bluuebunny/crossref_metadata_2025 huggingface dataset:
Exogenous Spermidine Inhibits Ethylene Production in Leaves of Cucumber Seedlings under NaCl Stress
Authors: Li Bin , Sang Ting , He Lizhong , Sun Jin , Li Juan , Guo Shirong
Published: January 2019

To examine whether 1 mm of spermidine (Spd) modifies plant ethylene production in response to short-term salt stress, cucumber (Cucumis sativus) seedlings were grown in nutrient solution with or without 75 mm NaCl stress for 3 days, and the leaves were sprayed with 1 mm Spd or water (control). We investigate the effects of the treatments on ethylene production, 1-aminocyclopropane-1-carboxylate (ACC) content, 1-(malonylamino) cycolpvopane-1-carboxylic acid (MACC) content, activities of 1-aminocyclopropane-1-carboxylate synthase (ACS), and 1-aminocyclopropane-1-carboxylate oxidase (ACO) and gene expression of acs2, aco1, and aco2 in the cucumber leaves. The results indicate that ethylene production was increased significantly under salt stress as did ACC and MACC content, the activities of ACS and ACO, and the transcriptional level of acs2, whereas the gene expression of aco1 and aco2 was somewhat decreased. However, exogenous Spd treatment depressed the content of ACC and MACC, ACS activity, and the level of acs2 transcripts in the leaves of salt-stressed cucumber. Although the activity of ACO and gene expressions of aco1 and aco2 increased by Spd, ethylene emission was inhibited. Our results suggest that application of exogenous Spd could reverse salinity-induced ethylene production by inhibiting the transcription and activity of ACS under salt stress. We conclude that exogenous Spd could modify the biosynthesis of ethylene to enhance the tolerance of cucumber seedlings to salt stress.
Study of the Female Fertility of an Odd-tetraploid of Lilium and Its Potential Breeding Significance
Authors: Zhou Shujun , Tan Xin , Fang Liqin , Jian Jia , Xu Ping , Yuan Guoliang
Published: January 2019

The primary objective of this research was to study the female fertility of the odd-tetraploid cultivar Honesty of Lilium containing one set of Longiflorum chromosomes and three sets of Asiatic chromosomes (LAAA) to open a new approach to Lilium breeding. To assess its female fertility, ‘Honesty’ was hybridized with four autotetraploid Asiatic lily cultivars. The results showed that the fruit of all ‘Honesty’ × tetraploid (4x × 4x) combinations developed well, and viable seedlings could be obtained, suggesting that ‘Honesty’, despite being male-sterile, has considerable female fertility. Genomic in situ hybridization showed that the progenies of the 4x × 4x hybridizations were aneuploid. Considering that lily is vegetatively propagated and aneuploids often demonstrate considerable phenotypic variation, odd-tetraploid lilies such as ‘Honesty’ may be useful maternal parents for breeding new lily cultivars.
Tracing Heterozygosity in the Vvlexp1 Locus in Grapevine by Sequencing and High-resolution Melt Analysis
Authors: Anhalt Ulrike C.M. , Martini Katharina , Ruehl Ernst-Heinrich , Forneck Astrid
Published: January 2019

Multiple loci in a continuously asexually reproducing genome such as vegetatively propagated grapevine (Vitis vinifera) can be heterozygote. The methodology to analyze heterozygous loci is manifold ranging from traditional breeding and studying segregating offspring, codominant marker analyses to whole sequence analysis. Results of heterozygosity studies on challenging loci need to be carefully confirmed to ensure accuracy and avoid misinterpretation. One of these methods is high-resolution melt (HRM) analysis in combination with sequencing and segregation analysis. We present first the adoption of HRM analyses for grapevine and its potential to confirm heterozygotic markers with low or no sequence size differences.
Seasonal Growth and Spatial Distribution of Apple Tree Roots on Different Rootstocks or Interstems
Authors: Ma Li , Hou Chang Wei , Zhang Xin Zhong , Li Hong Li , Han De Guo , Wang Yi , Han Zhen Hai
Published: January 2019

Understanding of root growth patterns and architecture of apple (Malus ×domestica Borkh.) trees is very important for commercial apple production. Most commercial apple trees are usually a grafted complex consisting of the scion and the rootstock, each of which is a different genotype. Recently, rootstocks of dwarf tree species have been used extensively to meet the convenience in management; however, this practice appears to negatively impact root development. Using minirhizotrons, we investigated root dynamics, root spatial distribution, and shoot growth in ‘Red Fuji’ scion grown: 1) directly on dwarf and vigorous root stocks and 2) on a dwarf root stock placed in between the non-dwarf scion and non-dwarf rootstock (hereinafter referred to as an interstem). The results showed that: 1) one or two peaks in total root length density (TRLD) were observed in each scion/rootstock combinations every year; 2) the greatest TRLD peaks were always observed in between May and December. The peaks of shoot growth were always asynchronous with that of white root length density; 3) compared with scion/vigorous rootstock combinations, inserting a dwarfing interstem between the scion and vigorous seedling rootstock reduced the TRLD; 4) scion/vigorous rootstock combinations had a relatively deep, widespread and large root system. Scion/dwarfing rootstock combinations had a root system distributed in a small region; and the root systems of scion/dwarfing interstem/vigorous rootstock combinations tended to be intermediate between those of scion/vigorous rootstock and scion/dwarfing rootstock. This implies that the insertion of interstems altered the root architecture by not only the quantity of roots, but also the spatial distribution.
Expression of Flower Promoting Genes in Sweet Orange during Floral Inductive Water Deficits
Authors: Chica Eduardo J. , Albrigo L. Gene
Published: January 2019

Cool ambient temperatures (5 to 20 °C) and water deficit are the only factors known to induce flowering in sweet orange (Citrus sinensis). Whereas the effects of cool ambient temperatures on flowering have been described extensively, reports on the mechanisms underlying floral induction by water deficit in sweet orange (and other tropical and subtropical species) are scarce. We report changes in the accumulation of transcripts of four flower-promoting genes, CsFT, CsSL1, CsAP1, and CsLFY, in sweet orange trees in response to water deficit or a combination of water deficit and cool temperatures under controlled conditions. Exposure to water deficit increased the accumulation of CsFT transcripts, whereas transcripts of CsSL1, CsAP1, and CsLFY were reduced. However, when water deficit was interrupted by irrigation, accumulation of CsFT transcripts returned rapidly to pre-treatment levels and accumulation of CsSL1, CsAP1, and CsLFY increased. The accumulation of CsFT transcripts in trees during the combined water deficit and cool temperatures treatment was higher than in trees exposed to either factor separately, and accumulation of CsAP1 and CsLFY transcripts after the combined treatment was also higher. These results suggest that water deficit induces flowering through the upregulation of CsFT and that CsFT is the leaf integrator of flower-inducing signals generated by the exposure to water deficit and cool temperatures in sweet orange.
Fruit Detachment in Rabbiteye Blueberry: Abscission and Physical Separation
Authors: Vashisth Tripti , Malladi Anish
Published: January 2019

A better understanding of fruit detachment and the processes mediating it is essential to improve the efficiency of mechanical harvesting in blueberry (Vaccinium sp.). In blueberry, fruit detachment may occur either at the point of attachment of the pedicel to the peduncle [peduncle–pedicel junction (PPJ)] or at the point of attachment of the pedicel to the fruit [fruit–pedicel junction (FPJ)]. The fruit detachment responses of the PPJ and the FPJ to different conditions are not entirely clear. Additionally, whether fruit detachment at these junctions is mediated by the physiological process of abscission or through physical separation of the organ from the parent plant is not well understood. In this study, a series of experiments were performed to determine the abscission zone (AZ) corresponding to the point of mature fruit detachment and to determine whether fruit detachment occurs as a result of abscission or physical separation in rabbiteye blueberry (Vaccinium ashei). Anatomical studies indicated the presence of an AZ at the PPJ. Greater than 92% of the natural detachment of mature fruit occurred at the PPJ. The morphology of the fracture plane at the PPJ in naturally detached fruit was even and uniform, consistent with fruit detachment through abscission at this location. Abscission agents such as methyl jasmonate (20 mm) and ethephon (1000 mg·L−1) enhanced the extent of fruit detachment at the PPJ, further indicating that mature fruit detachment through abscission occurred primarily at this location. Additionally, the fracture plane at the PPJ during fruit detachment in response to abscission agent applications was flattened and even, further supporting the conclusion that fruit detachment at this location occurred through abscission. In contrast, the majority of the fruit detachment in response to mechanical shaking occurred at the FPJ. Analysis of the morphology of the fracture plane at the FPJ during detachment in response to mechanical shaking indicated that fruit detachment at this location was associated with extensive tearing and mechanical disruption of cells, consistent with physical separation. Together, data from this study indicate that mature fruit detachment resulting from abscission occurs primarily at the PPJ, whereas fruit detachment during mechanical shaking occurs primarily at the FPJ as a result of physical breakage at this weak junction.
Flower Position and Size Impact Ovule Number per Flower, Fruitset, and Fruit Size in Pomegranate
Authors: Wetzstein Hazel Y. , Yi Weiguang , Porter Justin A. , Ravid Nadav
Published: January 2019

Pomegranate trees (Punica granatum) produce large numbers of both hermaphroditic (bisexual) flowers that produce fruit and functionally male flowers that characteristically abort. Excessive production of male flowers can result in decreased yields resulting from their inability to set fruit. Within hermaphroditic flowers, sex expression appears to follow a spectrum ranging from those exhibiting strong to weak pistil development. Unknown is the scope that flower quality plays in influencing fruit production. A description of floral characteristics and how they vary with flowers of different sizes and positions is lacking in pomegranate and was the focus of this study. Furthermore, the effects of flower size and position on fruit set and fruit size were evaluated. This study documents that flower size characteristics and ovule development can be quite variable and are related to flower type and position. Single and terminal flowers within a cluster were larger than lateral flowers. In addition, lateral flowers exhibited a high frequency of flowers with poor ovule development sufficient to negatively impact fruiting in that flower type. Ovule numbers per flower were significantly influenced by flower size with more ovules in larger flowers. Pollination studies verified significantly higher fruit set and fruit weight, and larger commercial size distributions were obtained with larger vs. smaller flowers. Thus, flower quality is an important issue in pomegranate. Cultural and environmental factors that influence flower size and vigor may have a direct consequence on fruit production and yield.
Within-season Stability of Strawberry Soluble Solids Content
Authors: Hasing Tomas N. , Osorio Luis F. , Whitaker Vance M.
Published: January 2019

Previous studies have recognized considerable variation in the soluble solids content (SSC) of strawberries (Fragaria ×ananassa) during Florida’s fruiting season. Cultivars with stable fruit SSC over time would be valued in the commercial industry as a result of their more uniform quality. The within-season stability of 410 genotypes from the strawberry breeding program of the University of Florida was estimated using data from clonally replicated first-year seedlings and advanced selections evaluated at two locations over two consecutive seasons. Stability was measured using a linear regression approach. For each genotype, the SSC measured at different harvest dates was regressed on the mean SSC of an independent set of genotypes at each harvest date. Genotypes with steep slopes are sensitive to small environmental and physiological changes and are considered unstable compared with genotypes with slopes close to zero. Approximately 90% of individual genotype slopes were not different from the population slope value and were classified in the average stability group, whereas the remaining 10% were equally distributed between the unstable and stable groups. Although a preliminary genetic analysis indicated that SSC stability may have low narrow-sense heritability (h2 = 0.06 ± 0.05), a group of genotypes exhibited stability across multiple environments. Soluble solids content stability and mean soluble solids were independent, and genotypes with both stable and high levels of SSC were observed.
Identification and Expression of Skinning Injury-responsive Genes in Sweetpotato
Authors: Effendy Jollanda , La Bonte Don R. , Baisakh Niranjan
Published: January 2019

Skinning injury in sweetpotatoes (Ipomoea batatas) is responsible for significant postharvest loss resulting from storage diseases and weight loss. Unfortunately, there is no report on the genes involved in wound healing of sweetpotato and a better understanding will facilitate improved breeding strategies. An annealing control primer (ACP) system was used to identify genes expressed after skinning injury of sweetpotato cultivar LA 07-146 storage roots. Using 20 ACPs, 63 differentially expressed genes (DEGs) were identified. Functional annotation of the DEGs revealed that genes previously shown to respond to dehydration, those involved in wounding response, and the lignin and suberin biosynthesis pathways were induced in response to skinning. Expression analysis of 18 DEGs through quantitative reverse transcription–polymerase chain reaction (PCR) showed that DEGs involved in lignin and suberin pathways were up-regulated after 8 and 12 hours of skinning. Other genes showed up- or down-regulation in their transcript abundance depending on the time the storage root was sampled after intentional skinning. The genes up-regulated in response to skinning may be useful to identify expression markers for screening sweetpotato lines tolerant to skinning injury in breeding programs.
A Fogging System Improves Antioxidative Defense Responses and Productivity in Tomato
Authors: Leyva Rocío , Constán-Aguilar Christian , Blasco Begoña , Sánchez-Rodríguez Eva , Soriano Teresa , Ruíz Juan M.
Published: January 2019

Crops cultivated during summer in greenhouses and screen-covered structures (screenhouses) are negatively affected by stressful temperatures and vapor pressure deficit (VPD), which in turn influence yield and product quality. Fogging systems have been proposed as cooling methods to mitigate the adverse effects of high evaporation and excess temperatures in greenhouses. To evaluate the possible action of the fogging system on antioxidant response in cherry tomato (Solanum lycopersicum) fruit production, we studied the behavior of reactive oxygen species (ROS) scavenger enzymes such as superoxide dismutase, catalase, guaiacol peroxidase, enzymes involved in the ascorbate-glutathione cycle (Halliwell-Asada cycle), and compounds with antioxidant functions such as ascorbate, glutathione, proline, and polyamines. Fogging-screenhouse treatments, SF (a fogging system inside the screenhouse) and SFS (fogging system with a plastic sheeting, to maintain the microclimate created by the fogging system in the screenhouse) showed the best performance in terms of radiation with a percentage reduction of incident radiation on the crop of 18% and 37% and a mean reduction of maximum VPD values of 0.4 and 0.2 kPa, respectively, compared with the unfogging treatment (S). These improved environmental conditions, besides promoting the highest activities of ROS-scavenging enzymes and Halliwell-Asada cycle, the redox state of the ascorbate, and a low proline:free putrescine ratio, would explain the increase in commercial weight of fruit by 21% and 17% in SF and SFS, respectively, with respect to S.
Development of EST-derived SSR Markers with Long-core Repeat in Olive and Their Use for Paternity Testing
Authors: De la Rosa Raúl , Belaj Angjelina , Muñoz-Mérida Antonio , Trelles Oswaldo , Ortíz-Martín Inmaculada , González-Plaza Juan José , Valpuesta Victoriano , Beuzón Carmen R.
Published: January 2019

In the present work, a set of eight new hexa-nucleotide simple sequence repeats (SSRs) is reported in olive (Olea europaea L). These SSRs loci were generated on the basis of expressed sequence tag (EST) sequences in the frame of an olive genomic project. The markers showed a high level of polymorphism when tested on a set of cultivars used as genitors in the olive breeding program of Córdoba, Spain. The long-core repeat motif of these markers allows a wider separation among alleles, thus permitting an accurate genotyping. Besides, these markers showed comparable levels of polymorphism to di-nucleotide SSRs, the only ones so far reported in olive. Selected on the basis of their discrimination capacity, four of the eight SSRs were used to test their ability for paternity testing in a total of 81 seedlings coming from 12 crosses. The paternity testing showed that seven crosses matched the alleged paternity and the remaining five were products of illicit pollinations. These results exactly matched with previous paternity testing performed with di-nucleotide SSR markers. These results demonstrate the usefulness of the developed hexa-nucleotide repeated motifs for checking the paternity of breeding progenies and suggest their use on variability studies.
Genetic Diversity and Dissemination Pathways of Common Bean in Central Europe
Authors: Maras Marko , Šuštar-Vozlič Jelka , Kainz Wolfgang , Meglič Vladimir
Published: January 2019

Common bean (Phaseolus vulgaris L.) was introduced in Europe from both Mesoamerican and Andean centers of origin and has been cultivated in central Europe for centuries. The first objective of this study was to evaluate genetic diversity and the population structure of 167 accessions divided into four groups according to geographical origin (Slovenia and Austria) and time periods (historical and present) using 14 simple sequence repeat (SSR) markers. The second objective was to improve our understanding of the pathways of dissemination and the evolution of this species in central Europe. Great allelic polymorphism was detected in all four groups of examined accessions, indicating that Slovene and Austrian bean germplasm in the past possessed significant variation that has been well preserved until today. In factorial correspondence analysis, accessions from different groups clustered together indicating potential gene flow between countries. The uncovered diversity corresponded very well to the two recognized gene pools (Andean and Mesoamerican). The majority of accessions in every single group belonged to the Andean gene pool. Strong predominance of Andean genotypes classifies Slovenia among other Mediterranean countries, like Spain and Italy. The latter appears as a most probable source of first beans in Slovenia and Austria. We assume that in the beginning of the previous century after very tight relationships between Slovenia and Austria loosened, introgression of genotypes from western and northern European countries took place in Austria, which resulted in a very high proportion of Mesoamerican genotypes that we found in the present Austrian germplasm (44%). Several putative hybrids between the Andean and Mesoamerican gene pools were detected in this study. Evolutionary significance, origin, and breeding potential of these recombinants are discussed here.
Haploid Induction in Hull-less Seed Pumpkin through Parthenogenesis Induced by X-ray-irradiated Pollen
Authors: Košmrlj Kristina , Murovec Jana , Bohanec Borut
Published: January 2019

Production of hull-less seeds of styrian oil pumpkin (Cucurbita pepo ssp. pepo var. styriaca) is increasing as a result of demand for aromatic seed oil and for other uses. Hybrid cultivars have recently been released but a method for haploid induction has not been established. We focused on the development of a parthenogenetic haploid induction protocol based on pollination with pollen irradiated with X-ray radiation at 0, 50, 100, 150, 200, 300, and 350 Gy. Fruit set largely decreased at 200 Gy, whereas a decline in embryo formation was observed at 100 Gy. Various accessions were tested as the female parent or as the pollen donor and large differences were found. The best parthenogenetic response was found in ‘Turkey #2’ (10.0%), ‘Gleisdorfer Ölkürbis’ (4.4%), and ‘Naked Seed’ (3.9%), whereas ‘GL Opal’ and ‘White Acorn’ were efficient as pollen donors. The ploidy level of 3830 putative parthenogenetic embryos was determined using flow cytometry. Four ploidy levels (n, 2n, 3n, and 4n) were found with the majority being diploid. Interestingly, a significant proportion was determined to be tetraploid and this was clearly correlated with increased radiation delivered to pollen grains. Using selected simple sequence repeat markers on diploid embryos, no spontaneous chromosome doubling could be confirmed. In this study, haploid induction in styrian oil pumpkin was elaborated for the first time. We also showed that X-ray pollen irradiation provides an alternative to gamma radiation treatment, yielding a sufficient percentage of haploid plantlets.
Night Temperature and Source-sink Effects on Growth, Leaf Carbon Exchange Rate, and Carbohydrate Accumulation in Bell Pepper Ovaries
Authors: Darnell Rebecca L. , Cruz-Huerta Nicacio , Williamson Jeffrey G.
Published: January 2019

Low night temperatures and/or high source-sink ratios increase ovary swelling and subsequent fruit malformation in many sweet peppers (Capsicum annuum), including bell pepper. Although this response has been correlated with increased ovary carbohydrate accumulation, evidence for this is limited. Furthermore, it is unknown how the combined effects of night temperature and source-sink ratio affect ovary carbohydrate accumulation and ovary swelling. The objectives of the present work were to determine night temperature and source-sink effects on ovary swelling, net carbon exchange rate (CER), and soluble sugar and starch concentrations in bell pepper ovaries at anthesis. Source-sink and temperature effects were tested by comparing fruiting (low source-sink ratio or high sink demand) with non-fruiting (high source-sink ratio or low sink demand) ‘Legionnaire’ bell pepper plants grown at 22/20 °C [high night temperature (HNT)] or 22/12 °C [low night temperature (LNT)] day:night temperatures. Flowers that opened after imposition of the temperature and fruiting treatments were harvested at anthesis. Ovaries from harvested flowers were weighed and analyzed for non-structural carbohydrates. Leaf gas exchange measurements were performed every 3 days. Ovary fresh weight of flowers harvested at anthesis was highest in non-fruiting plants under LNT and lowest in plants grown under HNT regardless of fruiting status. Mean CER averaged over the experimental period was significantly higher in fruiting plants under HNT compared with all other treatments. There were no significant interactions between night temperature and fruiting status on ovary soluble sugar or starch concentrations. Low night temperature increased glucose, fructose, and starch concentration and decreased sucrose concentration in the ovary wall compared with HNT. There were no differences in soluble sugar or starch concentrations in the ovary wall between fruiting and non-fruiting plants. Thus, although both low temperature and high source-sink ratio (i.e., non-fruiting plants) resulted in ovary swelling, the mechanisms appear to differ. Whereas LNT effects on ovary swelling were associated with increased ovary carbohydrate accumulation, this association was not apparent when ovary swelling occurred in response to high source-sink ratios.
Bud Development, Return Bloom, and External Bud Appearance Differ among Cranberry Cultivars
Authors: DeVetter Lisa Wasko , Harbut Rebecca , Colquhoun Jed
Published: January 2019

Recent cultivar releases of cranberry (Vaccinium macrocarpon) have been reported to differ in terminal bud development, biennial bearing tendencies, and external bud appearance. However, verification of these claims and cultivar comparisons with respect to these characteristics are lacking. The objectives of this project were to 1) evaluate flower initiation, bud development, and potential return bloom across several cultivars of cranberry, including recent introductions; and 2) determine the relationship between external appearance of buds and the presence/absence of flower initials. Samples of upright shoots representing the cultivars Searles, Stevens, HyRed, and Crimson Queen were collected from a commercial cranberry marsh located in central Wisconsin during the 2011 and 2012 growing seasons. Collected uprights were separated based on reproductive status (i.e., reproductive or vegetative). Buds were then dissected and analyzed for presence/absence of flower initials using light and scanning electron microscopy. Growing degree days (GDD) were calculated and related to the progression of bud development. Flower initials were first observed on 29 July 2011 and 10 July 2012, or 290 and 322 GDD, respectively. Excluding ‘Searles’, dates of initiation were the same across all cultivars and did not differ based on reproductive status. Descriptive bud data demonstrated that wider buds are more likely to contain flower initials and overall bud width tended to be greater among recent cultivar releases. Biennial bearing tendencies were also lower among recently released cultivars, as exhibited by greater occurrences of potential return bloom. Results from the study provide evidence that recently released cultivars differ in bud development, have an increased potential for return bloom, and overall wider buds. These findings suggest newer cultivars may have different mechanisms regulating mixed bud development and other yield-contributing factors.
Stomatal and Metabolic Limitations to Photosynthesis Resulting from NaCl Stress in Perennial Ryegrass Genotypes Differing in Salt Tolerance
Authors: Hu Tao , Yi Haiying , Hu Longxing , Fu Jinmin
Published: January 2019

Plants possess abiotic stress responses that alter photosynthetic metabolism under salinity stress. The objective of this study was to identify the stomatal and metabolic changes associated with photosynthetic responses to NaCl stress in perennial ryegrass (Lolium perenne). Five-week-old seedlings of two perennial ryegrass genotypes, PI 516605 (salt-sensitive) and BARLP 4317 (salt-tolerant), were subjected to 0 and 250 mm NaCl for 8 days. The salt tolerance in perennial ryegrass was significantly associated with leaf relative water content (RWC) and photosynthetic capacity through the maintenance of greater metabolic activities under prolonged salt stress. BARLP 4317 maintained greater turf quality, RWC, and stomatal limitations but a lower level of lipid peroxidation [malondialdehyde (MDA)] and intercellular CO2 concentration than PI 516605 at 8 days after treatment (DAT). Ribulose-1, 5-bisphosphate carboxylase:oxygenase (Rubisco) activity and activation state, transcriptional level of rbcL gene, and expression level of Rubisco large subunit (LSU) declined in stressed perennial ryegrass but were higher in salt-tolerant genotype at 8 DAT. Furthermore, photosynthetic rate increased linearly with increasing Rubisco activity, Rubisco activation state, and RWC in both genotypes. The same linear relationship was found between RWC and Rubisco activity. However, MDA content decreased linearly with increasing RWC in both genotypes. Salinity-induced inhibition of photosynthesis in perennial ryegrass was mainly the result of stomatal limitation during early salt stress and metabolic limitation associated with the inhibition of RWC, activity of Rubisco, expression level of rbcL gene, and LSU under a prolonged period of severe salinity.
Mitigation of Drought Stress Damage by Exogenous Application of a Non-Protein Amino Acid γ– Aminobutyric Acid on Perennial Ryegrass
Authors: Krishnan Sanalkumar , Laskowski Kevin , Shukla Vijaya , Merewitz Emily B.
Published: January 2019

Perennial ryegrass (Lolium perenne) is an important forage and turfgrass species that is sensitive to drought stress. The objective of this study was to investigate whether gamma aminobutyric acid (GABA) may play a role in promoting drought tolerance in grass species. GABA was exogenously applied as a foliar spray at the rate of 50 or 70 mm to perennial ryegrass ‘CSI’ under well-watered or drought-stressed conditions in a controlled-environment growth chamber. The effect of GABA on the growth physiology, drought stress response, antioxidant activity, and lipid peroxidation of perennial ryegrass exposed to drought stress was measured. GABA-treated perennial ryegrass exposed to drought stress had higher relative water content (RWC), turf quality, and peroxidase activity and lower wilt rating, canopy temperature depression, electrolyte leakage, and lipid peroxidation compared with untreated plants. GABA application had no significant effect on the activity of superoxide dismutase and catalase under well-watered and drought conditions. GABA application at 50 mm was found to be more effective in alleviating drought stress damage in perennial ryegrass. The results from this study suggest that GABA mitigated drought stress damage in perennial ryegrass by maintaining higher RWC and membrane stability.
Diversity in Seasonal Bloom Time and Floral Development among Apple Species and Hybrids
Authors: Gottschalk Chris , van Nocker Steve
Published: January 2019

Timing of flowering is a fundamental developmental transition that has great ecological and agricultural importance. For perennial plants, seasonal timing of bloom and anthesis, which is the ultimate stage of flowering, can be determined by the net effect of several preceding developmental steps: seasonal timing of floral initiation, rate and extent of floral development before winter dormancy, duration of dormancy, and rate of floral development after release from dormancy. In the domestic apple (Malus ×domestica), fruit production has generally favored cultivars that bloom relatively early in the season. However, floral tissues are easily damaged by freezing temperatures, and freeze injury is especially problematic in years when abnormally warm temperatures in early spring lead to rapid floral development. To facilitate identification of genes/alleles that govern bloom time, and that could add versatility to production systems for apple, we evaluated seasonal bloom time for accessions of M. ×domestica, wild apple species (Malus sp.), and Malus hybrids maintained in a large germplasm diversity collection.
Diversity Captured in the USDA-ARS National Plant Germplasm System Apple Core Collection
Authors: Gross Briana L. , Volk Gayle M. , Richards Christopher M. , Reeves Patrick A. , Henk Adam D. , Forsline Philip L. , Szewc-McFadden Amy , Fazio Gennaro , Chao C. Thomas
Published: January 2019

The USDA-ARS National Plant Germplasm System Malus collection is maintained by the Plant Genetic Resources Unit (PGRU) in Geneva, NY. In the 1990s, a core subset of 258 trees was hand-selected to be representative of the grafted Malus collection. We used a combination of genotypic and phenotypic data to compare the diversity of the 198 diploid trees in the original core subset with that of 2114 diploid trees in the grafted field collection for which data were available. The 198 trees capture 192 of the 232 total microsatellite alleles and have 78 of the 95 phenotypic characters. An addition of 67 specific individuals increases the coverage to 100% of the allelic and phenotypic character states. Several de novo core sets that capture all the allelic and phenotypic character states in 100 individuals are also provided. Use of these proposed sets of individuals will help ensure that a broad range of Malus diversity is included in evaluations that use the core subset of grafted trees in the PGRU collection.
Leaf:fruit Ratio Affects the Proteomic Profile of Grape Berry Skins
Authors: Wu Ben-Hong , Niu Ning , Li Ji-Hu , Li Shao-Hua
Published: January 2019

The most obvious effects of a low leaf:fruit (LF) ratio [two leaves for one cluster per shoot (LF2)] on grape (Vitis vinifera) berries are suppressed anthocyanin biosynthesis in the berry skin, decreased berry weight and soluble solids concentration, and increased titratable acidity. In this study, proteins isolated from berry skins grown under low and high LF ratio conditions, LF2 and LF12, respectively, were characterized by two-dimensional gel electrophoresis coupled to mass spectrometry. A survey of ≈600 to 700 spots from berry skin yielded 77 proteins with differential expression between LF12 and LF2 treatments. Of these, the 59 proteins that were identified consisted of 47 proteins that were down-regulated and 12 that were up-regulated under LF2 conditions compared with LF12 conditions. Most proteins involved in metabolism, energy, transcription, protein synthesis, binding function, signal transduction, and cell defense were down-regulated in LF2 berries, whereas two important enzymes of anthocyanin biosynthesis, chalcone synthase and dihydroflavonol reductase, were not detected. Only a few proteins (e.g., two heat shock proteins related to protein fate and nutrient reservoir storage protein) were found to be up-regulated in LF2 berries. This suggested that, with the exception of secondary metabolism, many proteomic events may have an effect on anthocyanin synthesis in the skins responding to LF.
High Temperature Alters Sorbitol Metabolism in Pyrus pyrifolia Leaves and Fruit Flesh during Late Stages of Fruit Enlargement
Authors: Liu Dongfeng , Ni Junbei , Wu Ruiyuan , Teng Yuanwen
Published: January 2019

Sorbitol is the main photosynthetic product and primary translocated carbohydrate in the Rosaceae and plays fundamental roles in plant growth, fruit quality, and osmotic stress adaptation. To investigate the effect of frequent high temperature during advanced fruit development on fruit quality of chinese sand pear [Pyrus pyrifolia (Burm. f.) Nakai], we analyzed sorbitol metabolism in mature leaves and fruit flesh of potted ‘Wonhwang’ pear trees. In mature leaves, sorbitol synthesis catalyzed by NADP+-dependent sorbitol-6-phosphate dehydrogenase (S6PDH) was repressed, while sorbitol utilization mainly catalyzed by NAD+-dependent sorbitol dehydrogenase (NAD+-SDH) and NADP+-dependent sorbitol dehydrogenase (NADP+-SDH) was higher than that before high-temperature treatment, which resulted in decreased sorbitol accumulation. In contrast, sucrose accumulation in mature leaves was significantly enhanced in response to high temperatures. In fruit flesh, accumulation of sorbitol and sucrose was increased at the time of harvest under high temperatures. Among sorbitol metabolic enzymes, only NAD+-SDH was sensitive to high temperature in fruit flesh, and significant decrease of NAD+-SDH activity indicated that the fruit sorbitol-uptake capacity was undermined under high temperatures. Transcription analysis revealed tissue-specific responses of NAD+-SDH genes (PpSDH1, PpSDH2, and PpSDH3) to high-temperature treatment. The NAD+-SDH activity and regulation of PpSDH1 and PpSDH3 were positively correlated in mature leaves. However, the downregulation of PpSDH1 and PpSDH2 was consistent with decreased enzyme activity in the fruit flesh. With regard to sorbitol transport, two sorbitol transporter genes (PpSOT1 and PpSOT2) were isolated, and downregulation of PpSOT2 expression in mature leaves indicated that the sorbitol-loading capability decreased under high-temperature conditions because of the limited sorbitol supply. These findings suggested that sorbitol metabolism responded differently in mature leaves and fruit flesh under high temperature, and that these dissimilar responses influenced fruit quality and may play important roles in adaptation to high temperatures.
Improving Cold Tolerance through In Vitro Selection for Somaclonal Variations in Seashore Paspalum
Authors: Liu June , Yang Zhimin , Li Weiling , Yu Jingjin , Huang Bingru
Published: January 2019

Cold stress is a major factor limiting the growth of warm-season turfgrass species. Cold tolerance in warm-season turfgrass species could be improved through in vitro selection for somaclonal variations. The objectives of this study were to establish an effective in vitro culture protocol for generating plants from calli using mature seeds of seashore paspalum (Paspalum vaginatum) and to determine whether in vitro cold selection of somaclonal variations would lead to improved cold tolerance in seashore paspalum. The optimal concentrations of supplemental compounds in the culture medium for callus induction, embryogenic callus formation, and plant regeneration were determined. The supplemental compounds included 2,4–dichlorophenoxy acetic acid (2,4-D), 6-benzylaminopurine (6-BA), kinetin (KT), naphthalene-1-acetic acid (NAA), CuSO4, and acidic hydrolysis casein (AHC). The highest rates of callus induction (97.50%), embryogenic callus formation (66.88%), and regeneration (55.94%) were obtained with the supplemental compounds of 3.0 mg·L−1 2,4-D and 10.0 mg·L−1 CuSO4 for callus induction; with 3.0 mg·L−1 2,4-D, 15 mg·L−1 CuSO4, and 1.0 g·L−1 AHC for embryogenic callus formation; and with 8.0 mg·L−1 6-BA, 0.2 mg·L−1 KT, 0.5 mg·L−1 NAA, and 10 mg·L−1 CuSO4 for plant regeneration. Embryogenic calli were subjected to 2 or 6 °C treatment for 90 days for in vitro cold selection of somaclonal variation. Plants regenerated from calli surviving cold treatment (cold-selected) for 45 or 60 days were then exposed to low temperatures [15/10 or 5/3 °C (day/night)]. Plant variants derived from cold-selected calli exhibited significant improvement in their tolerance to low temperature of either 15/10 or 5/3 °C (day/night), as manifested by higher turf quality, leaf chlorophyll content, and membrane stability as well as lower levels of lipid peroxidation compared with the control plants. This study demonstrated the feasibility of in vitro selection for cold tolerance in seashore paspalum. The cold-tolerant variants could be useful germplasm for breeding programs and further molecular characterization of cold tolerance mechanisms.
A Transcriptomic Analysis of Sensitive and Tolerant Citrus Rootstocks under Natural Iron Deficiency Conditions
Authors: Licciardello Concetta , Torrisi Biagio , Allegra Maria , Sciacca Fabiola , Roccuzzo Giancarlo , Intrigliolo Francesco , Recupero Giuseppe Reforgiato , Tononi Paola , Delledonne Massimo , Muccilli Vera
Published: January 2019

Iron chlorosis is one of the most serious abiotic stresses affecting citrus (Citrus sp.) culture in the Mediterranean Basin. A trial was performed with potted tolerant and sensitive rootstocks that were grown in volcanic and calcareous soils. Microarray analysis allowed for the identification of differentially expressed genes putatively involved in iron (Fe) deficiency. Most of the differentially expressed genes isolated from the root tips were of unknown function; the remaining genes were related to the oxidative stress response (e.g., glutathione peroxidase), hormone metabolism and signaling (e.g., small auxin up RNA family protein genes), biological regulation, protein turnover, and the tricarboxylic acid cycle (e.g., aconitase). Additionally, the majority of the Fe stress-related genes expressed in the sensitive Swingle citrumelo (Citrus paradisi × Poncirus trifoliata) and tolerant Carrizo citrange (Citrus sinensis × P. trifoliata) rootstocks identified using real-time reverse transcription–polymerase chain reaction (RT-PCR) were related to regulation, the oxidative stress response, and hormone metabolism and signaling, thereby confirming the array data. Furthermore, validation of the differentially expressed genes in seven tolerant and sensitive rootstocks grown in a field trial under chlorotic conditions was performed. In general, the gene expression profiles reflect the different responses of rootstocks, possibly as a result of the various genetic mechanisms involved in the response to Fe deficiency. Moreover, the expression of aconitase was analyzed in the roots and juice to evaluate the implication of the different aconitase isoforms (Aco), which are derived from specific cellular compartments, in the different tissues. The involvement of the mitochondrial isoform (Aco2) was directly correlated with the acidity of the juice, whereas the cytosolic one (Aco3), which corresponds to the aconitase isolated during the microarray analysis, was found specifically in the roots.
Freezing Tolerance Attributes during Spring Deacclimation for Three Asparagus Cultivars with Varying Adaptation to Southern Ontario
Authors: Panjtandoust Mahmoud , Wolyn David J.
Published: January 2019

Winterhardiness in asparagus (Asparagus officinalis) may be related to proper cold acclimation and induction of freezing tolerance in the fall, levels and maintenance of freezing tolerance in the winter, and the timing of deacclimation in the spring. Premature deacclimation and the inability to reacclimate could result in crown damage from spring freeze-thaw cycles. A field experiment was conducted, replicated over 2 years, to determine how three cultivars with varying adaptation to southern Ontario deacclimate in the spring by assessing LT50 (the temperature at which 50% of plants die) and biochemical and physiological parameters associated with freezing tolerance. ‘UC 157’ (UC), the least-adapted cultivar, deacclimated after soil temperatures rose above freezing; LT50 values increased linearly over time and were unaffected by fluctuations in soil temperature. ‘Jersey Giant’ (JG), a cultivar with moderate adaptation, rapidly deacclimated with increased soil temperature but appeared to partially reacclimate as temperatures decreased. For ‘Guelph Millennium’ (GM), the most-adapted cultivar, LT50 values did not change, maintaining the greatest levels of freezing tolerance during the spring sampling period. Although LT50 values did not differ among cultivars on the first spring sampling date, ranking for freezing tolerance at the final sampling in each year was GM>JG>UC, which is consistent with adaptation. Rhizome traits were most associated with freezing tolerance and included high concentrations of low-molecular-weight fructans (LFs), glucose, and proline and low percentage water and sucrose concentration. Overall, data suggest that the timing of deacclimation and loss of freezing tolerance in the spring may significantly affect winterhardiness; cultivars that lose freezing tolerance early and cannot reacclimate could suffer most from late spring freeze-thaw cycles.
Factors Affecting Mechanical Properties of the Skin of Sweet Cherry Fruit
Authors: Brüggenwirth Martin , Knoche Moritz
Published: January 2019

The skins of all fruit types are subject to sustained biaxial strain during the entire period of their growth. In sweet cherry (Prunus avium L.), failure of the skin greatly affects fruit quality. Mechanical properties were determined using a biaxial bulging test. The factors considered were the following: ripening, fruit water relations (including turgor, transpiration, and water uptake), and temperature. Excised discs of fruit skin were mounted in a custom elastometer and pressurized from their anatomically inner surfaces. This caused the skin disc to bulge outwards, stretching it biaxially, and increasing its surface area. Pressure (p) and biaxial strain (ε) due to bulging were quantified and the modulus of elasticity [E (synonyms elastic modulus, Young’s modulus)] was calculated. In a typical test, ε increased linearly with p until the skin fractured at pfracture and εfracture. Stiffness of the skin decreased in ripening late stage III fruit as indicated by a decrease in E. The value of pfracture also decreased, whereas that of εfracture remained about constant. Destroying cell turgor decreased E and pfracture relative to the turgescent control. The E value also decreased with increasing transpiration, while pfracture and (especially) εfracture increased. Water uptake had little effect on E, whereas εfracture and pfracture decreased slightly. Increasing temperature decreased E and pfracture, but had no effect on εfracture. Only the instantaneous elastic strain and the creep strain increased significantly at the highest temperatures. A decrease in E indicates decreasing skin stiffness that is probably the result of enzymatic softening of the cell walls of the skin in the ripening fruit, of relaxation of the cell walls on eliminating or decreasing turgor by transpiration and, possibly, of a decreasing viscosity of the pectin middle lamellae at higher temperatures. The effects are consistent with the conclusion that the epidermal and hypodermal cell layers represent the structural “backbone” of the sweet cherry fruit skin.
Single Nucleotide Polymorphisms and Indel Markers from the Transcriptome of Garlic
Authors: Havey Michael J. , Ahn Yul-Kyun
Published: January 2019

Garlic (Allium sativum) is cultivated worldwide and appreciated for its culinary uses. In spite of primarily being asexually propagated, garlic shows great morphological variation and adaptability to diverse production environments. Molecular markers and phenotypic characteristics have been used to assess the genetic diversity among garlics. In this study, we undertook transcriptome sequencing from a single garlic plant to identify molecular markers in expressed regions of the garlic genome. Garlic sequences were assembled and selected if they were similar to monomorphic sequences from a doubled haploid (DH) of onion (Allium cepa). Single nucleotide polymorphisms (SNPs) and insertion–deletion (indel) events were identified in 4355 independent garlic assemblies. A sample of the indels was verified using the original complementary DNA (cDNA) library and genomics DNAs from diverse garlics, and segregations confirmed by sexual progenies of garlic. These molecular markers from the garlic transcriptome should be useful for estimates of genetic diversity, identification and removal of duplicate accessions from germplasm collections, and the development of a detailed genetic map of this important vegetable crop.