bluuebunny/crossref_metadata_2025 huggingface dataset:
Backcross Introgression of the Cucumis hystrix Genome Increases Genetic Diversity in U.S. Processing Cucumber
Authors: Delannay Isabelle Y. , Staub Jack E. , Chen Jin Feng
Published: January 2019

The genetic base of commercial cucumber (Cucumis sativus L.) is extremely narrow (about 3%–8% polymorphism). Wide-based crosses within C. sativus [i.e., C. sativus var. sativus × C. sativus var. hardwickii (R.) Alef.] and interspecific hybridization attempts before 1995 have not substantially increased genetic diversity for plant improvement. However, in 1995, an amphidiploid (Cucumis hytivus Chen and Kirkbride) was derived from a C. sativus × Cucumis hystrix Chakr. mating. A derivative of this amphidiploid was used herein to broaden the genetic base of cucumber through backcross introgression [(C. sativus × C. hytivus) × C. sativus]. Initially, the combining ability of eight genetically diverse lines was investigated for days to anthesis (DA), sex expression (SEX), lateral branch number (LBN), fruit per plant (FP), fruit length:diameter ratio (L:D), and salt-processing ability [i.e., processed fruit color (exterior and interior), shape, and seed cavity characteristics]. Based on the combining ability, inbred backcross lines [IBL (BC2S3)] were developed from an original gynoecious determinate line WI 7023A [C. sativus (recurrent parent)] × monoecious indeterminate line WI 7012A (C. sativus × C. hytivus derived) mating, where 30 of 392 (8%) BC1 progeny were selected based on their diversity at 16 mapped marker loci. These progeny were used to develop BC2 progeny, which were then self-pollinated without further selection to produce 94 IBL. These IBL were genotyped and evaluated in the open field in two plantings in 2008 for DA, SEX, LBN, leaf size, FP, and L:D. The genetic distance (GD) between parental lines was 0.85, and the GD among IBL ranged between 0.16 and 0.75. Multivariate analyses indicated that IBL differed from parental lines and possessed considerable morphological and genotypic diversity that could be used to broaden the genetic base of commercial U.S. processing cucumber.
Profiling the Expression of Genes Related to Ethylene Biosynthesis, Ethylene Perception, and Cell Wall Degradation during Fruit Abscission and Fruit Ripening in Apple
Authors: Li Jianguo , Zhu Hong , Yuan Rongcai
Published: January 2019

The expression of genes for ethylene biosynthesis, ethylene perception, and cell wall degradation in the fruit cortex and fruit abscission zone (FAZ) was examined in relation to preharvest fruit abscission (PFA) and fruit ripening in ‘Golden Delicious’ and ‘Fuji’ apple (Malus ×domestica Borkh.). PFA, fruit ethylene production, and fruit softening increased rapidly during fruit ripening in ‘Golden Delicious’ apples, whereas no PFA, little fruit ethylene, and gradual fruit softening were recorded in ‘Fuji’ apples. The transcript levels of 1-aminocyclopropane-1-carboxylate (ACC) synthase genes, MdACS1, MdACS3, and MdACS5A, increased rapidly in the fruit cortex of ‘Golden Delicious’ apples during ripening, but not in ‘Fuji’ apples. However, only the level of MdACS5A mRNA was up-regulated in the FAZ of ‘Golden Delicious’ apples. The transcript level of ACC oxidase gene, MdACO1, increased in the fruit cortex for both cultivars but increased only in the FAZ of ‘Golden Delicious’ apples. Expression of the ethylene receptor genes, MdETR1, MdETR2, MdERS1, and MdERS2, increased in the fruit cortex for both cultivars, but only MdETR2 and MdERS2 increased in the FAZ of ‘Golden Delicious’ apples. The transcript levels of MdPG2, a polygalacturonase gene (PG), and MdEG1, a β-1,4-glucanase gene, markedly increased only in the FAZ of ‘Golden Delicious’ apples, whereas only MdPG1 rapidly increased in the fruit cortex of ‘Golden Delicious’ apples. Our results suggested that MdACS5A, MdACO1, MdPG2, and MdEG1 in the FAZ might be related to the difference in PFA between these two cultivars, whereas MdACS1 and MdPG1 were associated with fruit softening.
Ploidy Levels, Relative Genome Sizes, and Base Pair Composition in Magnolia
Authors: Parris J. Kevin , Ranney Thomas G. , Knap Halina T. , Baird W. Vance
Published: January 2019

The genus Magnolia includes over 250 species that range in ploidy level from diploid to hexaploid. Although there is basic information on ploidy levels of various species, sampling has been limited and little information on specific cultivars and hybrids is available. The objective of this research was to determine relative genome sizes and relationships to ploidy levels among a diverse collection of species, hybrids, and cultivars using flow cytometry. Nuclei were extracted, stained with 4′, 6-diamidino-2-phenylindole (DAPI), and analyzed using a flow cytometer. Relative genome sizes were determined using Pisum sativum as the reference genome. Genome size was calibrated with ploidy level for species with documented chromosome numbers. Relative genome size for a given ploidy level varied significantly among most taxonomic sections indicating these groups have undergone considerable genomic divergence. These data also indicate it is desirable to calibrate ploidy level with relative genome size for each section separately. Within a section, relative 2C genome sizes, for a given ploidy level, had narrow ranges and could be used to clearly distinguish between euploid levels. Genome size estimates, determined with DAPI or propidium iodide fluorochromes, varied (by 0% to 14%) as a function of species and base pair (bp) composition. Both methods were suitable for determining euploid level. Base pair composition of representative Magnolia species ranged from 61.6% to 63.91% AT. Genome sizes and ploidy levels are presented for a broad range of species and hybrids within genus Magnolia. This information also provides further insight into reproductive biology, substantiation of numerous hybrids and induced polyploids, and comparison of methods for determining genome size that will help facilitate the development of improved hybrids in the future.
Developing Moisture Characteristic Curves and Their Descriptive Functions at Low Tensions for Soilless Substrates
Authors: Altland James E. , Owen James S. , Fonteno William C.
Published: January 2019

Moisture characteristic curves (MCC) relate the water content in a substrate to the matric potential at a given tension or height. These curves are useful for comparing the water-holding characteristics of two or more soils or soilless substrates. Most techniques for developing MCC are not well suited for measuring low tensions (0 to 100 cm H2O) in coarse substrates used in container nursery production such as those composed of bark. The objectives of this research were to compare an inexpensive modified long column method with an established method for creating low-tension MCCs and then to determine the best model for describing MCCs of bark-based soilless substrates. Three substrates composed of douglas fir (Pseudotsuga menziesii) bark alone or mixed with either peatmoss or pumice were used to compare models. Both methods described differences among the three substrates, although MCC for each method differed within a substrate type. A four-parameter log-logistic function was determined to be the simplest and most explanatory model for describing MCC of bark-based substrates.
Genetic Mapping of PcDw Determining Pear Dwarf Trait
Authors: Wang Caihong , Tian Yike , Buck Emily J. , Gardiner Susan E. , Dai Hongyi , Jia Yanli
Published: January 2019

European pear (Pyrus communis) ‘Aihuali’ carrying the dwarf character originating from ‘Nain Vert’ was crossed with ‘Chili’ (Pyrus bretschneideri). A total of 352 F1 progenies was produced to investigate the inheritance of the dwarf trait, and 111 of these were used to develop molecular markers. Chi-square analysis showed that the character fitted a 1:1 ratio indicative of a single dominant gene, which we have named PcDw. Using a bulked segregant analysis approach with 500 random amplified polymorphic DNA (RAPD) and 51 simple sequence repeat (SSR) markers from pear (Pyrus pyrifolia and P. communis) and apple (Malus ×domestica), four markers were identified as cosegregating with the dwarf character. Two of these were fragments produced by the S1212 and S1172 RAPD primers, and the other two were the pear SSR markers KA14 and TsuENH022. The RAPD markers were converted into sequence-characterized amplified regions (SCARs) and designated S1212-SCAR318 and S1172-SCAR930 and, with the SSR markers KA14 and TsuENH022, were positioned 5.9, 9.5, 8.2, and 0.9 cM from the PcDw gene, respectively. Mapping of the KA14 and TsuENH022 markers enabled the location of the PcDw gene on LG 16 of the pear genetic linkage map.
Evaluation of Genetic Diversity and Pedigree within Crapemyrtle Cultivars Using Simple Sequence Repeat Markers
Authors: Wang Xinwang , Wadl Phillip A. , Pounders Cecil , Trigiano Robert N. , Cabrera Raul I. , Scheffler Brian E. , Pooler Margaret , Rinehart Timothy A.
Published: January 2019

Genetic diversity was estimated for 51 Lagerstroemia indica L. cultivars, five Lagerstroemia fauriei Koehne cultivars, and 37 interspecific hybrids using 78 simple sequence repeat (SSR) markers. SSR loci were highly variable among the cultivars, detecting an average of 6.6 alleles (amplicons) per locus. Each locus detected 13.6 genotypes on average. Cluster analysis identified three main groups that consisted of individual cultivars from L. indica, L. fauriei, and their interspecific hybrids. However, only 18.1% of the overall variation was the result of differences between these groups, which may be attributable to pedigree-based breeding strategies that use current cultivars as parents for future selections. Clustering within each group generally reflected breeding pedigrees but was not supported by bootstrap replicates. Low statistical support was likely the result of low genetic diversity estimates, which indicated that only 25.5% of the total allele size variation was attributable to differences between the species L. indica and L. fauriei. Most allele size variation, or 74.5%, was common to L. indica and L. fauriei. Thus, introgression of other Lagestroemia species such as Lagestroemia limii Merr. (L. chekiangensis Cheng), Lagestroemia speciosa (L.) Pers., and Lagestroemia subcostata Koehne may significantly expand crapemyrtle breeding programs. This study verified relationships between existing cultivars and identified potentially untapped sources of germplasm.
Anomalies in Structure, Growth Characteristics, and Nutritional Composition as Induced by 2,4-Dichlorophenoxy Acetic Acid Drift Phytotoxicity in Grapevine Leaves and Clusters
Authors: Bondada Bhaskar R.
Published: January 2019

Drift hazards and the effects of 2,4-dichlorophenoxy acetic acid (2,4-D) spray drift on woody perennials have been commonly observed since its discovery in the 1940s; however, 2,4-D-induced phytotoxicity, morphogenesis, and structural and compositional anomalies of their vegetative and reproductive structures are not well understood. Healthy and 2,4-D-injured shoots of grapevine (Vitis vinifera L.) from a commercial vineyard experiencing persistent drift were compared. The morphoanatomy of healthy and 2,4-D-injured leaves and berries were examined using light and scanning electron microscopy (SEM). Along with the microscopic examinations, stomatal conductance (gS), leaf growth characteristics, and mineral composition were also determined. The morphoanatomy of healthy leaves resembled that of a typical angiospermic leaf. By contrast, shoots exposed to 2,4-D phytotoxicity displayed epinastic behavior and developed grotesquely malformed leaves that were thick, fan-shaped, enated, and interveinally puckered as a result of fasciation of veins. The cellular architecture, including the vascular bundles, was altered as a result of the formation of parenchymatous replacement tissues. The gS, leaf index, leaf area, and petiole dimensions were significantly reduced in the 2,4-D-injured leaves. 2,4-D-injured leaves; however, accumulated high levels of nitrogen, potassium, and iron compared with healthy leaves. The clusters (fertilized inflorescences) of the injured shoots developed epinastic curvature and predominantly bore live green ovaries (seedless unripened pseudofruit) instead of true berries (fertilized fully ripened fleshy fruit). These abnormalities are expected to severely perturb the vital functions of photosynthesis and transpiration as evidenced by low gS and poor fruit set leading to senescence and localized necrosis ultimately causing death of current-season shoots.
Cold Acclimation Attributes of Two Asparagus Cultivars with Varying Patterns of Fern Senescence
Authors: Landry Erik J. , Wolyn David J.
Published: January 2019

Adequate winterhardiness is crucial for yield stability of asparagus (Asparagus officinalis) cultivars in southern Ontario, Canada, and could be influenced by pattern of the fall fern senescence. Fern of cultivar Guelph Millennium (GM) turns yellow or senesces by mid-October, before that of cultivar Jersey Giant (JG), which often remains green until a killing frost. Early fern senescence could be a signal for cold acclimation competency and consequently winterhardiness, explaining the superior stand longevity and yield observed for GM compared with JG. A field experiment was conducted from mid-August to November to measure physiological parameters related to cold acclimation in fern, rhizome, and storage roots. During fall, fern chlorophyll concentration, rhizome nitrogen concentration, percent water of the crown, and storage root LT50 (temperature at which 50% cell death occurs) decreased. Cultivars did not differ for storage root percent water; however, values were smaller (greater dehydration) for GM than JG in the rhizome. At the end of the sampling period, GM had higher and lower concentrations of rhizome low-molecular-weight, non-structural carbohydrates and sucrose, respectively, than JG, which could support a hypothesis of greater winterhardiness in GM. Storage root LT50 values of –19 °C and the lack of cultivar differences for this trait, in conjunction with differences between GM and JG for rhizome traits thought to be important for freezing tolerance, suggest characteristics of the rhizome in conjunction with timing of fern senescence may be important in cold acclimation of asparagus.
Ascorbic Acid Accumulation and Expression of Genes Involved in Its Biosynthesis and Recycling in Developing Apple Fruit
Authors: Li Mingjun , Chen Xuesen , Wang Pingping , Ma Fengwang
Published: January 2019

The objective of this study was to investigate ascorbic acid (AsA) accumulation, mRNA expression of genes involved in AsA biosynthesis as well as recycling, activity of key enzymes, and the relationship of them to AsA levels during the development of apple fruit (Malus ×domestica cv. Gala). AsA concentration, which mainly depends on biosynthesis, was the highest in young fruit post-anthesis and then decreased steadily toward maturation. However, AsA continued to accumulate over time because of the increase in fruit mass. Transcript levels of guanosine diphosphate (GDP)-L-galactose phosphorylase, GDP-mannose pyrophosphorylase, D-galacturonate reductase, and the post-transcriptionally regulated L-galactono-1,4-lactone dehydrogenase were not correlated with AsA accumulation in apple. In contrast, patterns of expression for L-galactose dehydrogenase, L-galactose-1-phosphate phosphatase, and GDP-mannose-3′,5′-epimerase showed a pattern of change similar to that of AsA accumulation. Although activities and expression levels of monodehydroascorbate reductase and dehydroascorbate reductase in fruit, which had less capacity for AsA recycling, were much lower than in leaves, they were not clearly correlated with AsA level during fruit development.
Antioxidant Enzyme Activities and Gene Expression Patterns in Leaves of Kentucky Bluegrass in Response to Drought and Post-drought Recovery
Authors: Xu Lixin , Han Liebao , Huang Bingru
Published: January 2019

The objectives of this study were to examine antioxidant enzyme responses to drought stress and rewatering at both enzymatic activity and transcript levels and to determine the major antioxidant processes associated with drought tolerance and post-drought recovery for a perennial grass species, kentucky bluegrass (Poa pratensis). Antioxidant enzyme responses to drought and rewatering in a drought-tolerant cultivar (Midnight) and a drought-sensitive cultivar (Brilliant) were compared in a growth chamber. Plants were exposed to 22 days of drought stress for ‘Midnight’ and 18 days for ‘Brilliant’ before rewatering to allow the leaf relative water content (RWC) of both cultivars to drop to the same level. ‘Midnight’ exhibited higher photochemical efficiency (Fv/Fm) and lower electrolyte leakage compared with ‘Brilliant’ when at the same water deficit status (26% to 28% RWC). After 6 days of rewatering, all physiological parameters returned to the control level for ‘Midnight’, but only Fv/Fm fully recovered for ‘Brilliant’. The transcript level of cytosolic copper/zinc superoxide dismutase (cyt Cu/Zn SOD) and ascorbate peroxidase (APX) was significantly higher in ‘Midnight’ than in ‘Brilliant’ when exposed to the same level of water deficit (26% to 28% RWC), suggesting that SOD and APX could be involved in scavenging oxidative stress-induced reactive oxygen species in kentucky bluegrass through changes in the level of gene expression. Significantly higher activities of APX, monodehydroascorbate reductase, glutathione reductase, and dehydroascorbate reductase as well as lower lipid peroxidation levels were observed in ‘Midnight’ versus ‘Brilliant’ when exposed to drought. However, the activities of SOD, catalase (CAT), and guaiacol peroxidase (POD) did not differ between the two cultivars. After 6 days of rewatering, ‘Midnight’ displayed significantly higher activity levels of CAT, POD, and APX compared with ‘Brilliant’. The enzyme activity results indicate that enzymes involved in the ascorbate–glutathine cycle may play important roles in antioxidant protection to drought damage, whereas CAT, POD, and APX could be associated with better post-drought recovery in kentucky bluegrass.
Immunohistochemical Localization of Indole-3-Acetic Acid During Induction of Adventitious Root Formation from Cotyledon Explants of Walnut
Authors: Dong Ningguang , Wang Qingmin , Zhang Junpei , Pei Dong
Published: January 2019

Cotyledon explants of walnut (Juglans regia) have been shown to generate adventitious roots on growth regulator-free medium. The spatial distribution of endogenous indole-3-acetic acid (IAA) and its dynamic changes during adventitious root formation were investigated using an in situ immunohistochemical approach. Before root induction, IAA signal was distributed throughout the freshly excised cotyledon explants. During provascular bundle differentiation, the IAA signal was mainly located in the provascular bundles. At the stage of annular meristematic zones formation, the IAA signal was mainly distributed in the meristematic zones and decreased in the vascular bundles and cotyledonous parenchyma. As primordia formed, the IAA signal became localized in the root primordia and gradually disappeared in the meristematic zones. In emerging roots, the IAA signal was mainly localized in the root cap and root meristem. These results suggest that accumulation of IAA in the provascular bundles may induce vascular differentiation and the increase in IAA through meristematic zones may be responsible for the adventitious root formation from walnut cotyledons. The direct evidence presented here indicates that IAA accumulated in the meristematic zones is not the sole signal needed to induce adventitious root.
Effects of Simulated Dark Shipping on the Carbohydrate Status and Post-shipping Performance of Phalaenopsis
Authors: Hou Jiunn-Yan , Miller William B. , Alex Chang Yao-Chien
Published: January 2019

Phalaenopsis is one of the most important ornamental crops and is frequently transported between continents. In this study, the effects of the duration and temperature of simulated dark shipping (SDS) and the temperature difference between cultivation greenhouses and shipping containers on the carbohydrate status and post-shipping performance were investigated. With a prolonged SDS from 0 to 40 days at 20 °C, the percentage of the vegetative Phalaenopsis Sogo Yukidian ‘V3’ plants with yellowed leaves increased from 0% to 50%, and the total carbohydrate contents in the shoot and roots gradually decreased over time. Furthermore, roots had greater reductions in glucose and fructose concentrations than the shoot after 40 days of SDS. After 7 days of SDS, the youngest bud and the nearly open bud on blooming plants of Phalaenopsis amabilis were found to be the most negatively affected among flowers and buds of all stages. These buds had lower soluble sugar concentrations and flower longevities compared with those of unshipped plants. The results of a temperature experiment showed that yellowing of the leaves and chilling injury (CI) occurred in Phalaenopsis Sogo Yukidian ‘V3’ after 21 days of SDS at 25 and 15 °C, respectively, regardless of pre-shipping temperature acclimation. However, 10 days of acclimation at 25/20 °C (day/night) before SDS reduced CI and reduced the time to inflorescence emergence. Higher accumulations of sucrose in the shoot and glucose and fructose in roots were found after 21 days of SDS at 15 °C compared with those at 25 and 20 °C. In conclusion, the carbohydrate status of Phalaenopsis was positively related to the post-performance quality. A reduction in the commercial quality after SDS may be attributed to a decline in carbohydrates. The optimal temperature for long-term dark shipping is 20 °C, and we recommend providing 10 days of lower-temperature acclimation (25/20 °C) before shipping to enhance the chilling tolerance and to promote early spiking of Phalaenopsis plants.
Characterization of Endogenous Gibberellins and Molecular Cloning of a Putative Gibberellin 3-Oxidase Gene in Bunching Onion
Authors: Shiraiwa Nobutaka , Kikuchi Kaori , Honda Ichiro , Shigyo Masayoshi , Yamazaki Hiroko , Tanaka Daisuke , Tanabe Kenji , Itai Akihiro
Published: January 2019

To clarify the role of gibberellin (GA) in the growth of bunching onion (Allium fistulosum), identification of endogenous GAs and expression analysis of a putative gibberellin 3-oxidase (AfGA3ox1) were conducted. GA1, GA3, GA4, GA9, GA20, and GA34 were identified with levels of GA4 and GA9 being higher than those of GA1, GA3, and GA20. The young seedlings were clearly elongated by exogenous GA4 treatment but not by GA3. These results indicate that the 13-non-hydroxylation pathway of GA biosynthesis may be predominant in shoots with GA4 playing an important role in the growth of bunching onion. Expression of AfGA3ox1 was higher in leaf sheaths than leaf blades during vegetative growth. In reproductive organs, expression of AfGA3ox1 was higher at early and middle development stages in the stalks but was detected at a late development stage in the umbels. AfGA3ox1 was mapped on chromosome 7A from shallot, a bunching onion-related species.
Applications of Plant Growth Regulators to Container-grown Citrus Trees Affect the Biology and Behavior of the Asian Citrus Psyllid
Authors: Tsagkarakis Antonios E. , Rogers Michael E. , Spann Timothy M.
Published: January 2019

Asian citrus psyllid [ACP (Diaphorina citri)] is an important pest of citrus (Citrus sp.) in many citrus-growing regions of the world because of its status as the vector of huanglongbing disease [HLB (citrus greening)]. There are currently no HLB-resistant citrus genotypes and no proven treatments for the disease; thus, vector control through the use of frequent prophylactic pesticide applications is key to managing the spread of this disease. However, this practice is unsustainable and other means of altering ACP biology or reducing populations are needed. To this end, six plant growth regulators (PGRs) were tested to determine their effect on citrus tree vegetative growth and the subsequent impact on the biology of ACP. In greenhouse and growth chamber experiments, ACP reared on trees treated with prohexadione calcium and mefluidide exhibited significant reductions in both fecundity and survivorship, whereas uniconazole affected only fecundity and paclobutrazol affected only survivorship. No significant effects of PGRs on adult ACP weight were observed except on uniconazole-treated trees. No eggs were laid on dikegulac sodium-treated trees; however, this was likely the result of severe phytotoxicity rather than a true PGR effect. Oviposition rate was lower on all the PGR-treated trees, except chlormequat chloride under greenhouse conditions, compared with untreated control trees. In general, oviposition was delayed on PGR-treated trees compared with untreated controls. The observed changes in ACP biology and behavior after PGR treatment were not the result of a reduction in the number of suitable oviposition sites (i.e., growth reduction) or toxicity of the PGRs to ACP, suggesting there were PGR-induced plant biochemical changes that altered host plant quality. Leaf nutrient analyses and photosynthesis indicated that there were no correlative changes in plant nutrient status or carbon assimilation that led to the changes in ACP behavior, although it is possible that phloem-specific nutrient or carbohydrate changes could have occurred that were not detected in our whole-leaf analyses. These results support previous studies in which the fitness of various insect species has been affected by PGR applications, but more research is needed to understand the changes in plant chemistry that are responsible.
Exogenous Glycine Betaine Ameliorates the Adverse Effect of Salt Stress on Perennial Ryegrass
Authors: Hu Longxing , Hu Tao , Zhang Xunzhong , Pang Huancheng , Fu Jinmin
Published: January 2019

Salinity stress may involve the accumulation of glycine betaine (GB). The objective of this study was to examine whether exogenous GB would ameliorate the detrimental effect of salinity stress on perennial ryegrass (Lolium perenne). The grass was subjected to two salinity levels (0 and 250 mm NaCl) and three GB levels (0, 20, and 50 mm). Salinity resulted in a remarkable decrease in vertical shoot growth rate (VSGR), shoot and root fresh weight, relative water content (RWC), relative transpiration rate (Tr), and chlorophyll (Chl) content, superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities. Plants subjected to salt exhibited an increase in leaf electrolyte leakage (EL), lipid peroxidation (MDA), and proline content. Application of GB reduced EL, MDA, and proline content in salt-stressed plants. Perennial ryegrass subjected to salt stress plus GB had a greater level of VSGR, RWC, relative Tr, Chl content, and activities of SOD, CAT, and APX when compared with salt-stressed without GB. Salt stress increased Na+ and decreased K+ content, which resulted in a higher Na+/K+ ratio in perennial ryegrass. Application of 20 mm GB suppressed Na+ accumulation, whereas the K+ content was significantly increased in shoot, which led to a higher K+/Na+ ratio under saline conditions. These results suggested that GB-enhanced salt tolerance in perennial ryegrass was mainly related to the elevated SOD, CAT, and APX activity and alleviation of cell membrane damage by reducing oxidation of membrane lipid and improving the ion homeostasis under salt stress.
Differential Effects of Abscisic Acid and Glycine Betaine on Physiological Responses to Drought and Salinity Stress for Two Perennial Grass Species
Authors: Yang Zhimin , Yu Jingjin , Merewitz Emily , Huang Bingru
Published: January 2019

Abscisic acid (ABA) and glycine betaine (GB) may regulate plant responses to drought or salinity stress. The objectives of this controlled-environment study were to determine whether foliar application of ABA or GB improves turf quality under drought or salinity and whether improved stress responses were associated changes in antioxidant metabolism in two C3 turfgrass species, creeping bentgrass (Agrostis stolonifera) and kentucky bluegrass (Poa pratensis). Physiological parameters evaluated included turf quality, leaf relative water content, membrane electrolyte leakage (EL), membrane lipid peroxidation [expressed as malondialdehyde (MDA) content], and activity of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX). Abscisic acid and GB were both effective in mitigating physiological damage resulting from drought or salinity for both grass species, but effects were more pronounced on kentucky bluegrass. The most notable effects of ABA or GB application were the suppression of EL and MDA accumulation and an increase in APX, POD, and SOD activities after prolonged periods of drought (21 days) or salinity stress (35 days). These results suggest foliar application of ABA or GB may alleviate physiological damage by drought or salinity stress in turfgrass and the maintenance of membrane stability and active antioxidant metabolism could contribute to the positive effects in the stress mitigation effects.
Effect of Nitric Oxide on Proline Metabolism in Cucumber Seedlings under Salinity Stress
Authors: Fan Huai-Fu , Du Chang-Xia , Guo Shi-Rong
Published: January 2019

Nitric oxide (NO), an endogenous signaling molecule in plants and animals, mediates responses to abiotic and biotic stresses. This study was conducted in a nutrient solution to investigate 1) the effects of exogenous sodium nitroprusside (SNP), an NO donor, on free proline (Pro) and protein content; and 2) the enzymes involved in Pro metabolism [pyrroline-5-carboxylate synthetase (P5CS) and proline dehydrogenase (PDH)] in cucumber (Cucumis sativus) seedling leaves and roots under NaCl stress. The results showed that the increases in free Pro and protein were significantly higher in the 50 mm NaCl solution but highly significant with the addition of 100 μM SNP to the 50 mm NaCl solution for the entire treatment period. Moreover, leaves maintained higher levels of free Pro and protein content than roots throughout the experiments. The P5CS activity increased in the saline treatment compared with the control, and this increase was greater in the 50 mm NaCl + 100 μM SNP solution than in the other treatments. On the other hand, the PDH activity was inhibited under NaCl stress but the reduction in activity was greater in the 50 mm NaCl + 100 μM SNP solution than in the others. These findings suggest that Pro metabolism was significantly altered during the exogenously applied NO under salt stress and that this alteration prompted the accumulation of higher levels of free Pro, which, in turn, maintained the turgor in the cucumber seedlings and helped protect them from salt stress. Moreover, the toxic effects generated by 50 mm NaCl were partially overcome by the application of NO, which could be used as a potential growth regulator to improve plant salinity tolerance. Therefore, it was concluded that NO could alleviate salinity damage in cucumber seedlings by regulating Pro metabolism. Overall, the adverse effects of salt stress could be lessened by the exogenous application of NO to cucumber seedlings.
Genetic Diversity within Chinese Watermelon Ecotypes Compared with Germplasm from Other Countries
Authors: Sheng Yunyan , Luan Feishi , Zhang Faxing , Davis Angela R.
Published: January 2019

Genetic diversity among 95 watermelon (Citrullus lanatus) ecotypes was evaluated and compared with representative Chinese, American, Japanese, and Russian watermelon cultigens, landraces, and a wild watermelon relative (Trichosanthes kirilowii). Open-pollinated, hybrid, and inbred lines were included for most of the ecotypes and are hereafter collectively referred to as cultigens unless an ecotype group is being discussed. Morphological characteristics (including days to flower, female to male flower ratio, branch number, fruit length and diameter ratio, fruit soluble solid content, fruit yield, and simple sequence repeat (SSR) markers were used to estimate genetic diversity. Of 398 watermelon primer pairs tested, 9.5% (38) produced polymerase chain reaction amplicons in watermelon. Of these 38 primer pairs, the average number of polymorphic bands among the 96 cultigens was 2.4, even with 12 primer pairs demonstrating monomorphic banding patterns. Based on the SSR data, the genetic similarity coefficients were calculated and a dendrogram constructed. All cultigens were clustered to six groups. The wild species and landraces formed distant clusters from the cultivated watermelon. The genetic similarity coefficients within the Chinese cultigens ranged from 0.37 to 0.99, but except for a wild relative to watermelon, most cultigens were closely related. The genetic distance among non-Chinese cultigens ranged from 0.67 to 0.91 with an average of 0.88. When combined morphological traits and molecular traits were assessed, Russian and U.S. fruit were more genetically similar to each other than to Chinese and Japanese cultigens. Crossing Russian and/or U.S. cultigens with Chinese or Japanese cultigens should thus improve genetic diversity and introduce new traits for the resulting watermelon cultigens.
Pollen-mediated Gene Flow from Coreopsis tinctoria to Coreopsis leavenworthii: Inheritance of Morphological Markers and Determination of Gene Flow Rates as Affected by Separation Distances
Authors: Smith Sarah M. , Deng Zhanao
Published: January 2019

The genus Coreospsis is Florida’s state wildflower. One species, Coreopsis leavenworthii, is nearly endemic to Florida and is highly desirable for use in highway beautification. Maintaining genetic integrity is critical for C. leavenworthii producers, growers, and users. Coreopsis tinctoria is closely related to and shares similar habitats with C. leavenworthii in Florida. Previous studies indicated that the two species could hybridize and the F1 hybrids showed chromosomal aberrations and reduced pollen stainability. There has been strong concern that pollen-mediated gene flow from C. tinctoria could contaminate the gene pool and compromise the genetic integrity of C. leavenworthii. In the current study, hand pollination showed that C. leavenworthii and C. tinctoria were highly compatible. F1 hybrids were fertile and readily produced F2 and BC1 individuals. Inheritance studies indicated that the maroon spot on the ray flower is controlled by a single dominant allele and is homozygous in C. tinctoria. This spot serves as a reliable, easy-to-score morphological marker to detect pollen-mediated gene flow from C. tinctoria to C. leavenworthii. Following a discontinuous design, gene flow studies were conducted under field conditions in central Florida over 2 years. The highest rate of pollen-mediated gene flow from C. tinctoria to C. leavenworthii was 4.2% and occurred when the two species were grown 1.5 m apart. Gene flow from C. tinctoria to C. leavenworthii under field conditions followed a leptokurtic curve. Based on the obtained regression equation, separating the two species by 60 m or more could lower the pollen-mediated gene flow from C. tinctoria to minimal levels and protect the genetic integrity of C. leavenworthii.
Estimation of Genetic Parameters for 12 Fruit and Vegetative Traits in the University of Florida Strawberry Breeding Population
Authors: Whitaker Vance M. , Osorio Luis F. , Hasing Tomas , Gezan Salvador
Published: January 2019

The University of Florida strawberry (Fragaria ×ananassa) breeding population has been continuously improved by recurrent selection since 1968. However, there is a lack of information on genetic parameters that may inform breeding decisions. Parameters were estimated in this population using 19 full-sib families from a 5 × 4 factorial mating design plus six additional biparental crosses and 14 control genotypes including some of the parents. During the 2010–11 season, clonal replicates of the seedling and parental genotypes were distributed within and among two field locations in west–central Florida. Twelve commercially important traits were measured including fruit chemical traits (soluble solids content and titratable acidity), other fruit and yield traits (early and total marketable yields, proportion of total cull fruit, proportion of misshapen fruit, proportion water-damaged fruit, and shape score), and vegetative traits (plant height and total runners). Heritabilities, genotype by environment interaction, and multiple correlations (phenotypic, genotypic, and genetic) were estimated using general mixed model analyses. Narrow-sense heritabilities varied from low to moderate (h2 = 0.13 ± 0.07 to 0.32 ± 0.09) except for shape score (h2 = 0.06 ± 0.04) and total average weight (h2 = 0.52 ± 0.07). Broad-sense heritabilities were larger (H2 = 0.18 ± 0.03 to 0.53 ± 0.04), and for more than half of the traits, over 50% of the total genetic variation was non-additive. Large genetic and genotypic correlations were found for some traits, most notably between soluble solids content and early marketable yield (–0.68 ± 0.22). Genetic gains for this pair of traits based on a Monte Carlo simulation illustrated the tradeoff between these two traits, showing that a 27% increase in early yield could be obtained through selection but at the expense of an 8% decrease in soluble solids. However, moderate gains can be made in both traits using the appropriate index coefficients.
Role of Membrane Lipid Peroxidation, Enzymatic and Non-enzymatic Antioxidative Systems in the Development of Chilling Injury in Japanese Plums
Authors: Singh Sukhvinder Pal , Singh Zora
Published: January 2019

Chilling injury (CI) is a major postharvest constraint in the long-term cold storage, transportation, and distribution of japanese plums (Prunus salicina). The aim of the work was to explain the development and severity of CI in japanese plums based on the oxidative stress theory following time course analysis of enzymatic and non-enzymatic antioxidants. Changes in membrane lipid peroxidation and enzymatic and non-enzymatic antioxidative systems in japanese plum cultivar Blackamber were determined at weekly intervals during 5 weeks of cold storage at 0 °C and at 2-day intervals during poststorage simulated shelf conditions (21 ± 1 °C) for 8 days after each week of cold storage. Fruit respiration and ethylene production rates showed typical climacteric patterns after removal from cold storage and these rates were relatively high after 4 and 5 weeks compared with 0 to 3 weeks of storage. The CI symptoms first appeared after 3 weeks of cold storage after fruit had been transferred to simulated shelf conditions. The incidence and severity of CI intensified with increasing storage duration. The extent of lipid peroxidation indicated by concentration of thiobarbituric acid-reactive substances and membrane damage manifested as electrolyte leakage increased with increasing duration of storage and subsequent simulated shelf conditions. Membrane lipid peroxidation exhibited positive correlation with the severity of CI. Activities of primary antioxidant enzymes and the enzymes involved in the ascorbate–glutathione cycle were determined to explain the levels of reduced and oxidized forms of cellular redox buffers, ascorbate and glutathione. In response to chilling stress, antioxidative protection systems operated efficiently during the first 3 weeks of cold storage, but extended storage resulted in loss of ability to ameliorate increasing levels of oxidative stress. In this study, the comprehensive analyses of various metabolites and antioxidative systems explain the series of events involved in development of CI in japanese plums in support of the oxidative stress theory.
First Fruiting Intergeneric Hybrids between Citrus and Citropsis
Authors: Smith Malcolm W. , Gultzow Debra L. , Newman Toni K.
Published: January 2019

Fruiting hybrids are reported for the first time between the genera Citrus L. and Citropsis (Engl.) Swing. & M.Kell. Conventional hybridization using the recently described species Citrus wakonai P.I.Forst. & M.W.Sm. and Citropsis gabunensis (Engl.) Swing. & M.Kell. resulted in high rates of fruit set and seed formation. Although seed were only half normal size, over 90% germinated without the need for embryo rescue techniques. Plant losses were high during the first few months but after six months, the 327 surviving hybrids were potted on. These grew vigorously on their own roots and 35 of them flowered within two years of sowing. Plants flowered continuously but all were pollen-sterile and ovaries abscised shortly after petal fall. However, at 25 months, two newly flowering hybrids began setting fruit. The development, identification, morphology, breeding efficiency, and future implications of this unique germplasm are described.
Application of an Analog of 9, 10-ketol-octadecadienoic acid (KODA), Affected Flower Bud Formation and MdTFL1 and MdFT1 Gene Expressions in Apple Buds under Heavy-crop and Shade Conditions
Authors: Kittikorn Monrudee , Okawa Katsuya , Ohara Hitoshi , Kondo Satoru , Kotoda Nobuhiro , Wada Masato , Yokoyama Mineyuki , Ifuku Ohji , Murata Ariake , Watanabe Naoharu
Published: January 2019

Changes of endogenous 9, 10-ketol-octadecadienoic acid (KODA) concentrations, which is synthesized from linolenic acid by 9-lipoxygenase, were analyzed in apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] buds. In addition, the effects of 15, 16-chloro, hydroxy-9-hydroxy-10-oxo-12(Z)-octadecenoic acid (CKODA) application, which is an analog of KODA, on flower bud formation and the expression of MdTFL1 (terminal flower 1) and MdFT1 (flowering locus t 1) genes in apple buds were investigated in heavy-crop treatment (HCT) and under shade. An increase of endogenous KODA in the buds in the fruit-thinning treatment, which resulted in a higher proportion of flower bud formation than in HCT, was observed at 63 days after full bloom, but no such increase was found in HCT. In the shade-treated and heavy-crop trees, the expression of MdTFL1 in the buds to which CKODA was applied was lower than that in untreated buds. In contrast, under shade, the expression of MdFT1 in the CKODA-treated buds was higher than that in untreated buds. These results suggest that endogenous KODA may be associated with flower bud formation, and its application may be effective at improving the proportion of flower bud formation through its effect on MdTFL1 and MdFT1.
Differential Root Proteome Expression in Tomato Genotypes with Contrasting Drought Tolerance Exposed to Dehydration
Authors: Zhou Suping , Palmer Marsha , Zhou Jing , Bhatti Sarabjit , Howe Kevin J. , Fish Tara , Thannhauser Theodore W.
Published: January 2019

A comparative proteomics study using isobaric tags for relative and absolute quantitation (iTRAQ) was performed on a mesophytic tomato (Solanum lycopersicum) cultivar and a dehydration-resistant wild species (Solanum chilense) to identify proteins that play key roles in tolerance to water deficit stress. In tomato ‘Walter’ LA3465, 130 proteins were identified, of which 104 (80%) were repressed and 26 (20%) were induced. In S. chilense LA1958, a total of 170 proteins were identified with 106 (62%) repressed and 64 (38%) induced. According to their putative molecular functions, the differentially expressed proteins belong to the following subgroups: stress proteins, gene expression, nascent protein processing, protein folding, protein degradation, carbohydrate metabolism, amino acid and nucleotide metabolism, lipid metabolism, signal transduction, and cell cycle regulation. Based on changes in protein abundance induced by the dehydration treatment, cellular metabolic activities and protein biosynthesis were suppressed by the stress. In S. chilense, dehydration treatment led to elevated accumulation of proteins involved in post-transcriptional gene regulation and fidelity in protein translation including prefoldin, which promotes protein folding without the use of adenosine-5′-triphosphate (ATP), several hydrophilic proteins, and calmodulin in the calcium signal transduction pathway. Those protein changes were not found in the susceptible tomato, ‘Walter’. Within each functional protein group, proteins showing opposite changes (dehydration induced vs. repressed) in the two species were identified and roles of those proteins in conferring tolerance to water deficit stress are discussed. Information provided in this report will be useful for selection of proteins or genes in analyzing or improving dehydration tolerance in tomato cultivars.
Screening Antimicrobial Peptides In Vitro for Use in Developing Transgenic Citrus Resistant to Huanglongbing and Citrus Canker
Authors: Stover Ed , Stange Richard R. , McCollum T. Gregory , Jaynes Jesse , Irey Michael , Mirkov Erik
Published: January 2019

Huanglongbing {HLB [associated with Candidatus Liberibacter sp. (CLas)]} and asiatic citrus canker {ACC [causal organism Xanthomonas citri ssp. citri (XCC)]} are bacterial diseases that seriously threaten sustainability of the Florida citrus (Citrus sp.) industry. Sweet orange (Citrus sinensis) and grapefruit (Citrus paradisi) are highly susceptible to ACC and improvement through conventional breeding is a long-term process, making transgenic solutions attractive. No strong HLB resistance has been identified within cultivated citrus scion types: creation of transgenic citrus that would permit economic citrus production where HLB is endemic is a high priority. Little is known about the HLB pathosystem and thus broad-spectrum antimicrobial peptides (AMPs) have been the focus for current work, and identification of safe and effective transgenes is essential to our efforts. In vitro assessment of minimum inhibitory concentration (MIC) for 44 AMPs was conducted using Sinorhizobium meliloti and Agrobacterium tumefaciens as surrogates for the unculturable CLas because they are closely related alpha proteobacteria (class Alphaproteobacteria). XCC is also a gram-negative bacterium and was included in these analyses in anticipation that HLB and ACC resistance can be achieved with the same AMP transgene if expressed using non-tissue-specific promoters. Twenty AMPs from diverse sources were initially tested. AMPs with the lowest MICs included tachyplesin I from horseshoe crab (Tachypleus tridentatus), SMAP-29 from sheep (Ovis aries), D4E1 and D2A21 (which are synthetic AMPs derived through evaluation of critical amino acid residues in AMPs, overall peptide structure, and AMP effectiveness), the human (Homo sapiens) LL-37, and the honeybee (Apis mellifera) venom AMP melittin. These AMPs inhibited growth of all three test bacterial species at 1 μM or less. An additional 20 synthetic AMPs were designed based on structures of the most effective AMPs and seven of these showed effectiveness at 1 μM or less across all three test bacteria. Most AMPs were comparable in effectiveness across the three bacterial species, but some species × AMP interactions were observed. Hemolytic activity was assessed by exposure of porcine erythrocytes (from Sus scrofa) to the AMPs. Hemolysis from most AMPs was not significantly different from water, whereas melittin was highly hemolytic.