bluuebunny/crossref_metadata_2025 huggingface dataset:
Creeping Bentgrass Responses to Drought Stress and Polyamine Application
Authors: Shukla Vijaya , Ma Yingmei , Merewitz Emily
Published: January 2019

Polyamines (PAs) such as spermidine (Spd), spermine (Spm), and putrescine are involved in various biological functions including abiotic stress response. Whether PAs play an important role in cool-season turfgrass tolerance of drought stress is not well investigated. We have conducted a series of growth chamber (GC) studies including one hydroponic and two soil-based GC studies with creeping bentgrass (Agrostis stolonifera) ‘Penncross’ and ‘Penn-G2’ to determine whether exogenous application of PAs may affect plant growth and stress tolerance. Application of relatively low concentrations of Spd (500 or 750 μM) or Spm (500 μM) promoted tillering rates under optimal growth conditions in hydroponics. The same levels of PA treatments moderated the damages associated with drought stress in the soil-based GC studies. The most notable differences in drought response associated with PA treatment were increased membrane health. This was observed as greater photochemical efficiency, higher quantum yield, less electrolyte leakage, and less lipid peroxidation (malondialdehyde content) in PA-treated plants compared with control plants. The relatively low level of exogenous PAs used in this study did not have a major effect on plant water relations under drought stress. Canopy temperatures and soil moisture content were unaffected by any PA treatment; however, on some days during early drought stress, relative water content was significantly higher in PA-treated plants compared with controls. PA could play a major role in protecting photosynthetic and cellular membranes during drought stress of creeping bentgrass.
Molecular Genetic Variability of Spigelia marilandica and S. gentianoides
Authors: Hershberger Amanda J. , Jenkins Tracie M. , Robacker Carol
Published: January 2019

Despite the ecologic and ornamental potential of southeastern U.S. native Spigelia, little is known about the intraspecific or the interpopulation genetic variation. The southeastern U.S. native Spigelia habitat is becoming more and more fragmented as a result of human activity, making it imperative to gain an understanding of natural genetic variation among and within species and populations for the purpose of obtaining variability for plant breeding and preserve the genetic variability in Spigelia. Therefore, the objective of this study was to use amplified fragment length polymorphism analysis to determine interspecific and intraspecific genetic variation and to evaluate gene flow. Thirteen populations of two species of native Spigelia, S. marilandica (SM), S. gentianoides var. gentianoides (SGG), and S. gentianoides var. alabamensis (SGA), were analyzed using four primer pairs that amplified a total of 269 bands. Based on analysis of molecular variance and estimates of Nei’s coefficients of gene diversity (percentage of polymorphic loci, average genetic diversity within populations, average genetic diversity within species, and proportion of species genetic diversity attributed to among population variation), the majority of variation found in Spigelia occurs within populations. Both among-species and among-population variation was low, likely the effect of common ancestry as well as relatively frequent introgression among individuals (and populations) of Spigelia. When all individuals were evaluated using Nei’s unbiased genetic distances and viewed as a unweighted pair group method with arithmetic mean phenogram, three main groups were shown, one with two samples of SGG from one population, one with 13 individuals from both SGG populations used in this study, and one with all of the SM, SGA, and remaining SGG individuals. Further evaluation using STRUCTURE software showed introgression between populations and species, although all allele clusters have not entirely introgressed into all populations. The significance of these results is discussed in relation to breeding in Spigelia.
Coordinated Regulation of Biosynthetic and Regulatory Genes Coincides with Anthocyanin Accumulation in Developing Eggplant Fruit
Authors: Stommel John R. , Dumm Judith M.
Published: January 2019

Violet to black pigmentation of eggplant (Solanum melongena L.) fruit is caused by anthocyanin accumulation. Model systems demonstrate the role of regulatory genes in the control of anthocyanin biosynthesis. Anthocyanin structural gene transcription requires the expression of at least one member of each of three transcription factor families: MYB, MYC, and WD. To determine the molecular genetic basis for anthocyanin pigmentation in eggplant fruit, we used real-time polymerase chain reaction (PCR) to evaluate the expression of anthocyanin biosynthetic (Chs, Dfr, Ans) and regulatory (Myc, MybB, MybC, Wd) genes in S. melongena genotypes that produce fruit with dark violet (‘Classic’) or white (‘Ghostbuster’) coloration, respectively. Transcript levels and anthocyanin content were evaluated in fruit at various stages of development ranging from small post-anthesis fruit to full-sized marketable fruit. Anthocyanin content increased 9-fold in developing violet-colored ‘Classic’ fruit, whereas low but detectable concentrations were found in white ‘Ghostbuster’ fruit. Chs, Dfr, and Ans as well as MybC and Myc transcript levels were significantly higher in ‘Classic’ in comparison with ‘Ghostbuster’ fruit at comparable stages of fruit development with greatest differences observed for Ans transcript levels. MybC and Myc transcript levels increased in developing ‘Classic’ fruit coincident with increasing anthocyanin content. MybB and Wd transcript levels were not coordinated with changes in biosynthetic transcript levels or anthocyanin concentration.
Expression of Target Gene Hsp70 and Membrane Stability Determine Heat Tolerance in Chili Pepper
Authors: Usman Magaji G. , Rafii Mohd Y. , Ismail Mohd Razi , Malek Mohammad Abdul , Latif Mohammad Abdul
Published: January 2019

Experiments were carried out to study the mechanisms for heat tolerance in chili pepper (Capsicum annuum). To assess these mechanisms, six genotypes were evaluated for cellular membrane thermostability (CMT) and for HSP70 gene expression. The plants were grown in an experimental plant growth chamber. The mean value of CMT indicates that membrane integrity was not damaged by the high temperature treatment (50 °C) in most of the genotypes. The genotypes were classified as follows: heat-tolerant (greater than 60%), moderately tolerant (30% to 60%), and susceptible (less than 30%). The heat-tolerant plants recorded the highest CMTs at 89.27%, 88.03%, and 85.10% for AVPP0702, AVPP0116, and AVPP9905, respectively, which might be the reason for the change in their cell membrane thermostability. AVPP9703 and AVPP0002 showed CMTs of 15.87% and 18.43%, which might indicate their sensitivity to heat stress. Heat shock protein 70 kDa was identified and found to be differentially expressed under the heat stress. Under heat stress, significantly increased levels of the HSP70 gene were detected after 2 h of temperature treatment at 42 °C, which indicated that this gene is quickly and sharply induced by heat shock. This was true for all genotypes tested, which were significantly up-regulated by more than 36.9-, 7.10-, 3.87-, and 3-fold for AVPP0702, AVPP0116, AVPP0002, and AVPP9703, respectively. The HSP70 gene was found to be significantly down-regulated under heat stress in ‘Kulai’. AVPP0702, AVPP9905, and AVPP0116 could be considered as heat-tolerant genotypes, whereas ‘Kulai’ and AVPP9703 were found to be heat-sensitive genotypes in this investigation.
Novel Peach Flower Types in a Segregating Population from ‘Helen Borchers’
Authors: Chen Chunxian , Okie William R.
Published: January 2019

Several new peach (Prunus persica) flower types were discovered in an F2 segregating population from an open-pollinated, non-showy-flowered F1 seedling of ‘Helen Borchers’, a double-flowered ornamental cultivar. The novel flower types were white and red single-flowered, non-showy blooms, as well as double-flowered, non-showy red, pink, white, and yellow phenotypes. The double, non-showy flowers were very attractive, and resembled pom-pom chrysanthemums. Yellow flower color is unknown in peach. Flower type in the F2 family segregated ≈3:1 for non-showy (Sh_) vs. showy (shsh), for anthocyanin-present vs. anthocyanin-absent, and for pink (R_) vs. red (rr), independently. Flower petal number segregated at about 9:3:4 for classes single:semi-double:double. Although both parents were late flowering, the F1 was not. The F2 seedlings showed a wide range in time of flowering. Higher petal number was correlated with later bloom, although it is unclear whether this is due to linkage or developmental differences in the flowers with extra petals. These novel flower types might be useful as ornamentals, and for use in genetics and breeding studies. Microsatellite analysis of possible pollen donors revealed that ‘Oldmixon Free’, a non-showy-flowered peach cultivar, was likely the pollen parent of the F1.
Diallel Crossing Among Doubled Haploids of Cucumber Reveals Significant Reciprocal-cross Differences
Authors: Shen Jia , Dirks Rob , Havey Michael J.
Published: January 2019

Cytoplasmic effects on plant performance have been documented, but are not well understood. Cucumber (Cucumis sativus) is a useful plant for studying organellar effects on phenotypes because chloroplasts show maternal transmission and mitochondria paternal transmission. We produced doubled haploids (DH) from divergent cucumber populations, generated reciprocal hybrids in a diallel crossing scheme, measured fresh and dry weights of plants 22–30 days after planting seed, estimated combining abilities and heterosis for early plant growth, and assessed performance differences between reciprocal hybrids with identical nuclear genotypes. Across experiments, general and specific combining abilities and reciprocal effects, as well as their interactions with replicated experiments, were all highly significant (P < 0.001). Hybrids consistently out-performed parental lines with average heterosis over midparent values between 14% and 30%. A mitochondrial mutant (MSC3) showed negative effects when used as the male due to paternal transmission of mitochondria, but not as the female parent. Reciprocal hybrids among wild-type DH parents were identified that differed significantly (P = 0.032 to 0.001) for dry and fresh weights across experiments, indicating that cucumber breeders should evaluate both directions of crosses when producing hybrid cultivars. Reciprocal hybrids from DH cucumbers offer a unique opportunity to study biological factors contributing to significantly better performances, due to specific nuclear-cytoplasmic combinations and/or parent-of-origin effects in identical nuclear backgrounds.
Effects of Polyamines on Self-incompatibility-like Responses in Pollen Tubes of Citrus Cultivars, Banpeiyu and Hyuganatsu
Authors: Li Yiran , Uchida Asuka , Abe Akiha , Yamamoto Akihiro , Hirano Tomonari , Kunitake Hisato
Published: January 2019

Citrus is a genus with gametophytic self-incompatibility, which prevents fertilization by self-pollination. Polyamines (PAs), as a class of active small molecules, widely participate in various cellular activities. To investigate the effects of the changes in PA contents [putrescine, spermidine (SPD), and spermine] on pollen tube growth in self-incompatible (SI) plants, we cultured pollen of Citrus maxima ‘Banpeiyu’ and C. tamurana ‘Hyuganatsu’ in a Citrus mature pollen culture system and detected the PA content changes in pollen by high-performance liquid chromatography (HPLC) analysis during germination and after treatment with crude protein extracts of compatible or incompatible styles. We profiled the PA content changes during the germination course in pollen of ‘Banpeiyu’ and ‘Hyuganatsu’ by HPLC, and identified increases of free and perchloric-acid-insoluble SPD contents in pollen tubes in the incompatible treatment. Exogenous SPD treatment obviously increased the SPD contents in the pollen tube, inhibited pollen tube elongation, and resulted in some abnormal morphological alterations, such as tip inflation, tube content leakage and tip twist, which were observed in both ‘Banpeiyu’ and ‘Hyuganatsu’ pollen tubes exposed to incompatible treatment. This finding implied that SPD might participate in the SI response in Citrus.
Proteomic Analysis of Cold Stress Responses in Banana Leaves
Authors: Feng Ren-jun , Zhang Li-li , Wang Jing-yi , Luo Jin-mei , Peng Ming , Qi Jun-feng , Zhang Yin-don , Lu Li-fang
Published: January 2019

Cold stress is one of the most important environmental factors affecting crop growth and agricultural production. Induced changes of gene expression and metabolism are critical for plants responding and acclimating to cold stress. Banana (Musa sp.) is one of the most important food crops in the tropical and subtropical countries of the world. Banana, which originated from tropical regions, is sensitive to cold, which can result in serious losses in commercial banana production. To investigate the response of the banana to cold stress conditions, changes in protein expression were analyzed using a comparative proteomics approach. ‘Brazil’ banana (Musa acuminata AAA group) is a common banana cultivar in southern China. ‘Brazil’ banana plantlets were exposed to 5 °C for 24 hours and then total crude protein was extracted from treatment and control leaves by phenol extraction, separated with two-dimensional gel electrophoresis, and subsequently identified by mass spectrometry (MS). Out of the more than 400 protein spots reproducibly detected, only 41 protein spots exhibited a change in intensity by at least 2-fold, with 26 proteins increasing and 15 proteins decreasing expression. Of these, 28 differentially expressed proteins were identified by MS. The identified proteins, including well-known and novel cold-responsive proteins, are involved in several cellular processes, including antioxidation and antipathogen, photosynthesis, chaperones, protein synthesis, signal transduction, energy metabolism, and other cellular functions. Proteins related to antioxidation, pathogen resistance, molecular chaperones, and energy metabolism were up-regulated, and proteins related to ethylene synthesis, protein synthesis, and epigenetic modification were down-regulated in response to cold temperature treatment. The banana plantlets incubated at cold temperatures demonstrated major changes in increased reactive oxygen species (ROS) scavenging, defense against diseases, and energy supply. Increased antioxidation capability in banana was also discovered in plantain, which has greater cold tolerance than banana in response to cold stress conditions. Therefore, we hypothesized that an increased antioxidation ability could be a common characteristic of banana and plantain in response to cold stress conditions. These findings may provide a better understanding of the physiological processes of banana in response to cold stress conditions.
Heritability of Fruit Rot Resistance in American Cranberry
Authors: Johnson-Cicalese Jennifer , Polashock James J. , Honig Josh A. , Vaiciunas Jennifer , Ward Daniel L. , Vorsa Nicholi
Published: January 2019

Fruit rot is the primary threat to cranberry (Vaccinium macrocarpon) production in the northeastern United States, and increasingly in other growing regions. Efficacy of chemical control is variable because the disease is caused by a complex of pathogenic fungi. In addition, cranberries are often grown in environmentally sensitive areas, placing restrictions on chemical control measures. Thus, a major focus of the cranberry breeding program is to develop cultivars with improved fruit rot resistance (FRR). Several genetically diverse sources of FRR have been identified in our germplasm collection. However, the most resistant accessions lack one or more attributes; e.g., productivity, required for commercial acceptance. These resistant accessions were used in crosses with elite high-yielding selections and in 2009, 1624 progeny from 50 crosses were planted in 2.3-m2 field plots. During 2011–13, under field conditions with very limited fungicide management, disease pressure was severe, allowing evaluation for FRR. Plots were rated on a 1–5 scale for incidence of fruit rot (where 1 = 0% to 20% rot and 5 = 81% to 100% rotted fruit), and rotted fruit counts were made from selected plots to validate the ratings. There was a good correlation in the ratings between years (2011 vs. 2012: r = 0.59, P < 0.0001; 2011 vs. 2013: r = 0.50, P < 0.0001; 2012 vs. 2013: r = 0.62, P < 0.0001), and between rot ratings and percent rotted fruit (r = 0.90, P < 0.0001). Significant differences were found between and within families for FRR. High heritability estimates (h2 = 0.81) were obtained with midparent-offspring regression of mean fruit rot ratings, indicating additive genetic variance for FRR. Introgression of FRR into higher yielding genetic backgrounds was also accomplished, as some progeny exhibiting high FRR also had commercially viable yield (>300 g/0.09 m2), as well as good berry size and color. Selections are being further evaluated for potential cultivar release.
Novel Formation of Ectopic (Nonplacental) Capsaicinoid Secreting Vesicles on Fruit Walls Explains the Morphological Mechanism for Super-hot Chile Peppers
Authors: Bosland Paul W. , Coon Danise , Cooke Peter H.
Published: January 2019

Chile peppers (Capsicum sp.) are one of the most important spices in the world and a significant vegetable, providing substantial amounts of vitamins A and C. Chile peppers are also used as a medicinal and lachrymator plant because of the characteristic burning sensation they cause when consumed by mammals. This sensation is caused by capsaicinoids that are alkaloids produced in vesicles inside the fruit. A novel class of chile peppers known as “super-hots” having greater than 1 million Scoville heat units have generated much interest. We compared the morphological structure of fruit pericarp and placental tissue of “super-hot” chile peppers to those of jalapeno and bell pepper. Most chile peppers including jalapenos, only produce the capsaicinoids in secreting vesicles found on the placenta. We report on the novel discovery that these “super-hot” chile peppers have developed accessorial vesicles on the pericarp tissue in addition to the vesicles on the placental tissue, thus leading to exceedingly high Scoville heat units for these plants.
Effects of Epichloë festucae Fungal Endophyte Infection on Drought and Heat Stress Responses of Strong Creeping Red Fescue
Authors: Tian Zipeng , Huang Bingru , Belanger Faith C.
Published: January 2019

Strong creeping red fescue (Festuca rubra ssp. rubra) is an important cool season turfgrass species. Cultivars are often infected with the fungal endophyte Epichloë festucae. Endophyte infection is known to confer insect and disease resistance to the plants. The effect of endophyte infection on drought or heat stress tolerance of strong creeping red fescue is not yet established. The objectives of this controlled-environment study were to determine if endophyte infection had any effect on physiological parameters associated with plant tolerance to drought or heat stress or the combination of the two stresses. In this study, endophyte status had no effect on turf quality (TQ), relative water content (RWC), photochemical efficiency, chlorophyll content, electrolyte leakage (EL), or malondialdehyde (MDA) content of the plants under any of the stress treatments. Our results suggested that E. festucae infection had no physiological effects on improving drought, heat or the combined stress tolerance in strong creeping red fescue.
Isolation and Functional Analysis of Flowering Locus T in Tree Peonies (PsFT)
Authors: Zhou Hua , Cheng Fang-Yun , Wu Jing , He Chaoying
Published: January 2019

Arabidopsis thaliana Flowering locus T (FT) homologs have been shown to be sufficient to trigger flowering and to regulate flowering time in a wide range of plants. However, such a homologue for the perennial ornamental shrub tree peony has not yet been characterized. In this study, we isolated PsFT, which is a closely related FT homolog from reblooming [Paeonia ×lemoinei ‘High Noon’ (HN)] and nonreblooming [P. ×suffruticosa ‘Luo Yang Hong’ (LYH)] cultivars of tree peonies, and identified its potential role in the regulation of flowering time. The PsFT alleles from the two cultivars encode the same protein, which indicates that the polymorphisms observed in the coding region do not contribute to the distinct flowering phenotypes of HN and LYH. Comparative analyses of the PsFT expression patterns in HN and LYH indicated that PsFT might be associated with reblooming. Transgenic A. thaliana plants ectopically expressing PsFT exhibited a phenotype that included significantly early flowering compared with the wild-type (WT) plants. Taken together, our data provide valuable clues for shortening the juvenile periods and extending the flowering periods of perennial woody plants, such as tree peonies.
Carbon Balance of Turfgrass Systems in Response to Seasonal Temperature Changes Under Different Mowing Heights
Authors: Song Yali , Burgess Patrick , Han Hairong , Huang Bingru
Published: January 2019

Turfgrass growth and physiological activities are sensitive to temperatures and are affected by mowing height. Increasing temperatures associated with global climate change may limit photosynthetic capacity of established turfgrass stands. The objective of this study was to determine the effects of mowing height on carbon exchange of a turfgrass system and consequential effects on turfgrass growth in response to temperature variations across the growing season in kentucky bluegrass (Poa pratensis cv. Baron) stands. Mature (8 years old) turfgrass was mowed at 7.6 cm [high mowing height (HM)] or 3.8 cm [low mowing height (LM)] during 2012 and 2013. Both LM and HM plots displayed significant decline in turf quality (TQ), shoot biomass, and canopy photosynthetic rate (Pn) with increasing air temperature above 23–24 °C in both years and the decline was more pronounced for LM plots. Turf plots were carbon emitters when total respiration rate of shoots, roots, and soil (Rtotal) exceeded canopy Pn under high temperatures during July–September but maintained net carbon gain during cooler seasons (May and June) due to greater Pn to Rtotal ratio (Pn:Rtotal). Lowering mowing height accelerated carbon loss by reducing canopy Pn, particularly under high temperatures. Our results suggested that whether mature turfgrass stands fix or emit carbon is heavily dependent on interaction between seasonal temperatures and mowing height gauging whole-stand photosynthetic capacity. Furthermore, increasing mowing height during summer months may offset the deleterious effects of high temperature by maintaining positive carbon balance within the turfgrass system.
Expression Pattern Analysis of Four Mlo Genes from Rose
Authors: Qiu Xianqin , Jian Hongying , Wang Qigang , Tang Kaixue , Bao Manzhu
Published: January 2019

Rose (Rosa hybrida) is one of the most economically important ornamentals worldwide. Powdery mildew (Podosphaera pannosa) is a major disease in cut and potted roses. In dicots such as arabidopsis (Arabidopsis thaliana), pea (Pisum sativum), and tomato (Solanum lycopersicum), loss-of-function mutations in mildew resistance locus o (Mlo) genes confer high levels of broad-spectrum resistance to powdery mildew. Here, we present spatiotemporal expression patterns of four Mlo genes from R. hybrida based on real-time fluorescence quantitative polymerase chain reaction (qPCR). Phylogenetically closely related R. hybrida mildew resistance locus o (RhMLO) genes showed similar or overlapping tissue specificity and analogous responsiveness to external stimuli. RhMLO1 and RhMLO2 transcriptional levels were upregulated more than 2-fold by external stimuli, especially by inoculation with powdery mildew fungus P. pannosa at early time points. This phenomenon was not found for RhMLO3 or RhMLO4. The results indicated that RhMLO1 and RhMLO2 might play important roles in rose–powdery mildew pathogen interactions. Our findings may provide useful information for the study of mechanisms of powdery mildew susceptibility in rose.
In Vitro Self-incompatible-like Response Applied for Protein Identification and Gene Expression Analysis in Citrus Cultivars, Banpeiyu and Hyuganatsu
Authors: Li Yiran , Abe Akiha , Fuse Takuichi , Hirano Tomonari , Hoshino Yoichiro , Kunitake Hisato
Published: January 2019

Self-incompatibility (SI) is an important mechanism in higher plants that promotes outcrossing and prevents self-fertilization. ‘Banpeiyu’ (Citrus maxima) and ‘Hyuganatsu’ (Citrus tamurana), two of the Citrus cultivars distributed in Kyusyu, Japan, show gametophytic SI. In this study, we used the Citrus mature pollen culture system and stylar crude protein extracts to simulate compatible (C) and SI responses in ‘Banpeiyu’ pollen tubes. We analyzed the protein changes in pollen tubes with the C- and SI-like treatments by nano-liquid chromatography–mass spectrometry (nano-LC-MS); 14 and 27 proteins were identified in C- and SI-like treatments, respectively. We picked up some candidate genes that were particularly prevalent in SI-like treatment and analyzed their expression level changes during C- and SI-like treatments in ‘Banpeiyu’ and ‘Hyuganatsu’ pollen tubes. The expression levels of copper/zinc superoxide dismutase (Cu/Zn SOD), manganese SOD (Mn SOD), catalase (CAT), and cysteine protease (CYP) increased after SI-like treatment. We used a fluorescent probe to visualize reactive oxygen species (ROS) level changes in ‘Banpeiyu’ and ‘Hyuganatsu’ pollen tubes after C- and SI-like treatments and found that 2-hour SI-like treatment induced ROS levels to increase in the pollen tubes of both cultivars. These results suggest that an ROS increase could be one of the key phenomena in the SI response of Citrus and that gene expression changes were responses to ROS generation.
Phytohormone Responses and Cell Viability during Salinity Stress in Two Creeping Bentgrass Cultivars Differing in Salt Tolerance
Authors: Krishnan Sanalkumar , Merewitz Emily B.
Published: January 2019

Salinity stress is becoming more prevalent in turfgrass management with the increasing use of recycled water for irrigation. Creeping bentgrass (Agrostis stolonifera) is a cool-season turfgrass species that contains significant cultivar variation in salt stress tolerance, but the mechanism related to this cultivar variation is not well understood. Our objectives were to determine whether differential hormone content could play a role in cultivar variation of salt responses and to evaluate whether cell viability assays using dye techniques could differentiate salt stress damage levels in turfgrass species. Therefore, a growth chamber study with potted plants was conducted to evaluate salt ion concentrations, physiological responses, and hormone analysis [abscisic acid (ABA), indole-3-acetic acid (IAA), jasmonic acid (JA), salicylic acid (SA), zeatin riboside (ZR), and ethylene] at 4, 8, and 12 dS·m−1 in relatively salt-tolerant ‘Mariner’ compared with salt-sensitive ‘Penncross’ creeping bentgrass. A hydroponics-based growth chamber study was performed for evaluation of whether dead-cell stains coupled with image analysis could be a quick method for indicating cell viability variation between cultivars. Greater salt tolerance was evident in ‘Mariner’ at 12 dS·m−1, which showed significantly lower electrolyte leakage, higher leaf relative water content (RWC), osmotic potential, photochemical efficiency, and photochemical yield compared with ‘Penncross’. A higher K+ and lower Na+ content was maintained in leaves of ‘Mariner’ compared with ‘Penncross’ while roots of ‘Mariner’ maintained higher Ca2+ content under stressed and nonstressed conditions. Phytohormone levels showed a decline in salt-stressed roots compared with nonstressed plants but ‘Mariner’ roots were able to maintain levels higher than ‘Penncross’. ‘Mariner’ leaves showed an increased accumulation of ABA, JA, SA, and ZR while roots maintained higher IAA and SA compared with ‘Penncross’. The results suggest that ‘Mariner’ was able to mitigate salt stress by better ion regulation and differential regulation of hormones compared with ‘Penncross’. ‘Mariner’ leaves and roots showed significantly lower dead cells compared with ‘Penncross’ under salt stress. The results suggest that staining for cell viability could be a useful technique for studying turfgrass stress or other cellular responses.
Dynamics of Polysaccharides and Neutral Lipids during Anther Development in Castor (Ricinus communis)
Authors: Wei Dongmei , Xu Huimin , Li Ruili
Published: January 2019

Anthers contain starch and neutral lipids, which have key roles in microspore ontogeny and gametophyte development. In this study, we observed the dynamic changes in starch and neutral lipids in the anther developmental processes of castor (Ricinus communis) by cytochemical methods. Starch grains and neutral lipids presented a regular dynamic distribution during anther development. In young anthers, some neutral lipids accumulated in sporogenous cells, whereas neutral lipids disappeared with microspore growth. At the late microspore stage, starch grains began to accumulate in microspores, and the starch content of bicellular pollen significantly increased after microspore mitosis. At anthesis, starch grains and neutral lipids accumulated in the mature pollen grains. Visible changes occurred in anther wall cells. The epidermis, middle layer, and tapetum were degenerated, and only a single layer of endothecium remained at anthesis. The dynamic variation of starch grains and neutral lipids in tapetal cells was consistent with the changes in microspores and pollen during anther development. All these findings demonstrated that tapetal cells directly interacted with the developing gametophytes. The tapetal cells play an important role in supplying nutritional substances for microspore absorption. Moreover, the endothecium protects the pollen and contributes to anther dehiscence. The results of this study provide a foundation for the further research on sexual reproduction in angiosperms.
MaRING2: A Positive Regulator of an Abscisic Acid-dependent Response to Cold Stress from Banana Fruit
Authors: Chen Jiao , Yuan De-bao , Wang Chao-zheng , Li Yi-xing , Li Fen-fang , Hong Ke-qian , Lu Wang-jin
Published: January 2019

Many reports indicate that an abundance of really interesting new gene (RING) play key roles in regulating defense responses against abiotic and biotic stresses in plants. In this study, the cloning and functional characterization of a RING gene, MaRING2, in banana (Musa acuminata) fruit are reported. MaRING2 belongs to the NEP1-interacting protein (NIP) RING-H2 finger protein family. Gene expression profiles revealed that MaRING2 was cold responsive and induced by abscisic acid (ABA) treatment during cold storage. In this study, the MaRING2 under control of the Cauliflower mosaic virus 35S (CaMV 35S) promoter was transformed to tobacco (Nicotiana benthamiana) using agrobacterium (Agrobacterium tumefaciens)-mediated transformation. The resultant MaRING2-overexpressing transgenic plants (35S:MaRING2) exhibited significantly increased tolerance to low temperatures and were hypersensitive to exogenous ABA in terms of germination and early seedling growth. In addition, overexpression of MaRING2 enhanced the expression of stress-responsive genes under normal (before cold stress) or cold conditions. These results demonstrate the biological role of MaRING2 in conferring cold tolerance. Taken together, these results suggest that MaRING2, a C3H2C3-type RING protein, is a positive regulator of the ABA-dependent stress response.
Involvement of miR156 in the Regulation of Vegetative Phase Change in Plants
Authors: Zhang Lu , Hu You-biao , Wang Hua-sen , Feng Sheng-jun , Zhang Yu-ting
Published: January 2019

Plant growth and development are determined by complex exogenous and endogenous cues. A plant follows several temporally distinct developmental stages, including embryonic, vegetative, and reproductive. The vegetative stage, which is usually the longest stage, can be subdivided into juvenile and adult phases. The transition from the juvenile to the adult phase, also called the vegetative phase change, is characterized by anatomical, morphological, and physiological changes in the vegetative parts of the shoot. Recent studies in several systems have identified the genetic temporal mechanisms of this process, which is regulated by an endogenous age cue (i.e., microRNA156/157) and its targeted genes (i.e., Squamosa promoter binding protein-box transcription factors). This review summarizes the recent advances in the study of the underlying regulatory mechanisms of vegetative phase change. This review also describes the modes of miRNA action and the functions of their targeted genes in this highly conserved developmental process.
Inheritance of Resistance to Downy Mildew in Sweet Basil
Authors: Pyne Robert M. , Koroch Adolfina R. , Wyenandt Christian A. , Simon James E.
Published: January 2019

Sweet basil (Ocimum basilicum) is one of the most economically important culinary herbs in the world, yet global production has become increasingly challenging due to the destructive disease downy mildew (Peronospora belbahrii). Although multiple sources of resistance have been identified, there are no resistant sweet basil cultivars with a commercially acceptable chemotype and phenotype available. The commercial basil cultivar Mrihani (MRI) was identified as resistant and crossed with a Rutgers University susceptible sweet basil inbred line (SB22) to generate a full-sibling family. To determine the mode of inheritance for resistance to downy mildew in basil, six related generations of the MRI × SB22 family were evaluated using a disease severity index (DSI) at northern and southern New Jersey locations over 2 years. All siblings in the F1 and BC1P2 generations were resistant (0.33 > DSI) providing strong evidence that inheritance of resistance from MRI was conferred by dominant alleles. Segregation ratios in the F2 and backcross to the susceptible parent (BCP1) generations demonstrated chi-square goodness of fit to the two-gene complementary (F2: P = 0.11, BC1P1: P = 0.04) and recessive epistatic (F2: P = 0.03, BC1P1: P = 0.63) models. Further analyses of gene effects using a weighted six-parameter scaling test provided evidence that nonallelic additive × additive and additive × dominant gene effects were highly significant (P < 0.001) and resistance reducing. This is the first report of heritable genetic resistance that can be introduced to sweet basil without the issue of sterility barriers. Plant breeding strategies using the MRI × SB22 family should exploit dominant gene action and remove recessive, resistance-reducing alleles from the population.
Physiological Effects of Aquaporin in Regulating Drought Tolerance through Overexpressing of Festuca arundinacea Aquaporin Gene FaPIP2;1
Authors: Zhuang Lili , Liu Mengxian , Yuan Xiuyun , Yang Zhimin , Huang Bingru
Published: January 2019

Aquaporin (AQP) proteins serve important roles in regulating water movement across cellular membranes and affect plant responses to drought stress. The objective of this study was to characterize and examine functions of an AQP gene FaPIP2;1, isolated from a drought-tolerant perennial grass species tall fescue (Festuca arundinacea), for involvement in leaf dehydration status during water stress by overexpressing the gene in arabidopsis (Arabidopsis thaliana). FaPIP2;1 had characteristic transmembrane domains and Asn–Pro–Ala motifs and was similar to PIP2;1 in rice (Oryza sativa) and maize (Zea mays). Quantitative real-time reverse transcriptase polymerase chain reaction analysis showed that FaPIP2;1 was upregulated during moderate water stress (hydroponic culture, osmotic potential (ΨS) at −0.47 and −0.78 MPa) and the transcript level decreased as ΨS further decreased. Transgenic arabidopsis plants overexpressing FaPIP2;1 showed greater number of leaves per plant and improved survival rate compared with the wild type (WT) during drought stress. Transgenic plants also maintained higher leaf relative water content (RWC), chlorophyll content (Chl), net photosynthetic rate (Pn), and lower leaf electrolyte leakage (EL) than the WT. However, there was no difference in root length between the transgenic and WT plants following drought stress. The results demonstrated that overexpressing FaPIP2;1 could improve plant tolerance to drought stress by enhancing leaf water status, Chl, and photosynthetic rate, as well as maintaining improved cellular membrane stability relative to the WT plants. FaPIP2;1 may be used as a candidate gene for genetic modification of perennial grasses to develop new drought-tolerant germplasm and cultivars.
Cybridization of Grapefruit with ‘Dancy’ Mandarin Leads to Improved Fruit Characteristics
Authors: Satpute Aditi D. , Chen Chunxian , Gmitter Fredrick G. , Ling Peng , Yu Qibin , Grosser Melinda R. , Grosser Jude W. , Chase Christine D.
Published: January 2019

In cybridization, new combinations of nuclear and cytoplasmic genes result in a unique genotype that may bring cellular, physical, physiological, and biochemical changes to the plant. This has been demonstrated in the unexpected cybrids generated from the fusion of citrus (Citrus sp.) protoplasts in two independent experiments. The first experiment was conducted to generate potentially seedless triploids by fusing diploid protoplasts of embryogenic ‘Dancy’ mandarin (Citrus reticulata) suspension culture cells with haploid ‘Ruby Red’ grapefruit (C. paradisi) protoplasts derived from tetrad-stage microspores. After multiple attempts, only one triploid was recovered, but several diploid plants with typical grapefruit morphology were also regenerated. In the second experiment, protoplasts derived from embryogenic ‘Dancy’ mandarin suspension culture were fused with nonembryogenic protoplasts from ‘Duncan’ grapefruit leaves in an effort to produce an allotetraploid somatic hybrid. The fruit from the resulting trees resembled grapefruit in morphology and type, and maintained excellent quality throughout the summer, when commercial grapefruit rapidly loses quality. Fruit on these trees remained firm with exceptional sweetness and good flavor into August, and without seed germination. The regenerants obtained in the protoplast fusion experiments were confirmed as cybrids by genetic marker analyses. The test grapefruit were identical to commercial ‘Ruby Red’ grapefruit at six nuclear simple sequence repeat (SSR) marker loci, but identical to ‘Dancy’ with respect to a mitochondrial intron marker. The plastid genomes of individual trees originated from either fusion partner. In the first experiment, haploid ‘Ruby Red’ protoplast preparations must have also contained contaminant diploid protoplasts. Apart from the value of altered fruit quality attributes in the marketplace, these plants provide an opportunity to understand the contributions of cytoplasmic organelle genetics to important citrus fruit-breeding objectives.
Genome Size and Ploidy of Phlox paniculata and Related Germplasm in Subsections Paniculatae and Phlox
Authors: Zale Peter J. , Jourdan Pablo
Published: January 2019

Phlox is an important genus of herbaceous ornamental plants previously targeted for germplasm development, characterization, and enhancement by the U.S. Department of Agriculture, National Plant Germplasm System. Among Phlox in cultivation, Phlox paniculata is the most widely grown and intensively bred species, but little is known about variation in genome size and ploidy of this species or of related taxa that may be used for germplasm enhancement. The objective of this study was to assess cytotype variation in a diverse collection of cultivars and wild germplasm of P. paniculata (subsection Paniculatae) and of related taxa in subsections Paniculatae and Phlox. The collection included 138 accessions from seven species and two interspecific hybrids. Flow cytometry was used to estimate holoploid (2C) genome sizes and to infer ploidy levels. Chromosome counts were made to calibrate ploidy with genome size for a subset of taxa. Most cultivars were diploid (2n = 2x = 14) and had mean genome sizes that did not vary between subsections Paniculatae (14.33 pg) and Phlox (14.23 pg) although size variation was greater among cultivars within subsection Phlox. Triploid cultivars of P. paniculata, with a mean genome size of 21.36 pg and mitotic chromosome counts of 2n = 3x = 21, were identified. Such triploids suggests previous interploid hybridization within this taxon. Five tetraploid (2n = 4x = 28) cultivars were found in subsection Phlox; all were selections of P. glaberrima ssp. triflora, and had a mean genome size of 25.44 pg; chromosome counts in one of these confirmed they were tetraploid. The putative hybrid Phlox Suffruticosa Group ‘Miss Lingard’ showed an intermediate genome size of 21.21 pg supporting a triploid, hybrid origin of this taxon. Mean 2C genome sizes among wild-collected accessions were similar to values reported for cultivars (Paniculatae = 14.59 pg, Phlox = 14.23 pg), but taxa in subsection Phlox exhibited greater variation that included two tetraploids identified among wild-collected accessions; one, of P. pulchra, had a mean genome size of 26.17 pg, representing the first report of polyploidy in the taxon. This is the first report on genome size for the majority of species in the study. Although genome size could not be used to differentiate taxa in subsections Paniculatae and Phlox, the data provide further insights into cytotype variation of Phlox germplasm useful for plant breeders and systematists.
Hyperspectral Surface Reflectance Data Detect Low Moisture Status of Pecan Orchards during Flood Irrigation
Authors: Othman Yahia , Steele Caiti , VanLeeuwen Dawn , St. Hilaire Rolston
Published: January 2019

For large fields, remote sensing might permit plant low moisture status to be detected early, and this may improve drought detection and monitoring. The objective of this study was to determine whether canopy and soil surface reflectance data derived from a handheld spectroradiometer can detect moisture status assessed using midday stem water potential (ψsmd) in pecan (Carya illinoinensis) during cyclic flood irrigations. We conducted the study simultaneously on two mature pecan orchards, one in a sandy loam (La Mancha) and the other in a clay loam (Leyendecker) soil. We were particularly interested in detecting moisture status in the −0.90 to −1.5 MPa ψsmd range because our previous studies indicated this was the critical range for irrigating pecan. Midday stem water potential, photosynthesis (A) and canopy and soil surface reflectance measurements were taken over the course of irrigation dry-down cycles at ψsmd levels of −0.40 to −0.85 MPa (well watered) and −0.9 to −1.5 MPa (water deficit). The decline in A averaged 34% in La Mancha and 25% in Leyendecker orchard when ψsmd ranged from −0.9 to −1.5 MPa. Average canopy surface reflectance of well-watered trees (ψsmd −0.4 to −0.85 MPa) was significantly higher than the same trees experiencing water deficits (ψsmd −0.9 to −1.5 MPa) within the 350- to 2500-nm bands range. Conversely, soil surface reflectance of well-watered trees was lower than water deficit trees over all bands. At both orchards, coefficient of determinations between ψsmd and all soil and canopy bands and surface reflectance indices were less than 0.62. But discriminant analysis models derived from combining soil and canopy reflectance data of well-watered and water-deficit trees had high classification accuracy (overall and cross-validation classification accuracy >80%). A discriminant model that included triangular vegetation index (TVI), photochemical reflectance index (PRI), and normalized soil moisture index (NSMI) had 85% overall accuracy and 82% cross-validation accuracy at La Mancha orchard. At Leyendecker, either a discriminant model weighted with two soil bands (690 and 2430 nm) or a discriminant model that used PRI and soil band 2430 nm had an overall classification and cross-validation accuracy of 99%. In summary, the results presented here suggest that canopy and soil hyperspectral data derived from a handheld spectroradiometer hold promise for discerning the ψsmd of pecan orchards subjected to flood irrigation.
Sweet Cherry Skin Has a Less Negative Osmotic Potential than the Flesh
Authors: Grimm Eckhard , Knoche Moritz
Published: January 2019

The skin is the primary load-bearing structure in a sweet cherry fruit (Prunus avium L.). Failure of the skin in rain cracking is considered to be related to water uptake. Little is known of the skin’s water potential, its osmotic potential (ΨΠS), and turgor. The objective here was to quantify ΨΠS relative to the osmotic potential of the flesh (ΨΠF). Spatial resolution was achieved by monitoring plasmolysis in epidermal cells in tissue sections, incubated in selected osmotica using a light microscope method. Decreasing the osmotic potential [ΨΠ (more negative)] of the incubation medium increased the proportion (percent) of plasmolyzed epidermal cells. The pattern of increasing plasmolysis was sigmoidal with increasing osmolyte concentration. The value of ΨΠ for 50% of cells plasmolyzed, depended to some extent on the osmolyte used. The value of ΨΠ became slightly less negative for the osmolytes tested in the order: 1) mannitol, 2) sucrose, and 3) artificial cherry juice (a solution comprising the five major osmolytes of sweet cherry juice in the appropriate proportions and concentrations). There was little difference in the value of ΨΠ at 50% plasmolysis between the cultivars Hedelfinger, Sam, and Sweetheart. In all three cultivars, the value of ΨΠF (measured for expressed juice using an osmometer) was markedly more negative than that of ΨΠS (measured for 50% plasmolysis). Incubating skin segments in juice from the same fruit resulted in the plasmolysis of most (85.7% to 96.4%) of the epidermal cells. As fruit development progressed from stage II [27 day after full bloom (DAFB)] to the fully mature stage III (97 DAFB), plasmolysis occurred for increasingly more negative values of ΨΠ. Moreover, the difference between the osmotic potential values recorded for the flesh ΨΠF and for the skin ΨΠS increased. Plasmolysis of epidermal cells was accompanied by a marked swelling of their walls. The results indicate a marked difference in the osmotic potential of flesh (ΨΠF trended more negative) and skin cells (ΨΠS trended less negative).