bluuebunny/crossref_metadata_2025 huggingface dataset:
Yield of Leafy Greens in High Tunnel Winter Production in the Northwest United States
Authors: Borrelli Kristy , Koenig Richard T. , Jaeckel Brad M. , Miles Carol A.
Published: February 2019

Season extension structures like high tunnels make it possible to produce cold-tolerant crops during winter months for both a longer cropping season and a winter market season. The effects of location and planting date on the fresh yield of several cultivars of Asian greens (Brassica rapa L.), lettuce (Lactuca sativa L.), and spinach (Spinacia oleracea L.) were examined at Moscow, ID/Pullman, WA, and Vancouver, WA, a cold temperate climate and a mild marine climate, respectively. In Winter 2005–06, 20 cultivars were evaluated and in Winter 2006–07 a subset of 12 cultivars were evaluated. Location impacted yield, and higher yields overall were attained at Vancouver than at Moscow/Pullman, likely as a result of more consistent, warmer soil and air temperatures as well as increasing irradiance in February and March at Vancouver. Asian green cultivars had the highest overall yield resulting from faster growth compared with spinach and lettuce cultivars at both locations. Although most lettuce cultivars grew throughout the winter, further research is needed to identify the most suitable cultivars, seeding dates, and planting densities to optimize winter production of this crop and for Asian greens and spinach. Planting date influenced yields with the highest yields obtained for the third planting date for all trials except at Moscow/Pullman in the second year. Overall, this research suggests that it is possible to grow many cold-tolerant cultivars of Asian greens, spinach, and lettuce in a high tunnel during the winter months in both mild and cold temperate northern climates.
Consumer Preferences for Local and Sustainable Plant Production Characteristics
Authors: Behe Bridget K. , Campbell Benjamin L. , Hall Charles R. , Khachatryan Hayk , Dennis Jennifer H. , Yue Chengyan
Published: February 2019

Some consumers are becoming more interested in and purchasing products that are locally grown and/or ecologically friendly. Market segmentation and product targeting are efficient methods to allocate a firm’s scarce marketing resources to supply heterogeneous markets. This study’s objective was to identify consumer segments, focusing on their gardening purchases, to determine whether there were differences in consumer preferences for provenance and environmental attributes for transplant purchases. Using a consumer survey of U.S. and Canadian consumers, we found that participants who purchased different plant types had distinct preferences for varying environmental attributes and provenances. We profiled nine consumer segments, identifying their plant purchases and preferences for local and sustainably grown products and plant containers. Results provide plant producers and retailers with market segments that can be identified and targeted and provide a basis for customizable marketing communications to enhance profits.
The Chilean Strawberry (Fragaria chiloensis): Over 1000 Years of Domestication
Authors: Finn Chad E. , Retamales Jorge B. , Lobos Gustavo A. , Hancock James F.
Published: February 2019

The cultivated strawberry of South America, the octoploid Fragaria chiloensis, has a long and interesting history. Although the origin of the species in Chile has not been completely determined, it may have been introduced from North America by birds. After making landfall in Chile, the species spread from the coast into the mountains eventually developing four biotypes. At least two native peoples, the Mapuche, between Rio Bío-Bío and south–central Chile, and the Picunche, between Rio Itata and Rio Bío-Bío, began the domestication process. Although white- and red-fruited forms were domesticated, the white form (likely because of its fruit size) may have been preferred because the red-fruited types are not mentioned as frequently in the literature. At the time of the Spanish invasion of Chile, F. chiloensis was widely grown in small garden plots. Under the Spanish rule, larger plantings, first of 1 to 2 ha and later of many hectares, were grown. As the Spanish continued their exploration and conquest of South America, they carried F. chiloensis with them up the western coast to Perú and Ecuador. For many years these scattered plantings were the source of fresh fruit for the burgeoning human populations. The cultivated F. ×ananassa was introduced in Chile ≈1830 but F. chiloensis was still preferentially grown. In the early 1900s, a large canning industry emerged serving hundreds of acres of F. chiloensis. By the 1950s, F. ×ananassa began to predominate and the rise in importance of the University of California and European-developed cultivars displaced much of the traditional F. chiloensis production. An increased awareness of this vast native Chilean genetic resource arose in the 1980s and 1990s. Scientists at the Universidad de Talca, associated with USDA-ARS Plant Exploration Office-sponsored trips to Chile, and with El Instituto de Investigaciones Agropecuarias–Cauquenes in Chile have collected and characterized germplasm that represents not only tremendous diversity, but captures many of the land races that have been developed. This germplasm has been used in small commercial plantings (0.1 to 0.3 ha) and in breeding programs to further develop F. chiloensis commercial cultivars. A small but vibrant community of small growers, particularly in Chile and Ecuador, produce the land races for commercial sale in local markets. Approximately 30 to 40 ha of open-field plantings are cultivated in Chile with yields averaging ≈3 to 4 tons/ha. The selected F. chiloensis genotypes and collected clones from the wild have served as a valuable source of germplasm in modern breeding programs and the development of new cultivars with the white color and aromatic flavor typical of some of the traditional selections well underway.
Yield, Water-, and Nitrogen-use Efficiency in Field-grown, Grafted Tomatoes
Authors: Djidonou Desire , Zhao Xin , Simonne Eric H. , Koch Karen E. , Erickson John E.
Published: February 2019

In addition to managing soilborne diseases, grafting with vigorous rootstocks has been shown to improve yield in tomato (Solanum lycopersicum L.) production. However, the influence of different levels of nitrogen (N) and irrigation supplies on grafted tomato plants has not been fully examined in comparison with non-grafted plants, especially under field conditions. The objective of this two-year study was to determine the effects of different irrigation regimes and N rates on yield, irrigation water use efficiency (iWUE), and N use efficiency (NUE) of grafted tomato plants grown with drip irrigation in sandy soils of north Florida. The determinate tomato cultivar Florida 47 was grafted onto two interspecific hybrid rootstocks, ‘Beaufort’ and ‘Multifort’ (S. lycopersicum × S. habrochaites S. Knapp & D.M. Spooner). Non-grafted ‘Florida 47’ was used as a control. Plants were grown in a fumigated field under 12 combinations of two drip irrigation regimes (50% and 100% of commonly used irrigation regime) and six N rates (56, 112, 168, 224, 280, and 336 kg·ha−1). The field experiments were arranged in a split-plot design with four replications. The whole plots consisted of the irrigation regime and N rate combination treatments, whereas the subplots represented the two grafting treatments and the non-grafted plants. Self-grafted ‘Florida 47’ was also included in the 100% irrigation and 224 kg N/ha fertilization treatment as a control. In 2010, the 50% irrigation regime resulted in higher total and marketable yields than the 100% irrigation regime. Tomato yield was significantly influenced by N rates, but similar yields were achieved at 168 kg·ha−1 and above. Plants grafted onto ‘Beaufort’ and ‘Multifort’ showed an average increase of 27% and 30% in total and marketable fruit yields, respectively, relative to non-grafted plants. In 2011, fruit yields were affected by a significant irrigation by N rate interaction. Grafting significantly increased tomato yields, whereas grafted plants showed greater potential for yield improvement with increasing N rates compared with non-grafted plants. Self-grafting did not affect tomato yields. More fruit per plant and higher average fruit weight as a result of grafting were observed in both years. Grafting with the two rootstocks significantly improved the irrigation water and N use efficiency in tomato production. Results from this study suggested the need for developing irrigation and N fertilization recommendations for grafted tomato production in sandy soils.
Impact of Hybrid Bluegrass and Tall Fescue Seeding Combinations on Brown Patch Severity and Weed Encroachment
Authors: Cutulle Matthew A. , Derr Jeffrey F. , McCall David , Horvath Brandon , Nichols Adam D.
Published: February 2019

Tall fescue (Festuca arundinacea) and hybrid bluegrass (Poa pratensis L. × Poa arachnifera) can both be successfully grown in the transition zone of the United States. However, each grass has limitations. Tall fescue is susceptible to the fungal pathogen Rhizoctonia solani, whereas slow establishment and susceptibility to weed infestations limit hybrid bluegrass. Previous studies have shown the benefits of combining kentucky bluegrass with tall fescue in seeding mixtures. Research was conducted to evaluate the impact of two seeding combinations of hybrid bluegrass and tall fescue (one combination seeded at a 1.9:1 seed count ratio favoring tall fescue, the other combination seeded at a 1:1.8 seed count ratio favoring hybrid bluegrass) as well as monocultures of the species on turfgrass cover, weed species infestation, brown patch disease severity caused by R. solani, sod strength and species ecology. The seeding combinations had lower weed density during establishment and greater turf cover than the monoculture of hybrid bluegrass. The monoculture of tall fescue was subjected to more brown patch disease than the seeding combinations during and after the first year of establishment. Brown patch infestations likely reduced tall fescue cover and led to a species shift favoring hybrid bluegrass in the seeding combinations based on tiller count and weight data. Seeding combinations of tall fescue and hybrid bluegrass are beneficial from an epidemiological perspective because they reduce disease and weed infestations compared with monocultures of either species. From an agronomic perspective, the seeding combination favoring tall fescue provided the densest turf, whereas the seeding combination favoring hybrid had the greatest sod strength. Chemical name used: clopyralid (3,6 dichloropyridine-2 carboxylic acid)
Development of a Fruitlet Growth Model to Predict Thinner Response on Apples
Authors: Greene Duane W. , Lakso Alan N. , Robinson Terence L. , Schwallier Phillip
Published: February 2019

Previous reports have provided evidence that measuring fruit growth rate may be a viable method to predict if a fruit will abscise or persist through the June drop period. A series of experiments were carried out over several years to develop a procedure that could be used to predict the response to a chemical thinner application within 7 to 8 days after application and before thinners exhibit their final effect. The procedure developed involves tagging 105 spurs on seven individual trees distributed appropriately in the orchard. A minimum of two measurements must be made, one 3 to 4 days after application and again 7 to 8 days after application. This model requires that fruit measurement should not start before fruit grow to a diameter of 6 mm and individual fruit within a spur should be numbered and identified. The model is based on the assumption that if fruit growth rate of a particular fruit over the measurement period is less than 50% of the growth rate of the fastest growing fruit on the tree during the same growth period, it will abscise, whereas if fruit growth rate exceeds 50% of the growth rate of the fastest growing fruit, it will persist. All data can be entered into an Excel spreadsheet and the output in the summary page gives the predicted fruit set expressed as percentage of the total number of fruit present. The strategy for crop load adjustment with chemical thinners has evolved over the years to a point where most orchardists plan and are prepared to make two or more thinner applications. The dilemma associated with this approach is to determine if additional thinner applications are necessary. Up to this point a tool designed specifically to provide this information has not been developed.
Isolation, Characterization, and Expression Analysis of the MaMDH Gene in Banana
Authors: Jia Cai-Hong , Liu Ju-Hua , Jin Zhi-Qiang , Deng Qiu-Ju , Zhang Jian-Bin , Xu Bi-Yu
Published: February 2019

A full-length cDNA isolated from banana (Musa acuminata L. AAA group) fruit was named MaMDH, containing an open reading frame encoding 332 amino acids that represents the gene for cytoplasmic malic dehydrogenase (MDH). Sequence analysis showed that MaMDH shares high similarity with MDHs from castor bean (XP_002533463), tobacco (CAC12826), peach (AAL11502), and chickpeas (CAC10208). Real-time quantitative polymerase chain reaction (PCR) analysis of MaMDH spatial expression showed that it was expressed in all organs examined: roots, rhizomes, leaves, flowers, and fruits. The expression was the highest in flowers followed by the fruits and roots, whereas the rhizomes and leaves displayed the lowest expression levels. Real-time quantitative PCR revealed that MaMDH exhibited differential expression patterns in post-harvest banana fruits correlating with ethylene biosynthesis. In naturally ripened banana fruits, MaMDH expression was in accordance with ethylene biosynthesis. In accordance, for banana fruits treated with the ethylene analog 1-methylclopropene (1-MCP), MaMDH expression levels were inhibited and remained constant. After treatment with ethylene, MaMDH expression in banana fruits significantly increased with ethylene biosynthesis and peaked 3 days after harvest, which was 11 days earlier than that in naturally ripened banana fruits. These results suggest that MaMDH expression is induced by ethylene to regulate post-harvest banana fruits ripening.
Vitamins, Flavonoids, and Phenolic Acid Levels in Early- and Late-ripening Apricot (Prunus armeniaca L.) Cultivars from Turkey
Authors: Gündoğdu Muttalip , Kan Tuncay , Gecer Mustafa Kenan
Published: February 2019

This study aimed at determination of vitamin (A, E, C, β-carotene, and lycopene), phenolic, and flavonoid contents in apricots at different stages of ripening using high-performance liquid chromatography (HPLC). The effect of ripening in terms of phytochemical contents was investigated. Early period apricots showed 2.5 to three times higher level of vitamins (A, E, C, and β-carotene, and lycopene) in all types of apricots than others (P < 0.05). Early-ripened cultivar, Boccuia, showed the highest level of vitamins, although a higher level of vitamin C was measured in late-ripened cultivar Levent (P < 0.05). No lycopenes were determined in late-period apricots in contrary to early- and middle-period apricots. Levels of phenolics and flavonoids were measured in all types (3-B-Q-D, procyanidin B1, B2, B3, caffeic acid, gallic acid, p-coumaric acid, epigallocatechine, catechine, epictechine, chlorogenic acid, ferrulic acid, and routine) and statistical deviation of all types was noted (P < 0.05). Among all, the cultivar Özal showed the highest level of chlorogenic acid (45,843.00 μg·g−1 dry matter) in all ripening periods, where middle-ripened cultivar Adilcevaz showed the lowest level of p-coumaric acid (7.93 μg·g−1 dry matter content base).
Evaluation of Lettuce Genotypes for Seed Thermotolerance
Authors: Lafta Abbas , Mou Beiquan
Published: February 2019

Thermoinhibition of lettuce (Lactuca sativa L.) seed germination is a common problem associated with lettuce production. Depending on lettuce cultivars, seed germination may be inhibited when temperatures exceed 28 °C. The delay or inhibition of seed germination at high temperatures may reduce seedling emergence and stand establishment of lettuce in the field, leading to a reduction in economic yield. To identify heat-tolerant lettuce genotypes, lettuce varieties and germplasm accessions were screened for the ability to germinate under high-temperature stress. Twenty-four to 26 genotypes were selected from each lettuce types (crisphead, romaine, butterhead, loose leaf, and wild species) and their seeds were placed in petri dishes to test their ability to germinate at high temperatures (29 and 34 °C) as compared with controls at 24 °C. Some lettuce genotypes showed thermotolerance to 34 °C (less than 20% reduction in germination) such as Elizabeth, PI 342533, PI 358025, Florida Buttercrisp, Kordaat, Corsair, FL 50105, PRO 425, PI 278070, Noemie, Picarde, Gaillarde, L. serriola (PI 491112, UC96US23, PI 491147), L. virosa (PI 274378 D), L. saligna (PI 491159), and primitive (PI 187238 A, PI 289063 C). The germination rates were consistent with the germination percentage at the high temperatures. Seed germination in the field was very low and positively correlated with seed germination at 29 and 34 °C. The highest field germination percentages (greater than 40%) were observed in Belluro, Mantilia, Mid Queen, Headmaster, PRO 874, PRO 425, FL 50105, Corsair, Romaine SSC 1148, Romaine Romea, Green Forest, Grenadier, FL 43007, Squadron, Xena, Noemie, Green Wave, Picarde, and Red Giant. The results of this study indicated that lettuce genotypes differ greatly in their ability to germinate at high temperatures as determined by the percentages and the rates of germination. Our research indicates that thermoinsensitive varieties could be used to expand lettuce production seasons in warm and low land cost areas and reduce the need for seed priming, lowering the production costs. The information may also be useful for growers to better choose cultivars for warm environments and for lettuce breeders to improve the crop for adaptation to global warming and climate change.
Fertilizer Effects of Soy-plastic Containers during Crop Production and Transplant Establishment
Authors: Schrader James A. , Srinivasan Gowrishankar , Grewell David , McCabe Kenneth G. , Graves William R.
Published: February 2019

As part of a project to develop and assess bio-based, biodegradable plastics for their potential to replace petroleum-based plastics in specialty-crop containers, we evaluated prototype containers made of protein-based polymers from soybean [Glycine max (L.) Merr.] for their effectiveness during production of plants in greenhouses and subsequent establishment of those plants outdoors. Our objective was to assess the function and biodegradation of soy-based plastic containers with special attention to whether a fertilizer effect results from degrading containers before and after plants are moved outdoors. In our first experiment, plants of tomato (Solanum lycopersicum L.) and pepper (Capsicum annuum L.) were grown in soy-plastic containers and control containers of petroleum-based (polypropylene) plastic under greenhouse conditions for 4 weeks. Each plant then was transplanted and grown in an outdoor garden plot for 5 weeks with the container removed, broken into pieces less than 4 cm in diameter, and installed beneath the roots of the transplant. Three additional experiments were performed: a greenhouse trial to quantify the relative concentration and form of plant-available nitrogen (N) released from soy-plastic containers of three types [soy plastic, soy plastic coated with polylactic acid (PLA), and soy–PLA polymer blended 50:50 by weight] during production; a greenhouse trial to evaluate the same three container types under production conditions with five container-crop species; and a field trial to assess the effects of the 50:50 soy–PLA container on transplant establishment. Plant-available N was released from soy-based plastic containers during greenhouse production, and transplant establishment was enhanced when the soy-based container was removed, crushed, and installed in the soil near plant roots. During greenhouse production, containers of high-percentage soy plastic released N at an excessive rate (623 mg·L−1 in leachate) and predominantly in the form of NH4+ (99.4% at 3 weeks of culture). Containers made by blending soy plastic with PLA released N at a favorable rate during production. In both field trials, growth and health of plants cultured in soy containers were better than those of controls. Although the design and material formulation of soy-plastic containers need to be improved to optimize container integrity and plant health during production, our results illustrate the potential to use soy-based plastics in biodegradable containers that release N at rates that promote growth and health of plants during greenhouse production and establishment of transplants outdoors.
Growing Media and Nutrient Solution Concentration Affect Vegetative Growth and Nutrition of Laelia anceps Lindl
Authors: Jiménez-Peña Nadia , Valdez-Aguilar Luis A. , Castillo-González Ana M. , Colinas-León María T. , Cartmill Andrew D. , Cartmill Donita L.
Published: February 2019

The domestication of wild orchids for commercial production is a new endeavor, which may represent a sustainable alternative to the collection/harvest from natural populations of threatened or endangered orchid species. In the present study, the growth and nutrition of vegetative plants of Laelia anceps Lindl. as affected by three components of the growing medium (peat, volcanic rock, and/or horticultural grade charcoal) and the nutrient solution concentration, measured as osmotic potential (ψS), were assessed using mixture experiments methodology. Leaf dry mass (DM) was the highest when plants were irrigated with nutrient solutions of –0.076 MPa. The lower leaf DM at lower or higher ψS was influenced by the medium because plants grown in 100% volcanic rock exhibited no effect, whereas plants grown in either 100% charcoal or 100% peat had a marked reduction. Regardless of the ψS of the nutrient solution, the highest leaf DM was observed in mixtures of two components containing charcoal and peat at high proportions. Dry mass of pseudobulbs and roots was highest in plants irrigated with solutions of –0.051 MPa, especially in mixtures with charcoal or 100% peat. Decreasing the ψS of the nutrient solution resulted in increased shoot nitrogen (N) and potassium (K) concentrations and decreased concentration of phosphorus (P), calcium (Ca), magnesium (Mg), boron (B), manganese (Mn), zinc (Zn), and copper (Cu). Increasing charcoal proportion in the growing media resulted in increased plant iron (Fe) and Cu concentration. However, increasing volcanic rock reduced plant P and K and increased Mn concentration. A higher proportion of peat was correlated with a decrease in plant Fe concentration. Leaf DM fit models on which macronutrient:micronutrient or micronutrient:micronutrient ratios were calculated, suggesting that nutrient imbalance may be responsible for a plant’s responses. The coefficients with the higher values included a micronutrient:micronutrient ratio, suggesting that an extremely fine balance in the uptake of a given micronutrient in relation to other micro- or macronutrient is of major importance for adequate growth of Laelia.
Variation in Nitrogen Rate and Local Availability Alter Root Architecture Attributes at the Onset of Storage Root Initiation in ‘Beauregard’ Sweetpotato
Authors: Villordon Arthur , LaBonte Don , Firon Nurit , Carey Edward
Published: February 2019

This study characterized the influence of nitrogen (N) rates and variation in local availability on root architecture as measured by lateral root (LR) development attributes during the onset of the storage root (SR) initiation stage in ‘Beauregard’ sweetpotato adventitious roots (ARs). In N rate experiments, plants grown without fertilizer N showed significantly lower values for all measured LR attributes compared with fertilized plants. Total first- (1LR) and second-order LR (2LR) length increased by 78% and 2873%, respectively, as N was increased from 0 to 50 kg·ha−1. Total 1LR and 2LR number increased by 32% and 1465%, respectively. Increasing the N rates to 100 and 200 kg·ha−1 did not result in further increases for all LR attributes measured. There were no differences in AR number between untreated controls and plants fertilized with 50 kg N/ha. However, the number of ARs increased by 65% when fertilizer N was increased from 50 to 100 kg·ha−1. Increasing the rate to 200 kg·ha−1 did not result in further increases in AR number. In split-root experiments, roots grown in the compartment with 50 kg N/ha had 135% and 2916% increase in total 1LR and 2LR length, respectively, compared with roots grown in the compartment without fertilizer N. Total 1LR and 2LR number increased by 110% and 2114%, respectively. There were 111% more ARs in the fertilized compartment relative to the unfertilized compartment. There were no differences in LR attributes and AR number between compartments that received similar fertilizer N rates. In fertilizer placement experiments, there were no differences in LR attributes between pre-mixing fertilizer N and placement of fertilizer ≈4 cm below the surface of the growth substrate. There were also no differences between the unfertilized control and placement of fertilizer ≈4 cm from the bottom of the pot. Plants grown in substrate with pre-mixed N showed 38% and 342% increase in 1LR and 2LR length, respectively, relative to the bottom placement of N. Total number of 1LR and 2LR in the growth substrate with pre-mixed N increased by 30% and 312%, respectively, relative to the bottom placement of N. These results represent the first evidence for the association between sweetpotato root architectural attributes and variation in N rate and localized availability. These results are also consistent with findings in model systems in which local N presence is necessary for LR development. This information can be used to further optimize SR yield by helping to ensure the availability of N at the optimum rate across time and space.
Long-term Yield of Horticultural Crops in Wisconsin in Relation to Seasonal Climate in Comparison with Southern Ontario, Canada
Authors: Tesfaendrias Michael T. , McDonald Mary Ruth , Warland Jon
Published: February 2019

The relationship between long-term weather and yield of 11 horticultural crops and one field crop in Wisconsin was determined for a 55-year period (1950–2005). The relationships among weather parameters and yield in Wisconsin were also compared with associations between weather and yields in Ontario, Canada, from a previous study. The number of days in a growing season with maximum temperatures 30 °C or greater (hot days) was negatively correlated with yields of beet for canning (r2 = 0.15), green pea (r2 = 0.16), onion (r2 = 0.08), and sweet corn for processing (r2 = 0.16) in Wisconsin. Hot days were also negatively correlated with yield of green pea (r2 = 0.16) in Ontario, Canada. Growing season precipitation in Wisconsin was positively correlated with yields of beet for canning (r2 = 0.18) and green pea (r2 = 0.09). An increase in yields of beet for canning in Wisconsin and green pea from Ontario was also observed with an increase in number of days with rainfall during the growing season (r2 = 0.12 and 0.15, respectively). Monthly minimum and maximum temperatures and hot days had an effect on vegetable yields in Wisconsin. A high number of days with precipitation in May and July was associated with yields of most vegetables and grain corn in Wisconsin. These results indicated the importance of the total and frequency of seasonal precipitation and the negative effect of exposure of crops to extreme temperatures on yields of vegetable crops.
Modeling Daily Water Use of Hydrangea macrophylla and Gardenia jasminoides as Affected by Environmental Conditions
Authors: O’Meara Lucas , van Iersel Marc W. , Chappell Matthew R.
Published: February 2019

Irrigation is an essential component of ornamental plant production, yet relatively little is known about how much water nursery crops require to maintain optimal growth rates. Our objectives were to precisely determine the daily water use (DWU) of Hydrangea macrophylla and Gardenia jasminoides grown in 6-L containers, quantify how this is affected by environmental conditions, develop a quantitative model describing DWU, evaluate this model with an independent data set, and determine the feasibility of using crop coefficients (Kc) for irrigation scheduling. In 2010, we quantified the DWU of two Hydrangea macrophylla cultivars, Fasan and Pia. There was little difference in DWU of the two cultivars, which ranged from 50 to 300 mL/plant/day depending on plant age and environmental (hoophouse) conditions. In 2010, daily light integral (DLI) had the greatest influence on DWU with DWU increasing with increasing DLI. The combination of plant age, final leaf area, DLI, and their interactions explained 83.2% and 90.8% of day-to-day variation in DWU of ‘Fasan’ and ‘Pia’, respectively. In July 2011, a follow-up study was conducted using Hydrangea macrophylla ‘Fasan’ and Gardenia jasminoides ‘Radicans’. DWU of ‘Fasan’ ranged from 50 to 200 mL/plant/day and DWU of ‘Radicans’ ranged from 50 to 560 mL/plant/day. The lower DWU of ‘Fasan’ in 2011 compared with 2010 was the result of stunted growth of the hydrangeas, a result of elevated temperatures within the hoophouse during the plants initial growth flush. Vapor pressure deficit (VPD) explained more of the daily fluctuations in DWU in 2011 compared with 2010. Predicting DWU of the 2011 ‘Fasan’ crop using 2011 environmental conditions and the model developed using the 2010 data resulted in DWU estimates that were on average 64% too high. This discrepancy is likely the result of slower overall growth rate and a 15.4% reduction in ‘Fasan’ total growth in 2011 compared with 2010 and points to the challenges of modeling DWU. There were distinct seasonal changes in Kc values for the crops, but the trends differed between 2010 and 2011. Our results suggest that an accurate measure of canopy size may improve performance of predictive water use models.
Impact of Demethylation Inhibitor (DMI) Fungicides on Clipping Yield and Rooting Depth of Creeping Bentgrass
Authors: Mitkowski Nathaniel A. , Chaves Arielle
Published: February 2019

Demethylation inhibitor fungicides (DMIs) have been used to manage a wide range of turfgrass diseases for many decades. Unfortunately, this class of fungicide can have unwanted plant growth regulator (PGR) effects on amenity turfgrasses. Recently, a number of new DMI fungicides have been registered for turfgrasses and are seeing expanded use. To determine if differences exist in the PGR-related activity among products, a 2-year field study was conducted examining six different DMI fungicides. Fungicides were applied to creeping bentgrass maintained at 0.33 cm and applied five or six times every 14 days at equivalent active ingredient rates. The results demonstrated that although paclobutrazol statistically reduced clipping weights, there was very little effect from DMI fungicides. In the first study year, propiconazole did produce higher clipping weights on two rating dates but this was not observed in the second year. Rooting depth was unaffected by any of the chemicals in either year. Although phytotoxicity may be a concern of turfgrass managers when applying DMI fungicides during the summer, it seems unlikely that these materials applied without the additional use of labeled PGRs will have any noticeable negative effects on foliar and root growth of creeping bentgrass in New England.
Evaluation of Strawberry Species and Cultivars for Powdery Mildew Resistance in Open-field and High Tunnel Production Systems
Authors: Kennedy Colleen , Hasing Tomas N. , Peres Natalia A. , Whitaker Vance M.
Published: February 2019

Many breeders have turned to wild relatives in search of beneficial traits such as disease resistance. In strawberry, the wild octoploid species Fragaria virginiana and F. chiloensis are fully interfertile with the cultivated species, F. ×ananassa, and are therefore potential sources of resistance. Powdery mildew may increase in economic importance in Florida in the near future as a result of the use of high tunnels and rowcovers for freeze protection, which limit free water and provide a favorable environment for disease development. The objective of this study was to screen an elite group of wild strawberry accessions for resistance to powdery mildew under two production systems. In 2010–11 and 2012–13, wild accessions, commercial standard cultivars, and susceptible controls were planted in open-field and high tunnel environments at the Gulf Coast Research and Education Center in Balm, FL. Although there was a significant year × genotype effect, some taxa showed high levels of resistance that were consistent across years. There was a high correlation for ratings of powdery mildew between the high tunnel and the open field for all genotypes (r = 0.89, P < 0.001). This information may be useful for breeders, because sources of resistance to powdery mildew are available within the tested genotypes. However, some accessions are highly susceptible to powdery mildew, and this must be considered when using these genotypes in breeding programs.
Retention of the Soil Fumigant Dimethyl Disulfide by Virtually and Totally Impermeable Film Mulches
Authors: McAvoy Theodore P. , Freeman Joshua H.
Published: February 2019

Alternative soil fumigants are needed to replace methyl bromide (MBr). One possible MBr alternative is dimethyl disulfide (DMDS). Highly impermeable plastic films such as virtually impermeable film (VIF) and totally impermeable film (TIF) can be used to increase fumigant retention. Possible advantages of increased fumigant retention are decreased fumigant use rates, decreased buffer zone requirements, reduced fumigant emissions, and improved pest control. Reduced fumigant emission may be especially important with DMDS because it has a sulfur odor, which is easily perceivable by the human nose. One potential drawback of decreasing film permeability may be longer plant back intervals, especially during periods with cool wet soils. The objective of these experiments was to evaluate the effect of TIF on DMDS retention at various rates compared with VIF. Experiments were conducted at the Virginia Tech Eastern Shore Agricultural Research and Extension Center (ESAREC) in Painter, VA, using high (561 L·ha−1), standard (468 L·ha−1), and reduced application rates (374, 281, and 187 L·ha−1) of DMDS in combination with TIF and VIF during spring and fall seasons. Soil temperature and fumigant concentration within the soil were recorded. A stepwise decrease in fumigant retention was seen as fumigant rates were reduced under TIF. Retention periods were impacted by soil temperature. High temperatures decreased the retention period and low temperatures increased the retention period. Standard fumigant rates (468 L·ha−1) under VIF resulted in similar fumigant concentrations in the soil as 281 L·ha−1 under TIF. Similar fumigant concentrations and possibly similar planting interval can be achieved by reducing fumigant use rates ≈40% to 50% under TIF compared with VIF.
An Efficient Ex Vitro Rooting and Acclimatization Method for Horticultural Plants Using Float Hydroculture
Authors: Clapa Doina , Fira Alexandru , Joshee Nirmal
Published: February 2019

This article presents a new acclimatization method, ex vitro acclimatization in float hydroculture. This protocol ensures the ex vitro acclimatization of the plantlets obtained in vitro in the rooting stage or the ex vitro rooting and acclimatization of the shoots obtained in the multiplication stage. Our hydroculture method is different from the techniques of flotation hydroculture because no fertilizers or plant growth regulators or other biostimulators are used and water oxygenation by bubbling is not provided. Ex vitro rooting and acclimatization in one stage without an in vitro rooting stage in floating cell trays was successfully carried out in Rubus fruticosus and Rosa hybrida cultivars, whereas ex vitro acclimatization of in vitro-rooted plantlets was successfully carried out in Rubus idaeus, Ribes nigrum, Prunus cerasus × P. canescens, Lycium barbarum (Goji berry), Amelanchier canadensis, Drosera rotundifolia, Drosera capillaris, and Nephrolepis sp. In another set of experiments, the floating cell trays were replaced with layers of floating perlite and the latter method was also tested for non-rooted shoots obtained in vitro in the multiplication stage or rooted plantlets obtained in the rooting stage. Direct ex vitro rooting in floating perlite was successful in ‘Tayberry’ (Rubus fruticosus × Rubus idaeus) (78.12% rooting); Amelanchier canadensis, Rubus fruticosus ‘Chester’, Rubus idaeus ‘Erntesegen’, Vaccinium macrocarpon, and Vaccinium corymbosum with rooting percentages above 80%; and Rubus idaeus ‘Willamette’ and Rosa hybrida ‘Cristiana’ with rooting percentages above 80%.
Prolonged Drought and Recovery Responses of Kentucky Bluegrass and Ornamental Groundcovers
Authors: Domenghini Jacob C. , Bremer Dale J. , Fry Jack D. , Davis Gregory L.
Published: February 2019

Municipalities often restrict irrigation of urban landscapes, causing plants to experience drought stress. Few data are available regarding drought resistance of non-turfgrass landscape species. This study evaluated the performance of one turfgrass (Poa pratensis L. ‘Apollo’) and eight herbaceous landscape species (Achillea millifolium L., Ajuga reptans L. ‘Bronze Beauty’, Liriope muscari Decne., Pachysandra terminalis Siebold and Zucc., Sedum album L., Thymus serpyllum L., Vinca major L., and Vinca minor L.) during a severe drydown and subsequent recovery. This greenhouse study was conducted in the spring/summer and again in the fall of 2010. S. album performed the best, averaging 254 days to decline to a drought rating of 1 (1 to 9 scale, 1 = dead/dormant and 9 = best quality). L. muscari and P. terminalis also performed well, averaging 86 days to a drought rating of 1. V. minor and V. major declined faster than the previous species, averaging 63 days. A. millifolium, A. reptans, P. pratensis, and T. serpyllum declined the fastest to a drought rating of 1 (mean 52 days). Thereafter, the only species to recover after 60 days of resuming irrigation were P. pratensis [46% pot cover (PC)], S. album (38% PC), and V. major (35% PC) in the spring/summer study; no species recovered during the fall study. Results indicate S. album, L. muscari, and P. terminalis are the most drought-resistant among the species evaluated in landscapes where severe drought may occur. V. minor and V. major are good selections in less severe droughts as is P. pratensis if periods of dormancy are acceptable.
Effect of Reflective Fabric on Yield of Mature ‘d’Anjou’ Pear Trees
Authors: Einhorn Todd C. , Turner Janet , Laraway Debra
Published: February 2019

Reflective fabric was installed before bloom in 2009 and 2010 in alleyways of a mature, low-density ‘Anjou’ pear orchard (269 trees/ha). Four treatments were applied to study intracanopy light environments on fruit growth rate and size, cropload, yield, and fruit quality: 1) no fabric (NF); 2) partial-season fabric applied before full bloom (FB) and removed 75 days after full bloom (dafb) (PSF); 3) full-season fabric applied before FB and removed at harvest (FSF); and 4) shadecloth (60%) applied 60 dafb through harvest (SC). PSF and FSF improved yield by 12% and 18%, respectively, over the two-year period relative to NF. The high yields of fabric treatments were attributed to fruit number in the lower (less than 2.4 m) interior, mid-, and exterior zones of the canopy. Photosynthetic active radiation (PAR) was increased by fabric 28%, 95%, and 30% in the lower exterior, mid-, and interior canopy, respectively. Photosynthesis:light response curves indicated improved carbon assimilation of pear leaves developing in the elevated PAR environment of the lower canopy. Fruit growth rate and final size were unaffected by fabric treatments. FSF fruit size was similar to NF despite higher fruit density. Compared with NF, FSF had a small, non-significant effect on fruit maturity (increased softening) at harvest. Yield and fruit size of SC fruit were significantly reduced. The number of fruit in SC trees did not differ from NF in 2009, but the effect of shade reduced fruit number in 2010. Fabric did not affect fruit quality attributes after three and six months of regular atmosphere cold storage. Pears from SC trees did not attain ripening capacity after three months of cold storage and a 7-day ripening period and had lower sugar content compared with other treatments. The cumulative yield advantages associated with FSF support its use in mature pear orchards.
Resistance to Species of Phytophthora Identified among Clones of Juglans microcarpa × J. regia
Authors: Browne Gregory T. , Leslie Charles A. , Grant Joseph A. , Bhat Ravindra G. , Schmidt Leigh S. , Hackett Wesley P. , Kluepfel Daniel A. , Robinson Reid , McGranahan Gale H.
Published: February 2019

Species of Phytophthora are serious soilborne pathogens of persian (english) walnut, causing crown and root rot and associated production losses worldwide. To facilitate the development of improved walnut rootstocks, we examined resistance of 48 diverse clones and seedlings of Juglans species to P. cinnamomi and P. citricola. Plants were micropropagated, acclimatized to a greenhouse environment, and then exposed to the pathogens in artificially infested potting soil mix. Inoculated plants, as well as noninoculated controls, were subjected to soil flooding for 48 hours every 2 weeks to facilitate infection by the pathogens. Two to 3 months after inoculation, resistance to the pathogens was assessed according to the severity of crown and root rot. Clonal hybrids of J. californica × J. regia were highly susceptible to the pathogens (means 52% to 76% root crown length rotted), while several clones of J. microcarpa × J. regia were significantly less susceptible (means 8% to 79% crown length rotted). Among clones of other parentages tested, including: J. microcarpa, (J. californica × J. nigra) × J. regia, J. hindsii × J. regia, (J. hindsii × J. regia) × J. regia, [(J. major × J. hindsii) × J. nigra] × J. regia, and J. nigra × J. regia, responses varied, but tended to be intermediate. When ‘Serr’ scions were budded or grafted on J. microcarpa × J. regia clone ‘RX1’ or Paradox (J. hindsii × J. regia) seedling rootstocks in a commercial orchard infested with P. cinnamomi, all trees on ‘RX1’ remained healthy, whereas only 49% of those on Paradox survived. Thus, useful resistance to Phytophthora is available among J. microcarpa × J. regia hybrids and is evident in ‘RX1’ rootstock.
Resilience, Stability, and Productivity of Alfalfa Cultivars in Rainfed Regions of North America
Authors: Picasso Valentin D. , Casler Michael D. , Undersander Dan
Published: February 2019

Resilient, stable, and productive forage systems are needed to endure increasingly frequent climatic extremes. Resilience is the ability of a forage system to withstand a climatic crisis with high yields, stability is the minimal variability of yields across normal years, and productivity is the average yield across normal years. The goal of this research was to quantify resilience, stability, and productivity of alfalfa (Medicago sativa L.) cultivars to identify superior ones. Forage yield means from alfalfa cultivar trials from 11 US states and one Canadian province over 19 yr (1995–2013) were analyzed using linear mixed models. Locations with an extreme crisis year were identified, and quantitative measures for resilience and stability for each cultivar were calculated. Productivity, stability, and resilience were different among cultivars across locations, showing that some cultivars were consistently superior for each variable. Cultivar stability was not associated with productivity, and it was negatively associated with disease resistance. Cultivar resilience was negatively associated with productivity, and not associated with other traits. Cultivar productivity has increased with year of release of cultivar, stability has not changed, and resilience has decreased. Therefore, stability and resilience are different dimensions, explained by different traits. A coordinated evaluation effort across locations is needed to test and improve cultivar resilience in the future, and develop alfalfa cultivars more profitable for the long term.
Morphological Traits Associated with the Quantitative Trait Locus for Lodging Tolerance in Soybean
Authors: Kitabatake Takuya , Yamaguchi Naoya , Sayama Takashi , Taguchi-Shiobara Fumio , Suzuki Haruka , Ishimoto Masao , Yoshihira Taiki
Published: February 2019

Lodging tolerance is an important trait of soybean [Glycine max (L.) Merr.] that affects yield stability and combine‐harvesting efficiency. Previously, a quantitative trait locus analysis of lodging scores was performed using recombinant inbred lines developed by crossing the lodging‐susceptible cultivar Toyomusume with the lodging‐tolerant cultivar Toyoharuka, and the major quantitative trait locus qLS19‐1 was identified. However, the morphological traits associated with qLS19‐1 remain unclear. To develop high‐precision DNA markers for qLS19‐1, it is necessary to identify its associated lodging tolerance‐related traits. Here, we studied the effects of qLS19‐1 on lodging‐related traits, primarily pushing resistance, using the Toyomusume‐backcrossed line and near isogenic lines (NILs). The Toyoharuka allele at qLS19‐1 may increase the number of primary lateral roots and cause a high pushing resistance, resulting in a lower ratio of the pushing resistance moment. The negative correlation between the number of primary lateral roots and the lodging scores in 2 yr suggests that this trait's influence on lodging score is stable. The numbers of primary lateral roots of six recombinant NILs were evaluated for the fine mapping of qLS19‐1. Sat_099 and BARCSOYSSR_19_1255 were the molecular markers that correlated with changes in the number of primary lateral roots among the recombinant NILs. We believe that the gene responsible for controlling primary lateral root number is located within the associated 356‐kb region. Thus, the investigation of the number of primary lateral roots and/or the marker‐assisted selection for qLS19‐1 may improve lodging tolerance in breeding programs.
Decadal Changes in Soil Organic Matter Due to Microaggregate and Hot Water Extractable Pools
Authors: Lambie Suzanne M. , Ghani Anwar , Mudge Paul L. , Stevenson Bryan A.
Published: February 2019

Core Ideas

Hot water extractable and microaggregate C explained 60% of soil C change over time.

Hot water extractable and microaggregate N explained 47% of soil N change over time.

No significant soil order effects on changes in C and N in fractions.

Storage of C and N within aggregates is important for long‐term stabilization of soil organic matter (SOM). We investigated whether changes in C and N associated with physical soil fractions and the hot water extractable pool were correlated to changes in topsoil C and N over three decades. Archived soil samples from three soil orders collected from 46 sites across New Zealand were physically fractionated and the aggregate abundance (and C and N contents) of fractions determined; hot water extractable C (HWC) and hot water extractable N (HWN) were also measured. Together the change of C and N in hot water extractable SOM, microaggregate within macroaggregate, and free microaggregate fractions explained 60 and 47% of the change in whole soil C and N, respectively. Soil order was not a significant factor in the model suggesting that similar processes were operating in all three soil types. In summary, the development of strategies that enhance the storage of labile SOM and microaggregates could reverse the trend of loss of SOM and its associated ecosystems services.