bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicted and Realized Response of Strawberry Production Traits to Selection in Differing Environments and Propagation Systems
Authors: Pringle Gregory J. , Shaw Douglas V.
Published: January 2019

Strawberry (Fragaria ×ananassa Duch.) seedlings from a factorial mating design were tested in each of two locations using two propagule types (seedlings and runners). Genotypic correlations were used to indicate G × E interaction across these locations and propagation systems and to predict correlated responses between selection under specific conditions and commercial propagation. A combined index on relatives was constructed and used to select four groups of individuals—one for each location-propagule combination—for each of two production traits. Comparison was then made with realized responses from subsequent clonal testing at a single site representing the commercial environment. Although selection in the commercial environment (Watsonville) was predicted to give the greatest selection response, realized responses were greatest for the Wolfskill site. Additionally, the present system of selecting seedlings at Wolfskill and testing clones at Watsonville offers considerable logistical advantages that may outweight genetic considerations. The concept of effective index heritability was introduced to enable the calculation of predicted response based on index selection. Neither the use of clonally tested parents nor a comparative seedling set selected for another trait was ideal for estimating realized response.
Inheritance and Linkage Relationships of Isozymes in Easter Cactus
Authors: O'Leary Maureen C. , Boyle Thomas H.
Published: January 2019

Polyacrylamide gel electrophoresis was used to study inheritance and linkage of isozymes in Easter cactus (Hatiora species and interspecific hybrids). Five isozyme systems were analyzed: aspartate aminotransferase (AAT), glucose-6-phosphate isomerase (GPI), malate dehydrogenase (MDH), phosphoglucomutase (PGM), and triosephosphate isomerase (TPI). F1, F2, BC1, and S1 progeny were used for inheritance studies. Six polymorphic loci (Aat-1, Gpi-1, Mdh-1, Pgm-1, Pgm-2, and Tpi-2) were identified. Aat-1 and Pgm-1 were linked (recombination frequency = 26% ± 7%), but the other isozyme loci assorted independently. Aberrant segregation ratios were observed in at least one segregating family for all six isozyme loci. We hypothesize that segregation distortion was due to linkage between isozyme loci and other genes subject to pre- or postzygotic selection. The existence of five additional isozyme loci (Aat-2, Gpi-2, Mdh-2, Mdh-3, and Tpi-1) was inferred from segregation patterns and by comparison of isozyme profiles from phylloclades and pollen. These isozyme loci may prove useful for confirming hybridity in intra- and interspecific crosses, determining parentage of cultivars, and assessing genetic diversity in germplasm collections.
Ice Nucleation, Freezing Injury, and Colonization of `Totem' Strawberry Flowers with Ice-nucleation-active (INA) Bacteria
Authors: Warmund Michele R. , English James T.
Published: January 2019

INA bacteria were isolated from primary flowers of `Totem' strawberry (Fragaria ×ananassa Duch.) plants that had been previously inoculated with strain Cit 7 of Pseudomonas syringae van Hall or noninoculated to determine their relationship to ice-nucleation temperature and floral injury. Mean ice-nucleation temperature of inoculated and noninoculated flowers was -2.2 and -2.8 °C, respectively. Primary flowers of noninoculated plants survived lower temperatures than those of inoculated plants. In another experiment, noninoculated plants were misted with sterile deionized water and incubated for 0, 12, 24, 36, or 48 hours at 25 °C day/10 °C night, and naturally occurring INA bacteria were isolated from primary flowers. INA bacterial densities increased exponentially with increasing incubation period. The critical wetness period for INA bacteria to establish a sufficient density to increase the likelihood of floral injury at -2.5 °C was 24 hours. Longer wetness periods resulted in higher INA bacterial densities but did not increase the floral mortality rate. Thermal analysis demonstrated that the ice nucleation temperature was associated with strawberry floral injury. Thus, low temperature survival of flowers was adversely affected by moisture for ≥24 h due to the presence of a sufficient density of INA bacteria to incite ice formation and floral injury.
Comparing Gompertz and Richards Functions to Estimate Freezing Injury in Rhododendron Using Electrolyte Leakage
Authors: Lim Chon C. , Arora Rajeev , Townsend Edwin C.
Published: January 2019

Seasonal patterns in freezing tolerance of five Rhododendron cultivars that vary in feezing tolerance were estimated. Electrolyte leakage was used, and raw leakage data were transformed to percent leakage, percent injury, and percent adjusted injury. These data were compared with visual estimates of injury. Percent adjusted injury was highly correlated (0.753) to visual estimates. Two asymmetric sigmoid functions—Richards and Gompertz—were fitted to the seasonal percent adjusted injury data for all cultivars. Two quantitative measures of leaf freezing tolerance—Lt50 and Tmax (temperature at maximum rate of injury)—were estimated from the fitted sigmoidal curves. When compared to the General Linear Model, the Gompertz function had a better fit (lower mean error sum of squares) than Richards function. Correlation analysis of all freezing tolerance estimates made by Gompertz and Richards functions with visual LT50 revealed similar closeness (0.77 to 0.79). However, the Gompertz function and Tmax were selected as the criteria for comparing relative freezing tolerance among cultivars due to the better data fitting of Gompertz function (than Richards) and more descriptive physiological representation of Tmax (than LT50). Based on the Tmax (°C) values at maximum cold acclimation of respective cultivars, we ranked `Autumn Gold' and `Grumpy Yellow' in the relatively tender group, `Vulcan's Flame' in intermediate group, and `Chionoides' and `Roseum Elegans' in the hardy group. These relative rankings are consistent with midwinter bud hardiness values reported by nurseries.
Sources of Resistance to Eastern Filbert Blight in Hazelnut
Authors: Coyne Clarice J. , Mehlenbacher Shawn A. , Smith David C.
Published: January 2019

Eastern filbert blight is an economically significant disease in European hazelnut (Corylus avellana L.) production in the United States. Since genetic resistance is the only viable disease control strategy to this fungal disease caused by Anisogramma anomala (Peck) E. Müller, greenhouse and field screening of germplasm was undertaken to study the inheritance from known resistant sources and to identify new sources for inclusion in the breeding program. We confirmed that `Gasaway' resistance to this disease is conferred by a single dominant gene. No major gen was identified in the field-resistant cultivar Gem. Representatives of six Corylus species were screened to identify new resistant germplasm. Corylus cornuta Marshall var. cornuta, C. cornuta var. californica (A.DC.) Sharp, C. heterophylla Fischer, and C. sieboldiana Blume were highly resistant, as were most C. americana Marshall genotypes and one C. colurna L. clone tested, but C. jacquenontii Decaisne was highly susceptible. In several cases, hybrids of these species with susceptible C. avellana were also resistant. These new sources of resisstance are being incorporated in the resistance breeding effort.
Active Oxygen Species Metabolism in `White Angel' × `Rome Beauty' Apple Selections Resistant and Susceptible to Superficial Scald
Authors: Rao Mulpuri V. , Watkins Christopher B. , Brown Susan K. , Weeden Norman F.
Published: January 2019

Fruit from seedlings selected from a population obtained by crossing superficial scald-resistant `White Angel' and superficial scald-susceptible `Rome Beauty' apple (Malus ×domestica Borkh.) were used to investigate the role of oxidative processes in the development of superficial scald. Selections were identified for study based on fruit coloration and scald susceptibility. Plant material had one of the following three physiognomies: 1) red-skinned fruit resistant to scald; 2) red-skinned fruit susceptible to scald; and 3) yellow-skinned fruit susceptible to scald. The concentrations of α-farnesene, conjugated triene (CT) species, hydrogen peroxide (H2O2), thiobarbituric acid-reactive substances, carbonyl groups, and the activities of superoxide dismutase, guaiacol-peroxidase, and catalase were measured at harvest and during 0.5 °C storage. Relationships were poor between scald susceptibility and α-farnesene and its oxidation products, CT258, CT281, and the CT258/CT281 ratio. Tissue concentrations of H2O2 were lower in scald-resistant than in scald-susceptible fruit at harvest and after storage, and these lower concentrations were associated with less damage to cellular membranes (lipid peroxidation) and proteins (carbonyl group content). Higher activities of the H2O2-degrading enzymes, guaiacol-peroxidases, and catalases, were related to lower H2O2 content and lower scald susceptibility. Activities of superoxide dismutase, a H2O2-generating enzyme, were not related to scald susceptibility or storage period. We hypothesize that fruit susceptibility to scald is strongly influenced by cellular efficiency in metabolizing active oxygen species such as H2O2.
5-kD Zinc-binding Protein Accumulation in Macrophylla-decline-affected Citrus
Authors: Taylor K.C. , Geitzenauer H.L.
Published: January 2019

Macrophylla-decline (MD)-affected citrus display apparent nutrient deficiencies in a sectorial pattern within the citrus tree canopy. The status of several elements (Ca, Cu, Fe, Mg, Mn, and Zn) was assessed in MD and healthy citrus selected from the same citrus orchards. Leaf and phloem tissues were sampled from mature, reproductive trees. Levels of Ca, Cu, Fe, Mg, and Mn were unaffected by the disorder in leaf or phloem tissues. Zinc was diminished in the leaves of MD citrus, and elevated in the whole phloem tissue (2.57-fold on a dry mass basis). Calcium and Cu were sufficient, while Mg, Fe, and Mn were slightly diminished in the leaf tissue, but phloem levels of these elements were not significantly different from that present in the phloem of healthy trees. Since Zn appeared to be redistributed to the phloem tissue from the leaves, the accumulation of the phloem specific, 5-kD Zn-binding protein (ZBP) was assessed in Macrophylla decline trees relative to healthy trees. The 5-kD ZBP was 4.77-fold greater in the phloem of MD citrus relative to healthy. This appears to account for the 2.4-fold greater level of Zn (on a fresh mass basis) found in the crude phloem extracts of the decline-affected citrus relative to healthy. In the purified ZBP fraction from decline-affected citrus, there was 4.73-fold greater Zn than in the ZBP purified from healthy. However, the ratios of Zn to ZBP were equivalent between MD citrus and healthy citrus, suggesting that phloem Zn accumulation in MD citrus is associated with the 5-kD ZBP.
Heritability of Length of Reproductive Period and Rate of Seed Mass Accumulation in Common Beans
Authors: Beaver James S. , Rosas Juan Carlos
Published: January 2019

Heritability of length of the reproductive period and rate of seed mass accumulation in beans (Phaseolus vulgaris L.) was estimated using 170 randomly derived F6 and F7 lines from three populations evaluated in the field in Puerto Rico and Honduras during two growing seasons. Narrow-sense heritability for length of reproductive period ranged from moderate (0.43) to high (0.83), and transgressive segregation for shorter and longer reproductive period was observed for the three populations. Heritability of rate of seed mass accumulation was low (0.24) to intermediate (0.49). Lines with high yield potential, which matured 4 to 7 days earlier than the later parents L227-1 and `Catrachita', were selected. Most of the superior lines combined earlier maturity with high yield potential by having greater rates of seed mass accumulation than the early parents `Cuarentena' and `Cuarenteño'. Low to intermediate heritabilities for rate of seed mass accumulation suggest that selection for this trait would be more effective by evaluating advanced generation lines in replicated trials. Several lines yielded significantly more than L227-1 or `Catrachita' by combining long reproductive period with fast rate of seed mass accumulation.
Characterization of a Type II Chlorophyll a/b-binding Protein Gene (Lhcb2*Pp1) in Peach: I. Isolation, Identification, and Abundance in Developing Leaves of Mature `Loring' Trees in the Absence of Flowering
Authors: Bassett Carole , Callahan Ann , Dunn Linda
Published: January 2019

A gene (Lhcb2*Pp1) encoding a type II chlorophyll a/b-binding protein (LHCB) was isolated from peach [Prunus persica (L.) Batsch]. The gene was sequenced and compared to a variety of other genes encoding LHCB polypeptides associated with photosystem II. Similarity at the nucleotide and amino acid level was highest between Lhcb2*Pp1 and other type II genes and was lowest with type I and III genes from other species. Expression of Lhcb2*Pp1 was followed by determining abundance of transcripts in developing leaves of field grown trees in the absence of flowering. Expression was monitored at three times during the first phase of the growing season and was shown to be highest in leaves which were at or near full expansion at each sampling time. These results are consistent with the function of this gene and indicate that it can serve as a marker of photosynthetic maturity under field conditions.
Nickel Supplements Improve Growth when Foliar Urea is the Sole Nitrogen Source for Tomato
Authors: Nicoulaud Bernard A. L. , Bloom Arnold J.
Published: January 2019

Concentrations of up to 1.0 μm NiCl2 in a nutrient solution improved growth of tomato (Lycopersicon esculentum Mill. `T-5') seedlings that received foliar urea as their sole nitrogen source. Nickel in the nutrient solution decreased the amount of urea present in the shoots and increased the amount in the roots, although it had no significant effect upon leaf urease activity. These results indicate that a) the presence of nickel in the nutrient solution improves growth of plants receiving foliar urea and b) the effect of nickel was related more to increased urea translocation from shoot to root than to enhanced leaf urease activity.
AMMI and Stability Analyses of Bunch Mass in Multilocational Testing of Musa Germplasm in Sub-Saharan Africa
Authors: Ortiz Rodomiro
Published: January 2019

There is a genuine need within a plantain and banana (Musa spp.) breeding program to assess thoroughly the experimental materials through a sequence of trials. This will result in the selection of promising clones as potential new cultivars in the targeted agroecozone. Stability analyses and the additive main effects and multiplicative interaction (AMMI) model provide together a means for the identification of clones with 1) homeostatic responses to environmental changes, 2) a genotypic response to environmental changes, and 3) adaptation to specific niches. Fourteen polyploid clones (10 tetraploid hybrids and 4 triploid cultivars) were evaluated in a broad range of environments in sub-Saharan Africa to determine the value of stability and AMMI analyses in Musa trials. The interpretation of the results, especially those concerning the genotype × environment interaction, was facilitated by the combination of stability and AMMI analyses. Tetraploid hybrids combining heavy and stable bunch mass were identified. The results also suggested that a clone should be assessed in the ratoon cycle because plantain and banana are perennial crops. Likewise, high yielding clones with specific adaptation should be selected in environments showing the respective environmental or biotic stress.
Inheritance of Resistance to Bean Golden Mosaic Virus in Common Bean
Authors: Velez Jose J. , Bassett Mark J. , Beaver James S. , Molina Albeiro
Published: January 2019

The inheritance of resistance to bean golden mosaic virus (BGMV) in common bean (Phaseolus vulgaris L.) was studied in crosses between susceptible bean variety XAN176 and resistant breeding lines 9236-6 (T446/A429) and 9245-94 (DOR303/T968). Disease response data were taken on plants from four generations derived from each cross (parents, F1, F2, and backcrosses (BCs) of F1 to both parents) at 25 days after plants were inoculated with BGMV, using whiteflies (Bemisia argentifolii Bellows & Perring) as vectors. The segregation ratios obtained from F2 and BC generations were consistent with the hypothesis that resistance in 9236-6, which prevents a chlorotic response, is conferred by a single recessive gene. The disease response in 9245-94 was controlled by two genes—a dominant gene controlling a dwarfing reaction and a recessive resistance gene preventing a chlorotic response to BGMV infection. An allelism test demonstrated that the gene controlling resistance in 9236-6 is nonallelic with the recessive gene controlling resistance in 9245-94. The gene symbol bgm is proposed for the recessive resistance gene (originally from A429) in 9236-6. The gene symbol bgm-2 is proposed for the recessive resistance gene (originally from DOR303) in 9245-94.
Using Hydrotime and ABA-time Models to Quantify Seed Quality of Brassicas during Development
Authors: Still David W. , Bradford Kent J.
Published: January 2019

With many seed crops, the most difficult production decision is when to harvest. In indeterminate crops such as Brassica species, early harvests result in immature seed of low vigor while late harvests risk seed deterioration and seed loss due to shattering. To provide a biological basis on which to determine harvest timing, we have characterized seed development in rape seed (Brassica napus L. `Weststar') and red cabbage (Brassica oleracea L. Group Capitata) using population-based hydrotime and ABA-time models. These models provide information relevant to assessing physiological maturity, and therefore, seed quality. The hydrotime and ABA-time models quantify germination rate, the uniformity of germination, viability, and the sensitivity of germination to water potential and ABA. Indices derived from these models, along with maximum germination and t50 values, were used to determine physiological maturity (maximum seed quality) of the seeds during development. The overall trends in seed development were similar in both species: as seeds matured, germination became more uniform and less sensitive to low Ψ and externally applied ABA. The models accurately described germination time courses and final germination percentages except for seeds imbibed at very high concentrations of ABA. In rape seed, physiological maturity was attained several days after maximum seed dry mass, while in red cabbage physiological maturity occurred at or after maximum seed dry mass. Vigor indices were correlated with easily discerned traits such as moisture content and silique phenotypic characteristics. The results of these experiments suggest that hydrotime and ABA-time models can be successfully used to provide a biological basis on which to determine harvest in brassicas.
Interaction of Crop Level and Fruit Cluster Exposure on `Seyval Blanc' Fruit Composition
Authors: Hummell Ann K. , Ferree David C.
Published: January 2019

`Seyval blanc' grapevines (Vitis spp.) were cluster thinned 7 days after full bloom to 20, 40, and 80 clusters per vine to create light, moderate, and heavy crop levels. Vines were also shoot positioned at veraison to create exposed, partially shaded, and densely shaded cluster microclimates to examine the interactions between crop level and light exposure on fruit composition during stage III of berry development. Clusters were harvested using one of two criteria: on the same date or at similar soluble solids concentrations. Cluster mass and berries per cluster decreased with increasing crop level regardless of harvesting criterion. When harvested on the same date, soluble solids concentration, pH and malic acid concentration of juice decreased with increasing crop level. When harvested at similar soluble solids concentrations, increasing crop level delayed harvest and reduced titratable acidity (TA), tartaric acid, and malic acid. As cluster light exposure increased, soluble solids and pH increased and TA and malic acid decreased when clusters were harvested on the same date. When harvested at similar soluble solids concentration, increasing light exposure advanced harvest date and pH, TA, tartaric acid, and malic acid decreased. If clusters were harvested on the same date, significant interactions were found between crop level and light exposure for soluble solids concentration and the hue angle of berries. Significant interactions were found for berry mass, pH, TA, and tartaric acid when clusters were harvested at similar soluble solids. When harvested on the same date in 1995, soluble solids concentration of densely shaded clusters declined as crop level increased, whereas the soluble solids of exposed and partially shaded clusters declined as cluster number increased from 20 to 40 clusters per vine but remained constant from 40 to 80 clusters. In 1995, the hue angles of exposed clusters decreased with increasing crop level, while those of partially shaded and densely shaded clusters increased. When harvested at similar soluble solids concentration, berry mass of exposed and partially shaded clusters was similar across crop levels, whereas berry mass of densely shaded clusters declined as crop levels increased. Based on contribution to treatment error, crop level influenced pH more, and TA less, than did light exposure if harvested at the same date. Conversely, crop level influenced TA more, and pH less, than did light exposure if harvest was done at similar soluble solids concentrations. Regardless of harvest criterion, crop level influenced yield components, and soluble solids concentration to a greater extent and hue angle to a lesser extent than did light exposure.
Membrane Competence among and within Fragaria Species Varies in Response to Dehydration Stress
Authors: McDonald Suzanne S. , Archbold Douglas D.
Published: January 2019

The effect of dehydration stress on membrane competence among and within Fragaria species was evaluated using index of injury, Id, and tissue ionic conductance, gTi. Single accessions of F. chiloensis ssp. lucida Duch., F. virginiana ssp. glauca (S. Watson) Staudt, F. virginiana ssp. virginiana Duch., F. ×ananassa Duch., and F. vesca L. were used to study interspecific variation. Leaf thickness and total electrolyte content were greatest for the F. chiloensis ssp. lucida accession and least for the F. virginiana ssp. glauca accession, but foliar electrolyte concentration did not vary across accessions. The gTi values were >5-fold higher from 0 to 2 hours than for other intervals, declining over time. Significant differences in gTi and Id values were only evident at 2 and 4 hours within stress levels, and increased as stress level increased. While the F. chiloensis ssp. lucida accession exhibited low gTi values at 70% relative water content (RWC), it showed greater relative membrane injury than the other species expressed as gTi, Id, or the ratio of stress gTi to control gTi as dehydration level increased. Although the F. virginiana ssp. glauca accession had the highest gTi values, even at 100% RWC, its relative injury as stress level increased was not as great as that of the F. chiloensis accession. In a second experiment, intraspecific variation was examined using four accessions each of F. chiloensis and of F. virginiana which were dehydrated to 50% RWC. The species mean gTi, Id, and gTi ratio values at 2 and 4 hours for the F. chiloensis accessions were lower than those for the F. virginiana accessions, but significant intraspecific variation was also observed. In spite of the differences between species means, the evidence of intraspecific variation indicates that not all accessions of a species exhibit similar drought responses (i.e., membrane competence). Due to the consistent conclusions derived from using either gTi or Id after 2 or 4 hours of incubation for characterization of membrane competence, gTi and Id were comparable techniques for identification of potential drought tolerance in Fragaria.
Molecular Characterization of Common Olive Varieties in Israel and the West Bank Using Randomly Amplified Polymorphic DNA (RAPD) Markers
Authors: Wiesman Z. , Avidan N. , Lavee S. , Quebedeaux B.
Published: January 2019

RAPD analysis was performed on the main traditional and introduced varieties of olive grown in Israel and the West Bank. Primers were identified and used in combination to discriminate between different varieties. Significant biodiversity was demonstrated among `Nabali' olive trees growing along the central mountain ridge of the West Bank, suggesting that the grouping known as `Nabali' is actually a mixture of genetically distinct variants. On the other hand, RAPD profiles of selected variants of `Souri', cultivated mainly in the northern mountains of Israel, revealed a high degree of similarity, indicating that these variants represent environmental phenotypes of the same genome. Molecular differences were demonstrated between the `Nabali' group variants and `Souri'. Other more recently developed or introduced varieties showed individually distinct RAPD profiles. Possible future developments based on these data are mentioned.
Chlorophyll Fluorescence in Relation to Superficial Scald Development in Apple
Authors: Mir Nazir , Wendorf Michael , Perez Rufino , Beaudry Randolph M.
Published: January 2019

The relationship between chlorophyll fluorescence of `Cortland', `Redchief Delicious', and `Empire' apple (Malus ×domestica Borkh.) fruit and the development of superficial scald was studied during 120 days of refrigerated air (RA) storage at 0 °C and during 7 days of poststorage holding at 22 °C. Minimal fluorescence (Fo), maximal fluorescence (Fm), photochemical efficiency (Fv/Fm, where Fv=Fm=Fo) and coefficient of photochemical fluorescence quenching (qp) were measured. During storage, while Fv/Fm and Fm declined in `Cortland' and `Redchief Delicious' fruit over time, these two measures of chlorophyll fluorescence remained stable in `Empire' fruit. Of the three cultivars, only `Empire' is resistant to and did not develop superficial scald. A decline in Fv/Fm preceded scald development in `Cortland' and `Redchief Delicious' fruit. After 30 days of storage, qp began to decrease in fruit from all three cultivars. Prestorage diphenylamine (DPA) application had no effect on Fv/Fm, Fo, and Fm and only marginally improved maintenance of qp, but completely prevented the development of superficial scald. Poststorage holding at 22 °C accelerated the rate of change in most fluorescence measurements. The decline in the Fv/Fm ratio and/or qp with storage time may be in response to senescence-related factors that also enhance scald susceptibility, however, Fv/Fm does not appear to be directly related to superficial scald susceptibility per se.
Near-infrared Spectrometric Method for Nondestructive Determination of Soluble Solids Content of Peaches
Authors: Peiris K.H.S. , Dull G.G. , Leffler R.G. , Kays S.J.
Published: January 2019

A nondestructive method for measuring the soluble solids (SS) content of peaches [Prunus persica (L.) Batsch] was developed using near-infrared (NIR) spectrometry. NIR transmittance in the 800 to 1050 nm region was measured for four cultivars of peaches (`Blake', `Encore', `Red Haven', and `Winblo'), over a period of three seasons (1993 through 1995). Each fruit was scanned on both halves keeping the suture away from the incident light beam. Soluble solids contents of flesh samples taken from corresponding scanned areas were determined using a refractometer. Multiple linear regression models using two wavelengths were developed with second derivative spectral data and laboratory measurements of SS content. Multiple correlation coefficients (R) for individual cultivar calibrations within a single season ranged from 0.76 to 0.98 with standard error of calibration (SEC) values from 0.35% to 1.22%. Selected spectra and corresponding SS data in individual cultivar calibration data sets were combined to create season and cultivar calibration data sets to cover the entire range of SS contents within the season or within the cultivar. These combined calibrations resulted in R values of 0.92 to 0.97 with SEC values ranging from 0.37% to 0.79%. Simple correlations of validations (r) ranged from 0.20 to 0.94 and the standard error of prediction (SEP) ranged from 0.49% to 1.63% while the bias varied from -0.01% to -2.62%. Lower r values and higher SEP and bias values resulted when individual cultivar calibrations were used to predict SS levels in other cultivar validation data sets. Cultivar calibrations, season calibrations and the overall calibration predicted SS content of all validation data sets with a smaller bias and SEP and with higher r values. These results indicate that NIR spectrometry is suitable for rapid nondestructive determination of SS in peaches. Feasible applications of the method include packinghouse sorting of peaches for sweetness and parent and progeny fruit quality assessment in peach breeding programs. Using this technique fruit may be sorted into two or three sweetness classes. The technique may also potentially be extended to other fruit.
Relationship between Sensory and Instrumental Analysis for Tomato Flavor
Authors: Baldwin E.A. , Scott J.W. , Einstein M.A. , Malundo T.M.M. , Carr B.T. , Shewfelt R.L. , Tandon K.S.
Published: January 2019

The major components of flavor in tomato (Lycopersicon esculentum Mill.) and other fruit are thought to be sugars, acids, and flavor volatiles. Tomato overall acceptability, tomato-like flavor, sweetness, and sourness for six to nine tomato cultivars were analyzed by experienced panels using a nine-point scale and by trained descriptive analysis panels using a 15-cm line scale for sweetness, sourness, three to five aroma and three to seven taste descriptors in three seasons. Relationships between sensory data and instrumental analyses, including flavor volatiles, soluble solids (SS), individual sugars converted to sucrose equivalents (SE), titratable acidity (TA), pH, SS/TA, and SE/TA, were established using correlation and multiple linear regression. For instrumental data, SS/TA, SE/TA, TA, and cis-3-hexenol correlated with overall acceptability (P = 0.05); SE, SE/TA (P≤0.03), geranylacetone, 2+3-methylbutanol and 6-methyl-5-hepten-2-one (P = 0.11) with tomato-like flavor; SE, pH, cis-3-hexenal, trans-2-hexenal, hexanal, cis-3-hexenol, geranylacetone, 2+3-methylbutanol, trans-2 heptenal, 6-methyl-5-hepten-2-one, and 1-nitro-2-phenylethane (P≤0.11) with sweetness; and SS, pH, acetaldehyde, aceton, 2-isobutylthiazole, geranlyacetone, β-ionone, ethanol, hexanal and cis-3-hexenal with sourness (P≤0.15) for experienced or trained panel data. Measurements for SS/TA correlated with overall taste (P=0.09) and SS with astringency, bitter aftertaste, and saltiness (P≤0.07) for trained panel data. In addition to the above mentioned flavor volatiles, methanol and 1-penten-3-one significantly affected sensory responses (P = 0.13) for certain aroma descriptors. Levels of aroma compounds affected perception of sweetness and sourness and measurements of SS showed a closer relationship to sourness, astringency, and bitterness than to sweetness.
Measuring Soil Water Content under Turfgrass Using the Dual-probe Heat-pulse Technique
Authors: Song Y. , Ham J.M. , Kirkham M.B. , Kluitenberg G.J.
Published: January 2019

Measurements of soil water content near the soil surface often are required for efficient turfgrass water management. Experiments were conducted in a greenhouse to determine if the dual-probe heat-pulse (DPHP) technique can be used to monitor changes in soil volumetric water content (θv) and turfgrass water use. `Kentucky 31' Tall fescue (Festuca arundinacea Schreb.) was planted in 20-cm-diameter containers packed with Haynie sandy loam (coarse-silty, mixed, calcareous, mesic Typic Udifluvents). Water content was measured with the DPHP sensors that were placed horizontally at different depths between 1.5 and 14.4 cm from the surface in the soil column. Water content also was monitored gravimetrically from changes in container mass. Measurements started when the soil surface was covered completely by tall fescue. Hence, changes in θv could be attributed entirely to water being taken up by roots of tall fescue. Daily measurements were taken over multiple 6- or 7-day drying cycles. Each drying cycle was preceded by an irrigation, and free drainage had ceased before measurements were initiated. Soil water content dropped from ≈0.35 to 0.10 m3·m-3 during each drying cycle. Correlation was excellent between θv and changes in water content determined by the DPHP and gravimetric methods. Comparisons with the gravimetric method showed that the DPHP sensors could measure average container θv within 0.03 m3·m-3 and changes in soil water content within 0.01 m3·m-3.
Using a Puncture Test to Identify the Role of Seed Coverings on Thermotolerant Lettuce Seed Germination
Authors: Sung Yu , Cantliffe Daniel J. , Nagata Russell
Published: January 2019

Temperature is an important environmental factor that affects lettuce (Lactuca sativa L.) germination. The present research was conducted to determine the role of seed coverings on lettuce seed germination at high temperature. Five lettuce genotypes were primed in order to bypass thermoinhibitional effects on germination. During germination of primed and nonprimed seeds, imbibition followed a normal triphasic pattern. Primed seeds had higher final water content, a decreased imbibitional phase II, and germinated at 36 °C compared to nonprimed seeds of thermosensitive genotypes, which did not germinate at 36 °C. Puncture tests were conducted to determine the force required to penetrate the whole seed or endosperm of the five genotypes at 24 and 33 °C. `Dark Green Boston', a thermosensitive genotype, had the highest mean resistance (0.207 N) and PI 251245, a thermotolerant genotype, had the lowest (0.139 N). Resistance to penetration of the endopserm of the five genotypes was different at both temperatures. However, three thermotolerant genotypes had lower endosperm resistance than two thermosensitive types. At 36 °C, the penetration force for primed and nonprimed seeds was compared after the first hour of imbibition and 1 hour before radicle protrusion. The force required to penetrate the seed was affected by genotype, seed priming, and duration of imbibition. Puncture force decreased as imbibition time at 36 °C increased in primed and nonprimed seed of each thermotolerant genotype but not in the thermosensitive genotypes. Priming reduced the initial force necessary to penetrate the seed and endosperm in all genotypes. Thus, for radicle protrusion to occur, there must first be a decrease in the resistance of the endosperm layer as evidenced by priming or thermotolerant genotype. Then, the pericarp and integument are sufficiently weakened so that tissue resistance is lower than the turgor pressure of the expanding embryo, allowing germination to be completed.
Anatomical Analysis of Double-flower Morphogenesis in a Nicotiana alata Mutant
Authors: Zainol Rozlaily , Stimart Dennis P. , Evert Ray F.
Published: January 2019

Anatomical analysis was performed using a double-flowered mutant of Nicotiana alata Link & Otto. Flower doubleness resulted from petaloid modification of the androecium. Vascularized petal-like outgrowths arose from the anther, connective, and filament of the stamen. The vasculature in petaloid outgrowths from the anther and upper part of the filament originated from and was continuous with the vascular bundle of the filament. In contrast, the vascular bundles formed in the outgrowths from the lower part of the filament developed independently of the vascular bundle of the filament and were not connected to it at any time. Emergences consisting of epidermal and ground parenchyma tissue and lacking vascularization arose from the filament.
Genotype, Location, and Harvest Date Effects on the Sensory Character of Fresh and Frozen Red Raspberries
Authors: Morel Séverine , Harrison Richard E. , Muir Donald D. , Hunter E. Anthony
Published: January 2019

Fruit from three red raspberry (Rubus idaeus L.) cultivars—`Glen Clova', `Glen Lyon', and `Glen Moy'—were harvested from four sites on two harvest dates and evaluated fresh or following storage at -20 °C to determine the relative importance of genotype, harvest date, location and freezing effects on 19 sensory attributes using a trained sensory panel. Freezing and cultivar × freezing interaction effects were relatively large while site, harvest date, and other interactions were of minor importance. The cultivar × freezing interaction was caused by differential responses among cultivars for the sensory attributes purple, juicy, sweet, and raspberry aroma with less discrimination among cultivars postfreezing. `Glen Clova' fresh fruit received the highest values for juicy, fruity, sweet, and raspberry aroma; `Glen Moy' fresh fruit received the highest values for purple; `Glen Lyon' fresh fruit received the lowest values for juicy, postfreezing, `Glen Lyon' received the highest values for purple and sweet and all three cultivars were similar for the other attributes. These data suggest that selection for improved postfreezing sensory characteristics should not rely solely on fresh fruit evaluations although further study of a more genetically diverse group of genotypes would be beneficial. The significant cultivar and minimal harvest date and location effects suggest that these fruit sensory analysis methods should be useful in selecting raspberry genotypes with superior fruit quality.
A Study of Photosynthetic Activities of Eight Asparagus Genotypes under Field Conditions
Authors: Bai Yuyu , Kelly John F.
Published: January 2019

Net photosynthesis from whole plants of eight asparagus (Asparagus officinalis L.) genotypes was measured at two locations in an open infrared gas analysis system. Measurements started at about the completion of full fern growth, which occurred at the end of July and lasted through the season until fern senescence in late September. Net photosynthesis of the eight genotypes ranged from 15.67 to 27.79 μmol·m-2·s-1. Significant differences (P < 0.1) in net photosynthesis were found among the eight genotypes. Both yield and specific leaf mass (SLM) were correlated significantly with net photosynthesis. We suggest that specific leaf mass can be used as a criterion for selecting genotype of high photosynthetic ability. Daily photosynthetic rate patterns were studied and appear to be related to daily changes of stomatal conductance. Seasonal changes of asparagus' photosynthetic activity were studied. High photosynthetic activity was observed from July through August. Photosynthetic activity decreased greatly in September along with the fern maturation and unfavorable changes in environmental conditions.
A Plant Process Economic Model for Weed Management Decisions in Irrigated Onion
Authors: Dunan Claudio M. , Westra Philip , Moore Frank D.
Published: January 2019

A simulation model was built as a decision aid for management of five weed species in direct seeded irrigated onion (Allium cepa L.). The model uses the state variable approach and simulations are driven by temperature and sunlight as photosynthetically active radiation (PAR). It predicts yield reduction caused by competition for PAR according to the ratio of crop leaf area index (LAI) to weed LAI and respective light extinction coefficients (k). Input variables are plant density by species and average number of leaves by species. Number of leaves per plant is used by the model to provide an estimate of initial leaf area per plant. The model calculates initial species LAIs by multiplying species density times average leaf area per plant. The model accurately describes competitive interactions, taking into account respective plant densities, time of emergence, and time of weed removal. It permits economic evaluation of management factors such as handweeding, chemical weed control, herbicide phytotoxicity due to early application, and control of weed flushes during the season. The model is also used to evaluate mechanisms of plant competition for sunlight. In a sensitivity analysis, onion yield loss was more sensitive to weed PAR interception than to PAR use efficiency, the latter a species-dependent constant in the model.
Identification of Plastome Variants useful for Cytoplasmic Selection and Cultivar Identification in Onion
Authors: Alcalá Josefina , Pike Leonard M. , Giovannoni James J.
Published: January 2019

The relatively low evolution rate of the chloroplast DNA has made it an ideal tool to study evolutionary processes in plants above the species levels. However, recent studies have demonstrated that intraspecific variation in the chloroplast DNA is also common. This variation has provided useful insights into population level evolutionary processes. The polymerase chain reaction and sequencing of a noncoding chloroplast region used to classify onion lines for cytoplasmic type facilitated the identification of one sterile and two normal plastome variants in onion (Allium cepa L.). Sequence comparison revealed that differences between plastome variants included the presence of single-nucleotide polymorphisms associated with cytoplasmic type and variable numbers of tandem repeats, possibly resulting from slipped-strand mispairing. Our observations support the use of chloroplast-specific markers to assist in the selection of specific cytoplasmic types, suggest the potential to facilitate genotype determination, and demonstrate the presence of additional variation within cytoplasm type which gives insight into plastome evolution and may facilitate more accurate genotyping and selection.
Composition and Variability of Epicuticular Lipids of Azaleas and their Relationship to Azalea Lace Bug Resistance
Authors: Wang Yuefang , Braman S. Kristine , Robacker Carol D. , Latimer Joyce G. , Espelie Karl E.
Published: January 2019

Epicuticular lipids were extracted from the foliage of six deciduous and one evergreen azalea genotypes (Rhododendron sp.) and identified by gas chromatography-mass spectrometry. The relationship of leaf-surface lipid composition with measures of resistance to azalea lace bug, Stephanitis pyrioides Scott, was evaluated. Each genotype had a distinct epicuticular lipid composition. The major surface lipid components from all test taxa were n-alkanes and triterpenoids. In the most resistant genotypes [R. canescens Michaux and R. periclymenoides (Michaux) Shinners] ursolic acid, n-hentriacontane, and n-nonacosane were the most abundant epicuticular lipids. The lipids present in largest proportion among all susceptible deciduous genotypes tested were α-amyrin, β-amyrin, and n-nonacosane. The proportions of the lipid components from the same plant of each genotype varied between spring and fall samples. Among classes of lipids, n-alkanes, n-1-alkanols, and triterpenoids had significant correlations with azalea lace bug behavior on host plants. Among individual components, heptadecanoic acid, n-hentriacontane, oleanolic acid, ursolic acid and one unknown compound (with major mass spectra 73/179/192/284/311) were significantly negatively correlated with host plant susceptibility to azalea lace bug, as measured by oviposition, leaf area damaged, egg and nymphal development, and nymphal survivorship. Triacontanol, α-amyrin, β-amyrin, and three unknowns were significantly positively correlated with host plant susceptibility. Acceptance or rejection by azalea lace bug to a particular plant may be mediated by a balance of positively and negatively interpreted sensory signals evoked by plant chemicals. This study indicated that the high levels of resistance observed in R. canescens and R. periclymenoides may be due to the lesser amount or the absence of attractants and stimulants for feeding or oviposition.
Testcross Performance of Three Selection Cycles from Four Pickling Cucumber Populations
Authors: Cramer Christopher S. , Wehner Todd C.
Published: January 2019

Progress was measured in four populations of cucumber (Cucumis sativus L.) improved by recurrent selection. The populations were the North Carolina wide base pickle (NCWBP), medium base pickle (NCMBP), elite pickle 1 (NCEP1), and hardwickii 1 (NCH1). Families from each of three cycles (early, intermediate, and late) from each population were randomly chosen and crossed with Gy 14 to produce gynoecious hybrids. Gy 14 is a gynoecious inbred used commonly as a female parent in the production of pickling cucumber hybrids. Once the plants had 10% oversized (>51 mm in diameter) fruit, plots were sprayed with paraquat to simulate once-over harvest. Selection cycles were evaluated for total, early, and marketable yield, and fruit shape. Testcross performance for fruit shape rating increased over cycles for the NCWBP and NCMBP populations when tested in either season. Testcross performance for total and early yield of the NCEP1 population tested in the spring decreased with selection, but remained constant over cycles in the summer season. The majority of yield traits in each population remained unchanged across selection cycles. Of the four populations studied, the NCMBP population had the greatest gain (7%) in testcross performance over cycles and averaged over all traits. In addition, testcross performance for fruit shape rating had the greatest gain (11%) with selection and averaged over populations. Years and seasons greatly influenced testcross performance for fruit yield and shape rating. In most instances, the fruit yield and shape of Gy 14 was higher than the testcross performance of population-cycle combinations. The performance of several families exceeded that of Gy 14 when testcross combinations were made. Those families could be selected for use in the development of elite cultivars. Chemical name used: 1,1'-dimethyl-4,4'-bipyridinium ion (paraquat).
Relationships between Floral Morphology, Breeding Behavior, and Flower Longevity in Easter Cactus
Authors: Karle Renate , Boyle Thomas H.
Published: January 2019

The effects of floral morphology and breeding behavior on flower longevity were investigated in Easter cactus [Hatiora ×graeseri (Werderm.) Barthlott)]. Four clones were studied: two diploid (n = 11) clones (`Evita' and `Purple Pride') that were highly self-incompatible (SI), and two cytochimeras (diploid epidermis and tetraploid subepidermis) that were recovered from the diploid cultivars, both of which were self-compatible (SC). The clones exhibited differences in the stage of floral development in which autogamy commenced. Autogamy commenced on the day of anthesis in the two `Evita' clones and occurred ≈5 days after anthesis in the `Purple Pride' cytochimera. In the `Purple Pride' diploid clone, anthers and stigmatic lobes remained spatially separated during the period from anthesis to senescence. Examination of styles collected from senesced, undisturbed flowers showed that few pollen tubes traversed to the base of the styles for the two SI diploid clones, whereas large numbers of pollen tubes were present at the base of the styles for the two SC cytochimeras. Flower longevity for the `Evita' cytochimera was significantly less than for `Evita' diploid, but the diploid and cytochimeral clones of `Purple Pride' exhibited similar flower longevities. Application of 2 mm silver thiosulfate, an inhibitor of ethylene (C2H4) action, did not affect flower longevity of `Evita' cytochimera. Our results show that flower longevity in Easter cactus is influenced by breeding behavior and the stage of floral development at which autogamy commences.