bluuebunny/crossref_metadata_2025 huggingface dataset:
Model Selection for Nondestructive Quantification of Fruit Growth in Pepper
Authors: Wubs A. Maaike , Ma Yun T. , Heuvelink Ep , Hemerik Lia , Marcelis Leo F.M.
Published: January 2019

Quantifying fruit growth can be desirable for several purposes (e.g., prediction of fruit yield and size, or for the use in crop simulation models). The goal of this article was to determine the best sigmoid function to describe fruit growth of pepper (Capsicum annuum) from nondestructive fruit growth measurements. The Richards, Gompertz, logistic, and beta growth functions were tested. Fruit growth of sweet pepper was measured nondestructively in an experiment with three different average daily temperatures (18, 21, and 24 °C) and in an experiment with six cultivars with different fruit sizes (20 to 205 g fresh weight). Measurements of fruit length and fruit diameter or circumference were performed twice per week. From these, fruit volume was estimated. A linear relationship related fruit fresh weight to estimated fruit volume, and a Ricker or polynomial function related fruit dry matter content to fruit age. These relations were used to convert estimated fruit volume into fruit fresh and dry weights. As dry weight increased until harvest, fitting the sigmoid function to the dry weight data was less suitable: it would create uncertainty in the estimated asymptote. Therefore, the sigmoid functions were fitted to fresh weight growth of the fruit. The Richards function was the best function in each data set, closely followed by the Gompertz function. The fruit dry weight growth is obtained by multiplication of the sigmoid function and the function relating fruit dry matter content to fruit age.
Inheritance of Resistance to Loquat Canker (Group C) in Progenies Derived from ‘Shiromogi’ Loquat
Authors: Hiehata Naofumi , Sato Yoshihiko , Fukuda Shinji , Tominaga Yukiko , Terai Osamu , Nesumi Hirohisa
Published: January 2019

Loquat canker (Pseudomonas syringae pv. eriobotryae) is a serious disease of loquat (Eriobotrya japonica), and no commercial cultivar in Japan is resistant to all strains of the disease. Loquat cultivar Shiromogi, which was selected from progeny seedlings of ‘Mogi’, is resistant to loquat canker Group C and has good fruit characteristics. This study was conducted to determine the inheritance of resistance to loquat canker Group C in ‘Shiromogi’. Seedlings produced from crosses between two resistant and 13 susceptible genotypes were classified as either resistant (R) or susceptible (S) based on the appearance of black–brown cankers ≈2 months after inoculation with a bacterial suspension of loquat canker Group C. Cross combinations between resistant parents ‘Champagne’ and ‘Shiromogi’ and selfing of ‘Shiromogi’ produced all resistant seedlings. Most crosses between ‘Shiromogi’ and susceptible parents either produced only susceptible seedlings or segregated for resistance in a ratio of 1 R:1 S. Seedlings produced by selfing two of the susceptible parents segregated in a ratio of 1 R:3 S. These results indicate that the resistance to loquat canker Group C of ‘Shiromogi’ is conferred by a single recessive gene, designated pse-c. Based on the crossing tests, we conclude that resistant parents ‘Shiromogi’ and ‘Champagne’ are homozygous for pse-c; the susceptible parents ‘Fukuharawase’, ‘Fusahikari’, ‘Gold Nugget’, ‘Kusunoki’, Nagasaki No. 2, ‘Tanaka’, ‘Tsukumo’, and ‘Yougyoku’ are homozygous for Pse-c; and the other susceptible parents in this experiment (‘Mogi’, ‘Nagasakiwase’, Nagasaki No. 3, ‘Taisho’, and 75-142) are heterozygous. Based on the pedigree of ‘Shiromogi’ and the results reported here, pse-c is probably derived from ‘Mogi’, a major cultivar in Japan.
Fruit Photosynthesis and Phosphoenolpyruvate Carboxylase Activity as Affected by Lightproof Fruit Bagging in Satsuma Mandarin
Authors: Hiratsuka Shin , Yokoyama Yuka , Nishimura Hiroshi , Miyazaki Takayuki , Nada Kazuyoshi
Published: January 2019

To clarify why fruit bagging reduces sugar content at harvest, we investigated its effect on carbon dioxide assimilation by Satsuma mandarin (Citrus unshiu) fruit through photosynthesis and phosphoenolpyruvate carboxylase (PEPC; enzyme code 4.1.1.31). Seasonal changes in gross photosynthesis ranged from 70 to 400 μmol·d−2·h−1 O2 with a peak at 99 days after full bloom (DAFB) when the assimilation rate of fruit was comparable to that of leaves. However, a peak showing net photosynthesis appeared at 112 DAFB because of high fruit respiration. When fruit were bagged at 85 DAFB, the net photosynthetic peak disappeared, perhaps as a result of the decline in chlorophyll content in the rind. Sugar and organic acid content in the bagged fruit were 0.3% and 0.16% less, respectively, than controls at the mature stage (204 DAFB). PEPC activity in the rind was much higher than in leaves on a protein basis; it increased between 92 and 112 DAFB and showed a peak of 72 units. The PEPC activity peak was also 90% of control after fruit bagging. Thus, just before their color development, mandarin fruit assimilate CO2 actively through photosynthesis and PEPC. However, these activities are inhibited by bagging, likely resulting in lower sugar content at harvest. The concomitant activation of PEPC and photosynthesis between 99 and 126 DAFB indicates that CO2 fixed by PEPC might be used for photosynthesis in mandarin fruit, because photosynthesis in several fruit such as apple (Malus pumila) and pea (Pisum sativum) is considered to have an intermediate status among C3, non-autotrophic tissue, and C4/CAM photosynthesis.
Severe Shading Reduces Early Fruit Growth in Apple by Decreasing Cell Production and Expansion
Authors: Dash Madhumita , Johnson Lisa K. , Malladi Anish
Published: January 2019

Shading during early fruit development reduces fruit growth and initiates fruit abscission in apple (Malus ×domestica). The mechanisms mediating the decline in fruit growth in response to shading are not well understood. In this study, the effects of shading during early fruit development on cell production and expansion were investigated. Additionally, the effects of shading on the expression of genes associated with carbohydrate metabolism, fruit growth, and cell production and expansion were investigated to develop a better understanding of the molecular mechanisms and to identify genes that mediate the reduction in fruit growth. Shading of isolated branches or entire trees ≈15 to 18 days after full bloom resulted in a sharp decline in fruit growth by 3 days after treatment. Reduction in fruit growth was consistently mediated by a decline in cell production within 3 days after treatment. Reduced fruit growth was also associated with lower cell size by 3 to 7 days after shading in two different years. These data indicate that the reduction in fruit growth as a result of shading is mediated by a reduction in cell production and expansion. The expression of two sorbitol dehydrogenase (SDH) genes, MdSDH1 and MdSDH2, was higher in the shaded fruit by up to 10-fold, suggesting an increase in SDH activity to meet the immediate respiratory demands of the developing fruit. The auxin response factor (ARF), MdARF106, displayed ≈3-fold higher expression in the shaded fruit, suggesting its involvement in regulating mechanisms that mediate the reduction in fruit growth. Two A2-type cyclins, MdCYCA2;2 and MdCYCA2;3, which are positively associated with cell production, displayed lower expression in the shaded fruit by up to 4.6-fold. Conversely, MdKRP4 and MdKRP5, cell cycle genes negatively associated with cell production, displayed 3.9- and 5.3-fold higher expression in the shaded fruit, respectively. Additionally, two genes associated with cell expansion, MdCOB1 (cobra1) and MdEXPA10;1 (expansin), displayed lower expression in the shaded fruit. Together, these data indicate that shading results in coordinated changes in the expression of carbohydrate metabolism-related genes, key transcription factors related to fruit growth, and genes associated with cell production and expansion. These changes may subsequently decrease the progression of the primary processes that mediate fruit growth.
Characterization of Genetic Diversity of Stone Fruit Rootstocks Used in Chile by Means of Microsatellite Markers
Authors: Arismendi María José , Hinrichsen Patricio , Almada Ruben , Pimentel Paula , Pinto Manuel , Sagredo Boris
Published: January 2019

Stone fruit (Prunus L.) production in Chile covers ≈43,000 ha and includes a wide variety of soils and climates requiring a large diversity of rootstocks. The most commercially important rootstock cultivars are 26 genotypes from three different taxonomic groups belonging to the subgenera Amygdalus (L.) Benth. Hook. (peach group), Prunus Focke [= Prunophora (Neck.)] Focke (plum group), and Cerasus (Adans.) Focke (cherry group) with eight, seven, and 10 individuals, respectively. To determine their genetic diversity, characterization by microsatellite markers [simple sequence repeat (SSR)] was conducted. Of a total of 20 SSR markers evaluated, 12 generated amplified products that were consistent in the three taxonomic groups. The number of alleles per marker ranged from 18 for PSM-3 to four in CPPCT-002. Clustering analysis, by both traditional hierarchical and model-based approaches, indicate that all genotypes are clustered in their respective taxonomic groups, including the interspecific hybrids. Genetic diversity, measured as the average distances (expected heterozygosity) between individuals in the same cluster, was higher in Cerasus (0.78) followed by Prunus (0.72) and Amygdalus (0.64). Total number of alleles observed was 133, of which 14, 33, and 35 from six, 10, and 10 loci were unique for the peach, plum, and cherry rootstock groups, respectively. Alleles shared among peach/plum, plum/cherry, and peach/cherry rootstock genotypes were 13, 14, and 18 from nine, seven, and seven loci, respectively. Only six alleles from five loci were common to the three taxonomic groups. In addition, to develop a rootstock identification system based on SSR markers, a minimum set of three markers (PMS-3, BPPCT-037, and BPPCT-036) able to differentiate the 26 genotypes was identified. This study is the first step toward establishing a stone fruit rootstock breeding program in Chile.
Proteomic Responses during Cold Acclimation in Association with Freezing Tolerance of Velvet Bentgrass
Authors: Espevig Tatsiana , Xu Chenping , Aamlid Trygve S. , DaCosta Michelle , Huang Bingru
Published: January 2019

Cold acclimation improves freezing tolerance in various plants, including perennial grass species. The objectives of this study were to determine protein changes in crowns of velvet bentgrass (Agrostis canina) during cold acclimation in association with freezing tolerance. Treatments consisted of: 1) nonacclimated (NA) plants maintained at 18/12 °C (day/night); 2) plants acclimated at a constant 2 °C for 4 weeks with a 10-hour photoperiod [A4 (cold acclimation)]; and 3) plants acclimated at a constant 2 °C for 4 weeks with additional subzero acclimation (SZA) at a constant –2 °C for 2 weeks (A4 + SZA2). Exposing plants to A4 significantly increased freezing tolerance, but additional SZA had no further beneficial effects on freezing tolerance, as demonstrated by the lethal temperature for 50% of the test population (LT50). Thirteen protein spots with increased abundance (up-regulated) or with decreased abundance (down-regulated) during cold acclimation were identified for biological functions. Proteins up-regulated after cold acclimation (A4 or A4 + SZA2) included methionine synthase, serine hydroxymethyltransferase, aconitase, UDP-D-glucuronate decarboxylase, and putative glycine-rich protein. Cold acclimation-responsive proteins involved in amino acid metabolism, energy production, stress defense, and secondary metabolism could contribute to the improved freezing tolerance induced by cold acclimation in velvet bentgrass.
Characterizing Concentration Effects of Exogenous Abscisic Acid on Gas Exchange, Water Relations, and Growth of Muskmelon Seedlings during Water Stress and Rehydration
Authors: Agehara Shinsuke , Leskovar Daniel I.
Published: January 2019

Excess transpiration relative to water uptake often causes water stress in transplanted vegetable seedlings. Abscisic acid (ABA) can limit transpirational water loss by inducing stomatal closure and inhibiting leaf expansion. We examined the concentration effect of exogenous ABA on growth and physiology of muskmelon (Cucumis melo L.) seedlings during water stress and rehydration. Plants were treated with seven concentrations of ABA (0, 0.24, 0.47, 0.95, 1.89, 3.78, and 7.57 mm) and subjected to 4-day water withholding. Application of ABA improved the maintenance of leaf water potential and relative water content, while reducing electrolyte leakage. These effects were linear or exponential to ABA concentration and maximized at 7.57 mm. Gas-exchange measurements provided evidence that such stress control is attributed to ABA-induced stomatal closure. First, net CO2 assimilation rate and stomatal conductance initially decreased with increasing ABA concentration by up to 95% and 70%, respectively. A follow-up study (≤1.89 mm ABA) confirmed this result with or without water stress and further revealed a close positive correlation between intercellular CO2 concentration and net CO2 assimilation rate 1 day after treatment (r2 > 0.83). In contrast, ABA did not affect leaf elongation, indicating that stress alleviation was not mediated by leaf area adjustment. After 18 days of post-stress daily irrigation, dry matter accumulation showed a quadratic concentration-response, increasing up to 1.89 mm by 38% and 44% in shoot and roots, respectively, followed by 16% to 18% decreases at >1.89 mm ABA. These results suggest that excess levels of ABA delay post-stress growth, despite the positive effect on the maintenance of water status and membrane integrity. Another negative side effect was chlorosis, which accelerated linearly with increasing ABA concentration, although it was reversible upon re-watering. The optimal application rate of ABA should minimize these negative effects, while keeping plant water stress to an acceptable level.
Physiological Race Characterization of Phytophthora capsici Isolates from Several Host Plant Species in Brazil Using New Mexico Recombinant Inbred Lines of Capsicum annuum at Two Inoculum Levels
Authors: da Costa Ribeiro Cláudia S. , Bosland Paul W.
Published: January 2019

Phytophthora blight, caused by Phytophthora capsici, is one of the most destructive diseases worldwide that affects Capsicum pepper. Attempts to provide universally resistant cultivars has been unsuccessful, which may be the result of the use of different resistance sources, pathotypes, or races of P. capsici isolates and screening techniques. The screening method used at Embrapa Vegetables in Brazil to detect resistance to P. capsici in Capsicum was compared with the screening method used at New Mexico State University. Both screening methods produced similar and consistent results when a range of P. capsici isolates were used. It was concluded that either method can successfully differentiate resistant and susceptible individuals. In addition, 20 P. capsici isolates from Brazil were characterized for virulence using a subset of 26 New Mexico recombinant inbred lines of pepper (Capsicum annuum). Within the P. capsici populations from Brazil, eight new physiological races for the root rot disease syndrome were identified. A total of nine isolates were pathogenic only on the susceptible control, ‘Camelot’. The ability to identify physiological races of P. capsici occurring in Brazil allows for a better understanding about race-specific resistance leading to improved approaches in breeding for durable resistant cultivars.
Trait Diversity and Potential for Selection Indices Based on Variation Among Regionally Adapted Processing Tomato Germplasm
Authors: Merk Heather L. , Yarnes Shawn C. , Van Deynze Allen , Tong Nankui , Menda Naama , Mueller Lukas A. , Mutschler Martha A. , Loewen Steven A. , Myers James R. , Francis David M.
Published: January 2019

For many horticultural crops, selection is based on quality as well as yield. To investigate the distribution of trait variation and identify those attributes appropriate for developing selection indices, we collected and organized information related to fruit size, shape, color, soluble solids, acid, and yield traits for 143 processing tomato (Solanum lycopersicum L.) lines from North America. Evaluation of the germplasm panel was conducted in a multiyear, multilocation trial. Data were stored in a flat-file format and in a trait ontology database, providing a public archive. We estimated variance components and proportion of variance resulting from genetics for each trait. Genetic variance was low to moderate (range, 0.03–0.51) for most traits, indicating high environmental influence on trait expression and/or complex genetic architecture. Phenotypic values for each line were estimated across environments as best linear unbiased predictors (BLUPs). Principal components (PC) analysis using the trait BLUPs provided a means to assess which traits explained variation in the germplasm. The first two PCs explained 28.0% and 16.2% of the variance and were heavily weighted by measures of fruit shape and size. The third PC explained 12.9% of the phenotypic variance and was determined by fruit color and yield components. Trait BLUPs and the first three PCs were also used to explore the relationship between phenotypes and the origin of the accessions. We were able to differentiate germplasm for fruit size, fruit shape, yield, soluble solids, and color based on origin, indicating regional breeding programs provide a source of trait variation. These analyses suggest that multitrait selection indices could be established that encompass quality traits in addition to yield. However, such indices will need to balance trait correlations and be consistent with market valuation.
Systematic Analysis of Branching Patterns of Three Almond Cultivars with Different Tree Architectures
Authors: Negrón Claudia , Contador Loreto , Lampinen Bruce D. , Metcalf Samuel G. , DeJong Theodore M. , Guédon Yann , Costes Evelyne
Published: January 2019

Different almond (Prunus dulcis) cultivars have been characterized by their contrasting shoot branching patterns; however, the differences between patterns have been difficult to quantify. This study aimed to model the branching patterns of 2-year-old proleptic shoots on three almond cultivars (Nonpareil, Aldrich, and Winters) representing different tree architectures. The effects of branching pattern on flowering were also studied. The branching patterns of shoots of different length categories were assessed by a single hidden semi-Markov model for each cultivar. The models identified zones of homogeneous branching composition along shoots and were used to extract the occurrence and number of nodes of the zones according to shoot length categories. The numbers of flower buds were also determined for each shoot length category in each cultivar. The models of branching patterns of ‘Nonpareil’ and ‘Aldrich’ were similar and differed from the ‘Winters’ model. ‘Winters’ shoots produced more zones, but some of the zones had similar characteristics as previous zones and thus appeared to be repeated. This cultivar also had more spurs and sylleptic shoots than the other cultivars. The occurrence and node number of the central zones decreased along with reduction in shoot length in all the cultivars. ‘Aldrich’ tended to have more flower buds than comparable-length shoots of the other two cultivars. This study provides a quantitative description of the shoot branching patterns of three important cultivars and explains how branching changes in relation to shoot length, whereas production of flower buds varies despite similar branching patterns.
Molecular Cloning and Characterization of the HOS1 Gene from ‘Muscat Hamburg’ Grapevine
Authors: Li Jitao , Wang Nian , Wang Lina , Xin Haiping , Li Shaohua
Published: January 2019

Cold stress is an important factor that limits grape (Vitis sp.) production around the world. The high expression of osmotically responsive genes 1 (HOS1) protein acts as a repressor of cold-responsive genes in plants. To increase understanding of mechanism regulating cold tolerance in grape, we isolated and characterized a novel HOS1 gene, designated VvHOS1 from ‘Muscat Hamburg’ grapevine (Vitis vinifera). Real-time polymerase chain reaction (PCR) analysis revealed that the expression of VvHOS1 could be induced by the application of exogenous abscisic acid and various abiotic environmental conditions such as low temperature, drought, and salinity. Moreover, VvHOS1 expression could also be induced by cold plus drought conditions (4 °C, 10% polyethylene glycol 6000). In addition, overexpression of VvHOS1 in arabidopsis (Arabidopsis thaliana) decreased the plants’ tolerance to cold, drought, and salt as well as negatively regulated the expression level of two stress-responsive genes, AtRD29A and AtCOR47. The results obtained in this study should help us to elucidate the function of VvHOS1 and understand the cold-responsive pathway in grapevine.
Nitrogen Source for Inflorescence Development in Phalaenopsis: II. Effect of Reduced Fertilizer Level on Stored Nitrogen Use
Authors: Susilo Hadi , Alex Chang Yao-Chien
Published: January 2019

Plants of Phalaenopsis orchid are known for their great resilience and ability to flower under less than ideal conditions, including long periods without fertilization. Significant nutrient storage is thought to account for this characteristic; however, the use of stored nutrients in Phalaenopsis has not been fully studied. We used 15N-labeled Johnson’s solution to trace the use of stored nitrogen (N) and recently absorbed fertilizer N in Phalaenopsis given various fertilizer levels during forcing. By separately labeling fertilizer N applied to Phalaenopsis Sogo Yukidian ‘V3’ plants 6 weeks before and 6 weeks into forcing, we found in the inflorescence that the ratio of N derived from fertilizer applied 6 weeks before forcing to the N derived from fertilizer applied 6 weeks into forcing was 43% to 57%. With 90% reduction in fertilizer concentration during the reproductive stage, the ratio increased to 89% to 11%, indicating that stored N becomes a significant N source for inflorescence development when fertility becomes limited. Reducing fertilizer level during the reproductive stage from full-strength Johnson’s solution down to zero decreased the dry weight of newly grown leaves, reduced the number of flowers from 10.8 to 8.9, and slightly increased the time required between initiation of forcing and anthesis. However, the overall effect of reduced fertilization on the growth and flowering of Phalaenopsis Sogo Yukidian ‘V3’ plants in this study was slight, because under little or no fertilization, more stored N was mobilized and this was sufficient to meet most of the N demand for inflorescence development.
Selection of Suitable Reference Genes for Quantitative Real-time Polymerase Chain Reaction in Prunus mume during Flowering Stages and under Different Abiotic Stress Conditions
Authors: Wang Tao , Hao Ruijie , Pan Huitang , Cheng Tangren , Zhang Qixiang
Published: January 2019

Mei (Prunus mume) is widely cultivated in eastern Asia owing to its favored ornamental characteristics and its tolerance for low temperatures. Reverse transcription quantitative real-time polymerase chain reaction (qRT-PCR) is a widely used method for gene expression analysis, requiring carefully selected reference genes to ensure data reliability. The aim of this study was to identify and evaluate reference genes for qRT-PCR in mei. Ten candidate reference genes were chosen, and their expression levels were assessed by qRT-PCR in four sample sets: 1) flowering mei; 2) mei undergoing abiotic stress; 3) different genotypes of Prunus species; and 4) all mei samples. The stability and suitability of the candidate reference genes were validated using commercially available software. We found that protein phosphatase 2A-1 (PP2A-1) and PP2A-2 were suitable reference genes for flowering with ubiquitin-conjugating enzyme E2 (UBC) also being suitable for different genotypes of Prunus species. UBC and actin (ACT) were most stably expressed under abiotic stress. Finally, the expression of an AGAMOUS homolog of Arabidopsis thaliana (PmAG) and a putative homolog of Group 2 late embryogenesis abundant protein gene in A. thaliana (PmLEA) were assessed to allow comparisons between selected candidate reference genes, highlighting the importance of careful reference gene selection.
Cloning and Expression of Two Soluble Acid Invertase Gene Isoforms from Rhododendron
Authors: Lisi He , Jiale Su , Xiaoqing Liu , Chang Li , Shangping Chen
Published: January 2019

Soluble acid invertase [SAI (Enzyme Commission 3.2.1.26)] plays an important role in catalyzing the hydrolysis of sucrose into hexoses and regulates floral development. Full-length cDNAs encoding RhSAI1 and RhSAI2 isoforms were cloned from Rhododendron hybrid ‘Yuqilin’ and they exhibited high amino acid sequence identity (89%) to each other. The protein sequences contain highly conserved motifs present in all SAIs, including the β-fructosidase motif N-D-P-(D/N), a putative active site W-E-C-(I/V)-D, and R-D-P. The expression of RhSAI1 and RhSAI2 genes was under spatial and temporal control. Expression of both RhSAI1 and RhSAI2 genes was most abundant in stems, and expression was lowest in roots and leaves, respectively. The expression of RhSAI2 was significantly lower than that of RhSAI1 in all organs. During floral development, RhSAI1 was highly expressed at the earliest stage (Stage I), decreased until Stage III, and increased again at the terminal stage. The pattern of RhSAI2 expression was distinctly different, showing a continuous increase during floral development. Consistent with the levels of RhSAI1 expression, SAI activity decreased during floral development and was inversely correlated with the soluble sugar content. Abundant expression of RhSAI1 at the transcriptional level in addition to high SAI activity during the initial stages of floral development may play a vital role in supplying the energy needed for rapid cell division and growth of flowers.
Axillary Budbreak in a Cut Rose Crop as Influenced by Light Intensity and Red:far-red Ratio at Bud Level
Authors: Wubs A. Maaike , Heuvelink Ep , Marcelis Leo F.M. , Buck-Sorlin Gerhard H. , Vos Jan
Published: January 2019

When flower-bearing shoots in cut rose (Rosa ×hybrida) are harvested, a varying number of repressed axillary buds on the shoot remainder start to grow into new shoots (budbreak). Earlier experiments indicated that light reaching the bud affected the number of budbreaks. In all these studies, whole plants were illuminated with different light intensities or light spectra. The aim of this article is to disentangle the effects of light intensity and light spectrum, in this case red:far-red ratio, at the level of the buds on budbreak in a rose crop. Three experiments were conducted in which light intensity and red:far-red ratio at the level of the buds were independently varied, whereas intensity and red:far-red ratio of incident light on the crop were not changed. Light intensity and red:far-red ratio at the position of the buds were quantified and related to budbreak on the shoot remainders. Removal of vertical shoots increased light intensity and red:far-red ratio as well as budbreak (1.9 budbreaks per shoot remainder compared with 0.4 budbreaks when five vertical shoots were present). No vertical shoots and red light-absorbing shading paper over the plant base mimicked the effect of vertical shoots with respect to light intensity and red:far-red ratio, but budbreak (1.0 budbreaks) was intermediate compared with treatments with and without shoots. This suggested that the presence of shoots exerts an inhibiting effect on budbreak through both effects on light at the bud and correlative inhibition. When plants had no vertical shoots and light intensity and red:far-red ratio at bud level were changed by neutral and red light-absorbing shading paper, there was a positive effect of light intensity on budbreak (0.3 more budbreaks per shoot remainder) and no effect of red:far-red ratio. Combinations of high and low light intensity with high and low red:far-red ratio on axillary buds showed that there was a positive effect of light intensity on budbreak (0.5 more budbreaks per shoot remainder) and no effect of red:far-red ratio. Our study reveals that when light intensity and red:far-red ratio received by the plant are similar but differ at bud level, budbreak was affected by light intensity and not by red:far-red ratio.
Mechanical Properties of Apple Skin Are Determined by Epidermis and Hypodermis
Authors: Khanal Bishnu P. , Knoche Moritz
Published: January 2019

Mechanical failure of the fruit skin is an early event in the etiology of the disorders russeting and skin spots in a number of apple cultivars including ‘Elstar’ (Malus ×domestica Borkh.). The objective was to quantify the mechanical properties of excised epidermal segments (ES) of fruit skin and of enzymatically isolated cuticular membranes (CM) using uniaxial tensile tests. ES thickness ranged from 0.25 to 1.8 mm because thin ES samples of more uniform thickness are difficult to prepare. Sample values for stiffness (S), maximum force () and strain at () were recorded. Measured values were adjusted by regression to refer to a hypothetical standard ES of 0.5 mm thickness. Generally, S and values were positively related to ES thickness during the preharvest period from 51 to 141 days after full bloom (DAFB) and during the postharvest period from 141 to 259 DAFB in cold storage (1.7 °C, 92% relative humidity). The recorded were independent of ES thickness. The S of a standardized ES decreased slightly from 51 to 90 DAFB, then increased up to 161 DAFB, and then declined. There were essentially no differences in S recorded for isolated CM and ES. The and were highest in young fruit at 51 DAFB but decreased steadily toward harvest and continued to decrease in cold storage after harvest but at a lower rate. The and were markedly lower for CM samples than for ES ones. Monitoring the increased incidence of CM microcracking during a tensile test performed on an ES revealed that CM failure preceded ES failure. The decrease in the for ES during fruit development was accounted for in part by a decrease in the mass of cell wall per unit surface area. Our results show that the epidermal and hypodermal cell layers represent the structural backbone of an apple skin during pre- and postharvest development. Furthermore, CM microcracking has limited relevance to the overall mechanical properties of the skin.
Compound Identification of Selected Rose Species and Cultivars: an Insight to Petal and Leaf Phenolic Profiles
Authors: Cunja Vlasta , Mikulic-Petkovsek Maja , Stampar Franci , Schmitzer Valentina
Published: January 2019

Using high-performance liquid chromatography/mass spectrometry, leaf and petal phenolic profiles of four rose (Rosa) species (R. canina, R. glauca, R. rubiginosa, R. sempervirens) traditionally used for medicinal purposes and three modern rose cultivars (Rosarium Uetersen, Ulrich Brunner Fils, Schwanensee) were determined. An abundance of phenolic constituents was identified: seven different anthocyanins and 31 flavonols in petals; 30 flavonols, 14 phenolic acids, and their derivatives; 15 flavanols; and 20 hydrolysable tannins in leaves. Additionally, petal color was measured with a colorimeter and regression analysis indicated a strong correlation between color parameter a* and total anthocyanin content. The content and composition of phenolic compounds varied significantly among species and cultivars and plant organs investigated. Distinct differences in the distribution of leaf phenolic compounds were observed, especially between Rosa species and modern rose cultivars. In general, leaves of analyzed species were richer in content of most phenolic groups and individual components compared with cultivars. Multivariate statistical analysis clustered the investigated species and cultivars into three distinct groups. Among species, leaves of R. canina stood out with their high and varied phenolic content. Conversely, leaves of the susceptible cultivar Schwanensee appeared most dissimilar as a result of their low levels of phenolic constituents.
Qualitative Analysis of Volatiles in Rabbiteye Blueberry Cultivars at Various Maturities Using Rapid Solid-phase Microextraction
Authors: Beaulieu John C. , Stein-Chisholm Rebecca E. , Boykin Deborah L.
Published: January 2019

There are very few studies detailing the aroma, astringency, and flavor of rabbiteye blueberry [RAB (Vaccinium ashei)] fruit typically grown in the southeastern United States. The objectives were to investigate the rapid and qualitative solid-phase microextraction gas chromatographic–mass spectrometry volatile composition of several local RAB cultivars with an overall goal to build a database of possible flavor and aroma compounds. Volatile profiles were obtained in five Louisiana-grown RAB cultivars (Brightwell, Climax, Premier, Powder Blue, and Tifblue) assayed at four maturities. The method routinely captured 53 volatiles, including 12 aldehydes, six alcohols, 11 esters, four ketones, 17 terpenoids, one furan, and two aromatics. Of the 33 compounds considered important in blueberries, 17 were recovered in the RAB cultivars assessed. Herein, 10 compounds were recovered for the first time in blueberry (Vaccinium sp.) and five of those compounds were confirmed with standards [2-ethylfuran, (E)-2-pentenal, (Z)-dehydroxylinalool oxide, (E)-dehydroxylinalool oxide and 1,4-cineole]. In general, terpenoids and their subclass linalools were the most significant volatiles followed closely by esters, aldehydes, and then alcohols. Terpenoids and linalools displayed the greatest significant differences in ‘Powder Blue’ and ‘Premier’. Esters and aldehydes were the most significant compound classes based on cultivar effect per maturity in firm-ripe fruit. From the suite of 17 of the 33 important compounds in upright blueberry, 10 were recovered across the five cultivars at four maturities that displayed a high level of significance. These were linalool, methyl 3-methylbutanoate, 1,8-cineole, (E)-2-hexanal, (Z)-3-hexenal, (Z)-3-hexenyl acetate, limonene, hexyl acetate, hexanal, and α-terpineol. These data will be useful to evaluate aroma volatiles in RAB and changes in processed and value-added byproducts.
Resistance to Fusarium oxysporum f. sp. fragariae and Predicted Breeding Values in Strawberry
Authors: Paynter Michelle L. , De Faveri Joanne , Herrington Mark E.
Published: January 2019

Fusarium wilt of strawberry, incited by Fusarium oxysporum f. sp. fragariae (Fof), is a major disease of the cultivated strawberry (Fragaria ×ananassa) worldwide. An increase in disease outbreaks of the pathogen in Western Australia and Queensland plus the search for alternative disease management strategies place emphasis on the development of resistant cultivars. In response, a partial incomplete diallel cross involving four parents was performed for use in glasshouse resistance screenings. The resulting progeny were evaluated for their susceptibility to Fof. Best-performing progeny and suitability of progenies as parents were determined using data from disease severity ratings and analyzed using a linear mixed model incorporating a pedigree to produce best linear unbiased predictions of breeding values. Variation in disease response, ranging from highly susceptible to resistant, indicates a quantitative effect. The estimate of the narrow-sense heritability was 0.49 ± 0.04 (se), suggesting the population should be responsive to phenotypic recurrent selection. Several progeny genotypes have predicted breeding values higher than any of the parents. Knowledge of Fof resistance derived from this study can help select best parents for future crosses for the development of new strawberry cultivars with Fof resistance.
Geographic Distribution of Incompatibility Alleles in Cultivars and Selections of European Hazelnut
Authors: Mehlenbacher Shawn A.
Published: January 2019

The european hazelnut (Corylus avellana L.) is native to most of Europe and nearby areas in Asia Minor and the Caucasus Mountains. Cross-pollination is enforced by sporophytic incompatibility under the control of a single locus with multiple alleles (haplotypes). Fluorescence microscopy is routinely used to determine if a pollination is compatible or incompatible, and use of an array of known testers allows identification of the alleles of cultivars and selections. Both alleles are expressed in the stigmas, but often only one is expressed in the pollen because of dominance. Cultivars are highly heterozygous diploids (2n = 2x = 22) and clonally propagated. Most of the world's leading cultivars were selected from local wild populations near where they are now planted on a commercial scale. Genetic improvement efforts are recent and, although tremendous genetic variability is available, such efforts have had little impact outside of Oregon and France. Studies of genetic diversity using simple sequence repeat markers have placed most cultivars in one of the four main groups: Spanish-Italian, Central European, English, or Black Sea. This study presents 17 years of data on incompatibility in hazelnut, including the discovery of six new S-alleles and determination of the dominance relationships among 105 new pairs of alleles. The total number of alleles now stands at 33. The S-alleles of 284 cultivars, 13 interspecific hybrids, and 522 selections of diverse origin are presented. The S-alleles identified in hazelnut cultivars is information that should be useful to breeders in the planning of crosses, to curators of germplasm collections, and to growers and nurseries as they choose cultivars and pollenizers when designing orchards. Differences in S-allele frequency seen in the cultivars and selections are related to geographic origin. The most common alleles of cultivars in the major geographical groups are S2 in the Spanish-Italian group, S5 in the Central European group, S3 in the English group, and S4 in the Black Sea group. Most selections belonged to the Black Sea group, and S4 was by far the most common allele. Differences in allele frequency were also observed among seed lots within a country.
Genetic Characterization of the Cacao Cultivar CCN 51: Its Impact and Significance on Global Cacao Improvement and Production
Authors: Boza Edward J. , Motamayor Juan Carlos , Amores Freddy M. , Cedeño-Amador Sergio , Tondo Cecile L. , Livingstone Donald S. , Schnell Raymond J. , Gutiérrez Osman A.
Published: January 2019

Cacao (Theobroma cacao L.) is an important cash crop in tropical growing regions of the world and particularly for small cacao farmers. Over the past two decades, ‘CCN 51’ has become one of the most planted cultivars in Ecuador, mainly as a result of its high productivity and disease resistance. Intermixing of Nacional fine flavor Ecuadorian beans with beans of ‘CCN 51’ has become common practice, reducing overall bean quality and decreasing value. The primary goals of this study were to determine the genetic identity, structure, and allelic richness of ‘CCN 51’, its maternal origin and to compare ‘CCN 51’s’ agronomic characteristics against a composite group of Nacional cultivars. To investigate the complex genetic background of this cultivar, 70 simple sequence repeat loci were used. The high heterozygosity observed (56 of 70 loci) for ‘CCN 51’ is not characteristic of traditional Nacional cultivars. Comparison of agronomic characteristics between ‘CCN 51’ and several Nacional cultivars indicates significant differences in cacao dry bean weight, yield potential, production efficiency, percent healthy pods, and witches' broom [Moniliophthora perniciosa (Stahel) Aime & Phillips-Mora] disease incidence. Additionally, physical, chemical, and organoleptic characteristics suggest that ‘CCN 51’ is different from those of Nacional lineage. Based on population structure analysis, the predominant ancestries for ‘CCN 51’ are Iquitos (45.4%), Criollo (22.2%), and Amelonado (21.5%) genetic groups. A lesser proportion of its genome was accounted for by genetic groups Contamana (3.9%), Purús (2.5%), Marañon (2.1%), and Nacional (1.1%) admixtures. Results of phylogenetic analyses using the unweighted pair group method with arithmetic mean yielding high bootstrap values strongly support the relatedness of ‘CCN 51’ with Iquitos, Criollo, and Amelonado genetic groups. Moreover, seven mitochondrial simple sequence repeat loci revealed that ‘CCN 51’ maternally inherited the ‘IMC 67’ cytotype. ‘CCN 51’ constitutes a valuable cacao genetic resource that is currently used not only in its country of origin, but also in many other national breeding and selection programs worldwide.
Growth, Yield, and Metabolic Responses of Temperature-stressed Tomato to Grafting onto Rootstocks Differing in Cold Tolerance
Authors: Ntatsi Georgia , Savvas Dimitrios , Ntatsi Georgia , Kläring Hans-Peter , Schwarz Dietmar
Published: January 2019

Tomato (Solanum lycopersicum cv. Kommeet) plants were either self-grafted, grafted onto the cold-sensitive cultivar Moneymaker or onto LA 1777, a cold-tolerant accession of Solanum habrochaites. Plants were grown at three different temperatures (T): optimal (19.4 °C), intermediate (17 °C), or low (14.6 °C). Grafting tomato ‘Kommeet’ onto LA 1777 increased shoot growth at intermediate and optimal T and root growth at low or intermediate T in comparison with self-grafting or grafting onto ‘Moneymaker’. Reducing T significantly suppressed fruit yield as a result of reduced fruit number per plant without any interaction with grafting treatments. Grafting ‘Kommeet’ onto LA 1777 remarkably restricted fresh and dry fruit mass in comparison with self-grafting of ‘Kommeet’ as a result of a reduction in the fruit number per plant while not influencing flower number per plant and mean fruit mass, regardless of T regime. Negative effect of LA 1777 on fruit setting points to impairment of pollen fertility indicating signals originating from the root. At low and intermediate T, plants grafted onto LA 1777 were capable of increasing soluble carbohydrates, total amino acids, and guaiacol peroxidase activity in roots to higher levels than those grafted onto S. lycopersicum rootstocks while maintaining a significantly lower malondialdehyde content. These differences point to a much weaker oxidative stress in roots of plants grafted onto S. habrochaitis than those grafted onto S. lycopersicum rootstocks when exposed to low and intermediate T. Furthermore, plants grafted onto LA 1777 exhibited significantly higher levels of soluble carbohydrates, total amino acids, and guaiacol peroxidase activity in leaves and fruit and superoxide dismutase in fruit at low and intermediate T, which indicates that LA 1777 improved the level of antioxidant compounds in tomato shoots, thereby enhancing its adaptation to lower T than optimal.
Fine Mapping a Clubroot Resistance Locus in Chinese Cabbage
Authors: Gao Feng , Hirani Arvind H. , Liu Jun , Liu Zheng , Fu Guohua , Wu Chunren , McVetty Peter B.E. , Li Genyi
Published: January 2019

There are various clubroot pathogen (Plasmodiophora brassicae) resistance genes within Brassica species with european turnip (B. rapa ssp. rapifera) being identified as potentially the best source of resistance for the development of clubroot-resistant cultivars in chinese cabbage (B. rapa ssp. pekinensis). To use clubroot resistance genes effectively, it is necessary to map these genes so that molecular markers inside or closely linked to these resistance genes can be developed. Using molecular marker-assisted selection, the clubroot resistance genes can be effectively transferred from cultivar to cultivar and from species to species. In this report, one clubroot resistance locus was mapped on linkage group A3 using five segregating populations developed from five chinese cabbage cultivars, suggesting that all the five cultivars shared the same clubroot resistance locus. Furthermore, one of these five chinese cabbage cultivars was used to develop a large segregating population to fine-map this clubroot resistance locus to a 187-kilobp chromosomal region. Molecular markers that are closely linked to the mapped clubroot resistance locus have been developed that can be used for marker-assisted selection in chinese cabbage and canola/rapeseed (B. rapa and B. napus) breeding programs.
Abscisic Acid Increases Carotenoid and Chlorophyll Concentrations in Leaves and Fruit of Two Tomato Genotypes
Authors: Barickman T. Casey , Kopsell Dean A. , Sams Carl E.
Published: January 2019

One important regulator that coordinates response to environmental stress is the hormone abscisic acid (ABA), which is synthesized from xanthophyll pigments. Despite the fact that there is strong evidence of increases in ABA concentrations under various environmental stresses, information concerning the effects of exogenous ABA applications on leaf pigments and fruit carotenoids in tomato (Solanum lycopersicum) is lacking. This study investigated the impacts of root tissue ABA applications on tomato leaf and fruit pigmentation concentrations of ‘MicroTina’ and ‘MicroGold’ tomato plants. Tomato plants were treated with increasing concentrations of ABA in the nutrient solution. Therefore, the purpose of this study was to determine dose–response effects of ABA treatment in solution culture for maximum leaf pigmentation and fruit carotenoids in two distinct genotypes of dwarf tomato. Because ABA is a product of the carotenoid biosynthetic pathway, we hypothesized that applications of ABA treatments would have a positive impact on leaf chlorophylls and carotenoids. Applications of ABA treatments may also have a positive impact on tomato fruit carotenoids. The results indicated that ‘MicroTina’ plants treated with ABA (0.5, 5.0, and 10.0 mg·L−1) had a significant increase in β-carotene [BC (P ≤ 0.001)], lutein [LUT (P ≤ 0.001)], zeaxanthin [ZEA (P ≤ 0.05)], and neoxanthin [NEO (P ≤ 0.001)] in the leaf tissue. In ‘MicroGold’ tomato plants, carotenoids responded similarly. For example, there were significant increases in BC (P ≤ 0.01), LUT (P ≤ 0.001), ZEA (P ≤ 0.05), and NEO (P ≤ 0.001). In ‘MicroTina’ tomato leaves, there were significant increases in chlorophyll a [Chl a (P ≤ 0.001)] and chlorophyll b [Chl b (P ≤ 0.001)] concentrations. Furthermore, there were significant increases in Chl a (P ≤ 0.001) and Chl b (P ≤ 0.001) in ‘MicroGold’ leaf tissue. In ‘MicroTina’ tomato fruit tissue, the concentration increased significantly for lycopene [LYCO (P ≤ 0.01)]. However, in ‘MicroGold’, there were no significant changes in BC and LUT concentrations. In addition, LYCO was found to be below detection limits in ‘MicroGold’ tomato fruit. Therefore, ABA has been shown to positively change tomato leaf pigments in both genotypes and fruit tissue carotenoid concentrations in ‘MicroTina’ tomato.