were evaluated again in 2013 with an additional two PI lines, 12 cultivars, two inbred lines, and 12 carrot wild relatives. In the 2013 trial, severity of foliar blight 6 weeks post-inoculation ranged from 0% to 90% (11.8% ± 0.4%), and Xhc population ranged from 4.90 × 104 to 1.30 × 1011 CFU/g dry foliage (1.00 × 1010 ± 5.29 × 108 CFU/g) for individual plants. Spearman’s correlation coefficient between the Xhc population detected and severity of bacterial blight was highly significant in the 2012 and 2013 trials (r = 0.52 and 0.62, respectively, at P < 0.0001). PI lines 418967, 432905, and 432906 were the most resistant based on Xhc population detected and could be used to develop resistant cultivars. Of the 12 carrot wild relatives screened, only Ames 7674 and SS10 OR displayed a relatively low severity of bacterial blight and population of Xhc on the foliage.
Yield Performance and Bean Quality Traits of Cacao Propagated by Grafting and Somatic Embryo-derived Cuttings
Authors: Goenaga Ricardo , Guiltinan Mark , Maximova Siela , Seguine Ed , Irizarry Heber
Published: February 2019

Twelve cacao (Theobroma cacao) clones propagated by grafting and orthotropic rooted cuttings of somatic embryo-derived plants were grown on an Ultisol soil at Corozal, Puerto Rico, and evaluated for 6 years of production under intensive management. Year, variety, year × variety, and propagation treatment × variety interactions indicated significant effects for dry bean yield, number of pods produced, pod index, plant height, and stem diameter. Propagation treatments had a significant effect on dry bean yield and pod index but not on number of pods produced. Average yield across varieties for both propagation treatments was 2087.9 kg·ha−1 per year of dry beans. There was a highly significant variety effect. ‘UF-668’ was the top yielder averaging 2536.7 kg·ha−1 per year of dry beans; however, this yield was not significantly different from the average yield of varieties ‘TARS-30’, ‘TARS-1’, ‘TARS-13’, ‘TARS-14’, and ‘TARS-2’, which averaged 2427.0 kg·ha−1 per year. Except for ‘UF-668’, the TARS varieties were released in 2009 as high-yielding selections. Propagation treatments had a significant effect on dry bean yield. Dry bean yield of varieties propagated by grafting was 7% higher (2166.7 kg·ha−1 per year) than those propagated by orthotropic rooted cuttings of somatic embryo-derived plants (2009.2 kg·ha−1 per year). This yield difference could not be attributed to grafted plants being more vigorous nor by differences in root architecture. The lowest pod index value in both propagation treatments was obtained by ‘UF-668’; however, pod index for this variety did not differ significantly from values for ‘TARS-2’ and ‘TARS-23’ in grafted plants and from ‘TARS-2’, ‘TARS-23’, and ‘TARS-1’ in plants propagated by orthotropic rooted cuttings of somatic embryo-derived plants. With few exceptions, flavor characteristics were not significantly affected by propagation treatments. Although there were significant differences between plant propagation treatments for some of the variables measured in this study, these were not of a magnitude that would preclude the use of somatic embryogenesis as a viable propagation system for cacao.
Hydrogen Sulfide Alleviates Dark-promoted Senescence in Postharvest Broccoli
Authors: Li Zhi-Rong , Hu Kang-Di , Zhang Fen-Qin , Li Shi-Ping , Hu Lan-Ying , Li Yan-Hong , Wang Song-Hua , Zhang Hua
Published: February 2019

Broccoli (Brassica oleracea var. italica) is an important vegetable crop rich in vitamins and sulforaphane. However, the floral heads of broccoli experience rapid postharvest senescence. Here we found that hydrogen sulfide (H2S) treatment alleviated dark-promoted senescence in broccoli florets. H2S delayed the symptoms of senescence and maintained higher levels of chlorophyll and Rubisco and lower protease activity compared with water control. Gene expression analysis showed that H2S down-regulated the expression of chlorophyll degradation-related genes BoSGR, BoNYC, BoCLH1, BoPPH, and BoRCCR. Expression of lipoxygenase gene BoLOX1 and the genes involved in the ethylene synthesis pathway, BoACS2 and BoACS3, were also down-regulated by H2S. The reduced expression level in cysteine protease gene BoCP3 and aspartic protease gene BoLSC807 suggested the role of H2S in alleviating protein degradation during broccoli senescence. H2S up-regulated the expression of sulfur metabolism genes BoSR and BoOASTL, and the antioxidant gene BoCAT. These results show that H2S plays a vital role in alleviating broccoli senescence through a broad regulation on gene expression of reactive oxygen species (ROS) metabolism genes, ethylene synthesis genes, and protease genes.
Germination Response of Dormant Tanglehead (Heteropogon contortus) Seeds to Smoke-infused Water and the Smoke-associated Stimulatory Compounds, Karrikinolide and Cyanide
Authors: Baldos Orville C. , DeFrank Joseph , Sakamoto Glenn S.
Published: February 2019

Tanglehead (Heteropogon contortus) is a native Hawaiian grass that has been used in restoration and has potential for expanded re-vegetation use. Although interest and demand for tanglehead re-vegetation has increased, the supply of tanglehead seeds has remained limited as a result of a lack of seed production protocols addressing seed dormancy. Smoke water from burning vegetation may provide an economical and practical seed treatment because aerosol smoke has been reported to stimulate tanglehead seed germination. Dose rate and side-by-side comparison studies were conducted to evaluate the germination stimulation efficacy of food-grade liquid smoke, xylose smoke-infused water, tanglehead smoke-infused water, karrikinolide (KAR1), and cyanide (i.e., mandelonitrile and potassium cyanide). Optimum smoke water dilutions were 1% v/v for food-grade liquid smoke and undiluted for xylose smoke-infused water and tanglehead smoke-infused water. KAR1 was not stimulatory at concentrations between 0.0067 and 66.7 μm. Potassium cyanide stimulated tanglehead seed germination at concentrations between 50 to 500 μm. Germination was promoted to even greater levels with the cyanohydrin, mandelonitrile, indicating a role for benzaldehyde (a byproduct of mandelonitrile decomposition) in stimulating tanglehead seed germination. Benzaldehyde was confirmed to be stimulatory at concentrations between 50 to 100 μm. The presence of cyanide at stimulatory levels was confirmed in tanglehead smoke-infused water (i.e., ≈100 μm), but not in food-grade liquid smoke or xylose smoke-infused water. Germination with non-cyanide-containing smoke waters indicates the presence of other compounds in smoke that can stimulate tanglehead germination. In the side-by-side comparison study, food-grade liquid smoke (1% v/v) and undiluted tanglehead smoke-infused water provided consistent germination stimulation comparable to 500 μm potassium cyanide. Undiluted xylose smoke-infused water did not provide significant germination stimulation in the comparison studies. This may be the result of differences in seed batch sensitivity to the germination stimulant, seed storage duration as well as subtle differences in the preparation of xylose smoke-infused water.
In Vitro Shoot Proliferation of Apple Rootstocks ‘B.9’, ‘G.30’, and ‘G.41’ Grown under Red and Blue Light
Authors: Geng Fang , Moran Renae , Day Michael , Halteman William , Zhang Donglin
Published: February 2019

The influence of red and blue light wavelengths was tested to improve the initial in vitro multiplication of apple (Malus × domestica) rootstock cultivars Budagovsky 9 (B.9), Geneva 30 (G.30), and Geneva 41 (G.41). Single-node segments were established in semisolid Murashige and Skoog media and then transferred to proliferation media and cultured 40 days under white, red, or blue light irradiance. In a second experiment, G.30 was cultured under red, blue, or white light with and without gibberellic acid (GA3). The three rootstocks responded similarly under white light in terms of shoot number, length of the longest shoot, and the number of elongated shoots. Red light increased the number of shoots, length of the longest shoot, and the number of elongated shoots of B.9 and G.30 when compared with white or blue light. Red light increased the number of elongated B.9 and G.30 shoots to five per explant compared with one per explant under white light. In contrast, shoot growth of G.41 showed no difference under the three light quality treatments, and the number of elongated shoots per explant was less than one. When compared with an absence of GA3, a concentration of GA3 at 0.5 mg·L−1 promoted in vitro shoot growth of G.30 under red and blue light.
Capture of Sprinkler Irrigation Water by Container-grown Ornamental Plants
Authors: Million Jeff B. , Yeager Thomas H.
Published: February 2019

The capacity for container-grown plants to capture sprinkler irrigation water plays a critical role in adjusting irrigation rates to deliver required amounts of water to the container substrate. The capture factor (CF) used to describe this capacity was defined as the amount of water captured with a plant relative to the amount captured without a plant. A wind-sheltered, irrigation test area was established to measure CF as affected by plant species, plant size, container size, container spacing, and sprinkler type. CF values for 11 marketable-sized, commonly grown plant species ranged from 1 to 4 with highest values exhibited by plant species with an upright, spreading growth habit. CF values increased as plant size increased. Close container spacings (less than one container diameter between adjacent containers) reduced CF when the allotted area outside the container limited the potential amount of water that could be captured. Compared with impact sprinklers, wobbler sprinklers increased irrigation capture 7% for Ligustrum japonicum grown in 27-cm-diameter containers but not in 16-cm-diameter containers. Results showed that CF is a dynamic parameter that depends on canopy size, container size, container spacing, and sprinkler type. A working knowledge of CF is crucial for determining irrigation requirements to maximize sprinkler irrigation efficiency in container nurseries.
Monitoring and Controlling Ebb-and-flow Subirrigation with Soil Moisture Sensors
Authors: Ferrarezi Rhuanito Soranz , van Iersel Marc W. , Testezlaf Roberto
Published: February 2019

Subirrigation can reduce water loss and nutrient runoff from greenhouses, because used nutrient solution is collected and recirculated. Capacitance moisture sensors can monitor substrate volumetric water content (θ) and control subirrigation based on minimum θ thresholds, providing an alternative to timers. Our objectives were to automate an ebb-and-flow subirrigation system using capacitance moisture sensors, monitor moisture dynamics within the containers, and determine the effect of five θ thresholds (0.10, 0.18, 0.26, 0.34, or 0.42 m3·m−3) on hibiscus (Hibiscus acetosella Welw. ex Hiern.) ‘Panama Red’ (PP20,121) growth. Subirrigation was monitored using capacitance sensors connected to a multiplexer and a data logger and controlled using a relay driver connected to submersible pumps. As the substrate θ dropped below the thresholds, irrigation was turned on for 3 min followed by 3-min drainage. Capacitance sensors effectively controlled subirrigation by irrigating only when substrate θ dropped below the thresholds. Each irrigation cycle resulted in a rapid increase in substrate θ, from 0.10 to ≈0.33 m3·m−3 with the 0.10-m3·m−3 irrigation threshold vs. an increase in θ from 0.42 to 0.49 m3·m−3 with the 0.42-m3·m−3 irrigation threshold. Less nutrient solution was used in the lower θ threshold treatments, indicating that sensor control can reduce water and thus fertilizer use in subirrigation systems. The water dynamics showed that the bottom part of the pots was saturated after irrigation with θ decreasing quickly after an irrigation event, presumably because of drainage. However, the water movement among substrate layers was slow with the 0.10-m3·m−3 irrigation threshold with water reaching the upper layer 5.5 to 20 h after irrigation. The 0.10-m3·m−3 θ threshold resulted in 81% fewer irrigations and 70% less nutrient solution use compared with the 0.42-m3·m−3 θ threshold. However, the 0.10-m3·m−3 θ threshold also reduced hibiscus shoot height by 30%, shoot dry weight 74%, and compactness by 63% compared with the 0.42-m3·m−3 θ threshold. Our results indicate that soil moisture sensors can be used to control subirrigation based on plant water use and substrate water and to manipulate plant growth, thus providing a tool to improve control over plant quality in subirrigation systems.
Sustaining Soil Quality in Intensively Managed High Tunnel Vegetable Production Systems: A Role for Green Manures and Chicken Litter
Authors: Rudisill Matt A. , Bordelon Bruce P. , Turco Ronald F. , Hoagland Lori A.
Published: February 2019

Use of high tunnel crop production is expected to increase to meet the growing demand for locally produced fresh market vegetables. These structures have the potential to offer many production benefits; however, managing soil quality in these structures is challenging and work in the area is limited. In this 3-year study, we compared the impacts of organic and inorganic fertility amendments on soil quality, nutrient availability, and the productivity of chard (Beta vulgaris L.) and sweet peppers (Capsicum annuum L.) produced in high tunnel and open field systems. Fertility amendments included a green manure treatment [hairy vetch (Vicia villosa Roth) and dehydrated alfalfa meal], partially composted and pelletized chicken litter, urea, and an unfertilized control. Chard was grown in 2011, and peppers were grown in 2012 and 2013. Soil nutrients, microbial activity, active carbon, pH, electrical conductivity (EC), total soil organic matter, and yield were quantified. Chard yield was lower in the high tunnel compared with the open field in 2011, but pepper yield was greater in the high tunnel in 2012 and 2013. Productivity of chard was lower in the green manure compared with urea in 2011 across high tunnel and open field production systems, but no difference in pepper yield was observed between plants receiving fertility inputs in either 2012 or 2013. Repeated application of green manure and chicken litter resulted in soils with increased microbial activity and active carbon, but the green manure was the only treatment successful at accruing carbon in the high tunnel over time. High tunnel production resulted in greater EC compared with the open field, but levels were not considered inhibitory for chard or peppers. High tunnels can increase vegetable crop productivity in the midwest United States, and organic fertility amendments can improve soil quality as measured by soil microbial activity and active carbon in high tunnel and open field production systems.
Growth and Fruit Production of Highbush Blueberry Fertilized with Ammonium Sulfate and Urea Applied by Fertigation or as Granular Fertilizer
Authors: Vargas Oscar L. , Bryla David R.
Published: February 2019

Fertigation with liquid sources of nitrogen (N) fertilizers, including ammonium sulfate and urea, were compared with granular applications of the fertilizers in northern highbush blueberry (Vaccinium corymbosum L. ‘Bluecrop’) during the first 5 years of fruit production (2008–12). The planting was established in Apr. 2006 at a field site located in western Oregon. The plants were grown on raised beds and mulched every 2 years with sawdust. Liquid fertilizers were injected through a drip system in equal weekly applications from mid-April to early August. Granular fertilizers were applied on each side of the plants, in three split applications from mid-April to mid-June, and washed into the soil using microsprinklers. Each fertilizer was applied at three N rates, which were increased each year as the plants matured (63 to 93, 133 to 187, and 200 to 280 kg·ha−1 N) and compared with non-fertilized treatments (0 kg·ha−1 N). Canopy cover, which was measured in 2008 only, and fresh pruning weight were greater with fertigation than with granular fertilizer and often increased with N rate when the plants were fertigated but decreased at the highest rate when granular fertilizer was applied. Yield also increased with N fertilizer and was 12% to 40% greater with fertigation than with granular fertilizer each year as well as 17% greater with ammonium sulfate than with urea in 2011. The response of berry weight to the treatments was variable but decreased with higher N rates during the first 3 years of fruit production. Leaf N concentration was greater with fertigation in 4 of 5 years and averaged 1.68% with fertigation and 1.61% with granular fertilizer. Leaf N was also often greater with ammonium sulfate than with urea and increased as more N was applied. Soil pH declined with increasing N rates and was lower with granular fertilizer than with fertigation during the first 3 years of fruit production and lower with ammonium sulfate than with urea in every year but 2010. Soil electrical conductivity (EC) was less than 1 dS·m−1 in each treatment but was an average of two to three times greater with granular fertilizer than with fertigation and 1.4 to 1.8 times greater with ammonium sulfate than with urea. Overall, total yield averaged 32 to 63 t·ha−1 in each treatment over the first 5 years of fruit production and was greatest when plants were fertigated with ammonium sulfate or urea at rates of at least 63 to 93 kg·ha−1 N per year.
Regulation with Trinexapac-ethyl and Dew Removal at the Time of Fungicide Application Did Not Influence Dollar Spot Control
Authors: Huang Yu , Kaminski John E. , Landschoot Peter J.
Published: February 2019

Dollar spot, caused by Sclerotinia homoeocarpa F.T. Bennett, is an important disease of creeping bentgrass (Agrostis stolonifera L.) on golf courses in the northern United States. Canopy moisture in the form of dew plays an important role in the development of dollar spot and routine displacement has been shown to reduce disease severity. The use of plant growth regulators (PGRs) is a common management practice for maintaining creeping bentgrass fairways, but their influence on dollar spot is unclear. The objective of this field study was to elucidate the influence of dew removal at the time of fungicide application on dollar spot control in creeping bentgrass regulated by trinexapac-ethyl (TE). Main factors in the study included three dew removal strategies (non-treated, dew removed–mowed, and dew removed–not mowed) before the application of four fungicide treatments (non-treated, chlorothalonil, propiconazole, and iprodione). All fungicide treatments were applied once to turfgrass previously treated with TE or not treated. The presence or absence of dew at the time of fungicide application generally had no influence on fungicide performance with respect to dollar spot control. Based on the results of this study, dew removal before the application of fungicides targeting dollar spot is unnecessary. Applications of TE before fungicides reduced dollar spot severity in some cases, but reductions in symptom expression were limited and did not result in markedly improved dollar spot control.
Light-emitting Diode Light Transmission through Leaf Tissue of Seven Different Crops
Authors: Massa Gioia , Graham Thomas , Haire Tim , Flemming Cedric , Newsham Gerard , Wheeler Raymond
Published: February 2019

Significant advances in controlled-environment (CE) plant production lighting have been made in recent years, driven by rapid improvements in light-emitting diode (LED) technologies. Aside from energy efficiency gains, LEDs offer the ability to customize the spectrum delivered to a crop, which may have untold benefits for growers and researchers alike. Understanding how these specific wavebands are attenuated by plant tissue is important if lighting engineers are to fully optimize systems for CE plant production. In this study, seven different greenhouse and field crops (radish, Raphanus sativus ‘Cherry Bomb II’; red romaine lettuce, Lactuca sativa ‘Outredgeous’, green leaf lettuce, Lactuca sativa ‘Waldmann’s Green’; pepper, Capsicum annuum ‘Fruit Basket’; soybean, Glycine max ’Hoyt’; cucumber, Cucumis sativus ‘Spacemaster’; canola, Brassica napus ‘Westar’) were grown in CE chambers under two different light intensities (225 and 420 μmol·m−2·s−1). Intact, fully expanded upper canopy leaves were used to determine the level of light transmission, at two to three different plant ages, across seven different wavebands with peaks at 400, 450, 530, 595, 630, 655, and 735 nm. The photosynthetic photon flux (PPF) environment that plants were grown in affected light transmission across the different LED wavelengths in a crop-dependent manner. Plant age had no effect on light transmission at the time intervals examined. Specific waveband transmission from the seven LED sources varied similarly across plant types with low transmission of blue and red wavelengths, intermediate transmission of green and amber wavelengths, and the highest transmission at the far-red wavelengths. Higher native PPF increased anthocyanin levels in red romaine lettuce compared with the lower native PPF treatment. Understanding the differences in light transmission will inform the development of novel, energy-saving lighting architectures for CE plant growth.
Growth and Acclimation of Impatiens, Salvia, Petunia, and Tomato Seedlings to Blue and Red Light
Authors: Wollaeger Heidi M. , Runkle Erik S.
Published: February 2019

Plant growth is plastic and adaptive to the light environment; characteristics such as extension growth, architecture, and leaf morphology change, depending on the light spectrum. Although blue (B; 400–500 nm) and red (R; 600–700 nm) light are generally considered the most efficient wavelengths for eliciting photosynthesis, both are often required for relatively normal growth. Our objective was to quantify how the B:R influenced plant seedling growth and morphology and understand how plants acclimated to these light environments. We grew seedlings of three ornamental annuals and tomato under six sole-source light-emitting diode (LED) lighting treatments or one cool-white fluorescent treatment that each delivered a photosynthetic photon flux (PPF) of 160 µmol·m−2·s–1 for 18 h·d−1. The following treatments were provided with B (peak = 446 nm) and R (peaks = 634 and 664 nm) LEDs: B160 (160 µmol·m−2·s−1 of B light only), B80+R80, B40+R120, B20+R140, B10+R150, and R160. Seedlings of impatiens (Impatiens walleriana), salvia (Salvia splendens), petunia (Petunia ×hybrida), and tomato (Solanum lycopersicum) were grown for 31 to 37 days at a constant 20 °C. Plants with as little as 10 µmol·m−2·s−1 of B light were 23% to 50% shorter and had 17% to 50% smaller leaves than plants under only R light. Impatiens and salvia had 53% to 98% greater fresh shoot weight under treatments without B light than with ≥80 µmol·m−2·s−1. Plants grown under fluorescent lamps had the greatest chlorophyll content but also had among the thinnest leaves of treatments. Blue-rich light increased flowering in impatiens and reduced incidence of intumescences on tomato. We conclude that, in sole-source lighting of propagules, B light inhibits leaf and stem expansion, which subsequently limits photon capture and constrains biomass accumulation. As little as 10 µmol·m−2·s−1 of B light in an R-dominant background can elicit desirable growth responses for the production of young plants and for other situations in which compact growth is desired.
Brassica Green Manure Amendments for Management of Rhizoctonia solani in Two Annual Ornamental Crops in the Field
Authors: Cochran Kimberly A. , Rothrock Craig S.
Published: February 2019

Brassica green manure soil amendments are a possible alternative to chemical management of soilborne diseases of ornamental landscape and bedding plants. The objective of this study was to determine the importance of crop selection and application rate of brassica green manures for disease caused by Rhizoctonia solani on impatiens and petunia. Microplot experiments were conducted over 2 years using brassica green manure soil amendments for R. solani management of both petunias and impatiens. Brassica crops used were Brassica juncea ‘Fumus’ and ‘Bionute’, and Brassica napus ‘Jetton’, at the application rates of 700, 1400, and 4200 g·m−2 fresh weight aboveground biomass. Microplots were artificially infested to evaluate disease on these ornamentals, with a second set of experiments using noninfested plots to examine effects of the green manure alone on plant growth. All brassica green manure crops reduced disease symptoms in both impatiens and petunias. Rate of brassica application was more important than brassica crop variety for use as a green manure. The highest rate of the brassica green manure decreased crown lesions by 21% and 24%, root discoloration by 9% and 7%, and R. solani isolation by 15% and 8% for impatiens and petunias, respectively, for 4200 g·m−2 compared with 700 g·m−2 rates of application. No phytotoxic effects were observed from the brassica green manures following a waiting period of 4 weeks between amending the soil and planting the ornamental crops.
Response of Oriental Hybrid Lily (Lilium oriental cv. Sorbonne) Flowers to Exogenous Fluridone and Abscisic Acid Application and Responses of Endogenous Abscisic Acid and Gibberellic Acid 3
Authors: Yang Liu , Xie Zhongkui , Wu Zhijiang , Wang Yajun , Guo Zhihong , Zhang Yubao , Wang Ruoyu
Published: February 2019

The oriental hybrid lily (Lilium oriental cv. Sorbonne) is an economically important flower noted for its pink petals. Flower quality is determined by plant height, number of flowers per plant, and flower diameter. The commercial value can be increased by improving flower quality through cultural practices such as exogenous application of hormones; however, information on this practice is unavailable for this lily hybrid. In the present study, we soaked lily bulbs for 24 hours in one of four concentrations of abscisic acid (ABA) or one of three concentrations of the ABA biosynthesis inhibitor fluridone before subjecting the bulbs to a cold storage treatment at 4 °C. During cold storage, bulbs were sampled and buds were collected every 10 days for 80 days (that is, lasting eight times). The ABA and gibberellic acid 3 (GA3) contents of buds of treatments that showed a significant difference with the control were measured in a 10-day interval. Greenhouse experiments with different cold storage durations of bulbs that measured height, flower number per plant, and flower diameter were conducted. The interaction of hormone treatments and cold storage duration played nonsignificant roles in parameters of flower quality. Exogenous fluridone application to bulbs at 12 mg·L−1 improved flower quality: height and flower number increased significantly compared with the control, but flower diameter did not change. ABA had no effect on flower quality. Because the fluctuation of endogenous GA3 is more remarkable than ABA after the application of fluridone that led to the improvement of flower quality, it can be inferred that this influence on flower quality is achieved through fluridone’s regulation on the content of endogenous GA3. A low endogenous GA3/ABA ratio was associated with improved flower quality: 12 mg·L−1 fluridone decreased the GA3/ABA ratio in most times of the cold treatment. In addition, cold storage duration affected flower quality; the 50-day cold storage can achieve the highest height, the most flower number, and bigger flower diameter simultaneously. The results of the present study suggest that soaking bulbs in 12 mg·L−1 fluridone before cold treatment followed by 50 days of cold storage before planting will increase plant height and flower number per plant.
Controlled Water Deficit as an Alternative to Plant Growth Retardants for Regulation of Poinsettia Stem Elongation
Authors: Alem Peter , Thomas Paul A. , van Iersel Marc W.
Published: February 2019

Production of poinsettias (Euphorbia pulcherrima) often involves intensive use of plant growth retardants (PGRs) to regulate height. Height control is necessary for visual appeal and postharvest handling. Since PGRs do not always provide consistent height control and can have unwanted side effects, there is interest in alternative methods of height control. Since turgor potential drives cell expansion, and thus stem elongation, drought stress has potential for regulating plant height. Through soil moisture sensor-controlled irrigation, the severity of drought stress can be both monitored and controlled. The objective of our study was to compare poinsettia ‘Classic Red’ height control using PGRs (spray, mixture of daminozide and chlormequat at 1000 mg·L−1 each and drench, 0.25 mg·L−1 paclobutrazol) with the use of controlled water deficit (WD). Graphical tracking of plant height, using a final target height of 43.5 cm, was used to determine when to apply PGR or controlled WD. In the WD treatment, substrate volumetric water content (θ) was reduced from 0.40 to 0.20 m3·m−3 when actual height exceeded the expected height. PGR applications (spray or drench) reduced poinsettia height to 39 cm, below the final target level of 43.5 cm. WD resulted in a height of 44.5 cm, closest to the target height, while control plants were taller (49.4 cm). There was no effect of PGR drenches or WD on bract size, while spraying PGR reduced bract size by ≈ 40%. Bract chroma was unaffected by WD or PGR treatments. There was no difference in shoot dry weight between PGR- and WD-treated plants. Lateral growth was reduced by the PGR treatments, but not by WD. These results indicate that controlled WD can be used to regulate poinsettia height.
Meeting Initial Snap Bean Seedling Requirements with Starter Phosphorus or Bicarbonate to Solubilize Soil Phosphorus in High-phosphorus Soils
Authors: Björkman Thomas , Reiners Stephen
Published: February 2019

Starter phosphorus (P) is often recommended for warm-season vegetables sown in cool soil, even if soil P index levels are already high. The cost and environmental risk associated with excessive P fertilization justify re-examination of the practice. The objective of the study was to confirm that performance of early plantings of snap bean (Phaseolus vulgaris L.) is improved by starter P application and to test whether solubilizing soil P with potassium bicarbonate (KHCO3) can serve as an alternative in western New York soils. Addition of starter fertilizer at either recommended (15 kg·ha−1) or supraoptimal (35 kg·ha−1) P rates did not generally improve seedling tissue P concentration, early growth (biomass at flowering), or pod yield. Starter P application increased tissue P in only two of 11 experiments, and it never increased yield. Application of 6 kg·ha−1 KHCO3 to release soil-bound phosphate was not phytotoxic to snap beans. In the two experiments in which starter P increased tissue P, KHCO3 application had a smaller effect in one and no effect in the other. KHCO3 application did not increase yield in any of the six experiments where it was tested. A direct test of the contribution of P limitation to the poorer performance of early plantings showed that neither starter P nor KHCO3 application increased yield at early planting. Seasonal differences in crop performance could not be attributed to mineralization of soil phosphate after soil warmed. Water-extractable soil P was not lower in the spring than in summer, remaining constant at all 11 bean fields that were sampled from mid-April through mid-July. In these trials, P was likely not growth-limiting in the cool soils tested. Because starter P may not be necessary in vegetable soils testing high or very high for P, vegetables would also not likely benefit from bicarbonate application under high P conditions.
Artificially Induced Polyploidization in Lobularia maritima (L.) Desv. and Its Effect on Morphological Traits
Authors: Huang Renwei , Liu Daofeng , Zhao Min , Li Zhineng , Li Mingyang , Sui Shunzhao
Published: February 2019

Lobularia maritima (L.) Desv. is an important ornamental plant. We investigated an efficient method to induce tetraploid plants of L. maritima (L.) Desv. by treating germinating seeds and apical growing points of seedlings with a range of concentrations of colchicine for different periods of time. Examination of the ploidy level by counting chromosome numbers at metaphase confirmed that the chromosome number of diploid plants was 2n = 2x = 24, whereas 2n = 4x = 48 was observed in tetraploid plants. The morphological characteristics of the diploid and colchicine-induced tetraploid plants were compared. Increases in the size of leaves, flowers, and stomata were observed in the tetraploid plants compared with the diploids. However, the stomatal density and plant height of the tetraploid plants were lower than for the diploid plants. This study presents the first report of autotetraploid plants of L. maritima (L.) Desv., and of the successful generation of tetraploid plants with improved ornamental traits by colchicine treatment.