bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Relationships of Codiaeum variegatum Cultivars Analyzed by Amplified Fragment Length Polymorphism Markers
Authors: Deng Min , Chen Jianjun , Henny Richard J. , Li Qiansheng
Published: February 2019

Codiaeum variegatum (L.) Blume, commonly known as crotons, are among the most popular ornamental foliage plants cultivated for either landscaping or interiorscaping. Currently, more than 300 cultivars are available; each has a distinct phenotype, particularly in leaf morphology. Thus far, there is no information regarding their genetic relationships. In this study, genetic relatedness of 44 cultivars of C. variegatum was investigated using amplified fragment length polymorphism (AFLP) markers. Fourteen primer combinations generated a total of 549 AFLP fragments, which were used to estimate genetic distances and construct dendrograms based on the neighbor-joining method. The 44 cultivars were divided into seven clusters, which concurred with the known history of croton geographical isolation, adaptation, introduction, and breeding activities but differed from the classification made by the Croton Society based on leaf morphology. The established genetic relationships could be important for future germplasm identification and conservation and new cultivar development. Additionally, genetic distance among the 44 cultivars was 0.322 or less, indicating that they have a narrow genetic base. The narrow genetic base may indicate that the cultivars were derived from a common progenitor. On the other hand, 81% of the 549 fragments were polymorphic and the average polymorphic information content was 0.22, which suggests that the cultivars are genetically highly polymorphic. The high polymorphisms may be attributed to significant gene loss or gain facilitated by mutation and/or chromosome variation, thus contributing to a wide range of leaf morphological differences among cultivars.
Influence of Elevating Tree Potassium on Fruit Drop and Yield of Pecan
Authors: Wood Bruce W. , Wells Lenny , Funderburke Frank
Published: February 2019

Excessive Stage II fruit drop (i.e., June drop) often limits profitability of certain pecan [Carya illinoinensis (Wangenh.) C. Koch] cultivars. Anecdotal evidence indicates that one cause of drop is linked to a nutrient element deficiency. This study examines the consequences of improving tree potassium (K) nutrition on fruit drop, nutmeat yield, and kernel quality (i.e., % kernel) in ‘Desirable’ orchards in which generally accepted foliar analysis standards indicate satisfactory tree K nutritional status (i.e., 0.75% or greater to 2.5% K/dry weight). Multiyear field studies of two such orchards found that elevating leaf and fruit K concentration through soil banding of potash over drip irrigation emitters: 1) increased fruit retention by reducing Stage II fruit drop; 2) increased in-shell nut yield; and 3) increased nut quality by increasing percentage kernel. Potash applied through soil banding elevated foliar and fruit K concentration by ≈ 0.1% to 0.4% units within a few months post-application depending on the amount applied; however, the beneficial effects of a single potash soil band application diminished after the first year. A comparison of the K concentration of retained fruit versus abscised fruit during the Stage II fruit drop window found that retained fruit possessed endogenous K concentrations of 1.2% to 1.7% (dry weight basis) in one orchard and 1.45% to 1.9% in a second orchard, whereas aborted fruit possessed K at 0.65% to 1.2% in one orchard and 0.75% to 1.2% in a second orchard, respectively, thus establishing ≈ 1.25% K as a “drop threshold” under conditions of this study. The total K concentration of retained fruit is typically 0.25% to 0.50 K/dry weight greater than dropped fruit. Considerable K-associated late-spring fruit drop can occur in ‘Desirable’, although early- to midsummer leaf analysis indicates trees were K-sufficient, hence implying that young fruit likely possesses a higher K requirement than does foliage. These K-associated benefits to trees meeting accepted K sufficiency criteria is evidence that K nutrition management of ‘Desirable’ pecan merits r-evaluation and possibly pecan K nutrition in general.
Stigmatic Morphology of Chinese Chestnut (Castanea mollissima Blume)
Authors: Shi Zhuogong , Xia Li
Published: February 2019

The stigmatic morphology of Chinese chestnut was studied with scanning electron microscopy. The stigma is typically needle-shaped with a small aperture ≈50 μm in diameter on the top. During late April and early May in Yunnan Province, China, stigma secretion begins and within 1 week, secretion increases quickly and completely covers the stigma aperture. In “high fruit load” trees, the stigma aperture appears larger than in “low fruit load” trees, which in turn have a larger aperture than “empty cupule” trees. Likewise, stigma secretion in female flowers on “high fruit load” trees was higher than “low fruit load” or “empty cupule” trees.
Effects of Preharvest Calcium Foliar Sprays on Several Fruit Quality Attributes and Nutritional Status of the Kiwifruit Cultivar Tsechelidis
Authors: Koutinas Nikolaos , Sotiropoulos Thomas , Petridis Antonios , Almaliotis Dimitrios , Deligeorgis Emmanuil , Therios Ioannis , Voulgarakis Nikolaos
Published: February 2019

The effect of various commercial calcium (Ca) -containing products applied as preharvest foliar sprays on several fruit quality attributes and nutritional status of the kiwifruit cultivar Tsechelidis for a 2-year period is reported. Foliar application of all Ca products plus boron did not affect mean fruit weight compared with the control. During the first year, the highest flesh firmness was measured after application of the Ca-containing products Acid CaLMg and Calfruit plus Qualyfruit. During the second year, the highest flesh firmness was measured after application of the product Acid CaLMg. The highest ascorbic acid content and total antioxidant power were recorded after application of the product Chelan CaP. Foliar application of Power-Ca resulted in an increase of Ca concentration of leaves compared with the control for the first year. During the second year, all Ca-containing products increased Ca concentration of leaves compared with the control. Foliar application of Calfruit plus Qualyfruit, Chelan CaP, Power Ca, and Acid CaLMg resulted in an increase of Ca concentration of fruits compared with the control. The efficacy of the foliar sprays on some of the tested parameters varied from year to year indicating the influence of other parameters on vine nutrition.
An Evaluation of Fertility in Arkansas Primocane-fruiting Blackberries
Authors: Ruple Alisha L. , Clark John R. , Garcia M. Elena
Published: February 2019

Floral fertility of five primocane-fruiting (PF) blackberry (Rubus L. subgenus Rubus Watson) genotypes (‘Prime-Jim’®, APF-31, ‘Prime-Ark® 45’, APF-59, and APF-77) and three floricane-fruiting (FF) genotypes (‘Navaho’, ‘Natchez’, and ‘Ouachita’) were tested under field conditions using floricane flowers with four pollination treatments: undisturbed open-pollinated, emasculated self-pollinated, emasculated and cross-pollinated with pollen from a similar fruiting type (PF × PF or FF × FF), and emasculated and cross-pollinated with pollen from a different fruiting type (PF × FF or FF × PF). During primocane flowering, three pollination treatments (undisturbed open-pollinated, emasculated selfed, and emasculated cross-pollinated) were used to further test the fertility of the five PF genotypes. Significant differences between cross-pollination treatments and self-pollination were seldom noted with more differences seen in ‘Prime-Jim’® than any other genotype. Cross-pollinating primocane flowers on ‘Prime-Jim’® resulted in significantly higher fruit set, drupelet set, and average berry weight compared with self-pollination. Fruit set among genotypes ranged from 68.5 to 96.7%, and drupelet set rating ranged from 4.3 to 6.9 for floricane flowers. For open-pollinated primocane flowers, fruit set ranged from 63.9 to 92.1%, and drupelet set rating ranged from 4.3 to 7.2. The genotypes APF-31, APF-59, and APF-77 showed a marked improvement over ‘Prime-Jim’® in both percent fruit set and drupelet set of floricane and primocane flowers. The results indicated that fertility appears to be sufficient in all the genotypes evaluated and that the later-generation PF genotypes show improvement in fertility over ‘Prime-Jim’®. Pollen viability (using both chemical viability testing and in vitro germination testing), stigma receptivity, and pollen tube growth (using florescence) were evaluated in a controlled environment to determine if any improvements could be noticed when comparing a selection of later-generation PF genotypes (APF-31,' Prime-Ark® 45', APF-59, and APF-77) with ‘Prime-Jim’® and ‘Prime-Jan’®. Genotypes APF-31, APF-59, and APF-77 had significantly more viable pollen and pollen germination than ‘Prime-Jan’®. Stigma receptivity was observed in all genotypes. Pollen tube growth did not appear to be inhibited after self-pollination in any genotype studied, although significantly greater florescence resulting from pollen tube growth was seen after cross-pollination compared with self-pollination for APF-59. There were no significant differences in pollen tube growth between cross- and self-pollination for any other genotype.
Evaluating Fertility of Triploid Clones of Hypericum androsaemum L. for Use as Non-invasive Landscape Plants
Authors: Trueblood Clara E. , Ranney Thomas G. , Lynch Nathan P. , Neal Joseph C. , Olsen Richard T.
Published: February 2019

Although Hypericum androsaemum L. is a valuable landscape plant, the species can be weedy and potentially invasive in certain locations. Infertile, non-invasive cultivars of H. androsaemum with desirable ornamental features would be ecologically beneficial and valuable for the horticultural industry. The male and female fertility of 10 triploid H. androsaemum, developed with a combination of variegation and foliage colors, was investigated under greenhouse (controlled pollination) and field conditions (natural pollination). Male fertility was evaluated based on pollen viability tests (pollen staining and pollen germination). Female fertility was based on fruit set, seed set, germinative capacity of seeds, and number of seedlings produced for each flower. Although values for different measures of fertility varied among triploid clones, pollen germination was significantly reduced for all triploids and nine of the 10 triploids produced no viable seed. These results represent 100% failure of ≈171,000 potential fertilization events based on fertility levels of diploid controls. The remaining triploid clone produced two seedlings per flower compared with 260 seedlings per flower for the controls. However, the seedlings produced by the triploid clone died shortly after germination. This research documented that the triploid H. androsaemum tested are highly infertile with no measurable female fertility. These clones will provide ideal alternatives to fertile forms of H. androsaemum where invasiveness is a concern. These methods also provide a useful protocol for evaluating fertility of other taxa that are selected or developed as non-invasive cultivars of potentially weedy species.
Spring Influences on Olive Flowering and Threshold Temperatures Related to Reproductive Structure Formation
Authors: Orlandi Fabio , Sgromo Carlo , Bonofiglio Tommaso , Ruga Luigia , Romano Bruno , Fornaciari Marco
Published: February 2019

Several bioclimatic studies have been developed over recent years considering temperature trends and their influence on vegetative and reproductive phenomena during plant growth. In the applied aerobiology laboratory of Perugia University, various studies of olive (Olea europaea L.) flowering and its relationship with climatic variables have been conducted. Since 1999, a flowering monitoring network in central–southern Italy has been working to track the biological phenomena over the years, the possible differences between the monitoring stations, and the relationships with climate. Olive flowering was monitored in 15 monitoring stations located in four Italian regions (Campania, Calabria, Puglia, and Sicily) representing ≈90% of national olive territories. The flowering phenophase was studied through pollen emission monitoring, making use of scientific instruments that capture defined volumes of atmosphere and allow us to ascertain the pollen emission trends, thereby determining daily average pollen concentrations (pollen grains/m3). The combined analysis of pollen monitoring and meteorological data permitted identifying various groups of stations characterized by the fact that better relationships between reproductive structure development and growing degree-days are obtained with different spring threshold temperatures (low 7 to 10 °C or high 11 to 14 °C). Moreover, the study permitted demonstrating particular meteorological and biological behaviors, providing useful information about plant–climate relationships in a species of economic interest affected by interincompatibility.
Abscission Agent Application and Canopy Shaker Frequency Effects on Mechanical Harvest Efficiency of Sweet Orange
Authors: Ebel Robert C. , Burns Jacqueline K. , Morgan Kelly T. , Roka Fritz
Published: February 2019

This study was conducted to determine the relationship of 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) concentration and canopy shaker frequency on fruit detachment force, pre-harvest fruit drop, and mechanical harvesting fruit removal of ‘Hamlin’ and ‘Valencia’ sweet orange cultivars. CMNP was applied at 0, 200, and 300 mg·L−1 in a carrier volume of 2806 L·ha−1. Four days after CMNP application, fruit were harvested with a canopy shaker that was operated at 3.0, 3.7, and 4.3 Hz at a tractor speed of 1.6 km·h−1. The experiment was repeated 3× for ‘Hamlin’ (December, early January, and late January) and twice for ‘Valencia’ (March and April) during the 2008–2009 harvest season. Fruit detachment force was reduced by at least 50% for all CMNP-treated trees compared with the untreated controls at the time of harvest and was lower for 300 mg·L−1 than 200 mg·L−1 on three of the five dates tested. Pre-harvest fruit drop evaluated immediately before mechanical harvesting was higher for all CMNP-treated ‘Hamlin’ than untreated controls at all harvest dates, whereas 300 mg·L−1 application resulted in higher pre-harvest fruit drop in ‘Valencia’ when compared with 200 mg·L−1 or the untreated controls on both application dates. CMNP-induced fruit drop was higher in ‘Hamlin’ than ‘Valencia’. CMNP had a greater effect on fruit removal at lower canopy shaker frequencies. The interaction of total fruit weight removed was not significant on any date as a result of variability among trees in the study. These data indicate that the amount of loosening by CMNP was concentration-dependent and facilitated removal, especially with lower canopy shaker frequencies. Development of viable commercial practices should use the percent of the total crop harvested and not the actual weight of fruit removed in determining efficacy of CMNP and harvest efficiency of the mechanical harvesters.
Simultaneous Determination of Water Retention Curve and Unsaturated Hydraulic Conductivity of Substrates Using a Steady-state Laboratory Method
Authors: Londra Paraskevi A.
Published: February 2019

For effective irrigation and fertilization management, the knowledge of substrate hydraulic properties is essential. In this study, a steady-state laboratory method was used to determine simultaneously the water retention curve, θ(h), and unsaturated hydraulic conductivity as a function of volumetric water content, K(θ), and water pressure head, K(h), of five substrates used widely in horticulture. The substrates examined were pure peat, 75/25 peat/perlite, 50/50 peat/perlite, 50/50 coir/perlite, and pure perlite. The experimental retention curve results showed that in the case of peat and its mixtures with perlite, there is a hysteresis between drying and wetting branches of the retention curve. Whereas in the case of coir/perlite and perlite, the phenomenon of hysteresis was less pronounced. The increase of perlite proportion in the peat/perlite mixtures led to a decrease of total porosity and water-holding capacity and an increase of air space. Study of the K(θ) and K(h) experimental data showed that the hysteresis phenomenon of K(θ) was negligible compared with the K(h) data for all substrates examined. Within a narrow range of water pressure head (0 to –70 cm H2O) that occurs between two successive irrigations, a sharp decrease of the unsaturated hydraulic conductivity was observed. The comparison of the K(θ) experimental data between the peat-based substrate mixtures and the coir-based substrate mixture showed that for water contents lower than 0.40 m3·m−3, the hydraulic conductivity of the 50/50 coir/perlite mixture was greater. The comparison between experimental water retention curves and predictions using Brooks-Corey and van Genuchten models showed a high correlation (0.992 ≤ R2 ≤ 1) for both models for all substrates examined. On the other hand, in the case of unsaturated hydraulic conductivity, the comparison showed a relatively good correlation (0.951 ≤ R2 ≤ 0.981) for the van Genuchten-Mualem model for all substrates used except perlite and a significant deviation (0.436 ≤ R2 ≤ 0.872) for the Brooks-Corey model for all substrates used.
Performance of an Elite Strawberry Population Derived from Wild Germplasm of Fragaria chiloensis and F. virginiana
Authors: Stegmeir Travis L. , Finn Chad E. , Warner Ryan M. , Hancock James F.
Published: February 2019

Fragaria ×ananassa Duchesne ex Rozier, or the cultivated strawberry, resulted from the hybridization of two wild species, F. chiloensis (L.) Miller and F. virginiana Miller. In an attempt to recreate the cultivated strawberry, elite clones of F. chiloensis and F. virginiana were crossed within species and then hybridized to produce 26 reconstructed populations. Of these populations, FVC11 [(Frederick 9 × LH 50-4) × (Scotts Creek × 2 MAR 1A)] had unusually large fruit size and was selected for further analysis. In the summer of 2008, 78 individuals of this population were evaluated for their seasonal flowering patterns, inflorescence number, inflorescence height, crown production, flower number, fruit size, yield, internal color, soluble solids, fruit firmness, and plant vigor. Progeny means were compared with those of the parental means and most traits exhibited transgressive segregation, most notably yield and fruit weight. Significant positive correlations were found between many of the production traits, although there were significant negative correlations between fruit firmness and flower number per inflorescence, fruit firmness and soluble solids, and yield per plant and soluble solids. Overall performance scores were assigned to each genotype by summing their relative performance for each trait in the population. Individuals were identified that combined high values for fruit weight and yield with higher than average values for fruit color, firmness, and soluble solids. Use of this population in breeding programs could help expand the genetic base of the cultivated strawberry with limited linkage drag.
Enzymatic Browning, Polyphenol Oxidase Activity, and Polyphenols in Four Apple Cultivars: Dynamics during Fruit Development
Authors: Holderbaum Daniel Ferreira , Kon Tomoyuki , Kudo Tsuyoshi , Guerra Miguel Pedro
Published: February 2019

Enzymatic browning is one of the most important reactions that occur in fruits and vegetables, usually resulting in negative effects on color, taste, flavor, and nutritional value. The reaction is a consequence of phenolic compounds' oxidation by polyphenol oxidase (PPO), which triggers the generation of dark pigments. This is particularly relevant for apples, which are rich in polyphenols and highly susceptible to enzymatic browning. The objective of the present work was to quantify enzymatic browning and PPO activity and identify and quantify target polyphenols in apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] pulp in the cultivars (cvs.) Aori27, Elstar, Fuji, and Mellow at three fruit developmental stages (FDS). The enzymatic browning was quantified by tristimulus colorimetry; PPO activity was quantified by an enzyme–substrate spectrophotometric assay; phenolic compounds were determined and quantified by reverse-phase high-performance liquid chromatography–ultraviolet/visible–mass spectrometry. Enzymatic browning showed significant difference among cvs. and FDSs and interaction between both factors. PPO activity showed significant difference among cultivars and FDSs. A significant difference was evidenced for polyphenol content among cultivars and FDSs with interaction between both factors. Chlorogenic acid was the major phenolic compound in ‘Aori27’ and ‘Mellow’. In ‘Fuji’, chlorogenic acid and (–)-epicatechin were the major phenolics and in ‘Elstar’ (–)-epicatechin and procyanidin B2 were the major phenolics at different FDSs. The enzymatic browning showed high correlation to polyphenol content in all cultivars and high correlation was observed between browning and PPO activity in ‘Aori27’ and ‘Elstar’. The magnitude of the correlation between browning and polyphenols and PPO activity is genotype-specific. At the commercial harvest, ‘Fuji’ showed the highest polyphenol content and ‘Aori27’ showed the lowest level for enzymatic browning. Chemical names used: 3-(3,4-dihydroxycinnamoyl) quinic acid (chlorogenic acid), (–)-cis-3,3′,4′,5,7-pentahydroxyflavane (epicatechin), and cis,cis″-4,8″-Bi(3,3′,4′,5,7-pentahydroxyflavane) (procyanidin B2).
Modeling Actual Evapotranspiration of Viburnum odoratissimum during Production from Rooted Cuttings to Market Size Plants in 11.4-L Containers
Authors: Beeson Richard C.
Published: February 2019

Rooted cuttings of Viburnum odoratissimum were grown outdoors to market size in 11.4-L containers. Actual evapotranspiration (ETA) of nine plants was determined daily as was evaporation from three control containers shaded with plastic foliage to mimic plant growth. The first 60 d after transplanting, substrate evaporation accounted for most of ETA. Substrate evaporation was generally constant the first 160 days before declining, but still remained ≈160 mL/day through harvest at market size. ETA increased with growth and generally followed variations in reference evapotranspiration (ETo). Mean ETA during most of the production cycle was less than 600 mL/day (11.8 mm based on upper container surface area). With the spring growth flush, mean ETA reached 1.3 L/day as plants achieved market size. Mean cumulative ETA to produce 90% of measured plants to market size was 155 L or 3.1-m depth per plant based on container surface area. Water need indices, similar to crop coefficients, were highly correlated with percent canopy closure (%Closure) using an exponential decay equation. When overlain with previous similar data for Ligustrum japonicum, the correlation for the combined data set had an r2 = 0.843. This suggests that the %Closure model may provide a method for ETo-based irrigation of woody shrub species based on canopy size and spacing.
The Optimum One-year-old Shoot Length to Optimize Yield and Fruit Size of Three Fig (Ficus carica L.) Cultivars
Authors: Gerber Hein J. , Steyn Willem J. , Theron Karen I.
Published: February 2019

The European fig cultivars Bourjasotte Noire, Col de Damme Noire, and Noire de Caromb were recently introduced to the Western Cape Province of South Africa. Producers struggle to implement effective commercial practices that will optimize yield of quality fruit. A phenological study was conducted to establish the optimum 1-year-old shoot length to maximize yield. The number of fruit, budbreak, and shoot growth on 1-year-old shoots comprising four length categories (‘Bourjasotte Noire’: 10 to 15, 25 to 40, 50 to 65, and 75+ cm; ‘Col de Damme Noire’ and ‘Noire de Caromb’: 10 to 20, 30 to 50, 60 to 80, and 100+ cm) were evaluated. In ‘Bourjasotte Noire’, all four categories seem to be suited for reproduction in the current season and also provide sufficient new shoot growth to ensure a fair yield the next season. In ‘Col de Damme Noire’, category four seems to be the best 1-year-old shoot length for reproduction both in terms of fruit number and fruit size. However, yield on these shoots may not be optimal the next season, because current-season shoots are too short. It seems that this cultivar will require pruning to stimulate strong new shoot growth that will ensure regular, high yields. In ‘Noire de Caromb’, category one shoots are very productive relative to their length. Categories two and three were also relatively productive, whereas category four was less productive but developed a large number of current-season shoots similar in length to category one that should be productive the next season. These results will allow us to develop pruning strategies to ensure an optimal balance between current-season yield and the development of new fruiting wood to ensure regular, high yields. It also suggests that the three cultivars studied will require differential application of horticultural practices to attain regular, high yields of large fruit.
Probing the Mechanisms of the Yellow Vine Syndrome Development in the American Cranberry: Shade Effect
Authors: Wei Zi , Jeranyama Peter , Zhang Fan , DeMoranville Carolyn , Hou Harvey J.M.
Published: February 2019

Yellow vine symptoms are often observed in cranberry bogs. To explore the mechanisms of the formation of yellow vine syndrome in cranberry leaves, the shade effect on the chlorophyll (Chl) content and photosynthetic activities in cranberry bogs were investigated by spectrometric, high-performance liquid chromatography (HPLC), and in vivo Chl fluorescence kinetics. Spectrometric and HPLC analyses revealed that the yellow vine leaves were associated with a 11% ± 5% and 14% ± 5% increase in Chl a/Chl b ratio after shading, respectively. The Chl a/Chl b ratio was the same in both types of leaves, suggesting the photosystem (PS) II organization remains invariant. The rise in chlorophyll content suggested that the number of reaction sites on PS II is increased in the shaded yellow vine leaves. The results of in vivo chlorophyll fluorescence analysis also indicated that the electron transport chain in the PS II is enhanced and that the size of the quinone pool is increased. In addition, the overall photosynthesis index is drastically improved by shading. These three lines of evidence imply that the shading of cranberry plants appeared to reduce the syndrome by improving the photosynthetic activity and increasing the chlorophyll content. The techniques presented here may be valuable for characterizing variations of plants by stress or disease.
A Sequence-amplified Characterized Region Marker for a Single, Dominant Gene in Melon PI 134198 that Confers Resistance to a Unique Race of Podosphaera xanthii in China
Authors: Liu Longzhou , Chen Youyuan , Su Zhenghong , Zhang Hui , Zhu Weiming
Published: February 2019

Melon production in China is threatened by cucurbit powdery mildew incited by Podosphaera xanthii, which can cause severe yield losses. Disease reactions of 10 melon P. xanthii race differentials indicated the presence of a unique race of P. xanthii, denoted pxCh1, in the Shanghai area. Resistance to P. xanthii race pxCh1 in melon PI 134198, which originated from India, was controlled by a single, dominant gene, designated Pm-8, in a cross with susceptible melon inbred S717. A search for a molecular marker linked to Pm-8 was initiated using the same cross. Bulk segregant analysis of their F2 progeny revealed one sequence-related amplified polymorphism (SRAP) marker of 148 bp linked to Pm-8, at 3.9 cM. The SRAP segment was recovered, cloned, and sequenced and converted into a sequence-amplified characterized region marker for marker-assisted selection of Pm-8 in breeding programs to develop melon cultivars resistant to P. xanthii race pxCh1.
Tolerance of the Trifoliate Citrus Hybrid US-897 (Citrus reticulata Blanco × Poncirus trifoliata L. Raf.) to Huanglongbing
Authors: Albrecht Ute , Bowman Kim D.
Published: February 2019

Huanglongbing (HLB) is a destructive disease of citrus in most citrus-producing countries worldwide. The disease, presumably caused by phloem-limited bacteria of the genus Candidatus Liberibacter, affects all known citrus species and citrus relatives with little known resistance. Typical disease symptoms are the production of abnormal-looking fruit and chlorosis or blotchy mottle of the leaves followed at advanced stages by tree decline and death. Trifoliate orange (P. trifoliata L. Raf.) and some of its hybrids reportedly lack distinct disease symptoms despite infection with the pathogen. US-897 is a hybrid of trifoliate orange and ‘Cleopatra’ mandarin (C. reticulata Blanco), the latter being highly susceptible to HLB. This study investigated whether field-grown, naturally infected trees and greenhouse-grown, graft-inoculated seedlings of this genotype display tolerance or resistance to HLB. It was shown that naturally infected US-897 trees exhibited no distinct disease symptoms commonly associated with HLB, except for the occurrence of few mottled leaves in a small percentage of trees. Analysis of fruit and seed from infected trees did not detect any growth reduction or otherwise negative impact on development. Graft-inoculated US-897 seedlings became polymerase chain reaction (PCR)-positive for the pathogen but exhibited a superior performance compared with ‘Cleopatra’ mandarin seedlings, which displayed severe disease symptoms soon after inoculation. Despite infection, most US-897 seedlings did not develop leaf symptoms typical for HLB. Foliar symptoms observed in a small number of plants at later stages of the disease were faint and difficult to discern. Contrary to ‘Cleopatra’ seedlings, growth in stem diameter was only moderately reduced or unaffected in infected US-897 seedlings. The superior performance of US-897 plants in greenhouse and field locations suggest tolerance of this genotype to Ca. L. asiaticus.
Photoperiodic Flower Induction of Several Kalanchoe Species and Ornamental Characteristics of the Flowering Species
Authors: Currey Christopher J. , Erwin John E.
Published: February 2019

Our objectives in this study were to identify the flowering response of Kalanchoe spp. to photoperiodic treatments and characterize flowering and vegetative characteristics of flowering plants. Twenty vegetatively propagated Kalanchoe spp. were grown under one of four photoperiodic treatments: 1) short days (SD; 8-h photoperiod) for 16 weeks; 2) night interruption lighting (NI; 2000 to 0200 hr) for 16 weeks; 3) SD for 8 weeks then transferred to NI for 8 weeks; or 4) NI for 8 weeks then transferred to SD for 8 weeks. Kalanchoe beauvardii, K. behariensis, K. fedtschenkoi, K. longiflora, K. marmorata, K. marnieriana, K. streptantha, K. tomentosa, and K. vigueridoi did not flower under any treatment. Kalanchoe laetivirens and K. rosei had minimal flowering when exposed to NI followed by SD, whereas K. pumila had minimal flowering when exposed to SD followed by NI. Kalanchoe glaucescens, K. laciniata, K. manginii, K. nyikae, K. rotundifolia, K. uniflora, and K. velutina flowered when exposed to SD for 8 or 16 weeks, and node number below the inflorescence and days to first open flower for these species increased when NI preceded SD. Kalanchoe millotii flowered under a 16-week SD treatment only. No plants flowered when grown under only NI. We classified K. glaucescens, K. laciniata, K. manginii, K. millotii, K. nyikae, K. rotundifolia, K. uniflora, and K. velutina as obligate SD plants. Flower diameter, total flower number, total color index, shoot length, branch number, and leaf length and width varied among species. Based on these ornamental characteristics, we identified K. glaucescens, K. laciniata, K. manginii, K. nyikae, K. uniflora, and K. velutina as potential ornamental flowering potted plants.
A Theory of Blossom Thinning to Consider Maximum Annual Flower Bud Numbers on Biennial Apple Trees
Authors: Pellerin Brian P. , Buszard Deborah , Iron David , Embree Charles G. , Marini Richard P. , Nichols Douglas S. , Neilsen Gerald H. , Neilsen Denise
Published: February 2019

Tree fruit growers use chemical and mechanical thinning techniques in an attempt to maintain regular annual flower production and maximum repeatable yields of varieties susceptible to biennial bearing. If the percentage of floral buds an apple tree could produce without causing yield depression in subsequent years was known, it would be possible to better manage crop-thinning regimes. This study proposes that thinning is a partial transfer of potential flower buds from one year to the next year and estimates the maximum repeatable sequence of flower buds without biennial bearing. The conceptual framework is tested on a 50-year simulation with 0% to 100% transfer of thinned flower buds. Results indicate that the maximum repeatable sequence of flower buds rises sharply when the final years of the orchard approach and declines when the percent transfer of thinned buds is near 0%.
Rooting Response of Azalea Cultivars to Hot Water Treatment Used for Pathogen Control
Authors: Copes Warren E. , Blythe Eugene K.
Published: February 2019

Submerging terminal leafy cuttings of Rhododendron L. ‘Gumpo White’ (‘Gumpo White’ azalea) in 50 °C water for 21 min was previously shown to eliminate binucleate Rhizoctonia species, the cause of azalea web blight, from plant tissues. Before considering commercial use of this practice, a better understanding of the rooting response and tissue sensitivity of evergreen azalea cultivars to 50 °C water was needed; therefore, the current study was conducted. Terminal cuttings of the azalea cultivars Conleb (Autumn Embers), Fashion, Formosa, Gumpo White, Hardy Gardenia, Hershey Red, Macrantha Pink, Midnight Flare, Red Ruffles, Renee Michelle, Roblel (Autumn Debutante), and Watchet were collected and submerged or not submerged in 50 °C water for 20 min before propagation in one experiment. All 12 cultivars tolerated 50 °C water for 20 min. Cuttings collected from the 12 cultivars were submerged in 50 °C water for 20, 40, 60, and 80 min in a second experiment. The cultivars varied in sensitivity when exposed to 50 °C water for 60 to 80 min resulting in differing responses in root development and final leaf count. In a third experiment, degrees of leaf damage caused by hot water submersion or by leaf removal were evaluated for the effect on root development and subsequent leaf count on rooted cuttings of ‘Gumpo White’ and ‘Roblel’. Induced incremental increases in leaf damage from hot water resulted in incremental reductions in the final leaf count and extent of root development for ‘Gumpo White’ and ‘Roblel’ while increasing percentage of leaf removal caused no reduction until 75% or greater leaf area was removed. Despite the risk imposed by submersing azalea cuttings in 50 °C water, all 12 azalea cultivars were tolerant of submersion durations long enough to eliminate binucleate Rhizoctonia species from stem and leaf tissue with only a low likelihood of sustaining detrimental damage.
Scientific Basis of a Unique Formulation for Reducing Sunburn of Fruits
Authors: Schrader Larry E.
Published: February 2019

Sunburn, a major type of solar radiation injury, causes large economic losses of several fruits, vegetables, and ornamentals. Sunburn necrosis occurs in attached apple (Malus domestica Borkh.) when excess solar radiation is converted to heat energy and causes a high fruit surface temperature (FST). When the FST reaches ≈52 °C, thermal death of cells is induced and sunburn necrosis appears later. A second type of sunburn, sunburn browning, is caused by the combination of high FST (46 to 49 °C) and high solar radiation. Cell death is not induced, but several pigment changes occur and the apple peel typically turns yellow or brown. The objective of this study was to develop a unique technology for protection of apples from sunburn necrosis and sunburn browning. Natural waxes in the cuticle and pigments in the upper epidermis of apple, which reflect and absorb ultraviolet radiation, attenuate only part of the harmful ultraviolet radiation. I hypothesized that applying additional wax as a sprayable emulsion would augment natural waxes in the cuticle and that addition of reflective compounds to the wax emulsion would reduce the heat load on the fruit. Synthesis of a formulation of this composition would be unique for plants and would be akin to sunscreens used by humans that generally contain organic (chemical) compounds to absorb harmful ultraviolet radiation and inorganic (physical) compounds to scatter, block, and/or reflect solar radiation. Emulsified carnauba wax, a natural plant wax, decreased transmission of ultraviolet radiation; addition of emulsified, organically modified clay to the wax emulsion enhanced reflectivity. When combined into a sprayable formulation, the carnauba wax and organoclay emulsion was more effective in protecting apples from sunburn browning than from sunburn necrosis. Spraying the unique formulation on apple trees caused no phytotoxicity on either leaves or fruit and did not decrease leaf chlorophyll fluorescence or whole-tree gas exchange, indicating no effect on photosynthesis or transpiration of apple trees. The unique formulation is patented as a sunburn protectant for fruits and vegetables and is marketed in several countries as RAYNOX®.
The Effect of Low-dose X-ray Irradiation on the Quality of Fresh-cut Asparagus in Microwaveable Vacuum Skin Packs
Authors: Shin Joongmin , Harte Bruce , Harte Janice , Dolan Kirk
Published: February 2019

Low-dose x-ray irradiation was used on vacuum skin-packaged fresh-cut asparagus to extend its shelf life and improve its microbial safety. Freshly imported Peruvian asparagus (Asparagus officinalis L.) spears were obtained from a local source, cleaned, trimmed, and sanitized and then vacuum skin-packaged (VSP) in a tray pack system. A breathable lid film was vacuum-sealed to protect the product from contamination and allow for gas exchange. Asparagus were packaged in VSP, which modified the package atmosphere, and exposed to a target dose of 1.0 kGy or left untreated. Asparagus were also placed in low-density polyethylene (LDPE) bags as a control. All samples were then stored at 4 °C for 24 days. To determine the effectiveness of the irradiation treatment, sample packages were periodically removed from storage and several measurements were used to evaluate the product, including headspace gas content, microbial growth, water soluble sugar content, and enzyme activity. A dose of 1.0 kGy reduced initial microbial population up to 3.8 log colony-forming units (cfu)/g and maintained 20% more of the initial sugar content relative to the non-irradiated VSP asparagus. Phenylalanine ammonia-lyase (PAL) activity in VSP asparagus was lower than in the control package (LDPE bag) regardless of irradiation treatment (P < 0.05). However, x-ray treatment increased the PAL activity of asparagus in VSP up to Day 8 (P < 0.05).
Early Detection of Salt Stress Tolerance of Prunus Rootstocks by Excised Root Culture
Authors: Andreu Pilar , Arbeloa Arancha , Lorente Pilar , Marín Juan A.
Published: February 2019

Salt tolerance varies between species and genotypes of plants, but evaluation of these differences is cumbersome, because whole plants that are highly complex systems show a variety of responses depending on the applied methodology. However, focusing on plant roots, which are in direct contact with the soil, could offer a simpler and more efficient model for analyzing salt stress tolerance in different species. This study explores whether root growth under salt stress is associated with genotypic differences in Prunus species with different degrees of salt tolerance. Excised root cultures were grown in vitro under increasing salt concentrations (0, 20, 60, and 180 mm NaCl). Root tips taken from in vitro-rooted shoots of Prunus species with different salt tolerance were measured after 3 weeks of culture in a shaker, and changes in their anatomy were examined. Both growth and starch content of in vitro root cultures were affected by salt concentration. Root length increments were related to salt stress tolerance at 60 mm NaCl, in which significant differences were also found between species. A significant inverse correlation was found between salt tolerance and starch accumulation in the maturation zone of root tips. Genotypic differences were observed in agreement with species' salt stress tolerance in vivo. These results suggest the use of excised root cultures for rapid, early detection of salt stress tolerance in plants. Chemical names: sodium chloride (NaCl).
Effective Reduction of Chimeric Tissue in Transgenics for the Stable Genetic Transformation of Lesquerella fendleri
Authors: Chen Grace Q.
Published: February 2019

To improve the potential of Lesquerella fendleri as a valuable industrial oilseed crop, a stable genetic transformation system was developed. Genetic transformation was performed by inoculating leaf segments with an Agrobacterium tumefaciens strain AGL1 containing binary vector pCAMBIA 1301.1, which contains a β-glucuronidase gene as a reporter gene and hygromycine phosphotransferase II as a selection marker gene. Primary shoots were regenerated from the leaf segments on the half-strength Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine, 1-naphthaleneacetic acid, and hygromycin. The frequency of primary shoot generation was between 22.5% and 60%, and 81.1% to 89.3% of these shoots were chimeras. The high frequency of chimeras was probably the result of efficient protection from the hygromycin of non-transformed cells by adjacent transformed ones. The non-transformed cells were removed by multiple rounds of successive shoot regenerations. The purified isogenic shoots were subcultured and roots were induced on the MS medium plus indole-3-butyric acid. Most of the plantlets were able to establish roots and acclimate successfully in the greenhouse. The insertion of the hptII gene was confirmed by segregation analysis in T1 seeds, and the stable inheritance of the transgenes was demonstrated by the characterization transgenic lines through T2 generation. This transformation system can be used to obtain stable transgenic lines for genetic engineering of L. fendleri.
Grafting Fraser Fir (Abies fraseri): Effect of Scion Origin (Crown Position and Branch Order)
Authors: Hibbert-Frey Haley , Frampton John , Blazich Frank A. , Hundley Doug , Hinesley L. Eric
Published: February 2019

Success and subsequent growth of fraser fir [Abies fraseri (Pursh) Poir.] cleft grafts were studied in relation to origin and type of scion material in the tree crown. First- and second-order shoots (current-year) were collected from five zones in the crown, ranging from top to bottom, and grafted to 5-year-old fraser fir transplants in April. Success rates were similar for first- and second-order scions, whereas budbreak and subsequent growth were best for first-order scions. In general, results were best for first-order scions taken from the upper crown. Plagiotropism of grafts was similar for all crown zones and shoot types.
Incidence and Severity of Huanglongbing and Candidatus Liberibacter asiaticus Titer among Field-infected Citrus Cultivars
Authors: Stover Ed , McCollum Greg
Published: February 2019

Incidence and severity of Huanglongbing (HLB) disease were assessed in Apr. 2010 among eight citrus cultivars representing diverse scion types growing in commercial groves in Florida's Indian River region, an area with a high incidence of HLB. In each grove, 20 trees of each cultivar were rated for visual HLB symptoms and leaves were collected for quantitative polymerase chain reaction quantification of Candidatus Liberibacter asiaticus (CLas), the presumptive causal agent of HLB. There was a strong correlation between HLB rating and CLas titer (titer represented by Ct, r2 = 0.37 and 0.40, for whole tree and leaf sample, respectively, both with P < 0.0001) across all cultivars and groves. Although incidence and severity of HLB varied considerably among the groves, scion-specific differences were apparent, even when analyses excluded potentially confounding grove effects. ‘Temple’ tangor showed the most consistently low incidence of HLB symptoms and CLas titer; in contrast, ‘Murcott’ tangor and ‘Minneola’ tangelo had the highest incidence of HLB symptoms and highest CLas titer. These results suggest useful resistance to HLB with reduced symptoms and reduced CLas titer may be found in conventional scion cultivars and further work is needed to assess this potential and its commercial value.
Fertility and Reproductive Pathways in Diploid and Triploid Miscanthus sinensis
Authors: Rounsaville Todd J. , Touchell Darren H. , Ranney Thomas G.
Published: February 2019

Miscanthus sinensis Andersson is a popular ornamental grass and has additional potential as a bioenergy crop. In some regards, the ability of M. sinensis to withstand a broad range of climatic and cultural conditions is desirable, but its propensity to rapidly colonize open and disturbed environments has allowed it to naturalize and become weedy in some regions in the United States. Considering the value of this crop, the development and documentation of infertile clones would be desirable. Triploid plants were evaluated for male and female fertility using pollen viability staining and seed set and germination, respectively. Pollen viability staining, seed set, and seed germination from triploid plants were reduced compared with diploids but varied considerably within each cytotype. Overall, relative female fertility of individual triploids clones [(% seed set × % germination for triploid)/(% seed set × % germination for diploid control)] was reduced substantially and ranged from 49% to 0.7%. Additionally, the reproductive pathways of triploid plants were examined by evaluating the 2C genome sizes of progeny derived from open pollination. The limited progeny arising from open-pollinated triploids were predominantly aneuploids with 2C genome sizes intermediate between diploids and triploids. There was no clear evidence of apomixis, selfing, or triploid × triploid fertilization events observed among triploid parents. Formation of unreduced gametes was rare for both ploidy levels (≈1%). The considerable reduction in female fertility in some triploid clones combined with the limited production of primarily aneuploid progeny provides highly infertile alternatives to existing diploid cultivars.