bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of Alien Addition Lines in Polyploid Bunching Onion (Allium fistulosum) Carrying 1A Chromosome(s) of Shallot (Allium cepa) and Their Application to Breeding for a New Vitamin C-Rich Vegetable
Authors: Yaguchi Shigenori , Atarashi Masanori , Iwai Masatoshi , Masuzaki Shin-ichi , Yamauchi Naoki , Shigyo Masayoshi
Published: January 2019

Eight Allium fistulosum L.–Allium cepa L. Aggregatum group (shallot) monosomic addition lines (2n = 17, FF+1A–FF+8A) have been useful in revealing the effects of single alien chromosomes from A. cepa on the production of l-ascorbic acid in the leaf tissue of A. fistulosum. In this study, the determination of ascorbic acid content revealed that the incorporation of alien chromosome 1A into a diploid background of A. fistulosum increased the internal ascorbic acid content of the leaf blade tissue. We produced a 1A disomic addition in the tetraploid of A. fistulosum (2n = 34) and demonstrated high-frequency transfer of the alien chromosome in crosses with A. fistulosum. Five plants of the 1A disomic additions were regenerated via apical meristem culture of the FF+1A on a Murashige and Skoog medium containing colchicine. These 1A disomic additions showed partial fertility for female and male gametes. Most of the progenies from selfing of the 1A disomic additions and reciprocal crossing with A. fistulosum possessed chromosome 1A. Interestingly, 64% (18 of 28) of the plants obtained from the reciprocal crosses were 1A monosomic additions in a triploid background of A. fistulosum. These monosomic additions were more vigorous and vitamin C-rich than euploid plants of A. fistulosum.
Genetic Diversity of Seven Deciduous Azalea Species (Rhododendron spp. section Pentanthera) Native to the Eastern United States
Authors: Chappell Matthew , Robacker Carol , Jenkins Tracie M.
Published: January 2019

Despite the ecologic and economic importance of native deciduous azaleas (Rhododendron L. section Pentanthera G. Don), our understanding of interspecific variation of North American deciduous azalea species comes principally from morphologic studies. Furthermore, little is known concerning intraspecific or interpopulation genetic variation. With ever-increasing loss and fragmentation of native azalea habitat in the eastern United States due to anthropogenic activity, it is imperative that an understanding of natural genetic variation among and within species and populations is acquired. The present study addresses questions of genetic diversity through the use of amplified fragment length polymorphism (AFLP) analysis. Twenty-five populations of seven species of native azalea were analyzed using three primer pairs that amplified a total of 417 bands. Based on analysis of molecular variance (AMOVA) and estimates of Nei's coefficients of gene diversity (H
S, H
T, and G
ST), the majority of variation found in deciduous azalea occurs within populations. Variation both among species and among population was low, likely the effect of common ancestry as well as frequent introgression among members (and populations) of section Pentanthera. The latter was evident in four populations of R. prunifolium (Small) Millais and R. canescens (Michaux) Sweet that were highly related to R. austrinum (Small) Rehder and R. viscosum (L.) Torrey, respectively. Despite these outliers, most populations were grouped into species based on Nei's unbiased genetic distances viewed as an unweighted pair group method with arithmetic mean (UPGMA) phenogram. The significance of these results is discussed in relation to breeding in section Pentanthera.
Genetic Diversity and Disease Resistance of Wild Malus orientalis from Turkey and Southern Russia
Authors: Volk Gayle M. , Richards Christopher M. , Reilley Ann A. , Henk Adam D. , Reeves Patrick A. , Forsline Philip L. , Aldwinckle Herb S.
Published: January 2019

Genetic diversity and disease resistance are described for 496 seedlings from wild populations of Malus orientalis Uglitzh. collected in southern Russia and Turkey in 1998 and 1999. Eighty-five half-sib families were genotyped using seven microsatellite markers, and disease resistance was determined for apple scab (Venturia inaequalis Cooke), cedar apple rust (Gymnosporangium juniperi-virginianae Schwein), and fire blight (Erwinia amylovora Burrill). Individuals from the two Russian Caucasus collection locations were homogeneous compared with populations from the four Turkish collection locations. Within three of the Turkish collection locations, some half-sib families were highly diverse and several of these families had unusually high levels of disease resistance. In all, twenty individuals exhibited resistance to all three diseases. Bayesian analyses of the population structure revealed six distinct clusters. Most of the individuals segregated into two clusters, one containing individuals primarily from southern Russia and the other containing individuals from both Russia and northern Turkey. Individuals in the four small clusters were specific to Turkish collection locations. These data suggest wild populations of M. orientalis from regions around the Black Sea are genetically distinguishable and show high levels of diversity.
Detection and Characterization of Genome-specific Microsatellite Markers in the Allotetraploid Prunus serotina
Authors: Pairon Marie , Jacquemart Anne-Laure , Potter Daniel
Published: January 2019

The utility of microsatellite markers to characterize the genetic diversity of a polyploid species with disomic inheritance is often hampered by the impossibility of determining allele frequencies and the complexity of inheritance patterns. The objective of this study was to solve these problems in the allotetraploid Prunus serotina Ehrh. by finding genome-specific primers (i.e., primers that are specific to one of the two genomes that initially formed the species). Sixty-seven microsatellite primers described in cultivated Prunus L. species were tested for cross-amplification in P. serotina, and evidence that conserved markers were genome-specific was found by demonstrating their typical Mendelian diploid inheritance in embryos resulting from controlled crosses. Among the 67 microsatellite markers tested, 26 produced successful amplification and five were genome-specific. No linkage disequilibrium was detected for these loci, but evidence was found for the presence of a null allele at one locus. We found both a high number of alleles per locus (three to 12) and a high mean expected heterozygosity (0.71), which were nonsignificantly different from the number of alleles and estimates of expected heterozygosity calculated for three non-genome-specific markers in the same population. The potential use of these genome-specific markers in population genetic studies is discussed.
Inheritance of Fruit, Foliar, and Plant Habit Attributes in Capsicum
Authors: Stommel John R. , Griesbach Robert J.
Published: January 2019

Considerable diversity exists in Capsicum L. germplasm for fruit and leaf shape, size, and color as well as plant habit. Using F1, F2, and backcross generations developed from diverse parental stocks, this report describes the inheritance patterns and relationships between unique foliar characters and diverse fruit and plant habit attributes. Our results demonstrate that pepper fruit color, shape, and fruit per cluster were simply inherited with modifying gene action. Broad-sense heritability for fruit color and shape and fruit per cluster was high, whereas narrow-sense heritability for these characters was moderate to low. Although fruit clustering was simply inherited, the number of fruit per cluster exhibited a quantitative mode of inheritance. High fruit counts per cluster were linked with red fruit color and anthocyanin pigmented foliage. Fruit shape was linked with immature fruit color and inherited independently of mature fruit color. Leaf color, length, and plant height were quantitatively inherited. Leaf shape did not vary, but leaf length varied and was positively correlated with leaf width. Broad-sense heritability for leaf characters, including leaf length, leaf width, and leaf color, was high. With the exception of leaf width, which exhibited low narrow-sense heritability, high narrow-sense heritability for leaf characters denoted additive gene action. Plant height displayed high broad-sense heritability. Moderate narrow-sense heritability suggested that additive effects also influence plant height. Analysis of segregating populations demonstrated that red and orange fruit color can be combined with all possible leaf colors from green to black. These results provide new data to clarify and extend available information on the inheritance of Capsicum fruit attributes and provide new information on the genetic control of leaf characters and plant habit.
Timing of Nutrient Termination and Reapplication for Growth, Flower Initiation, and Flowering of the Nobile Dendrobium Orchid
Authors: Yung-Ting Yen Christine , Starman Terri W. , Wang Yin-Tung , Holzenburg Andreas , Niu Genhua
Published: January 2019

Hybrids of Dendrobium nobile Lindl. have high potential to become a high-value pot plant, but detailed research to support the development of commercial production protocols was lacking. A 3 × 5 factorial experiment was conducted to investigate the effects of nutrient termination date (1 Aug., 1 Sept., or 1 Oct.) and nutrient reapplication time (at the beginning or in the middle of cooling, immediately after or 2 weeks after the completion of cooling, or no nutrient reapplication) on growth and flower development of Dendrobium Sea Mary ‘Snow King,’ a D. nobile hybrid. Interaction between nutrient termination date and reapplication time on growth and flowering was nonsignificant for all variables measured, and reapplication time had only a minor effect on leaves remaining. Regardless of nutrient reapplication time, delaying nutrient termination date resulted in improved growth and flowering. Nutrient termination on 1 Oct. resulted in taller plants with more nodes, leaves remaining, flowering nodes, and total flowers as well as fewer aborted flowers than an earlier termination date. Nutrient supply until 1 Oct. did not lead to differences in time required for anthesis but extended the time needed to reach full flowering by 1.5 d. The results suggest that flower development benefited more from the nutrients that were accumulated in mature pseudobulbs before nutrient termination rather than from those being taken from the reapplied fertilizers. Only lateral buds protruding 2 mm or more from the pseudobulb surface showed differentiated floral structures when examined histologically. The buds, excised 4 weeks after cooling treatments began, showed that nutrient termination on 1 Aug. resulted in larger flower primordia than those ended on 1 Oct., indicating an earlier or faster flower differentiation with earlier nutrient termination. No aerial shoot formation or reversion of reproductive to vegetative buds arose as a result of either late nutrient termination or resumption of nutrient application.
Substrate Acidification by Geranium: Light Effects and Phosphorus Uptake
Authors: Taylor Matthew D. , Nelson Paul V. , Frantz Jonathan M.
Published: January 2019

Sudden pH decline (SPD) describes the situation where crops growing at an appropriate pH rapidly (within 1–2 weeks) cause the substrate pH to shift downward one to two units. ‘Designer Dark Red’ geraniums (Pelargonium ×hortorum Bailey) were grown in three experiments to assess possible effects of light on SPD and phosphorous (P) uptake. The first experiment tested the effect of four light intensities (105, 210, 575, and 1020 ± 25 μmol·m−2·s−1) on substrate acidification. At 63 days, substrate pH declined from 6.0 to 4.8 as light intensity increased. Tissue P of plants grown at the highest two light levels was extremely low (0.10%–0.14% of dry weight). P stress has been reported to cause acidification. Because plants in the two lowest light treatments had adequate P, it was not possible to determine if the drop in substrate pH was a direct light effect or a combination of light and P. The second experiment used a factorial combination of the three highest light levels from Expt. 1 and five preplant P rates (0, 0.065, 0.13, 0.26, or 0.52 g·L−1 substrate) to assess this question. When tissue P concentrations were deficient, pH decreased by 0.6 to 1.0 pH units within 2 weeks and deficiency occurred more often with high light intensity. These data indicated that P deficiency caused substrate acidification and indicated the possibility that P uptake was suppressed by high light intensity. The third experiment was conducted in hydroponics to determine the direct effect of high light intensity on P uptake. In this experiment, cumulative P uptake per gram root and the rate of P uptake per gram root per day both decreased 20% when light intensity increased from 500 to 1100 μmol·m−2·s−1. It is clear from this study that P deficiency causes geraniums to acidify the substrate and that high light suppresses P uptake.
Genetics and Biochemistry of Flower Color in Stokes Aster
Authors: Barb Jessica G. , Werner Dennis J. , Griesbach Robert J.
Published: January 2019

Stokes aster [Stokesia laevis (J. Hill) Greene] is a herbaceous perennial endemic to the coastal plains of the southeastern United States. Anthocyanin and copigment aglycones from flowers were characterized using high-performance liquid chromatography. Blue, lavender, violet, and albescent flowers each contained the anthocyanidin petunidin, although albescent flowers contained a substantially smaller amount. Pale pink flowers were found to contain only cyanidin. Anthocyanins and carotenoids were not present in pale yellow flowers of this species. All flowers contained the flavone luteolin. Genetic analysis of F1, F2, and BC1 populations suggested that flower color in stokes aster is controlled by at least three loci. F2 populations of blue × albescent and blue × pale yellow flowering plants segregated in a 3:1 ratio of blue to albescent or pale yellow flowered progeny, indicating that albescent and pale yellow flower colors were recessive and each controlled by a single locus with two alleles. BC1 populations supported these results. We propose the symbols A and Y: AA and YY plants synthesize a normal amount of anthocyanins, aa plants synthesize a reduced amount of anthocyanins, and yy plants do not synthesize anthocyanins. When the two mutant phenotypes (i.e., albescent [aa] and pale yellow [yy]) were crossed, the F1s were blue, and the F2 segregated in a 9 blue:3 albescent:4 yellow ratio, indicating that the recessive locus (y), when homozygous, was epistatic to other loci involved in anthocyanin production (e.g., A), and that the genotypes of the parents used in these crosses were aaYY (albescent) and AAyy (pale yellow). F1, F2, and BC1 populations of blue (petunidin) × pale pink (cyanidin) flowering plants revealed that cyanidin production was recessive and controlled by a single locus, P, with two alleles, whereby PP plants synthesize petunidin and pp plants synthesize cyanidin. It was difficult to distinguish albescent- and pale pink-flowered progeny in segregating generations, therefore three genetic models were proposed and tested to determine the genotype(s) (i.e., AApp, Aapp, or aapp) of the pale pink-flowered plants. Based on these analyses, we propose a theoretical biochemical pathway for flavonoid biosynthesis in stokes aster.
Tomato Analyzer-color Test: A New Tool for Efficient Digital Phenotyping
Authors: Darrigues Audrey , Hall Jack , van der Knaap Esther , Francis David M. , Dujmovic Nancy , Gray Simon
Published: January 2019

Measuring plant characteristics via image analysis has the potential to increase the objectivity of phenotypic evaluations, provides data amenable to quantitative analysis, and is compatible with databases that aim to combine phenotypic and genotypic data. We describe a new tool, which is implemented in the Tomato Analyzer (TA) software application, called Color Test (TACT). This tool allows for accurate quantification of color and color uniformity, and allows scanning devices to be calibrated using color standards. To test the accuracy and precision of TACT, we measured internal fruit color of tomato (Solanum lycopersicum L.) with a colorimeter and from scanned images. We show high correlations (r > 0.96) and linearity of L*, a*, and b* values obtained with TACT and the colorimeter. We estimated genotypic variances associated with color parameters and show that the proportion of total phenotypic variance attributed to genotype for color and color uniformity measured with TACT was significantly higher than estimates obtained from the colorimeter. Genotypic variance nearly doubled for all color and color uniformity traits when collecting data with TACT. This digital phenotyping technique can also be applied to the characterization of color in other fruit and vegetable crops.
Flowering and Fruit Set of Olive Trees in Response to Nitrogen, Phosphorus, and Potassium
Authors: Erel Ran , Dag Arnon , Ben-Gal Alon , Schwartz Amnon , Yermiyahu Uri
Published: January 2019

The independent effects of nitrogen, phosphorus, and potassium concentrations in the irrigation solution on flowering and fruit set in olive trees (Olea europaea L. cv. Barnea) were studied in a container experiment. Treatments included eight levels of N ranging from 0.4 to 14.1 mm, seven levels of P ranging from 0.01 to 0.62 mm, and seven levels of K ranging from 0.25 to 5.33 mm. At low environmental concentrations of each of the minerals, additions led to large increases in their concentrations in leaves, and as the environmental concentrations became high, relative increases in leaf accumulation were reduced. Availability of N, P, and K was found to influence flowering intensity in the olive trees. Fruit set was affected by N and P, but not K levels. Total fruit load of olives was shown to be a function of flowering level multiplied by fruit set. The final number of olives per tree increased appreciably as leaf P and K increased from minimum levels, and relative increases in fruit load tapered at the highest measured leaf concentrations of the minerals. Maximum fruit load was found corresponding to ≈0.06 mol·kg−1 P and close to 0.35 mol·kg−1 K in leaves. Fruit load increased to a maximum as leaf N increased from 0.7 to 1.3 mol·kg−1 and then decreased as leaf N increased to 1.5 mol·kg−1. The findings indicate that each of the macronutrients plays a fundamental role in processes affecting olive tree productivity.
Carbohydrate Metabolism in Creeping Bentgrass as Influenced by Two Summer Irrigation Practices
Authors: Fu Jinmin , Dernoeden Peter H.
Published: January 2019

This field study was conducted to investigate carbon metabolic responses to deep and infrequent (DI) versus light and frequent (LF) irrigation in ‘Providence’ creeping bentgrass (Agrostis stolonifera L.). LF irrigation was performed daily to wet soil to a depth of 4 to 6 cm, whereas DI irrigation was performed at leaf wilt to wet soil to a depth of ≥24 cm. The creeping bentgrass was seeded into a sand-based root zone in 2005 and was maintained as a putting green during the 2006 and 2007 study years. Canopy net photosynthesis (Pn) and whole plant respiration (Rw) were monitored, and water-soluble carbohydrates [WSC (i.e., glucose, fructose, and sucrose)], storage carbohydrates [SC (i.e., fructan and starch)], and total nonstructural carbohydrates [TNC (i.e., the sum of water soluble and storage sugars)] in leaf and root tissue were quantified. Creeping bentgrass subjected to DI irrigation had a lower Pn and a generally similar Rw compared with LF-irrigated bentgrass. DI irrigated bentgrass generally had greater levels of WSC and TNC in leaf tissue in 2006 and similar levels in 2007 when compared with LF-irrigated bentgrass. Leaf SC levels were higher in DI- than LF-irrigated bentgrass in both years. Creeping bentgrass roots subjected to DI irrigation generally had greater SC and TNC levels in both years than were found in LF-irrigated plants. Root WSC levels were higher (2006) or similar (2007) in DI- versus LF-irrigated bentgrass. Irrigating creeping bentgrass at wilt rather than daily to maintain moist soil generally resulted in higher carbohydrate levels in leaves and roots, which may enable creeping bentgrass to better tolerate and recover from drought and other stresses.
Suppression Subtractive Hybridization and Differential Screening Reveals Endodormancy-associated Expression of an SVP/AGL24-type MADS-box Gene in Lateral Vegetative Buds of Japanese Apricot
Authors: Yamane Hisayo , Kashiwa Yukinobu , Ooka Tomomi , Tao Ryutaro , Yonemori Keizo
Published: January 2019

To understand the molecular basis of the endodormancy of buds of perennial plants, we searched for the genes that are expressed preferentially in endodormant lateral buds of the deciduous fruit tree japanese apricot (Prunus mume Sieb. et Zucc.) using suppression subtractive hybridization with mirror orientation selection (SSH/MOS). We generated two SSH/MOS libraries containing gene pools that are expressed preferentially in endodormant buds in comparison with paradormant or ecodormant buds to search for the genes that are upregulated by endodormancy induction or down-regulated by endodormancy release, respectively. Differential screening and sequencing indicated that genes involved in gibberellin metabolism, stress resistance, cell wall modification, and signal transduction, such as transcription factors, are upregulated in endodormant buds. After a further expression survey and full-length cDNA cloning, we found that a gene similar to the SVP/AGL24-type MADS-box transcription factor showed endodormancy-associated expression. Seasonal expression analysis suggested that the SVP/AGL24 homolog in japanese apricot might be involved in endodormancy regulation of its lateral buds.
Carbon and Nitrogen Reserves in Perennial Strawberry Affect Plant Growth and Yield
Authors: Acuña-Maldonado Laura Elisa , Pritts Marvin P.
Published: January 2019

Early spring growth of perennial strawberry (Fragaria ×ananassa Duch.) plants is supported by the carbohydrate and nitrogen (N) reserves accumulated from the previous growing season. The limitations of these reserves on the initial spring growth and yield of perennial strawberries have not been studied in detail, particularly the influence of N reserves. Differential N fertigation (0 to 20 mm N) was applied to potted strawberries during the growing season and a supplemental foliar urea application was applied to a portion of the plants in the fall to modify reserve N during dormancy. Plant N content and spring vegetative growth the year after fertigation increased nearly twofold with increasing N fertigation. Photosynthesis per unit leaf area also increased up to 10 mm of fertilizer N and then stabilized through 20 mm. Foliar urea application in fall further increased total plant N content and size, decreased carbohydrate concentration, and also decreased yield in plants with the most total N. Nitrogen fertigation was resumed on a portion of these plants in early spring, but new growth and subsequent yield were unaffected by spring N application. In a second experiment, CO2 enrichment with and without soil and foliar N application in the fall was used to vary carbon (C) and N reserves. CO2 enrichment in fall increased plant size and yield the next July by ≈20%, but total nonstructural carbohydrate and N concentrations were unaffected. Foliar urea application also increased N and C reserves (but not concentration) as well as yield in both enriched and unenriched plants. Although foliar urea in fall decreased carbohydrate concentration, total reserve levels were unaffected because treated plants were larger. In this experiment, spring N increased plant size by ≈50%, but yield was increased only 12%, suggesting that yields are mostly dependent on reserves. Increasing N reserves with a late fall foliar application is one strategy growers can use to efficiently enhance growth and yield in low to moderately fertilized plants.
Verification of Mandarin and Pummelo Somatic Hybrids by Expressed Sequence Tag–Simple Sequence Repeat Marker Analysis
Authors: Chen Chunxian , Grosser Jude W. , Ćalović Milica , Serrano Patricia , Pasquali Gemma , Gmitter Julie , Gmitter Fred G.
Published: January 2019

Somatic hybridization is a powerful tool for the genetic improvement of citrus rootstocks, and it is part of an efficient in vitro-based breeding system described here. An essential component of the system is the requirement of confirming tetraploidy and the combination of the two donor genomes. Expressed sequence tag–simple sequence repeat (EST-SSR) markers provide a means to accomplish both of these objectives, and their application to a population of pummelo [Citrus grandis (L.) Osbeck] + mandarin (C. reticulata Blanco) somatic hybrids developed for the specific purpose of providing alternative rootstocks for sour orange (Citrus aurantium L.) is detailed. Nineteen new somatic hybrids were produced from various mandarin and pummelo parents, and their ploidy level and the complementation of their nuclear genomes were confirmed using four EST-SSR markers. These markers were selected from markers previously mapped in sweet orange [C. sinensis (L.) Osbeck] and trifoliate orange [Poncirus trifoliata (L.) Raf.] and prescreened for suitable allelic polymorphism within the mandarin and pummelo lines used. After polymerase chain reaction amplification of sequences from the parents and putative hybrids, the products were separated on a genetic sequencer and visualized electronically. Additionally, EST-SSR markers identified the unexpected zygotic origin of a presumed nucellar embryogenic callus line. Integration of EST-SSR techniques for high-throughput genotyping with previously developed approaches to somatic hybrid creation increases substantially the effectiveness and efficiency of this in vitro-based breeding system for citrus rootstock improvement.
Genetic Diversity Analysis and Single-nucleotide Polymorphism Marker Development in Cultivated Bulb Onion Based on Expressed Sequence Tag–Simple Sequence Repeat Markers
Authors: McCallum John , Thomson Susan , Pither-Joyce Meeghan , Kenel Fernand , Clarke Andrew , Havey Michael J.
Published: January 2019

Bulb onion (Allium cepa L.) is a globally significant crop, but the structure of genetic variation within and among populations is poorly understood. We broadly surveyed genetic variation in a cultivated onion germplasm using simple sequence repeat (SSR) markers and sequenced regions flanking expressed sequence tag (EST)-SSRs to develop single-nucleotide polymorphism (SNP) markers. Samples from 89 inbred and open-pollinated (OP) bulb onion populations of wide geographical adaptation and four related Allium L. accessions were genotyped with 56 EST-SSR and four genomic SSR markers. Multivariate analysis of genetic distances among populations resolved long-day, short-day, and Indian populations. EST-SSR markers frequently revealed two major alleles at high frequency in OP populations. The median proportion of single-locus polymorphic loci was 0.70 in OP and landrace populations compared with 0.43 in inbred lines. Resequencing of 24 marker amplicons revealed additional SNPs in 17 (68%) and five SNP assays were developed from these, suggesting that resequencing of EST markers can readily provide SNP markers for purity testing of inbreds and other applications in Allium genetics.
Variation of Flavonoid Content Among Sweetpotato Accessions
Authors: Ojong Peter B. , Njiti Victor , Guo Zibao , Gao Ming , Besong Samuel , Barnes Sandra L.
Published: January 2019

The objective of this study was to characterize and quantify five commonly occurring flavonoids (quercetin, luteolin, apigenin, myricetin, and kaempferol) in storage roots and leaves of 10 sweetpotato [Ipomoea batatas L. (Lam.)] accessions: SC1149, ‘Excel’, ‘Vardaman’, ‘Hernandez’, ‘Picadito’, ‘Porto Rico’, ‘GA90-16’, PI531116, NC98-608 (Covington), and ‘Beauregard’ (B94-14-G2). The flavonoids were present in varying amounts (quercetin comprised greater than 79% and 55% of the mean flavonoid content in sweetpotato leaf and root samples, respectively) and were found to be more concentrated in the leaves (0.65% to 2.76% dry weight) than in the storage roots (0.27% to 1.69% dry weight). The results indicate significant variability in flavonoid content among different sweetpotato accessions, suggesting that there is the potential for genetic manipulation of sweetpotato to influence flavonoid content and profile through traditional breeding or biotechnological approaches.
Characterization of Polyphenol Oxidase from Walnut
Authors: Escobar Matthew A. , Shilling Andrew , Higgins Pine , Uratsu Sandra L. , Dandekar Abhaya M.
Published: January 2019

The enzyme polyphenol oxidase (PPO) is nearly ubiquitous in Kingdom Plantae and catalyzes the oxidation of phenolic compounds into highly reactive quinones. Although the functional importance of PPO in plants remains uncertain, a putative antipathogen role for walnut (Juglans regia) PPO was posited as early as 1911. However, despite the rich diversity of phenolics present in walnut leaves and hulls, walnut PPO has been little studied since the early 1900s. We cloned a PPO-encoding gene from a walnut pistillate flower cDNA library and designated the gene jrPPO1. Genomic Southern analysis demonstrated that jrPPO1 is the sole PPO gene in walnut. Transgenic tobacco (Nicotiana tabacum) plants expressing jrPPO1 display greater than 10-fold increases in leaf PPO activity compared with wild-type tobacco, demonstrating that jrPPO1 encodes a functional enzyme. The jrPPO1 protein is expressed primarily in the leaves, hulls, and flowers of walnut trees and is not regulated by wounding or methyl jasmonate. To examine whether walnut PPO could affect pathogen resistance, tobacco plants expressing jrPPO1 were challenged with Pseudomonas syringae pv. tabaci. Based on both symptom development and quantitative analyses of bacterial growth in planta, the PPO-expressing plants did not display increased resistance to this pathogen. Leaf extract browning assays indicated that tobacco leaves lack the endogenous phenolic substrates required for significant jrPPO1 activity and quinone production in planta.
New Insight into Wild Red Raspberry Populations using Simple Sequence Repeat Markers
Authors: Graham Julie , Woodhead Mary , Smith Kay , Russell Joanne , Marshall Bruce , Ramsay Gavin , Squire Geoff
Published: January 2019

Scottish wild red raspberry (Rubus idaeus) plants at 12 sites were re-examined 10 years after initial studies had been carried out to examine the decline in population size and to address an earlier finding that demonstrated significant population differentiation over a small scale. Ten simple sequence repeat (SSR) loci were screened on the plants and a total of 80 alleles were detected, half of which were unique to a particular population, with all populations containing unique SSR alleles. Only 18 of the 80 alleles present in the wild were found in cultivated raspberries, highlighting the genetic diversity available for future breeding. This finding makes the decline in population number observed a concern, as this unique diversity is being eroded, primarily due to human impact. An additional 17 unique alleles were identified in the cultivars that were not present in the wild individuals studied. Gene flow into one lowland site was identified by the gain of one new allele into progeny at the site, but three alleles were also lost from parents to progeny. SSR markers were used to estimate the levels of outcrossing in wild red raspberry for the first time, and confirmed that the populations studied were outcrossing, intermating populations. The nonsignificant global F
IS value indicates that red raspberry is an outbreeder (global F
IS = −0.117), but significant population differentiation was observed [global F
ST = 0.348 (P < 0.001)]. Diversity in this crop's wild relative and the population differentiation observed may have use in the future for breeding aimed at addressing climate change scenarios, and consideration should be given to means of conserving the diversity revealed by these studies.
Characterization of ‘Stoneless’: A Naturally Occurring, Partially Stoneless Plum Cultivar
Authors: Callahan Ann M. , Dardick Chris , Scorza Ralph
Published: January 2019

The plum (Prunus domestica) cultivar Stoneless was characterized to determine if the lack of stone was the result of reduced endocarp development or a decrease in lignification. Fruit were sampled at several times from 37 days before stone hardening (DBH) until the stone was too hard to cut with a knife and were compared with plum fruit that had normal stones. At all sampling times there was less endocarp tissue and reduced lignin staining in the ‘Stoneless’ plum fruit. The tissue that did stain appeared to be small endocarp remnants present in the ‘Stoneless’ plum, and was concentrated at the suture side and at the blossom end as well as the stem end. The lignin stain was detected in these regions beginning at 19 DBH, while the normal plums had a progression of staining beginning at the blossom end, suture side at 23 DBH and radiating up to the stem end and throughout the presumptive stone tissue at 8 DBH. Comparison of dry weight for dissected tissues agreed with the specific lack of endocarp tissue in the ‘Stoneless’ plum. Gene activity for the lignin pathway was analyzed using four known genes required for lignification. All four genes showed endocarp-specific expression in ‘Stoneless’ similar to that observed for the control. These results support the idea that the phenotype of ‘Stoneless’ plum fruit is due to a decrease in endocarp formation rather than a decrease in endocarp lignification.
Antioxidizing Enzyme Activities in Chilling-sensitive and Chilling-tolerant Pepper Fruit as Affected by Stage of Ripeness and Storage Temperature
Authors: Lim Chae Shin , Kang Seong Mo , Cho Jeoung Lai , Gross Kenneth C.
Published: January 2019

To study ripening-related chilling injury in pepper (Capsicum annuum L.), chilling-tolerant ‘Buchon’ and chilling-sensitive ‘Nockgwang’ fruit were harvested at mature green (MG), breaker (BR), and red-ripe (RR) stages and stored at 1, 5, and 10 °C for 21 d. ‘Buchon’ did not show surface pitting (SP) regardless of ripeness stage and storage temperature, whereas ‘Nockgwang’ at MG and BR exhibited SP at 1 and 5 °C. After 14 days of storage at 1 °C, chilling-sensitive ‘Nockgwang’ did not show SP when fruit were at the RR stage. Compared with ‘Buchon’, ‘Nockgwang’ at MG and BR had more electrolyte leakage increase during storage at 1 and 5 °C. ‘Buchon’ at all ripeness stages showed significantly higher ethylene production during storage regardless of storage temperatures. Contents of β-carotene and lycopene increased in both cultivars as ripening progressed. The contents of β-carotene and lycopene were similar between the two cultivars regardless of storage temperatures and ripeness stages. Susceptibility of pepper fruit to chilling appeared to be related to superoxide dismutase (SOD) and catalase (CAT). Activities of SOD and CAT were much higher in ‘Buchon’ than ‘Nockgwang’, more apparently at MG and BR. The results suggest that chilling-tolerant ‘Buchon’ and fruit at RR could have been equipped with a more efficient antioxidizing system, even if it was not clear whether oxidative stress is a cause or an effect of the CI in pepper.
Simple Linear Regression and Reflectance Sensitivity Analysis Used to Determine the Optimum Wavelengths for the Nondestructive Assessment of Chlorophyll in Fresh Leaves Using Spectral Reflectance
Authors: Ding Pinghai , Fuchigami Leslie H. , Scagel Carolyn F.
Published: January 2019

The accuracy of nondestructive optical methods for chlorophyll (Chl) assessment based on leaf spectral characteristics depends on the wavelengths used for Chl assessment. Using spectroscopy, the optimum wavelengths (OW) for Chl assessment were determined by using 1-year-old almond (Prunus dulcis), poplar (Populus trichocarpa × P. deltoides), and apple (Malus ×domestica) trees grown at different rates of nitrogen fertilization to produce leaves with different Chl concentrations. Spectral reflectance of leaf discs was measured using a spectroradiometer (300 to 1100 nm at 1-nm intervals), and total Chl concentration in leaf discs was extracted and determined in 80% acetone. The OW for nondestructive Chl assessment by reflectance spectroscopy was estimated using 1) the coefficient of determination (r
2) from simple linear regression; 2) reflectance sensitivity analysis (a measure for changes of spectral reflectance on unit change in leaf Chl concentration); and 3) the first spectral derivative method. Our results indicated that the first derivative method can be used only to identify OW in the red edge region of the spectrum, whereas r
2 and reflectance sensitivity analysis can be used to identify the OW in both the red edge and green regions. Our results indicate that using simple linear r
2 in combination with reflectance sensitivity and/or the first derivative analyses is a reliable method for determining OW in plant leaves tested. Two optimum wavebands with larger r
2, smaller root mean square error, and higher reflectance sensitivity were found in red edge (700 to 730 nm) and green (550 to 580 nm) regions, respectively, which can be used as common OW for Chl reflectance assessment in poplar, apple, and almond leaves tested. Single-wavelength indices if developed with OW were even more accurate than those more wavelength indices that developed without using OW. The accuracy of indices can be further improved if indices developed by using one OW and one Chl-insensitive wavelength from near infrared (NIR) (750 to 1100 nm) in the form of RNIR/ROW or (RNIR – ROW)/(RNIR + ROW).
Analysis of Genetic Variability among Phalaenopsis Species and Hybrids Using Amplified Fragment Length Polymorphism
Authors: Chang Yeun-Kyung , Veilleux Richard E. , Iqbal Muhammad Javed
Published: January 2019

Phalaenopsis is the second most valuable potted plant in the United States. Information on the genetic diversity and relationships among species and hybrids is important for breeding purposes and species conservation. In this study, genetic variability of 16 Phalaenopsis species and hybrids was analyzed using amplified fragment length polymorphism (AFLP) markers. Ten AFLP primer combinations amplified 1353 DNA fragments ranging in size from 100 to 350 bp and 1285 (95%) of them were polymorphic. The genetic similarity among Phalaenopsis species and hybrids ranged from 0.298 to 0.774 based on Dice coefficient. The dendrogram derived by the unweighted pair group method with arithmetic mean analysis clustered the germplasm into two main groups. Bootstrap values for the groups supported 70% of the clustering. A significant linear relationship (r = 0.724, P < 0.0001) was observed between known pedigrees and AFLP-derived genetic similarity for 136 pairwise comparisons of Phalaenopsis species and hybrids. The results of this study demonstrate the usefulness of AFLP analysis in Phalaenopsis and its potential application in breeding and species conservation.
A Genetic Linkage Map including Loci for Male Sterility, Sugars, and Ascorbic Acid in Melon
Authors: Park Soon O. , Hwang Hye Y. , Crosby Kevin M.
Published: January 2019

Our objectives were to construct a randomly amplified polymorphic DNA (RAPD) marker-based linkage map using an F2 population derived from the melon (Cucumis melo) cross of ‘Deltex’ × TGR 1551, and map quantitative trait loci (QTL) for sucrose, total soluble solids (TSS), ratio of sucrose to total sugars (RSTS), and ascorbic acid as well as the ms-3 locus for male sterility previously reported in other muskmelon crosses. Due to the dominant character of RAPD markers, we scored 192 ‘Deltex’- and 158 TGR 1551-derived markers. One hundred eighty (94%) of the 192 markers fit the expected 3:1 ratio. On the basis of the 180 markers, we constructed a ‘Deltex’ linkage map of 171 markers distributed on 12 linkage groups (LGs) with a total map distance of 1182 cM. One hundred fifty (95%) of the 158 markers were identified to be nondistorted. We developed a TGR 1551 linkage map of 138 markers distributed on 12 LGs with a total distance of 1163 cM. A combined map of 12 LGs with a total map distance of 1394 cM was made from 82 marker pairs expressing codominance. Nine LGs were integrated into those of the existing composite map by 17 anchor markers. We mapped the ms-3 locus for male sterility on LG 9, which corresponds to LG 10 of the classical map and LG VII of the composite map. Six QTL for sucrose were located on LGs 2, 3, 4, 6, and 11. Three on LGs 3, 4, and 6 and four on LGs 2, 3, 6, and 11 of the six QTL for sucrose were also noted to be QTL for TSS and RSTS, respectively. A single QTL for ascorbic acid was placed on LG 5. This map will also be used to identify QTL for fruit sweetness, quality, size, and shape traits, as well as disease resistance.
Growth and Physiological Responses of Four Rose Rootstocks to Drought Stress
Authors: Niu Genhua , Rodriguez Denise S.
Published: January 2019

Drought-tolerant garden roses (Rosa spp.) are needed in arid and semiarid regions where irrigation water is scarce. The vast majority of garden rose cultivars are budded or grafted onto rootstocks and are seldom grown on their own roots. The objective of this study was to compare the growth and physiological responses of four rose rootstocks to drought stress. Rosa ×hybrida ‘Dr. Huey’, R. ×fortuniana, R. multiflora, and R. odorata grown in 12-L containers were well-irrigated throughout the experiment or were subjected to mild drought stress for five or six cycles, depending on rootstocks, over 10 weeks. Following the mild drought stress cycles, plants that received the mild drought treatment were subjected to a severe dry-down before termination of the experiment. In R. ×fortuniana, drought stress did not affect any growth parameter. Compared with the well-irrigated plants, shoot dry weight of ‘Dr. Huey’, R. multiflora, and R. odorata were reduced by 22%, 33%, and 38%, respectively, by the drought treatment. The final leaf area of R. multiflora and R. odorata was reduced by 42% and 59%, respectively, compared with the control plants. The final leaf area of ‘Dr. Huey’ was not influenced by the drought treatment. Root to shoot ratio in ‘Dr. Huey’ was unaffected, while that of R. multiflora and R. odorata increased as a result of the drought treatment. As substrate moisture content decreased, leaf relative water content (RWC) of all rootstocks decreased linearly, with differences in decreasing slope or intercept of the linear regression lines among rootstocks. Predawn leaf water potential during the dry-down began to decrease rapidly when substrate moisture content decreased to below 20% (25% in R. odorata) in ‘Dr. Huey’, R. ×fortuniana, and R. multiflora. Leaf net photosynthetic rate (Pn), transpiration rate (E) and stomatal conductance (gs) of all rootstocks decreased rapidly during the dry-down as substrate moisture content decreased from 25%. In ‘Dr. Huey’ and R. ×fortuniana, Pn, E, and gs were closely correlated with leaf RWC, while E and gs of R. odorata were not. Correlations between gas exchange rates (Pn, E, and gs) and leaf RWC in R. multiflora were weaker than those in ‘Dr. Huey’ and R. ×fortuniana. At low substrate moisture content (below 15%), Pn, E, and gs in R. odorata were lower than those in other rootstocks. Growth reduction was greatest in R. odorata, regardless of the least water deficit of the substrate, followed by R. multiflora and ‘Dr. Huey’. The results of this study suggest that R. ×fortuniana was the most tolerant and R. odorata was the least tolerant to drought stress.
Mapping of Photoperiod-induced Growth Cessation in the Wild Grape Vitis riparia
Authors: Garris Amanda , Clark Lindsay , Owens Chris , McKay Steven , Luby James , Mathiason Kathy , Fennell Anne
Published: January 2019

In grapevines (Vitis spp.), the timing of growth cessation in the fall is an important aspect of adaptation and a key objective in breeding new grape cultivars suitable for continental climates. Growth cessation is a complex biological process that is initiated by environmental cues such as daylength and temperature, as well as water and nutrient availability. The genetic control of growth cessation in grapevines was studied by mapping quantitative trait loci (QTL) in a hybrid grape population. An F2 mapping population was developed by selfing a single F1 plant derived from a cross between an accession of the North American species Vitis riparia and the Vitis hybrid wine cultivar Seyval (Seyve-Villard 5–276). A linkage map was constructed using 115 simple sequence repeat (SSR) markers and six candidate genes in a population of 119 F2 progeny. The markers provided coverage of the 19 Vitis linkage groups with an average distance between markers of 8.4 cM. The critical photoperiod for growth cessation in lateral buds for the parents and F2 progeny was determined in a replicated field trial in 2001 and 2002 and under controlled photoperiod treatments in a greenhouse in 2002, 2003, and 2004. QTL analysis using composite interval mapping identified a single major QTL in the field and greenhouse trials. However, the field and greenhouse QTL mapped to different linkage groups in the two different environments, suggesting the presence of additional, nonphotoperiodic cues for induction of growth cessation in the field. In the greenhouse, where noninducing temperatures were maintained, a QTL on linkage group (LG) 13 explained 80.0% to 96.6% of the phenotypic variance of critical photoperiod for growth cessation. In the field, where vines experienced natural fluctuations in temperature and rainfall in addition to the naturally decreasing photoperiod, a QTL on LG 11 explained 85.4% to 94.3% of phenotypic variance.