bluuebunny/crossref_metadata_2025 huggingface dataset:
Directionality of Pollinator Movements in Watermelon Plantings
Authors: Walters S. Alan , Schultheis Jonathan R.
Published: February 2019

Insect pollinators such as honeybees (Apis mellifera L.) and bumble bees (Bombus spp.) are strongly directional in their movements among flowers and typically move to the nearest neighboring inflorescence, which is often in the same row. Pollinator movements in watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] were determined by tracking pollen flow with the incompletely dominant lobed-leaf trait of ‘Crimson Sweet’ (Nl) as the pollen donor and the incompletely recessive ‘Sunshade’ (nl) as the recipient. Mature ‘Sunshade’ watermelon fruit were collected at 3-m increments down selected rows and across all rows in both directions from the central donor plants that made up 1% of the planting. The resulting progenies from each fruit collected were screened to determine the directionality of pollinator movements by the occurrence of the Nlnl genotype (or lobed-leaf phenotype). The row that went through the central donor plant block had higher percentages of lobed-leaf seedlings compared with the other rows evaluated. However, lobed-leaf seedlings were observed on rows at significant distances (greater than 10 m) from the donor block. This resulted most likely from long-distance pollen transport, in-hive pollen transfer, or multiple transfers of pollen to staminate (male) and/or pistillate (female) flowers by pollinators before reaching the final destination on a stigmatic surface at a substantial distance from donor plants. Because watermelon vines grow out in all directions, including across rows, a pollinator can easily move to adjacent flowers on a vine growing across rows; thus, the movements of pollinators in watermelon (and most likely other vining cucurbits) are not as simple as maintaining a linear direction down the row.
Relationships Between Yield and Mineral Concentrations in Potato Tubers
Authors: White Philip J. , Bradshaw John E. , Finlay M. , Dale B. , Ramsay Gavin , Hammond John P. , Broadley Martin R.
Published: February 2019

There is concern that modern cultivars and/or agronomic practices have resulted in reduced concentrations of mineral elements essential to human nutrition in edible crops. Increased yields are often associated with reduced concentrations of mineral elements in produce, and a number of recent studies have indicated that, when grown under identical conditions, the concentrations of several mineral elements are lower in genotypes yielding more grain or shoot biomass than in older, lower-yielding genotypes. Potato is a significant crop, grown worldwide, yet few studies have investigated whether increasing yields, through agronomy or breeding, affects the concentrations of mineral elements in tubers. This article examines the hypothesis that increasing yields, either by the application of mineral fertilizers and/or by growing higher-yielding varieties, leads to decreased concentrations of mineral elements in tubers. It reports that the application of fertilizers influences tuber elemental composition in a complex manner, presumably as a consequence of soil chemistry and interactions between mineral elements within the plant, that considerable variation exists between potato genotypes in the concentrations of mineral elements in their tubers, and that, like in other crops, higher-yielding genotypes occasionally have lower concentrations of some mineral elements in their edible tissues than lower-yielding genotypes.
Sweet Basil Requires an Irradiance of 500 μ mol·m−2·s−1 for Greatest Edible Biomass Production
Authors: Beaman Angela R. , Gladon Richard J. , Schrader James A.
Published: February 2019

Energy conservation in controlled-environment agriculture is a major concern for both commercial and research facilities as well as extraterrestrial facilities for food production. Supplying optimal irradiance by using electrical lighting for the greatest edible biomass production potentially is the greatest draw on energy during earth-based or extraterrestrial food production in controlled environments. Our objective was to determine the optimal irradiance for greatest edible biomass production of three cultivars of basil (Basilicum ocimum L.) in a controlled-environment production system. Seedlings of the three cultivars were transplanted into soilless medium, one plant per pot, and grew for 17 days in reach-in growth chambers maintained at 25 ± 4 °C with a 16-h photoperiod. Canopy-level irradiances of 300, 400, 500, and 600 μmol·m−2·s−1 were provided by cool-white fluorescent and incandescent lamps. Shoot growth was measured as height, diameter, and number of leaves 0.5 cm long or greater; and edible biomass was measured as leaf fresh weight, shoot fresh weight, and shoot dry weight. There was no irradiance × cultivar interaction, but main effects of irradiance and cultivar were observed. Plant growth and edible biomass production were least at 300 μmol·m−2·s−1 and greatest at 500 or 600 μmol·m−2·s−1. In several cases, 400 μmol·m−2·s−1 yielded intermediate growth or edible biomass. Within the main effect of cultivar, Italian Large Leaf produced greater edible biomass than ‘Genovese’, and ‘Nufar’ yielded an intermediate amount of shoot fresh weight and dry weight. Under our environmental conditions that included ambient CO2 concentration and ambient relative humidity, the rate of growth peaked at 500 μmol·m−2·s−1, and no additional accumulation of edible biomass occurred at 600 μmol·m−2·s−1. Based on our results, canopy-level irradiance of 500 μmol·m−2·s−1 provides maximum edible biomass production of basil in a controlled-environment production system.
Organ Loss and Yield Impacts of ‘Valencia’ Sweet Orange in Response to Fruit Abscission Agents
Authors: Pozo Luis , Burns Jacqueline K.
Published: February 2019

To successfully use abscission agents for ‘Valencia’ sweet orange mechanical harvesting throughout the harvest season, unwanted flower, fruitlet, and leaf drop must be assessed and minimized. Ethephon (400 mg·L−1), 1-methylcyclopropene (1-MCP; 5 mm), ethephon + 1-MCP, 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP; 200 mg·L−1), and a kinetic adjuvant control [0.15% (v/v)] were applied to ‘Valencia’ branches at various times from full bloom in Mar. 2006 to the end of full bloom in Mar. 2008. Effects of these treatments on fruit detachment force (FDF) and abscission of developing and mature fruit, flowers, and leaves were recorded. Three separate response periods to abscission agent applications were observed: the first spanned the first 100 days after bloom (DAB) and was characterized by high initial response followed by decreasing sensitivity; the second spanned between 100 and 225 DAB and was characterized by little to no response; and the third spanned from 225 DAB to harvest and was characterized by a gain in sensitivity. Young fruitlets in the first response period were highly sensitive to ethephon but were less sensitive to CMNP or ethephon + 1-MCP. Mature fruit in the third response period were highly sensitive to CMNP and less sensitive to ethephon or ethephon + 1-MCP. The application of ethephon resulted in high leaf abscission and showed no clear sensitivity pattern throughout both cropping years. CMNP or ethephon + 1-MCP application caused minimal leaf abscission. The same abscission agent treatments were applied on whole tree canopies 6 and 28 DAB in Mar. 2007. Application date had no significant effect on the measured parameters. Although ethephon application induced high initial leaf drop, leaf area indices determined 7 months after any compound application were not significantly different. However, subsequent 2008 yield in trees sprayed with ethephon in 2007 was significantly less, whereas 2008 flower number was higher. The results indicate a complex interaction of fruitlet abscission and leaf loss during the first response period contributed to yield reduction and increased flower number in ethephon-treated trees.
Genetic Relatedness in Prunus Genus Revealed by Inter-simple Sequence Repeat Markers
Authors: Uğurtan Yılmaz Kadir , Ercişli Sezai , Asma Bayram Murat , Doğan Yıldız , Kafkas Salih
Published: February 2019

Inter-simple sequence repeat (ISSR) markers were used to study the genetic diversity and phylogenetic relationships among 16 genotypes from subgenus Prunus (six genotypes from section Prunophora, seven genotypes from section Armeniaca and two plumcot genotypes, and one genotype from subgenus Cerasus) in Prunus genus. From the polymerase chain reaction amplifications with 20 ISSR primers showing polymorphism among subgenera and sections, 180 polymorphic ISSR bands were detected and polymorphism ratio ranged from 57% to 100%. Based on the unweighted pair group method with arithmetic mean (UPGMA) analysis and principal coordinate analysis (PCoA) using the Jaccard coefficient, a dendrogram and three-dimensional plot were constructed including genotypes in Prunus genus. Two main groups formed in the dendrogram; one of them (Cluster I) included Cerasus, whereas Cluster II included Prunus. Cluster II also divided into three subgroups, including sections Prunophora, Armeniaca, and plumcot. Both UPGMA and the PCoA demonstrated that Armeniaca genotypes had lower genetic variation and plumcot genotypes are closer to the plums than the apricots. The ISSR-based phylogeny was generally consistent with Prunus taxonomy based on molecular evidence, suggesting the applicability of ISSR analysis for genotypic and phylogenetic studies in Prunus genus.
The Influence of Drip Irrigation or Subirrigation on Zucchini Squash Grown in Closed-loop Substrate Culture with High and Low Nutrient Solution Concentrations
Authors: Rouphael Youssef , Colla Giuseppe
Published: February 2019

Zucchini plants (Cucurbita pepo L. cultivar Afrodite) were grown during a summer–fall season in closed-soilless systems using a mixture peat–pumice to evaluate the effects of irrigation system (drip irrigation and subirrigation) and nutrient solution concentration (half = 1 dS·m−1 and full = 2 dS·m−1) in terms of substrate electrical conductivity (ECs) using the dilution 1:1.5 media:water method, growth, yield, leaf mineral composition, fruit quality, and mineral solution composition. At the end of the cultural cycle, the highest ECs at the upper (0 to 7.5 cm) and lower (7.5 to 15.0 cm) layers were recorded with subirrigation using a full nutrient solution concentration. The highest plant growth, yield, and leaf macroelements concentration (nitrogen, phosphorus, and potassium) were recorded in both irrigation systems using a full-strength solution, followed by drip irrigation, and finally by subirrigation treatment using a half-strength nutrient solution. Fruit yield, fruit mineral composition (phosphorus, potassium, calcium, and magnesium), and leaf macroelements concentration (nitrogen, phosphorus, potassium, and magnesium) were substantially reduced when the concentrations of macronutrients in the feed solution were lowered to 50% of control. Using half-nutrient solution concentration, the marketable yield reduction was more pronounced with subirrigation (58%) than with drip irrigation (42%). The variation of the macronutrient and EC in the solution during the growing cycle was less pronounced in the subirrigation than with the drip irrigation system, which represents an important aspect for the simplification of the closed-loop management of the nutrient solution.
Assessment of Partial Peat Substitutes for the Production of Camellia japonica
Authors: Larcher Federica , Scariot Valentina
Published: February 2019

Peat is widely used for container plant production. As a result of its high costs, decreasing availability, and environmental concerns, alternative substrates for potting ornamentals are needed. In the present study, five peat substitute materials (local green compost, pumice, coconut fibers, coconut “peat,” and pine bark) were evaluated to assess their suitability for containerized acidophilus ornamental plant production. Camellia was chosen as the indicator crop and, to verify the influence of genotype on cultivation response, three different cultivars were used. The main physical, chemical, and biological properties of the substrates were determined before and at the end of the culture and were in general within the acceptable ranges. Except for the negative effect of green compost, during the cultivation period (2 years), the alternative materials did not affect or slightly improved the plant development and the ornamental characteristics compared with the standard substrate. Among the materials tested, considering both technical and economical factors, coconut fibers were a good partial peat substitute for potted camellia production.
Determination of Photoperiod-sensitive Stages of Development of the Short-day Plant Celosia
Authors: Warner Ryan M.
Published: February 2019

Celosia argentea L. var. plumosa Voss. (celosia) is a bedding plant crop that often exhibits premature flowering during commercial production, resulting in plants of unacceptable quality. Celosia is a facultative short-day plant. Understanding the photoperiod-sensitive stages of development is critical for management of photoperiodic crops. Limited inductive photoperiod experiments, in which photoperiodic plants are moved from noninductive to inductive conditions for flowering at varying stages of development and for varying durations before returning to noninductive conditions, were conducted to determine when celosia becomes sensitive to floral-inducing short days and how many photoinductive cycles are necessary for floral induction. Plants became receptive to short days ≈9 to 12 days after seedling emergence (DAE). Between six and nine short photoperiods beginning 9 DAE were sufficient to commit plants to flowering, depending on the cultivar evaluated. Early flowering was highly correlated with reductions in plant quality parameters, including the number of inflorescences produced, the number of lateral branches, and shoot dry weight. By the time plants had developed five nodes, photoperiod no longer impacted time to flower, indicating that celosia remains photoperiod-sensitive for floral induction only from ≈9 to 45 DAE at 20 °C.
Bacterial Leaf Scorch, a New Blueberry Disease Caused by Xylella fastidiosa
Authors: Chang Chung-Jan , Donaldson Ruth , Brannen Phil , Krewer Gerard , Boland Robert
Published: February 2019

Since 2004, growers and scientists have observed a disorder described as “yellow twig” or “yellow stem” affecting a major selection of southern highbush blueberry, FL 86-19, in the south Georgia blueberry production region. The initial symptom observed was leaf marginal chlorosis and subsequent necrosis, which eventually progressed throughout the whole leaf resulting in early leaf fall. Thin, yellow twigs or yellow stems became evident on some cultivars. The described symptoms on blueberry were similar to those exhibited on grapes with Pierce's disease and on plum with leaf scald disease. This prompted the enzyme-linked immunosorbent assay (ELISA) tests and isolations of Xylella fastidiosa, which is the causal agent of the previously mentioned grape and plum diseases. Two leaf and two root tissue samples were collected from a diseased FL 86-19 plant for isolation and ELISA testing on 2 Mar. 2006. ELISA results indicated all four tissues tested positive for the bacterial pathogen, X. fastidiosa, whereas only the two root tissues provided positive isolations. One leaf and one root tissue sample were later collected from each of five additional diseased plants for isolation and ELISA testing. Both isolation and ELISA testing methods obtained positive results. Cultures were multiplied to inoculate seedlings of three cultivars: ‘Southern Belle’ (eight plants), ‘Premier’ (six), and ‘Powderblue’ (six) on 23 May 2006 and one selection, FL 86-19 (eight), on 31 May 2006. Two FL 86-19 plants started to show symptoms of marginal necrosis 54 days postinoculation, whereas one plant each of ‘Southern Belle’ and ‘Powderblue’ started to show symptoms of marginal necrosis 63 days postinoculation and ‘Premier’ stayed symptomless. All eight culture-inoculated FL 86-19 plants (100%) showed symptoms 72 days postinoculation, but no symptoms were observed on the control plants. One hundred twenty-six days postinoculation, two ‘Powderblue’ and four ‘Southern Belle’ plants showed mild symptoms, whereas all ‘Premier’ plants were asymptomatic. Positive reisolations of the bacteria from the inoculated symptomatic plants, not from asymptomatic plants, fulfilled Koch's postulates, which confirmed X. fastidiosa was the causal bacterium of the new blueberry disorder, the bacterial leaf scorch of blueberry.
Treatment with Peracetic Acid Extends the Vase Life of Lisianthus (Eustoma grandiflorum) Flowers
Authors: Riva Fernando de la , Mazuela Pilar Carolina , Álvaro Juan Eugenio , Urrestarazu Miguel
Published: February 2019

The effect of peracetic acid on the vase life and bud opening of cut flowers of Lisianthus was investigated. Eustoma grandiflorum is an attractive cut flower with a considerable length of vase life (usually weeks for freshly harvested stems). It is well known that the addition of sucrose into the vase solution increases significantly the longevity of cut flowers. Two different experiments of vase life were carried out. The first used cultivars of the Mariachi Series: Blue, Green, Blue Picotee, and Pink, whereas the second used Rosita White and Piccolo White 1. The control plants (T1) were supplied with tap water. Treatment 2 (T2) was similar to T1 with the addition of 3% sucrose. In the third (T3) and fourth (T4) treatments, sodium hypochlorite and a stabilized peracetic mixed system (PAA) were added, respectively. The number of flowers that opened from buds between cultivars was significantly different. With the addition of sucrose into the vase solution, a significant increase in longevity was recorded, which was also observed after the addition of both biocides to the respective treatments. This can be extended up to 15% by the addition of sucrose to the vase solution and up to 30% if PAA is incorporated into the vase solution. The results suggest that PAA can be a useful alternative to sodium hypochlorite for vase solutions because it is without the health drawbacks of trihalomethanes. The degradation of PAA is environmentally friendly, because it decomposes to form biodegradable acetic acid and eventually enters the environment as atomic oxygen.
Heterogeneous Distribution of Weedy Paspalum Species and Edaphic Variables in Turfgrass
Authors: Henry Gerald M. , Burton Michael G. , Yelverton Fred H.
Published: February 2019

Dallisgrass (Paspalum dilatatum Poir.) and bahiagrass (Paspalum notatum Fluegge) are two of the most troublesome weed species in managed turfgrass. These rhizomatous, perennial grass species affect appearance, texture, and playability of turf in home lawns, golf courses, and athletic fields. The severity and prevalence of these problem species as well as the difficulty of achieving control with herbicide management alone invite the examination of their realized niches for clues to improved management tactics. The distribution of these species was evaluated in both fairways and roughs of three holes on each of two golf courses in North Carolina. Golf courses were selected based on the presence of both weed species. Individual plants were mapped using a high-precision global positioning system unit. This unit was also used to delineate between the rough and fairway height of cut as well as obtain elevation characteristics of each hole. Soil moisture and soil compaction estimates were obtained by sampling on a 9-m grid. Environmental characteristics used for χ2 analysis consisted of mowing height, soil compaction, soil moisture, and elevation. Data were subjected to χ2 analysis to determine if the existing distribution of Paspalum spp. differed from an expected random distribution across all environmental factors. Bahiagrass growth and distribution was more affected by mowing height than dallisgrass. Bahiagrass was predominantly distributed in the rough, whereas dallisgrass occurred at both mowing heights. Similar responses were observed for both species with regard to soil compaction. Higher plant density for both species was observed in moderately compacted soil (40 to 60 N·m−2). Bahiagrass distribution was unaffected by soil moisture. Dallisgrass density was lower in areas with low volumetric soil water content (less than 27%). Although different from an expected uniform distribution on all six holes, the elevation with the highest Paspalum spp. density varied across holes. Results suggest that it may be possible to disadvantage Paspalum spp. in competitive interactions with desirable species through the alteration of landscape attributes. Substrate selection during construction, aeration, and mowing height may help create a landscape that discourages Paspalum spp. infestation.
Correlations of Leaf Relative Water Content, Canopy Temperature, and Spectral Reflectance in Perennial Ryegrass Under Water Deficit Conditions
Authors: Jiang Yiwei , Liu Huifen , Cline Van
Published: February 2019

Accurate, rapid, and nondestructive estimates of turfgrass leaf water status are important for site-specific irrigation and drought stress management. The objective of this study was to identify changes and correlations among the canopy reflectance, canopy temperature, and leaf relative water content (RWC) of perennial ryegrass (Lolium perenne L.) under water deficit conditions. Six cultivars of perennial ryegrass were subjected to dry-downs in the field from May to Aug. 2007 and from June to Aug. 2008. Turf quality was positively correlated with soil moisture (SM), RWC, and normalized difference vegetation index (NDVI), but negatively correlated with canopy and ambient temperature differentials (ΔT). ΔT was well correlated with RWC (r = –0.77 to –0.78) and SM (r = –0.66 to –0.74), whereas SM was correlated with RWC (r = 0.64 to 0.74) across seasons in both years. When a wide range of stress symptoms occurred in July and Aug., RWCs became highly correlated with ΔT (r = –0.80 to –0.89) and NDVI (r = 0.77 to 0.81), whereas ΔT was correlated with NDVI (r = –0.70 to –0.80) in both years. SM was well correlated with RWC (r = 0.71 to 0.80), NDVI (r = 0.70 to 0.73), and ΔT (r = –0.76 to –0.78) in July and August in both years. These results suggest that changes in ΔT can be used to predict well the leaf water and soil moisture content of perennial ryegrass under water deficit conditions. Combined with NDVI, the correlations can be used for direct mapping of the variability in grass water status, thus improving irrigation management.
Effect of Training System, Rootstock, and Cultivar on Sweet Cherry Powdery Mildew Foliar Infections
Authors: Calabro Jill Marie , Spotts Robert A. , Grove Gary G.
Published: February 2019

Selected orchard practices were evaluated for their influence on powdery mildew infections (caused by Podosphaera clandestina) of sweet cherry in two orchards in Oregon. Three training systems (Spanish bush, steep leader, and central leader), four rootstocks (Edabriz, Maxma 14, Mazzard, Pontaleb), and five cultivars (cvs. Bing, Lapins, Regina, Staccato, and Sweetheart) were included in our studies. Mildew severity was significantly the highest on trees trained on the Spanish bush system (10.7% and 16.6% of leaf surface colonized in 2003 and 2004, respectively) when compared with Vogel central leader (2.7% and 10.8% of leaf surface colonized in 2003 and 2004, respectively) and steep leader (5.3% and 6.9% of leaf surface colonized in 2003 and 2004, respectively) systems. Foliar mildew infections were significantly the lowest on rootstock Edabriz (0.5% and 1.5% of leaf surface colonized in 2003 and 2004, respectively). A range of susceptibilities was noted among the cultivars tested. Cv. Regina had the lowest level of foliar mildew infections in both 2003 and 2004 (0.1% and 0% of leaf surface colonized, respectively), whereas cvs. Staccato and Sweetheart had the highest (32.6% and 33.4% of leaf surface colonized, respectively). Results indicate that selection of training system, rootstock, and cultivar may impact the severity of powdery mildew infestations in sweet cherry orchards.
Novel Diversity Identified in a Wild Apple Population from the Kyrgyz Republic
Authors: Volk Gayle M. , Richards Christopher M. , Henk Adam D. , Reilley Ann , Miller Diane D. , Forsline Philip L.
Published: February 2019

The genetic diversity of a wild Malus population collected in the Kyrgyz Republic was compared with seedlings of Malus sieversii collected in Kazakhstan. Based on microsatellite marker results, we conclude that the population of 49 individuals collected in the Kyrgyz Republic includes private alleles and this population is assigned to a common genetic lineage with M. sieversii individuals found in the Karatau Mountain range of Kazakhstan. We recommend that a subset of these individuals be included in the National Plant Germplasm System Malus collection so they may be made available to breeders, physiologists, and other scientists for further examination.
Ethephon Residual Catalysis on Unrooted Impatiens hawkeri Cuttings and Stock Plants
Authors: Leatherwood W. Roland , Dole John M. , Faust James E.
Published: February 2019

Ethephon [(2-chloroethyl) phosphonic acid] is used to increase stock plant cutting productivity through increased flower and flower bud abscission and branching. However, ethylene evolution resulting from ethephon application is suspected to cause leaf abscission of unrooted cuttings during shipping. It was the objective of this study to assess ethylene evolution from ethephon-treated cuttings during storage and shipping of unrooted cuttings. Impatiens hawkeri W. Bull ‘Sonic Red’ and ‘Sonic White’ stock plants were treated with 0, 250, 500, or 1000 mg·L−1 ethephon. Cuttings were harvested from 1 to 21 days later and each harvest was stored at 20 °C in sealed jars for 24 h before ethylene measurement. Higher ethephon doses resulted in greater ethylene generation. Cuttings harvested 1 day after treatment with 0, 250, 500, or 1000 mg·L−1 ethephon evolved 0.07, 1.3, 1.7, or 5.8 μL·L−1·g−1 (fresh weight) ethylene in the first 24 h of storage at 20 °C, respectively. Twenty-one days after treatment, cuttings from the same plants evolved 0.05, 0.05, 0.15, or 0.14 μL·L−1·g−1 (fresh weight) ethylene in the first 24 h of storage at 20 °C, respectively. As cuttings were harvested from Day 1 to Day 21, ethylene concentrations evolved within the first 24 h of storage decreased exponentially. Rinsing cuttings, treated 24 h earlier with 500 mg·L−1 ethephon, by gently agitating for 10 s in deionized water reduced ethylene evolution to 0.7 μL·L−1·g−1 (fresh weight) as compared with 1.7 for unrinsed cuttings. Cuttings harvested 24 h after treatment with 500 mg·L−1 ethephon stored at 10, 15, 20, and 25 °C for 24 h evolved 0.37, 0.81, 2.03, and 3.55 μL·L−1·g−1 (fresh weight) ethylene. The resulting mean temperature coefficient (Q10) for the 10 to 25 °C range from all replications was 5.15 ± 0.85. Thus, ethylene continues to evolve from ethephon-treated Impatiens hawkeri stock plants for up to 21 days and can accumulate to high concentrations during cutting storage.
Identification of Historic Apple Trees in the Southwestern United States and Implications for Conservation
Authors: Routson Kanin J. , Reilley Ann A. , Henk Adam D. , Volk Gayle M.
Published: February 2019

Many apple varieties commonly planted in the United States a century ago can no longer be found in today's orchards and nurseries. Abandoned farmsteads and historic orchards harbor considerable agrobiodiversity, but the extent and location of that diversity is poorly understood. We assessed the genetic diversity of 280 apple (Malus ×domestica Borkh.) trees growing in 43 historic farmstead and orchard sites in Arizona, Utah, and New Mexico using seven microsatellite markers. We compared the samples to 109 cultivars likely introduced into the southwest in the late 19th and early 20th centuries. Genetic analysis revealed 144 genotypes represented in the 280 field samples. We identified 34 of these 144 genotypes as cultivars brought to the region by Stark Brothers Nursery and by USDA agricultural experiment stations. One hundred twenty of the total samples (43%) had DNA fingerprints that suggested they were representative of these 34 cultivars. The remaining 160 samples—representing 110 genotypes—had unique fingerprints that did not match any of the fingerprinted cultivars. The results of this study confirm for the first time that a high diversity of historic apple genotypes remain in homestead orchards in the U.S. southwest. Future efforts targeting orchards in the southwest should focus on conservation for all unique genotypes as a means to sustain both cultural heritage and biological genetic diversity.
Assessment of Genetic Diversity of Chinese Sand Pear Landraces (Pyrus pyrifolia Nakai) Using Simple Sequence Repeat Markers
Authors: Jiang Zhengwang , Tang Feiyan , Huang Hongwen , Hu Hongju , Chen Qiliang
Published: February 2019

The sand pear (Pyrus pyrifolia Nakai) is an important fruit crop in China. In this study, simple sequence repeats (SSRs) were used to estimate the level and pattern of genetic diversity among 233 sand pear landraces collected from 10 different geographic regions in China. The results demonstrated that the SSR technique is an effective tool for assessing genetic diversity and the geographic pattern of genetic variation among sand pear landraces of different origins. A total of 184 putative alleles was detected using 14 primer pairs with an average of 13.1 alleles per locus. The mean expected heterozygosity and observed heterozygosity across all loci were 0.705 and 0.671, respectively. High genetic diversity was found in all populations except for that originated from Jiangxi (Ae = 3.149; He = 0.655), whereas at the regional level, those from central China were less diverse than those from other regions. Analysis of molecular variance showed that most genetic differences resided among landraces within populations. Additionally, unweighted pair group with arithmetic average clustering and principal component analysis plotting based on Nei's genetic distance revealed distinct gene pools in agreement with geographic distribution.
Screening Citrus Rootstocks and Related Selections in Soil and Solution Culture for Tolerance to Low-iron Stress
Authors: Castle William S. , Nunnallee James , Manthey John A.
Published: February 2019

A broad range of plant selections across the orange subfamily Aurantioideae were screened in solution and soil culture for their tolerance to low iron (Fe) stress. Young seedlings grown in soil were transferred to tubs of +Fe nutrient solution, which was later replaced after a brief period with a –Fe solution. Over several trials, ≈20 white root tips were harvested periodically from the plants in each tub and assayed for their ability to reduce Fe3+. The procedure was miniaturized to determine if a fewer number of root tips could be assayed to screen individual plants and to estimate the required sample size. For solution screening, seven root tips were estimated to be adequate for representing a single plant. Seedlings of a few selections were also grown in small containers of soil amended with 0% to 5.9% CaCO3. The results in solution and soil culture were consistent with each other and with previous assessments of the various selections. Based on a summary of the solution and soil responses, the citrus selections were grouped in descending order of Fe3+ reduction rates as Volkamer lemon/Rangpur/sour orange selections/Citrus macrophylla > mandarins and mandarin hybrids > citranges > citrumelos > trifoliate orange. Of the citrus relatives tested in solution culture only, those in the genera Glycosmis, Citropsis, Clausena, and Murraya had high Fe reduction rates with good seedling growth and new leaves developed a light yellow color or showed no loss of greenness. Other citrus relatives in the genera Severinia, Atalantia, and Fortunella and most somatic hybrids had low seedling vigor and produced too few root tips to be properly assessed. The results are useful because of the breadth of selections screened, the identification of various citrus relatives as potential sources of low-Fe stress tolerance in breeding new rootstocks, and the apparent positive relationship between the Fe3+ reduction responses, soil screening responses, and field experiences with carbonate-induced Fe chlorosis responses.
Organic Mulch Impact on Vegetation Dynamics and Productivity of Highbush Blueberry Under Organic Production
Authors: Burkhard Nicole , Lynch Derek , Percival David , Sharifi Mehdi
Published: February 2019

A 2-year study in Nova Scotia examined the effectiveness of thickly applied organic mulches as a method of weed control in highbush blueberries (Vaccinium corymbosum L.), and assessed weed and mulch impact on crop growth, leaf nutrient concentration, yield, and quality under organic production management. Mulches, applied in-row at 20-cm depth, included pine needles (PN), manure–sawdust compost (MC), and seafood waste compost (SC). Competition from weeds negatively affected crop growth and productivity, reducing canopy volume (16% to 38%), leaf nitrogen concentration and berry yields (up to 92%), number (up to 91%), and specific weight (up to 21%). Among mulches, PN proved to be the most effective in suppressing weed growth with 55% less and 73% less aboveground weed biomass compared with the control in 2005 and 2006, respectively, although PN productivity effects were much more modest. One year after application, PN lost some efficacy at suppressing weeds but was still superior to both composts. Distribution of weed species was substantially altered by mulch treatment. Both composts prevented some weed emergence (i.e., sheep sorrel), but weed seeds germinating in composts, especially SC, experienced prolific growth likely as a result of available nutrients in composts. No detrimental effects on short-term plant productivity were noted despite high C:N ratios of PN and MC (72:1 and 48:1, respectively). Plant vigor and yield were typically higher for compost mulch treatments, especially in weed-free subplots, and composts provided more complete fertilization reflected in increased leaf tissue elemental (NPK) composition. Fruit soluble solid (sugar) content was found to be significantly lower in PN and MC compared with SC, whereas total phenolic content was unaffected by mulches. Mulch application can improve organic highbush blueberry productivity by improving soil properties, nutrient availability, and weed suppression; however, precautions should be taken to avoid excess nutrient loading and weed seed contamination of mulches.
Factors Influencing the Growth of Farmers' Markets in Indiana
Authors: Hofmann Christa , Dennis Jennifer H. , Marshall Maria
Published: February 2019

Nationally, the number of operating farmers' markets has increased 111% from 1755 markets in 1994 to 3706 in 2004. Indiana's farmers' markets have increased at double the rate in the same timeframe. An Internet and mail census was sent to market managers to assess operational procedures and factors that influence customer and vendor participation in the market. A two-stage least squares model was estimated for the vendor and customer model. Paying fees and the number of customers present were the two variables that had a significant, positive influence on vendor participation. The presence of WIC, number of products available, the absence or presence of live music, absence or presence of cooking demonstrations, and number of vendors were significant for the customer model. The absence or presence of concession stands and picnic areas was significant at the 0.10 level in the customer model.
Effects of Spring-sown Cover Crops on Establishment and Growth of Hairy Galinsoga (Galinsoga ciliata) and Four Vegetable Crops
Authors: Kumar Virender , Brainard Daniel C. , Bellinder Robin R.
Published: February 2019

Hairy galinsoga [Galinsoga ciliata (Raf.) Blake] has become a troublesome weed in vegetable crops. Field studies were conducted in 2006 and 2007 in central New York to determine the effects of: 1) spring-sown cover crops on hairy galinsoga growth and seed production during cover crop growth grown before subsequent short duration vegetable crops; and 2) cover crop residues on establishment of hairy galinsoga and four short-duration vegetable crops planted after cover crop incorporation. The cover crops [buckwheat (Fagopyrum esculentum Moench), brown mustard (Brassica juncea L.), yellow mustard (Sinapis alba L.), and oats (Avena sativa L.)] were planted in May and incorporated in early July. Lettuce (Lactuca sativa L.) and Swiss chard [Beta vulgaris var. cicla (L.) K. Koch] were transplanted and pea (Pisum sativum L.) and snap bean (Phaseolus vulgaris L.) were sown directly into freshly incorporated residues. Aboveground dry biomass produced by the cover crops was 4.2, 6.4, 6.8, and 9.7 mg·ha−1 for buckwheat, brown mustard, yellow mustard, and oats, respectively. Cover crops alone reduced the dry weight (90% to 99%) and seed production of hairy galinsoga (98%) during the cover crop-growing season compared with weedy controls. In 2006, only yellow mustard residue suppressed hairy galinsoga emergence (53%). However, in 2007, all cover crop residues reduced hairy galinsoga emergence (38% to 62%) and biomass production (25% to 60%) compared with bare soil, with yellow mustard providing the greatest suppression. Cover crop residues did not affect snap bean emergence, but reduced pea emergence 25% to 75%. All vegetable crops were suppressed by all cover crop residues with crops ranked as: pea > Swiss chard ≥ lettuce > snap bean in terms of sensitivity. The C:N ratios were 8.5, 18.3, 22.9, and 24.8 for buckwheat, brown mustard, yellow mustard, and oat residues, respectively. Decomposition rate and nitrogen release of brown mustard and buckwheat residues was rapid; it was slow for oats and yellow mustard residues. Spring-sown cover crops can contribute to weed management by reducing seed production, emergence, and growth of hairy galinsoga in subsequent crops, but crop emergence and growth may be compromised. Yellow mustard and buckwheat sown before late-planted snap beans deserve further testing as part of an integrated strategy for managing weeds while building soil health.
Studies on Seed Germination, Seedling Growth, and In Vitro Shoot Induction of Aloe ferox Mill., a Commercially Important Species
Authors: Bairu Michael W. , Kulkarni Manoj G. , Street Renée A. , Mulaudzi Rofhiwa B. , Van Staden Johannes
Published: February 2019

A study was done to investigate the effects of some physical and chemical factors on growth and development of Aloe ferox ex vitro and in vitro. The effects of light, temperature, and smoke–water on seed germination, ex vitro seedling growth requirements, and effect of germination medium and cytokinins on shoot induction and multiplication in vitro were investigated. The highest germination percentage of A. ferox seeds was recorded between 15 and 30 °C. Seed germination was inhibited at 10 and 35 °C. There was a nonsignificant increase in germination percentage (78%) for seeds that were germinated under constant dark conditions. Smoke–water-treated seeds showed significant improvement in percentage germination (80%) over the control (66%) at 25 °C with a 16-h photoperiod. Seedlings of A. ferox subjected to alternating temperatures (30/15 °C) or being irrigated three times weekly at 25 °C showed better seedling growth. In an in vitro experiment, seedlings germinated in distilled water and one-tenth strength Murashige and Skoog medium had superior shoot induction competence compared with the other germination media. The cytokinins meta-Topolin (mT) and meta-Topolin riboside (mTR) at 5 μm gave significantly higher shoot multiplication rates compared with the control and benzyladenine (BA)-treated plants. A higher abnormality index was recorded for BA-treated plants. The findings of this study will be beneficial for commercial propagation of Aloe ferox.
Petroleum Ether Separation and Seedcoat Removal Enhance Seed Germination of a Casuarina equisetifolia L. × C. glauca Sieb. ex Spreng Hybrid
Authors: Shen Xiuli , Castle William S. , Gmitter Frederick G.
Published: February 2019

Casuarina cunninghamiana Miq. is an introduced species to Florida that has potential as a windbreak plant to help manage canker in citrus groves; however, only Florida sources can be used for that purpose. Local sources of Casuarina are generally adequate seed producers, but germination percentages are frequently poor. Thus, the causes of low seed germination and methods to improve germination were investigated using C. cunninghamiana and a local hybrid (C. equisetifolia L. × C. glauca Sieb. ex Spreng.). Seeds of the hybrid were larger and heavier (88 mg/100 seeds) than those of C. cunninghamiana (mean wt. 67 mg/100 seeds). Shrunken, insect-damaged, and empty seeds, present in all unsorted seed lots, were responsible for poor seed germination of the four seed sources studied. Petroleum ether separation improved germination by dividing seeds into floaters and sinkers. The floater fraction consisted of 47.5% to 93% insect-damaged seeds compared with 9.0% to 43.5% among sinkers. More than 50% of the sinkers were filled seeds and less than 21% in floaters. No empty seeds were sinkers except for one source of C. cunninghamiana. In sorted hybrid seeds, petroleum ether separation eliminated a large proportion of ungerminable seeds (floaters) and seed germination among sinkers was faster with a higher germination percentage than floaters. Cumulative germination of hybrid seeds in a trial involving two temperatures was 23.0% for sunken seeds at 30 °C at the end of 8 weeks compared with 1% of unsorted seeds. Temperature had no significant effect on seed germination. The germination percentage of hybrid seeds with seedcoats removed was 91.0% in the first week of culture compared with only 1.2% in the first week and 12.6% seed germination at the end of 8 weeks' culture of intact seeds.
Phytotoxicity of Aqueous Ozone on Five Container-grown Nursery Species
Authors: Graham Thomas , Zhang Ping , Zheng Youbin , Dixon Michael A.
Published: February 2019

The phytotoxic threshold of five woody perennial nursery crops to applications of aqueous ozone was investigated to determine if aqueous ozone could be used for remediation of recycled nursery irrigation water and for pathogen control. The perennial nursery crops [Salix integra Thunb. ‘Hakura Nishiki’; Weigela florida Thunb. ‘Alexandra’; Spiraea japonica L.f. ‘Goldmound’; Hydrangea paniculata Seib. ‘Grandiflora’; Physocarpus opulifolius L. Maxim. ‘Summer Wine’] were evaluated for aqueous ozone phytotoxicity after 6 weeks of overhead spray irrigation in which five aqueous ozone treatments (0, 10.4, 31.2, 62.5, 125.0 μmol·L−1) were applied on a daily basis. The concentrations applied represent levels useful for irrigation system maintenance (pathogen and biofilm control) with the highest levels selected to clearly demonstrate phytotoxicity. Aqueous ozone solutions were prepared and injected in-line during irrigation for 7.5 min every day for 6 weeks, after which growth parameters (leaf area, shoot dry weight, root dry weight, height, flower number) were measured and leaf injury was evaluated. High residual aqueous ozone (62.5 μmol·L−1 or greater at emitter discharge; 0.3 m from canopy) in the irrigation water was shown to negatively affect the growth parameters measured; however, low residual ozone concentrations (31.2 μmol·L−1 or less at emitter discharge; 0.3 m from canopy) did not present any measurable risk to plant growth. Furthermore, even at higher dose levels, leaves produced during the treatment period showed reduced damage levels. It is concluded that ozone residuals of 31.2 μmol·L−1 (at emitter discharge) can remain in overhead irrigation water without negatively affecting the crop species examined under the application protocols used. At the ozone concentrations demonstrated to be tolerable by the crop species examined, it is reasonable to surmise that control of pathogens at all points within the irrigation system will be achievable using aqueous ozone as part of an irrigation management strategy. The use of aqueous ozone in this fashion could also aid in dramatically reducing chemical residuals on crops by reducing the input requirements of traditional chemical controls.
Comparison of Fertilizer Nitrogen Availability, Nitrogen Immobilization, Substrate Carbon Dioxide Efflux, and Nutrient Leaching in Peat-lite, Pine Bark, and Pine Tree Substrates
Authors: Jackson Brian E. , Wright Robert D. , Alley Mark M.
Published: February 2019

The objective of this study was to compare substrate solution nitrogen (N) availability, N immobilization, and nutrient leaching in a pine tree substrate (PTS), peat-lite (PL), and aged pine bark (PB) over time under greenhouse conditions. Pine tree substrate was produced from loblolly pine logs (Pinus taeda L.) that were chipped and hammer-milled to a desired particle size. Substrates used in this study were PTS ground through a 2.38-mm hammer mill screen, PL, and aged PB. A short-term (28-d) N immobilization study was conducted on substrates fertilized with 150 or 300 mg·L−1 NO3-N. Substrates were incubated for 4 days after fertilizing and NO3-N levels were determined initially and at the end of the incubation. A second medium-term study (10-week) was also conducted to evaluate the amount of N immobilized in each substrate when fertilized with 100, 200, 300, or 400 mg·L−1 N. In addition to determining the amounts of N immobilized, substrate carbon dioxide (CO2) efflux (μmol CO2/m−2·s−1) was also measured as an assessment of microbial activity, which can be an indication of N immobilization. A leaching study on all three substrates was also conducted to determine the amount of nitrate nitrogen (NO3-N), phosphorus, and potassium leached over 14 weeks under greenhouse conditions. Nitrogen immobilization was highest in PTS followed by PB and PL in both the short- and medium-term studies. Nitrogen immobilization increased as fertilizer rate increased from 100 mg·L−1 N to 200 mg·L−1 N in PL and from 100 mg·L−1 N to 300 mg·L−1 N for PB and PTS followed by a reduction or no further increase in immobilization when fertilizer rates increased beyond these levels. Nitrogen immobilization was generally highest in all substrates 2 weeks after potting, after which immobilization tended to decrease over the course of several weeks with less of a decrease for PTS compared with PL and PB. Substrate CO2 efflux levels were highest in PTS followed by PB and PL at each measurement in both the short- and medium-term studies. Patterns of substrate CO2 efflux levels (estimate of microbial populations/activity) at both fertilizer rates and over time were positively correlated to N immobilization occurrence during the studies. Nitrate leaching over 14 weeks was lower in PTS than in PB or PL through 14 weeks. This work provides evidence of increased microbial activity and N immobilization in PTS compared with PB and PL. Increased N immobilization in PTS explains the lower nutrient (primarily N) levels observed in PTS during crop production and justifies the additional fertilizer required for comparable plant growth to PL and PB. This work also provides evidence of less NO3-N leaching in PTS compared with PL or PB during greenhouse crop production despite the higher fertilizer rates required for optimal plant growth in PTS.