bluuebunny/crossref_metadata_2025 huggingface dataset:
Iron Efficiency in Different Cucumber Cultivars: The Importance of Optimizing the Use of Foliar Iron
Authors: Bacaicoa Eva , García-Mina Jose María
Published: January 2019

The ability of plant cultivars to deal with iron (Fe) deficiency (plant Fe efficiency capabilities) has a significant influence on crop yield and fruit quality. This study investigates Fe efficiency in four cucumber (Cucumis sativus L.) cultivars (Ashley, Anico, Trópico, and Serena) using a complementary approach. The ability to express the main Fe-stress root responses (rhizosphere acidification, Fe reduction, and specific morphological changes) and grow (dry matter production, nutrient acquisition, and efficiency of photosystem II) under Fe starvation were assessed. Results show that while the four cultivars were able to activate the main Fe-stress root responses, only ‘Ashley’ presented a significant capacity to grow and acquire nutrients under Fe deficiency. This ability to develop under Fe starvation was also reflected in the efficiency of photosystem II. Results suggest the existence of two different but probably inter-regulated mechanisms to deal with Fe deficiency in these plants. One would be related to the control of the expression of Fe-stress responses in the root and the other would be involved in optimizing the use of Fe present in the shoot, which is reflected in the plant's ability to develop under Fe deficiency. Among the cucumber cultivars studied, only ‘Ashley’ presented complete Fe efficiency, expressed in the development of Fe-stress root responses and in the ability to optimize Fe metabolic efficiency in the shoot. Likewise, this study evidences the need to consider Fe-stress root responses and the capacity to optimize the metabolic use of Fe in the shoot in studying plant Fe efficiency.
Blue Pattern Flower in Common Bean Expressed by Interaction of Prpi-2 with a New Gene tbp
Authors: Bassett Mark J. , Miklas Phillip N.
Published: January 2019

The inheritance of blue pattern flower (BPF) expression was investigated in common bean (Phaseolus vulgaris L.). The BPF trait was derived from accession line G07262, and the flowers express blue banner petal and white wings with blue veins. Crosses between a BPF stock and three other parents, t pmic long micropyle stripe BC3 5–593, t z Fib arcus BC4 5–593, and t Z bipana Fib marginata BC3 5–593, all segregated in F2 for BPF or white flowers in a 9:7 ratio, respectively. Progeny tests in F3 from two of the crosses supported the hypothesis that two complementary dominant genes control BPF expression and permitted a genetic linkage estimate of cM = 32.4 ± 7.91 map units between pmic and one of the two genes for BPF. A cross between t z fib virgarcus BC3 5–593 and T Prpi-2 V BC2 5–593 demonstrated that t Prpi-2 did not express BPF. Two crosses, T Prpi-2 V BC2 5–593 t pmic BC3 5–593 and 5–593 × a BPF stock, segregated in F2 for plants expressing BPF in a 3/16 frequency. The combined data demonstrated that a new gene, tbp (bp = blue pattern), interacts with Prpi-2 to express BPF and that P is linked with Prpi-2 by 32 map units. The dominance order at the T locus is T > tbp > t. The pedigree source of the tbp gene and the heterogeneity of PI 632736 (t pmic long micropyle stripe BC3 5–593) are discussed.
Capturing the Diversity of Wild Malus orientalis from Georgia, Armenia, Russia, and Turkey
Authors: Volk Gayle M. , Richards Christopher M. , Henk Adam D. , Reilley Ann A. , Reeves Patrick A. , Forsline Philip L. , Aldwinckle Herb S.
Published: January 2019

Seeds from wild Malus orientalis trees were collected during explorations to Armenia (2001, 2002), Georgia (2004), Turkey (1999), and Russia (1998). Seedling orchards with between eight and 171 individuals from each collection location were established at the U.S. Department of Agriculture–Agricultural Research Service Plant Genetic Resources Unit (PGRU) in Geneva, NY. Genotypic (seven microsatellite markers) and disease resistance data were collected for the 776 M. orientalis trees. The genetic diversity of the 280 individuals from Armenia and Georgia was compared with data previously published for the M. orientalis individuals from Russia and Turkey. A total of 106 alleles were identified in the trees from Georgia and Armenia and the average gene diversity ranged from 0.47 to 0.85 per locus. The genetic differentiation among sampling locations was greater than that found between the two countries. Six individuals from Armenia exhibited resistance to fire blight (Erwinia amylovora), apple scab (Venturia inaequalis), and cedar apple rust (Gymnosporangium juniperi-virginianae). The allelic richness across all loci in the individuals from Armenia and Georgia was statistically the same as that across all loci in the individuals from Russia and Turkey. A core set of 27 trees was selected to capture 93% of the alleles represented by the entire PGRU collection of 776 M. orientalis trees. This core set representing all four countries was selected based on genotypic data using a modified maximization algorithm. The trees selected for the M. orientalis core collection will be added to the main field collection at the PGRU.
Pawpaw Fruit Chilling Injury and Antioxidant Protection
Authors: Galli Federica , Archbold Douglas D. , Pomper Kirk W.
Published: January 2019

Pawpaw (Asimina triloba) fruit stored longer than 4 weeks at 4 °C fail to ripen normally and may develop internal discoloration, indicative of chilling injury (CI). To determine if loss of antioxidant protection in the fruit tissue during cold storage could be the cause of these problems, the levels of total, reduced, and oxidized glutathione and ascorbate and the key enzymes glutathione reductase (GR) and ascorbate peroxidase (APX) of the ascorbate-glutathione cycle were studied in fruit at 4 and 72 h after harvest and after 2, 4, 6, and 8 weeks of 4 °C storage. The total phenolic level was also studied due to its potential antioxidant role, and the activity of polyphenoloxidase (PPO) was assayed, as it may contribute to phenolic oxidation and tissue browning. Fruit ethylene production and respiration rates were in typical climacteric patterns during ripening after harvest and after up to 4 weeks of cold storage, increasing from 4 to 72 h after removal from cold storage, though maximum ethylene production declined after 2 weeks of cold storage. However, fruit showed higher respiration rates at 4 versus 72 h of ripening at 6 or 8 weeks of cold storage, opposite to that at earlier storage dates, possible evidence of CI. Ripening after harvest generally resulted in an increase in total and reduced glutathione, reduced ascorbate, and total phenolics. However, levels of total and reduced glutathione, total ascorbate, and total phenolics declined as storage time progressed. Neither GR nor APX exhibited changes during ripening or trends over the cold storage period. PPO activity increased as the storage period lengthened. Thus, the declining ability of these components of the protective antioxidant systems during the prolonged stress of low temperature storage may be one of the major causes of pawpaw CI limiting it to 4 weeks or less of cold storage. An increase in reactive oxygen species with prolonged storage, coupled with the increase in PPO activity, may have led to greater oxidative damage and been a major cause of the loss of ripening potential and the tissue browning that occurs in fruit stored for more than 4 weeks.
Vernalization Responses of Campanula ‘Birch Hybrid’
Authors: Padhye Sonali R. , Cameron Arthur C.
Published: January 2019

The objective of this study was to characterize the influence of vernalizing temperatures and durations based on different flowering responses of Campanula ‘Birch Hybrid’. Clonally propagated plants of Campanula ‘Birch Hybrid’ were exposed to −2.5, 0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5, or 20 °C for 0, 3, 5, 7, 9, or 12 weeks and were subsequently grown at 20 °C in a greenhouse. Campanula ‘Birch Hybrid’ exhibited a near-obligate vernalization requirement, and all flowering responses studied were influenced by the treatment temperatures, durations, and their interactions. The minimum and maximum cardinal temperatures for vernalization were <0 °C and between 15 and 17.5 °C, respectively. The range of optimal vernalizing temperatures (Topt) varied based on the flowering response assessed. For instance, Topt for flowering percentage ranged between 2.5 to 7.5 °C, while Topt for number of open flowers was 0 to 12.5 °C when plants were vernalized for 5 weeks. Topt for flowering time also varied when analyzed as rate to flower, time to flower from the end of temperature treatments, total time to flower measured from the start of temperature treatments, and thermal time to flower. For example, after 12 weeks of treatment, Topt for thermal time to flower was 0 to 2.5 °C yet shifted to 2.5 to 12.5 °C for total time to flower. Because the flowering response being assessed altered the Topt, this study reiterates the significance of considering all relevant flowering responses while developing and interpreting vernalization models.
Membrane Lipid Composition and Heat Tolerance in Cool-season Turfgrasses, including a Hybrid Bluegrass
Authors: Su Kemin , Bremer Dale J. , Jeannotte Richard , Welti Ruth , Yang Celeste
Published: January 2019

Cool-season turfgrasses may experience heat stress during summer. Hybrid bluegrasses (HBGs), crosses between kentucky bluegrass [KBG (Poa pratensis L.)] and native texas bluegrass (Poa arachnifera Torr.), have improved heat tolerance but the mechanisms of heat tolerance are poorly understood. Our objectives were to quantitatively profile membrane lipid molecular species in three cool-season turfgrasses exposed to optimal (22/15 °C, 14/10 h light/dark) and supra-optimal temperatures (35/25 °C and 40/30 °C, 14/10 h light/dark). Grasses included a low heat-tolerant tall fescue [TF (Festuca arundinacea Schreb. ‘Dynasty’)], a mid-heat–tolerant KBG (‘Apollo’), and a heat-tolerant HBG (‘Thermal Blue’). At high temperature, glycolipid digalactosyldiacylglycerol (DGDG) in HBG was 12% and 16% greater than in KBG and TF, respectively, and the ratio DGDG to monogalactosyldiacylglycerol was 19% and 44% greater in HBG than in KBG and TF, respectively. Greater heat tolerance in HBG and KBG was associated with higher contents of phosphatidylethanolamine and phosphatidylglycerol, and with reduced overall unsaturation compared with TF. Overall, 20 lipid molecular species were present in greater amounts and another 20 species in lesser amounts in HBG and KBG than in TF. Results suggest 40 membrane lipid molecules are potential biomarkers for heat tolerance and that compositional changes in membrane lipids in response to heat contribute to differences in heat tolerance among cool-season grasses.
Identification and Utility of Markers Linked to the Zucchini Yellow Mosaic Virus Resistance Gene in Watermelon
Authors: Harris Karen R. , Ling Kai-Shu , Wechter W. Patrick , Levi Amnon
Published: January 2019

Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses affecting watermelon [Citrullus lanatus (Thunb.) Matsun & Nakai var. lanatus] in the United States. The ZYMV-Florida strain (ZYMV-FL) is considered a major limitation to commercial watermelon production in the United States. Inheritance of resistance to ZYMV-FL is conferred by a recessive gene. This report describes the identification of single-reaction, polymerase chain reaction-based markers linked to the ZYMV-FL resistance gene in watermelon. In this study, we identified a marker ZYMV-resistant polymorphism (ZYRP) linked to the ZYMV-FL resistance gene locus (genetic distance of 8 cM) in an F2 population, and in a backcross one to the resistant parent population (BC1R) (genetic distance of 13 cM). The identification of a single nucleotide polymorphism within the ZYRP marker for the parental genotypes allowed the development of a sequence-characterized amplification region marker linked to the ZYMV-FL resistance gene. Experiments using a BC2F2 population derived from the U.S. Plant Introduction 595203 (C. lanatus var. lanatus) and the recurrent parent ‘Charleston Gray’ indicated that the ZYRP marker can be used in marker-assisted selection to identify genotypes containing the gene conferring ZYMV-FL resistance in watermelon.
Genetic Diversity in Spanish and Foreign Almond Germplasm Assessed by Molecular Characterization with Simple Sequence Repeats
Authors: Fernández i Martí Àngel , Alonso José M. , Espiau María T. , Rubio-Cabetas María J. , Socias i Company Rafel
Published: January 2019

Genetic diversity of the Spanish national almond (Prunus amygdalus Batsch) collection was characterized with 19 simple sequence repeat (SSR) markers selected because of their polymorphism in almond and other Prunus L. species. A total of 93 almond genotypes, including 63 Spanish cultivars from different growing regions, as well as some international cultivars and breeding releases were analyzed. All primers produced a successful amplification, giving a total of 323 fragments in the genotypes studied, with an average of 17 alleles per SSR, ranging from 4 (EPDCU5100) to 33 (BPPCT038). Allele size ranged from 88 bp at locus PMS40 to 260 bp at locus CPPCT022. The heterozygosity observed (0.72) was much higher not only than in other Prunus species, but also than in other almond pools already studied. The dendrogram generated using the variability observed classified most of the genotypes according to their geographical origin, confirming the particular evolution of different almond ecotypes. The SSR markers have consequently shown their usefulness for cultivar identification in almond, for establishing the genetic closeness among its cultivars, and for establishing genealogical relationships.
Modeling the Effects of Drought Stress on Leaf Development in a Brassica oleracea Doubled Haploid Population Using Two-phase Linear Functions
Authors: Uptmoor Ralf , Osei-Kwarteng Mildred , Gürtler Susanne , Stützel Hartmut
Published: January 2019

The combination of quantitative trait loci (QTL) analysis and ecophysiological modeling has been suggested as an approach to reveal the genetic basis of complex traits since phenotypes change with time and environmental conditions and the variation within populations can be described by genotype-specific parameterization of response curves on time and influential environmental factors. The objectives of the present study are a genotype-specific parameterization of a model describing leaf area development under well-watered and drought stress conditions, the use of QTL for estimating model input parameters, an evaluation of the model, and a comparison of the genotype-specific and QTL-based model parameterization. We used a two-phase linear function to describe preflowering leaf area development in a Brassica oleracea L. doubled haploid population. To illustrate effects of drought on leaf growth, the function was combined with a plateau function, which estimates the soil water status at which stress effects begin to reduce leaf expansion, a genotype-specific slope of the response to soil water status, and the soil water status at which leaf expansion becomes zero. A total number of 14 QTL were detected on the parameters of the two-phase linear function describing preflowering leaf area development and the plateau function describing the effects of drought on leaf area development. Nine of these QTL colocalized to QTL detected on data of static leaf area measurements and osmotic adjustment. The entire model was able to distinguish between genotypes during later growth stages under well-watered and drought stress conditions. However, the predictability was largely reduced when drought stress became more severe at the final measurement dates. Independent evaluation trials showed that the accuracy of the model was on the same level or even higher when genotype specific input parameters were replaced by allele-specific QTL effects.
Relationship between the Hormonal Balance and the Regulation of Iron Deficiency Stress Responses in Cucumber
Authors: Bacaicoa Eva , Zamarreño Ángel María , Leménager Diane , Baigorri Roberto , García-Mina José María
Published: January 2019

Some studies suggest that iron (Fe) stress root responses are regulated by variations in specific plant hormones. However, this question remains unclear. A time-course experiment dealing with the relationship between the expression of the Fe-stress root responses at transcriptional (CsFRO1, CsIRT1, CsHA1, and CsHA2) and enzymatic levels [root Fe(III)-chelate reductase and plasma membrane H+-ATPase], and the variation of phytohormone concentrations in the shoot and root of Fe-starved plants have been studied in a Fe-efficient cucumber cultivar (Cucumis sativus L. cv. Ashley). The results indicate that the expression over time of the physiological Fe-stress root responses at transcriptional and enzyme activity levels are consistent with significant increases in indole-3-acetic acid root (transient) and shoot (sustained) concentrations. Fe-starvation also caused transient changes in the root concentration of abscisic acid and nitric oxide. Finally, an increase in root ethylene production and a decrease in the root concentration of some cytokinins were observed under Fe starvation, but they were not clearly timely coordinated with the expression of Fe physiological root responses.
Development of Simple Sequence Repeat Markers in Chinese Chestnut and Their Characterization in Diverse Chestnut Cultivars
Authors: Inoue Eiichi , Ning Lin , Hara Hiromichi , Ruan Shuan , Anzai Hiroyuki
Published: January 2019

To develop and characterize valid simple sequence repeat (SSR) markers in chestnut (Castanea spp.), we used a selective hybridization method to perform SSR sequence enrichment in the genomic library of chinese chestnut (Castanea mollissima). From 47 sequences of the enriched library, we designed 24 primer pairs for SSR polymerase chain reaction (PCR). SSR PCR was performed for 23 chinese chestnut cultivars. Among the 24 primers, 22 primers amplified their respective SSR loci; 21 primer pairs yielded polymorphic fragments across the cultivars. Among these 21 primer pairs, 17 primer pairs amplified single SSR loci with polymorphisms. Multilocus amplification patterns were observed in the other four primers. For the corresponding 17 SSR loci, the number of alleles per locus was two to 13, and the average number of alleles was 7.19. The observed heterozygosity (number of genotypes of the heterozygote/total number of genotypes scored at that locus) ranged from 0.00 to 0.87 (average = 0.68), and the expected heterozygosity ranged from 0.00 to 0.87 (average = 0.68). One of the SSR loci—ICMA014—was a unique locus, because the primer pair for this locus did not amplify any fragment in any of the cultivars, except in Qianchi, which was used to construct the SSR-enriched genomic library. Cross-species amplifications using the 17 primer pairs were also successful in the other species of genus Castanea. A dendrogram depicting the relationships among the genotypes on the basis of genetic distances was generated using the unweighted pair group method with arithmetic mean cluster analysis. The genotypes were clearly separated into three large groups, which reflected the three cultivated species, namely, C. mollissima, C. crenata, and C. sativa.
Characterization of Fertile Homozygous Genotypes from Anther Culture in Apple
Authors: Okada Hatsuhiko , Ohashi Yoshitaka , Sato Mamoru , Matsuno Hideyuki , Yamamoto Toshiya , Kim Hoytaek , Tukuni Tatsuro , Komori Sadao
Published: January 2019

Doubled haploids can improve the efficiency of breeding and genetic study in apple (Malus ×domestica Borkh.). Seventeen homozygous genotypes were obtained by in vitro anther culture from ‘Senshu’ apple. Flow cytometry analysis revealed that the ploidy level of the anther-derived plantlets was diploid. Simple sequence repeat (SSR) analysis determined the origin and homozygous status of the anther-derived plantlets. The results of S-RNase polymerase chain reaction (PCR)-digestion analysis reinforced the homozygous state. The morphological characteristics and reproductive potential of the doubled haploids were investigated. It is especially interesting that one of the doubled haploids derived from anther culture had fertile pollen grains (rate of in vitro germination was 20.6%–33.0%), and several progenies were obtained from the cross between ‘Prima’ apple and the doubled haploid. The hybridism of these seedlings was confirmed by SSR analysis. Furthermore, the female gametes of the doubled haploid showed slight fertility. Thus, this doubled haploid will be valuable for breeding and genetic studies.
Isolation, Sequence Analysis, and Linkage Mapping of Nucleotide Binding Site–Leucine-rich Repeat Disease Resistance Gene Analogs in Watermelon
Authors: Harris Karen R. , Wechter W. Patrick , Levi Amnon
Published: January 2019

Sixty-six watermelon (Citrullus lanatus var. lanatus) disease resistance gene analogs were cloned from ‘Calhoun Gray’, PI 296341, and PI 595203 using degenerate primers to select for the nucleotide binding sites (NBS) from the NBS–leucine-rich repeat (LRR) resistance gene family. After contig assembly, watermelon resistance gene analogs (WRGA) were identified and amino acid sequence alignment revealed that these groups contained motifs characteristic of NBS-LRR resistance genes. Using cluster analysis, eight groups of WRGA were identified and further characterized as having homology to Drosophila Toll and mammalian interleukin-1 receptor (TIR) and non-TIR domains. Three of these WRGA as well as three disease-related watermelon expressed sequence tag homologs were placed on a test-cross map. Linkage mapping placed the WRGA on linkage group XIII, an area on the watermelon map where resistance gene analogs cluster. In addition, these WRGA sequence-tagged sites (STS) were amplified from various genera of the Cucurbitaceae indicating that conservation of resistance gene analogs exists among cucurbits. These WRGA-STS markers may be useful in marker-assisted selection for the improvement for disease resistance in watermelon.
Differential Gene Expression of Resistant and Susceptible Sweetpotato Plants after Infection with the Causal Agents of Sweet Potato Virus Disease
Authors: McGregor Cecilia E. , Miano Douglas W. , LaBonte Don R. , Hoy Mary , Clark Chris A. , Rosa Guilherme J.M.
Published: January 2019

Sweet potato virus disease (SPVD) is one of the most devastating diseases affecting sweetpotato (Ipomoea batatas), an important food crop in developing countries. SPVD develops when sweetpotato plants are dually infected with sweet potato feathery mottle virus (SPFMV) and sweet potato chlorotic stunt virus (SPCSV). To better understand the synergistic interaction between these viruses, global gene expression was previously studied in the susceptible cultivar Beauregard. In the current study, global gene expression between SPVD-affected plants and virus-tested control plants (VT) were compared in ‘Beauregard’ (Bx) and resistant ‘NASPOT 1’ (Nas) sweetpotato cultivars at 5, 9, 13, and 17 days post inoculation (DPI). Titer levels of SPFMV and SPCSV were significantly lower in inoculated resistant plants (Nas_SPVD) than in susceptible plants (Bx_SPVD) at most of the time points. Chloroplast genes and cell expansion-related genes (including xyloglucan endotransglucosylase/hydrolases) were suppressed in Bx_SPVD, while stress-related genes were induced. This trend was not observed in resistant NAS_SPVD. Genes related to protein synthesis (e.g., ribosomal proteins and elongation factor genes) were induced in resistant NAS_SPVD at 5 DPI before returning to levels comparable with NAS_VT plants. At this time (5 DPI), individual viruses could not be detected in NAS_SPVD samples, and no symptoms were observed. Induction of protein synthesis-related genes is common in susceptible plants after virus infection and is generally in proportion to virus accumulation. Our results show that induction of protein synthesis genes also occurs early in the infection process in resistant plants, while virus titers were below the level of detection, suggesting that virus accumulation is not required for induction.
Physiological Responses of Gold Kiwifruit (Actinidia chinensis) to Reduced Irrigation
Authors: Mills Tessa M. , Li Jianming , Behboudian M. Hossein
Published: January 2019

Information on water relations and water stress physiology of Actinidia chinensis Planch. is scant. We aimed at providing such information by exposing potted 1-year-old plants to reduced irrigation in a glasshouse. The treatments were control (C) receiving sufficient water to replace 100% of evapotranspiration, early (E) reduced irrigation for 13 days earlier in the experiment, late (L) reduced irrigation for 13 days later in the experiment, and recovery (R) undergoing E and L with 5 days of full irrigation in between to recover from E. All plants were fully watered between early and late episodes of reduced irrigation. Soil volumetric water content was lower in E, L, and R compared with C, leading to lower leaf water potential, photosynthetic rate (Pn), and stomatal conductance (gs). Pn was lower in the reduced irrigation vines only when gs was below 0.1 mol·m−2·s−1. High leaf temperature in the glasshouse imposed nonstomatal limitations to photosynthesis as indicated by elevated internal leaf CO2 concentrations (Ci). Following rewatering, the stressed vines showed rapid recovery of leaf water potential and photosynthesis. However, Ci and gs were slower to respond. There was an indication of osmotic adjustment in leaves under reduced irrigation. Discrimination against 13CO2 was the same among the treatments. A. chinensis had better stomatal control under water stress compared with Actinidia deliciosa, for which some information is available. Water stress history in A. chinensis encouraged more drought resistance in the subsequent water stress period, but this was not sustained. Although field performance of A. chinensis under water stress is expected to be better than what we have presented here, long periods of deficit irrigation for this species cannot be recommended.
Canopy Gas Exchange and Water Use Efficiency of ‘Empire’ Apple in Response to Particle Film, Irrigation, and Microclimatic Factors
Authors: Glenn D. Michael
Published: January 2019

This study examined the interaction between a reflective particle film and water use efficiency (WUE) response of irrigated and non-irrigated apple trees (Malus ×domestica) over a wide range of environmental conditions. The objectives were to measure isotopic discrimination (Δ13C and δ18O), specific gas exchange, and WUE response of ‘Empire’ apple treated with a reflective particle film (PF), with and without supplemental irrigation, compared with an untreated control, with and without supplemental irrigation, over a range of leaf area indices (LAI), seasonal evapotranspiration (ETo), and vapor pressure deficits (VPD) to determine the mechanisms of action affecting WUE in apple. Short-term whole canopy gas exchange studies and isotope discrimination analysis were used to test the hypothesis that WUE was modified by the use of a PF. In whole canopy gas exchange studies, carbon assimilation (A) and transpiration tended to increase, and WUE and canopy conductance tended to decrease, with VPD within each LAI class from 2 to 6. For VPD > 1 kPa, the PF irrigated treatment consistently had the greatest WUE and other treatments were intermediate for LAI of 2 to 4. The PF irrigated and non-irrigated treatments had greater WUE than the control irrigated and non-irrigated treatments for VPD ≤ 2 kPa and there were no treatment effects for VPD > 2 kPa in the LAI range of 4 to 6. The PF non-irrigated was equivalent to the control non-irrigated treatment at VPD of 1 to 3 kPa, but was significantly lower at VPD of 3 to 4 kPa. PF irrigated and non-irrigated treatments had the greatest carbon isotope discrimination (Δ13C), the control non-irrigated treatment had the lowest Δ13C, and the control-irrigated treatment was intermediate. Oxygen isotope enrichment (δ18O) was positively correlated with the mean growing season VPD and mean growing season evapotranspiration. Δ13C was significantly and positively correlated with δ18O. Seasonal WUE was negatively correlated with Δ13C and there was an interaction with LAI. The seasonal water use of apple is better evaluated with stable isotope discrimination integrating seasonal variation rather that the use of whole canopy gas exchange measurements that measure WUE for brief periods of time. Δ13C was an accurate measurement of apple WUE and indicated that the PF irrigated treatment had the greatest Δ13C and so the lowest WUE compared with the control non-irrigated treatment at LAI from 4 to 6. The reduced WUE of the PF irrigated treatment compared with the control non-irrigated treatment is likely due to increased gS from lower canopy temperature and increased canopy photosynthetically active radiation diffusion that drove increased A. δ18O was an indicator of seasonal water use over six growing seasons due to its high correlation with ETo. In ‘Empire’ apple, A can be increased with PF and irrigation treatments, but at the cost of decreased WUE.
Seed Production Enhanced by Antiauxin in the pat-2 Parthenocarpic Tomato Mutant
Authors: Johkan Masahumi , Chiba Tomoko , Mitsukuri Kazuhiko , Yamasaki Satoshi , Tanaka Hideyuki , Mishiba Kei-ichiro , Morikawa Toshinobu , Oda Masayuki , Yamamoto Chihiro , Ohkawa Hiroshi
Published: January 2019

There is concern that high temperatures resulting from global warming could reduce fruit set of tomato (Solanum lycopersicum). However, fruit set of parthenocarpic tomato genotypes, which often bears seedless fruit, is not reduced when grown under a high temperature. The cause of seedless fruit development was studied with the aim of increasing the seed number in parthenocarpic tomato. Ovule number at anthesis in parthenocarpic and non-parthenocarpic fruit did not differ, but the proportion of undeveloped ovules increased with time after anthesis in parthenocarpic tomato, whereas most ovules in non-parthenocarpic tomato developed normally. Pollen grains germinated on the stigma and extruded pollen tubes in parthenocarpic and non-parthenocarpic tomatoes, but in parthenocarpic tomato, pollen tube elongation was markedly inhibited in the style base. Elongation of pollen tubes on agar containing indoleacetic acid (IAA) was depressed in parthenocarpic and non-parthenocarpic tomato plants. p-Chlorophenoxyisobutyric acid (PCIB), which inhibits auxin action, did not affect the fruit set and fresh weight in either type of tomato, although seed number per fruit in parthenocarpic tomato was significantly increased from 13 ± 2 to 74 ± 6 seeds by PCIB treatment. These results indicated that a high IAA concentration in the ovary of parthenocarpic tomato inhibited pollen tube elongation, and that poor fertilization resulted in failure of ovule development. Moreover, floral organs in parthenocarpic tomato were normally developed as in non-parthenocarpic tomato, and seed development could be induced in parthenocarpic tomato by PCIB treatment.
The Dominant Ms Allele in Onion Shows Reduced Penetrance
Authors: Melgar Sergio , Havey Michael J.
Published: January 2019

The most commonly used source of cytoplasmic male sterility in onion (Allium cepa) is controlled by the interaction of the cytoplasm [male-sterile (S) or normal male-fertile (N)] and one nuclear male-fertility-restoration locus (Ms). Scoring of genotypes at Ms is generally done by testcrossing male-fertile to male-sterile (S msms) plants, followed by scoring of testcross progenies for male-fertility restoration. We identified two N-cytoplasmic families, one that was homozygous dominant and the other segregating at Ms. Plants from each of these two families were individually testcrossed to male-sterile onion. Nuclear restoration of male fertility in testcross progenies was evaluated in the field over 4 years. For male plants homozygous dominant at Ms, we expected testcross families to show 100% male-fertility restoration, but observed mean values between 46% and 100%. For plants segregating at Ms, we again observed lower than expected frequencies of male-fertility restoration. These results demonstrate that the dominant Ms allele shows reduced penetrance, requiring that male-fertility restoration be scored over years to more confidently assign genotypes at Ms.
Quantitative Genotyping for the Astringency Locus in Hexaploid Persimmon Cultivars using Quantitative Real-time PCR
Authors: Akagi Takashi , Takeda Yumi , Yonemori Keizo , Ikegami Ayako , Kono Atsushi , Yamada Masahiko , Kanzaki Shinya
Published: January 2019

Persimmon (Diospyros kaki Thunb.) is generally hexaploid, and a single AST locus controls the pollination-constant non-astringency trait on each of six corresponding chromosomes. The pollination-constant non-astringent (PCNA) genotype is nulliplex and requires homozygous recessive alleles (ast) at the AST locus. There are several non-PCNA cultivars/selections that could be cross parents; however, the probability of yielding nulliplex offspring depends on the number of recessive alleles (ast). In genotyping for the AST locus in hexaploid persimmon, in contrast to the situation in diploid plants, we need to detect the AST/ast allele dosage; this cannot be detected by common codominant markers. In this study, we detected the allele dosage of Mast, which is a marker allele strongly linked to the ast allele among cultivars, by quantitative real-time polymerase chain reaction (qPCR) using three reference sites, actin (DkAct), anthocyanin reductase (DkANR), and L5R, whose sequences are conserved in the genome of persimmon cultivars. Based on the allele dosage of the Mast, AST/ast genotypes were estimated for 63 non-astringent cultivars/selections, of which only five cultivars/selections were estimated to be simplex or duplex. The quantitative genotyping method using qPCR may be generally effective for polyploid plants.
Evaluation of Gynogenic Responsiveness and Pollen Viability of Selfed Doubled Haploid Onion Lines and Chromosome Doubling via Somatic Regeneration
Authors: Jakše Marijana , Hirschegger Pablo , Bohanec Borut , Havey Michael J.
Published: January 2019

Although haploid induction has been used in onions (Allium cepa L.) for over 20 years, several obstacles limit its use in plant breeding programs. To address these limitations, we evaluated the responsiveness of doubled haploid (DH) lines and their selfed progenies, an alternative protocol for chromosome doubling using somatic regeneration of haploid lines, and pollen viability of DH lines. Twenty-one DH lines were self pollinated and tested for haploid induction in the second generation. Among the DH lines, 18 lines showed an average of 20% decrease in gynogenic responsiveness compared with the original lines, while three lines registered an average increase of 5.7%. Using a two-step induction/regeneration procedure, 8,589 somatic regenerants were obtained from 16,170 flower buds from haploid plants, and shoot culture was established. A more laborious procedure using extraction of ovaries in the regeneration stage was found equal to flower bud culture. Chromosome doubling via somatic regeneration was found to be 83% and 100% efficient when the source material was haploid or mixoploid, respectively. Based on the results achieved in this and previous studies, an alternative protocol for chromosome doubling of gynogenic haploids is proposed.
Changes in Protein Expression Associated with Chilling Injury in Tomato Fruit
Authors: Vega-García Misael O. , López-Espinoza Greici , Ontiveros Jeanett Chávez , Caro-Corrales José J. , Vargas Francisco Delgado , López-Valenzuela José A.
Published: January 2019

Tomato (Solanum lycopersicum) fruit is susceptible to chilling injury (CI), a physiological disorder caused by low, non-freezing temperatures that affects fruit postharvest quality. Little is known about the biochemical basis of CI, and the aim of this study was to identify proteins related to this disorder in ‘Imperial’ tomato fruit. CI and protein expression changes were analyzed during fruit ripening (0, 4, 8, and 12 days at 21 °C) after storage under chilling (5 °C) and non-chilling conditions (21 °C) for 5, 15, and 25 days. The main CI symptoms observed were uneven fruit ripening and color development, pitting, and decay. Protein analysis of two-dimensional gels showed that 6% of the detected spots (≈300) changed their expression in response to cold. The identified proteins are involved in carbon metabolism, oxidative stress, photosynthesis, and protein processing and degradation; two were related to cold stress, showing higher accumulation in non-damaged tissue of chilled fruit: thioredoxin peroxidase (TPxI) and glycine-rich RNA-binding protein (GR-RBP). This is the first report suggesting an important role for TPxI and GR-RBP in cold response during tomato fruit ripening, and they may be acting through redox sensing and regulation of gene expression at low temperature. These enzymes and the other chilling-related proteins might be working together to maintain the cellular homeostasis under cold stress conditions.
Interactions of Temperature and Photoperiod Determine Expression of Repeat Flowering in Strawberry
Authors: Bradford Emma , Hancock James F. , Warner Ryan M.
Published: January 2019

Strawberry (Fragaria ×ananassa) cultivars vary greatly in the expression of remontancy, or repeat flowering. To more clearly define the roles of temperature and daylength in flowering control of strawberry, the non-remontant cultivar Honeoye, and two remontant genotypes classified as day-neutral, ‘Tribute’ and an elite clone of Fragaria virginiana ssp. virginiana, RH 30, were grown at 14, 17, 20, 23, 26, or 29 °C, under a short (9 h) or long (16 h) photoperiod. Differential flowering responses of genotypes across temperature and photoperiod treatments resulted from variation in 1) the photoperiod-insensitive permissive temperature range for flowering, 2) photoperiodic requirement if temperature exceeded the photoperiod-insensitive range, and 3) the rate of development of axillary meristems. The photoperiod-insensitive temperature range varied from 14 up to 20 °C for ‘Honeoye’, 23 °C for RH 30, and 26 °C for ‘Tribute’. When temperature exceeded the photoperiod-insensitive range, ‘Honeoye’ and RH 30 required short days for flowering, while ‘Tribute’ required long days. Flowering of ‘Honeoye’ lagged behind ‘Tribute’ and RH 30 by about 84 days in treatments where flowering occurred. These results indicate that temperature and floral initiation/development rate strongly influence the expression of remontancy, and that screening genotypes for day neutrality alone is unlikely to result in the development of robustly remontant cultivars.
Effects of ipt Gene Expression on Leaf Senescence Induced by Nitrogen or Phosphorus Deficiency in Creeping Bentgrass
Authors: Zhang Yan , Liang Cuiyue , Xu Yan , Gianfagna Thomas , Huang Bingru
Published: January 2019

The objective of the study was to determine whether the expression of a cytokinin (CK) biosynthesis gene encoding adenine isopentenyl transferase (ipt) would delay or suppress leaf senescence induced by nitrogen (N) or phosphorus (P) deficiency in a C3 grass species, creeping bentgrass (Agrostis stolonifera). The ipt gene was ligated to a senescence-associated promoter, SAG12, and was transferred into creeping bentgrass using an agrobacterium (Agrobacterium tumefaciens)-mediated transformation technique. Plants from an SAG12-ipt transgenic line (S41) and a null transformant (NT) control line were grown in nutrient solutions with all essential elements or without N (−N) or P (−P) for 21 days. Significant declines in leaf photochemical efficiency (Fv/Fm) and chlorophyll content of mature leaves were detected in NT and SAG12-ipt plants exposed to N or P deficiency. Compared to the NT control line, SAG12-ipt plants had higher levels of Fv/Fm, chlorophyll, and CK contents in leaves, and these differences between the NT control and SAG12-ipt line became more pronounced with treatment duration. The ipt expression was detected in the −P-treated and the −N-treated plants after 21 days, although the level of expression decreased under N or P deficiency. Under −P treatment, root acid phosphatase activity was greater in SAG12-ipt line than in the NT control line. No significant differences in nitrate reductase activity were detected in leaves or roots between the SAG12-ipt and the NT control lines. Our results demonstrated that SAG12-ipt expression suppressed leaf senescence induced by N or P deficiency in a perennial grass species. The suppressing effects on leaf senescence under P deficiency may be related to CK regulation of more efficient use of P in roots of the SAG12-ipt plants.
Differential Responses to Heat Stress in Activities and Isozymes of Four Antioxidant Enzymes for Two Cultivars of Kentucky Bluegrass Contrasting in Heat Tolerance
Authors: He Yali , Huang Bingru
Published: January 2019

Understanding antioxidant mechanisms for heat stress is important for improving heat tolerance in cool-season plant species. The objective of this study was to identify antioxidant enzymes associated with cultivar variations in heat tolerance in kentucky bluegrass (Poa pratensis) by comparing heat responses of activity and isoforms of antioxidant enzymes in two cultivars contrasting in heat tolerance. Plants of heat-tolerant ‘Eagleton’ and heat-sensitive ‘Brilliant’ were exposed to 20 °C (control) or 40 °C (heat stress) for 28 days in growth chambers. Chlorophyll (Chl) a content remained unchanged and Chl b content increased in ‘Eagleton’, while both of them decreased in ‘Brilliant’, and by 28 days, ‘Eagleton’ had significantly higher Chl a and b content than ‘Brilliant’. The activities of superoxide dismutase (SOD) were significantly higher in ‘Eagleton’ than in ‘Brilliant’ by 28 days of heat stress. An isozyme SOD2 was induced early during heat stress in ‘Eagleton’, while isozyme SOD3 degraded, to a lesser extent in ‘Eagleton’ than in ‘Brilliant’. Catalase (CAT) activity significantly increased in ‘Brilliant’ but remained constant in ‘Eagleton’, and ‘Brilliant’ had a significantly higher CAT activity and isozyme CAT1 than ‘Eagleton’ during heat stress. Significant increases in ascorbate peroxidase (APX) activities occurred under heat stress, to a greater extent in ‘Eagleton’, whereas isozymes did not exhibit difference between cultivars. Guaiacol-peroxidase (POD) activity declined during heat stress in both cultivars. The intensity of POD isozymes in ‘Brilliant’ remained constant, while ‘Eagleton’ showed a transient increases in POD1 at 7 days of heat stress. Our results indicated that antioxidant defense mechanisms for heat tolerance in kentucky bluegrass could be mainly associated with changes in activity and forms of isozymes of SOD for O2 scavenging and APX activity for H2O2 scavenging under heat stress.
Identification of Quantitative Trait Loci Conferring Resistance to Bemisia tabaci in an F2 Population of Solanum lycopersicum × Solanum habrochaites Accession LA1777
Authors: Momotaz Aliya , Scott Jay W. , Schuster David J.
Published: January 2019

Solanum habrochaites S. Knapp and D.M. Spooner accession LA1777 have reported resistance to the sweetpotato whitefly (SPWF), Bemisia tabaci (Genn.). An interspecific F2 population of 171 plants between tomato [Solanum lycopersicum L. (formerly Lycopersicon esculentum Mill.)] and LA1777 was bioassayed against adult SPWF in a greenhouse using clip cages. A selective genotyping analysis was used with 11 resistant and 10 susceptible plants to locate resistance genes by testing them with molecular markers spanning most of the tomato genome at about 10-cM intervals. Markers in four regions were found to be associated with resistance, where three of them showed significantly strong associations and one showed a weak association through chi-square and analyses of variance. However, through quantitative trait locus (QTL) analysis using molecular markers, all four regions were identified as major QTLs with logarithm of odds (LOD) values of 4.87 to 5.95. The four QTLs were identified near the markers TG313 on chromosome 10, C2_At2g41680 on chromosome 9, TG523/T0408 on chromosome 11, and TG400/cLEG-37-G17 on chromosome 11. Multiple regression analysis produced similar results as above with fixed effects of single loci as well as interaction among some of the QTLs.
Characterization and Identification of Pawpaw Cultivars and Advanced Selections by Simple Sequence Repeat Markers
Authors: Pomper Kirk W. , Lowe Jeremiah D. , Lu Li , Crabtree Sheri B. , Dutta Shandeep , Schneider Kyle , Tidwell James
Published: January 2019

Pawpaw [Asimina triloba (L.) Dunal.], a tree fruit native to eastern North America, is in the beginning stages of commercialization. Cultivars available in the early 20th century have been lost, and significant genetic erosion may have occurred. Polymorphic microsatellite marker loci were developed from enriched genomic libraries. Five marker loci were used to fingerprint 28 cultivars and 13 selections. For the 41 genotypes, 102 alleles were amplified and major allele frequency (0.16–0.94), number of genotypes (2–27), and allele size (144–343 bp) varied greatly by locus. Four loci were highly polymorphic, as indicated by values for expected heterozygosity (He), observed heterozygosity (Ho), and polymorphism information content, but only two alleles were detected at locus Pp-C104. A high level of genetic diversity was observed in the studied genotypes. The Ho (0.68) and He (0.70) were similar and indicated few null alleles. In the 41 genotypes, 39 unique fingerprints were observed. These new microsatellite marker loci will be useful for cultivar fingerprinting, management of collections, and investigation of genetic diversity in collections and wild populations. Grouping of genotypes in an unweighted pair group method with arithmetic mean dendrogram was generally consistent with their origins.
Molecular Cloning of Dormancy-associated MADS-box Gene Homologs and Their Characterization during Seasonal Endodormancy Transitional Phases of Japanese Pear
Authors: Ubi Benjamin Ewa , Sakamoto Daisuke , Ban Yusuke , Shimada Takehiko , Ito Akiko , Nakajima Ikuko , Takemura Yoshihiro , Tamura Fumio , Saito Toshihiro , Moriguchi Takaya
Published: January 2019

To understand the role of the MIKC-type dormancy-associated MADS-box (DAM) genes in the regulation of endodormancy in japanese pear (Pyrus pyrifolia), we isolated two DAM genes from ‘Kosui’ and characterized their expression throughout the seasonal endodormancy phases in ‘Kosui’, as well as in TP-85–119 taiwanese pear (P. pyrifolia), which is a less dormant type. Several copies of the corresponding DAM genes are present in the P. pyrifolia genome. Rapid amplification of cDNA ends enabled the isolation of two full-length cDNAs, designated as PpMADS13–1 and PpMADS13–2, with complete open reading frames encoding 227 and 234 amino acids, respectively. Multialignment of the two ‘Kosui’ and the database DAM genes (based on the deduced amino acid sequences) showed that PpMADS13–1 and PpMADS13–2 were highly identical to the Rosaceae DAM genes and encoded the conserved domains characteristic of other MIKC-type MADS-box genes. The phylogenetic relationships showed that PpMADS13–1 and PpMADS13–2 were more closely related to the Prunus DAM, though they formed a unique subclade. The specific expression analysis of PpMADS13–1 and PpMADS13–2 by real-time polymerase chain reaction showed that both DAM genes are gradually down-regulated concomitant with endodormancy breaking. PpMADS13–1 and PpMADS13–2 showed similar fluctuations in expression patterns, although PpMADS13–2 was more highly expressed relative to PpMADS13–1. The expression of PpMADS13–1 and PpMADS13–2 in the less dormant taiwanese pear, TP-85–119, was quite low (nearly zero level), which is consistent with a down-regulated pattern of expression of the DAM genes in japanese pear, peach (Prunus persica), and japanese apricot (Prunus mume). Differential genomic DNA methylation patterns detected in PpMADS13–1 and PpMADS13–2 were not concomitant with seasonal endodormancy transition phases, suggesting that DNA methylation in these loci under investigation may not be linked to endodormancy progression in ‘Kosui’.