bluuebunny/crossref_metadata_2025 huggingface dataset:
Resistance to Plum Pox Virus (Dideron Isolate RB3.30) in a Group of California Almonds and Transfer of Resistance to Peach
Authors: Martínez-Gómez P. , Rubio M. , Dicenta F. , Gradziel T.M.
Published: January 2019

Sharka [(plum pox virus (PPV)] mainly affects Prunus species, including apricot (Prunus armeniaca L.), peach (Prunus persica L.), plum (Prunus salicina Lindl., Prunus domestica L.), and, to a lesser degree, sweet (Prunus avium L.) and sour cherry (Prunus cerasus L.). Level of resistance to a Dideron isolate of PPV in seven California almond [P. dulcis (Miller) D.A. Webb], five processing peach cultivars, and two peach rootstocks was evaluated. In addition, almond and peach selections resulting from interspecific almond × peach hybridization and subsequent gene introgression were tested. Evaluations were conducted in controlled facilities after grafting the test genotypes onto inoculated GF305 peach rootstocks. Leaves were evaluated for PPV symptoms during three consecutive cycles of growth. ELISA-DASI and RT-PCR analysis were also employed to verify the presence or absence of PPV. Peach cultivars and rootstocks showed sharka symptoms and were ELISA-DASI or RT-PCR positive for some growth cycles, indicating their susceptibility to PPV. Almond cultivars and almond × peach hybrids did not show symptoms and were ELISA-DASI and RT-PCR negative, demonstrating resistance to PPV. Two (almond × peach) F2 selections as well as two of three backcrossed peach selections also showed a resistant behavior against the PPV-D isolate. Results demonstrate a high level of resistance in almond and indicate potential for PPV resistance transfer to commercial peach cultivars.
Cloning of a Zinc-binding Cysteine Proteinase Inhibitor in Citrus Vascular Tissue
Authors: Ellis Danielle R. , Taylor Kathryn C.
Published: January 2019

A partial cDNA (cvzbp-1) was cloned based on the N-terminal sequence of a citrus (Citrus L.) vascular Zn-binding protein (CVZBP) previously isolated from vascular tissue (Taylor et al., 2002). CVZBP has homology to the Kunitz soybean proteinase inhibitor (KSPI) family. Recombinant protein produced using the cDNA clone inhibited the cysteine proteinase, papain. Metal binding capacity has not been reported for any other member of this family. CVZBP was present in leaves, stems, and roots but not seeds of all citrus species examined. However, CVZBP was present in germinating seeds after the cotyledons had turned green. Within four hrs after wounding, CVZBP was undetectable in the wounded leaf and adjacent leaves. It has been suggested that many members of the KSPI family serve a function in defense. However, the expression of the CVZBP is in direct contrast with those of KSPI members that were implicated in defense response. Though systemically regulated during wounding, we suggest that CVZBP is not a defense protein but rather may function in vascular development.
Growth and Fruiting of Young `Concord' Grapevines in Relation to Reserve Nitrogen and Carbohydrates
Authors: Cheng Lailiang , Xia Guohai , Bates Terry
Published: January 2019

One-year-old `Concord' grapevines (Vitis labruscana Bailey) were fertigated with 0, 5, 10, 15, or 20 mm nitrogen by using a modified Hoagland's solution for 8 weeks during active vine growth in summer. Half of the vines at each N concentration were sprayed with 3% foliar urea twice in late September while the rest served as controls. After natural leaf fall, all the vines were overwintered in a cold room (2 to 4 °C). Four vines from each treatment were destructively sampled before budbreak for reserve N and carbohydrate analysis. The remaining vines were supplied with either no N or sufficient N (10 mm N) from 2 weeks before bloom to 1 month after bloom. All the vines were destructively harvested at 1 month after bloom. Total amount of N in dormant vines increased with increasing N fertigation concentration. Total nonstructural carbohydrates (TNC) increased with increasing N fertigation concentration from 0 to 10 mm, and then leveled off with further rises in N supply. Foliar urea application increased total N but decreased TNC of dormant vines at each given N fertigation level. When no N was provided during the regrowth period, vine total leaf area, fruit yield, and total dry weight increased with increasing N supply from fertigation the previous year. Vines sprayed with foliar urea the previous fall produced a larger total leaf area, a higher yield, and a higher total vine dry weight at each given N fertigation concentration. Providing vines with sufficient N during the regrowth period significantly increased total leaf area, fruit yield, and vine total dry weight across the previous N fertigation concentrations, but vines sprayed with foliar urea still had a larger leaf area, a higher yield, and a higher total vine dry weight at each given N fertigation concentration. Therefore, we conclude that both vegetative growth and fruiting of young `Concord' vines are largely determined by reserve nitrogen, not by reserve carbohydrates, and that current-season N supply plays a very important role in sustaining vine growth and development, especially fruit growth.
Genotypic Variation in the Micropropagation of Sri Lankan Exacum Hybrids
Authors: Riseman Andrew , Chennareddy Siva
Published: January 2019

Protocols for in vitro propagation are reported for interspecific hybrids of Exacum L., derived from Sri Lankan taxa. Four genotypes were used to evaluate the effects of MS (Murashige and Skoog) and WP (Woody Plant) media supplemented with 2-iP, BA, or KIN during establishment and multiplication phases. In addition, rhizogenesis and associated root characteristics were evaluated using MS medium supplemented with NAA or IBA. Overall, either 2-iP or BA was significantly more effective than kinetin in establishment and shoot proliferation with significant genotype × treatment interactions present. Maximum multiplication rates were achieved in the following genotype-hormone combinations: E-6, 2 mg·L-1 BA (4.5 per explant); E-23, E-32, and E-37, 2 mg·L-1 2-iP (3.5, 2.5, and 3.6 per explant, respectively). In vitro rhizogenesis was greatest in liquid MS medium supplemented with 1 mg·L-1 NAA while significantly reduced rooting was observed with IBA supplements. Our results demonstrate that micropropagation of Sri Lankan Exacum hybrids is possible and that adequate multiplication and rooting percentages can be achieved. However, the high level of genetic variation identified requires genotype-specific media modifications. Chemical names used: benzyladenine (BA); 2-isopentenyladenine (2-iP); indole-3-butyric acid (IBA); α-naphthaleneacetic acid (NAA); kinetin (KIN).
Screening Lettuce Germplasm for New Sources of Resistance to Corky Root
Authors: Mou Beiquan , Bull Carolee
Published: January 2019

Corky root is a major disease of lettuce (Lactuca sativa L.) observed in many production areas of the world. The pathogen Sphingomonas suberifaciens (van Bruggen et al.) Yabuuchi et al. varies with regard to virulence, and several strains have been isolated that can cause disease symptoms even on cultivars that have the only known resistance gene, cor. It is desirable to find new sources of resistance to diversify the genetic basis of the resistance and to confer resistance against isolates that are not adequately controlled by cor. More than 1000 plant introduction lines and cultivars were screened in assays conducted in the greenhouse, growth chamber, and field. Three L. serriola L. lines (PI 491239, PI 491096, and PI 491110) and a L. virosa L. line (PI 273597c) were highly resistant to corky root in all tests. Disease severity ratings in the field were correlated with the ratings in the greenhouse (r = 0.722) and in the growth chamber (r = 0.650). Significant genotype × environment interactions were observed for corky root severity. None of the four resistant lines had the two molecular markers closely linked to the cor allele. The information on disease resistance for these genotypes will be useful in future breeding work.
Molecular Markers for the Self-compatible S4′-haplotype, a Pollen-part Mutant in Sweet Cherry (Prunus avium L.)
Authors: Ikeda K. , Watari A. , Ushijima K. , Yamane H. , Hauck N.R. , Iezzoni A.F. , Tao R.
Published: January 2019

S4′ is a pollen-part mutant in sweet cherry (Prunus avium L.) that is extensively used to develop self-compatible cultivars. The S4′-haplotype is known to have a functional stylar component and a nonfunctional pollen component. The pollen component in sweet cherry necessary for the specificity of the pollen reaction is believed to be an S-haplotype specific F-box protein gene, called SFB. This study describes two molecular markers that distinguish between SFB4 and SFB4′ by taking advantage of a four base pair deletion in the mutant allele. The resulting polymerase chain reaction (PCR) products can either be separated directly on a polyacrylamide gel or they can be subjected to restriction enzyme digestion and the different sized products can be visualized on an agarose gel. The latter technique utilizes restriction sites created in the PCR products from the SFB4′ allele, but not the SFB4 allele. Because the primer sets created differential restriction sites, these primer sets were termed dCAPS (derived cleaved amplified polymorphism sequence) markers. These molecular assays can be used to verify self-compatibility conferred by the S4′-haplotype.
Acclimation of Wax Begonia to Light Intensity: Changes in Photosynthesis, Respiration, and Chlorophyll Concentration
Authors: Nemali Krishna S. , van Iersel Marc W.
Published: January 2019

Physiological acclimation of plants to light has been studied mostly at the leaf level; however whole-plant responses are more relevant in relation to crop growth. To examine the physiological changes associated with different daily light integrals (DLI) during growth of wax begonia (Begonia semperflorens-cultorum Hort.), we grew plants under DLI of 5.3, 9.5, 14.4, and 19.4 mol·m-2·d-1 in a whole-plant gas exchange system. Photosynthesis-light response curves of groups of 12 plants were determined after 25 d of growth. Physiological parameters were estimated per m2 ground area and per m2 leaf area. On a ground area basis, significant increases in dark respiration (Rd), quantum yield (α), the light compensation point (LCP), and maximum gross photosynthesis (Pg,max) were seen with increasing DLI. Variations in physiological parameters among different treatments were small when corrected for differences in leaf area. On a leaf area basis, α, LCP, and the light saturation point (LSP) did not change significantly, whereas significant increases in Rd and Pg,max were seen with increasing DLI. There was a small decrease in leaf chlorophyll concentration (6.3%, measured in SPAD units) with increasing DLI. This study indicates that wax begonias acclimate to low DLI by increasing their leaf chlorophyll concentration, presumably to more efficiently capture the available light, and to high DLI by increasing Pg,max to efficiently utilize the available light, thereby maximizing carbon gain under both situations.
Suppression of Avocado (Persea americana Mill.) Fruit Softening and Changes in Cell Wall Matrix Polysaccharides and Enzyme Activities: Differential Responses to 1-MCP and Delayed Ethylene Application
Authors: Jeong Jiwon , Huber Donald J.
Published: January 2019

Pre-ripe `Booth 7' avocado (Persea americana Mill.) fruit, a cross of West Indian and Guatemalan strains, were treated with 0.9 μL·L-1 1-methylcyclopropene (1-MCP) for 12 hours at 20 °C. After storage for 18 days in air at 13 °C, at which time whole fruit firmness values averaged about 83 N, half of the 1-MCP-treated fruit were treated with 100 μL·L-1 ethylene for 12 hours and then transferred to 20 °C. 1-MCP delayed softening, and fruit treated with 1-MCP retained more green color than air-treated fruit when full ripe (firmness 10 to 15 N). 1-MCP affected the activities of pectinmethylesterase (EC 3.2.1.11), α-(EC 3.2.1.22) and β-galactosidases (EC 3.2.1.23), and endo-β-1,4-glucanase (EC 3.2.1.4). The appearance of polygalacturonase (EC 3.2.1.15) activity was completely suppressed in 1-MCP-treated fruit for up to 24 days, at which time the firmness of 1-MCP-treated fruit had declined nearly 80% compared with initial values. The effect of exogenous ethylene applied to partially ripened 1-MCP-treated fruit differed for different ripening parameters. Ethylene applied to mid-ripe avocado exerted no effect on the on-going rate or final extent of softening of 1-MCP-treated fruit, even though polygalacturonase and endo-1,4-β-glucanase activities increased in response to ethylene. β-galactosidase decreased in 1-MCP-treated fruit in response to ethylene treatment. 1-MCP delayed the increase in solubility and depolymerization of water- and CDTA (1,2-cyclohexylenedinitrilotetraacetic acid)-soluble polyuronides, likely due to reduced polygalacturonase activity. At the full-ripe stage, the levels of arabinose, galactose, glucose, mannose, rhamnose, and xylose associated with the CDTA-soluble polyuronide fraction were similar among all treatments. In contrast, the galactose levels of water-soluble polyuronides declined 40% and 17% in control and 1-MCP treated fruit, respectively. Hemicellulose neutral sugar composition was unaffected by 1-MCP or ethylene treatment. The data indicate that the capacity of avocado fruit to recover from 1-MCP-mediated suppression of ripening can be only partially amended through short-term ethylene application and differs significantly for different ripening parameters.
Self-incompatibility in the Chilean Endemic Genus Leucocoryne Lindley
Authors: Mansur L. , Gonzalez M. , Rojas I. , Salas P.
Published: January 2019

The Chilean genus Leucocoryne has exceptional qualities as an ornamental plant that is being developed through breeding. Little is known about the origin of its genetic variation for flower phenotype. Our hypothesis is that, despite having a perfect flower, Leucocoryne has an outbreeding behavior due to self-incompatibility. Greenhouse studies were conducted to study self-incompatibility. In 2000, one species L. purpurea Gay. and two distinct populations Leucocoryne sp. Pichicuy and Leucocoryne sp. Chigualoco were used, whereas in 2001, L. coquimbensis F. Phil. and Leucocoryne sp. Alcones and Leucocoryne sp. Talinay were added. Field studies were carried out in 2001 at La Campana (lat. 29°S, Valparaíso Region, Chile) and Bosque de Fray Jorge (lat. 33°S, Coquimbo Region, Chile) National Parks with L. ixioides Lindley and L. purpurea, respectively. The index of self-genetic incompatibility (ISI) was measured as the average number of seeds per fruit produced by self-pollination divided by the average number of seeds per fruit produced from cross-pollination. The average ISI values for 2000 and 2001 were 0.08 and 0.06, respectively, meaning that Leucocoryne is largely self-incompatible. In the field seed set was compared between flowers that were isolated from insects and those that were not. None of the isolated flowers produced seeds, instead nonisolated flowers produced an average of 29 seeds per fruit at La Campana and 56 at Bosque de Fray Jorge. Leucocoryne's self-incompatibility and outcrossing behavior plus its capacity to fix any genotype via asexual reproduction, most likely contribute to its large variation for flower color, shape, size, design, and aroma. Due to Leucocoryne's reproductive behavior it would be difficult to breed for homozygous inbreds and pure hybrid cultivars
Bending Alters Water Balance and Reduces Photosynthesis of Rose Shoots
Authors: Kim Soo-Hyung , Shackel Kenneth A. , Lieth J. Heinrich
Published: January 2019

Shoot-bending has become a standard cultural practice in cut-flower rose (Rosa hybrida L.) production. Physiological effects of shoot-bending on leaf net photosynthesis (A), stomatal conductance (gs), transpiration rate (E), and stem water potential (ψ) were investigated for rose plants. With saturating light conditions, shoot-bending decreased rates of A, gs, and E in comparison with the rates prior to shoot-bending. A, gs, and E of bent shoots were significantly lower than those of the control shoots that were not bent. The differences in A between bent and control shoots decreased over time, disappearing within 3 weeks after bending. Bent shoots exhibited reduced ψ. Leaves projecting upward on a bent stem were found to have higher A, gs, and E than those projecting downward. This was probably due to the destruction of xylem vessels serving the leaves attached to the lower side (compression side) of the bent stem. Our results support the hypothesis that hydraulic conductivity is reduced in bent shoots probably due to disturbed xylem tissues, and that reduced photosynthetic rates of bent shoots are a function of water status.
The Effects of Ethephon on Saskatoon (Amelanchier alnifolia Nutt.) Fruit Ripening
Authors: McGarry Roisin , Ozga Jocelyn A. , Reinecke Dennis M.
Published: January 2019

Field experiments were conducted on two cultivars of saskatoon to test the effectiveness of ethephon in stimulating uniform fruit ripening without compromising fruit quality. Shrubs of cultivars Northline and Smoky were sprayed to runoff with ethephon (0, 250, 500, and 1000 mg·L-1 for `Northline'; 0, 500, and 1000 mg·L-1 for `Smoky') prior to fruit maturity. Fruit were harvested 4 to 8 days after treatment and sorted into ripeness categories by size, and the fully ripe fruit were evaluated for quality (surface color, firmness, mean fruit weight, soluble solids, and titratable acids). Ethephon significantly increased the percent ripe fruit per shrub (by up to 9.7%) in both cultivars, without a significant effect on fruit quality. At concentrations up to 1000 mg·L-1, ethephon may be an effective ripening agent for saskatoon fruit without reducing fruit quality. Although there were significant differences in yield from year to year for both cultivars because of their biennial-bearing habit, ethephon treatments did not significantly affect total yields.
Fruit Quality, Fermentation Products, and Activities of Associated Enzymes During Elevated CO2 Treatment of Strawberry Fruit at High and Low Temperatures
Authors: Zhang Jianzhi Jenny , Watkins Christopher B.
Published: January 2019

The effects of postharvest treatments of air and 20 kPa CO2 (in air) at 2 or 20 °C on color, firmness, accumulations of acetaldehyde, ethanol, and ethyl acetate, activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activity, and expression of an ADH gene were studied in strawberry fruit (Fragaria ×ananassa Duch. cv. Jewel). CO2 treatment enhanced strawberry fruit firmness at 2 °C but not 20 °C, while the rate of color changes was affected by CO2 treatment at 20 °C but not at 2 °C. Temperature also affected the accumulation of acetaldehyde, ethanol and ethyl acetate in CO2-treated fruit. All three compounds accumulated in fruits at 2 °C. At 20 °C, ethanol accumulated slightly by day 6, although ethyl acetate accumulated in fruit from both atmospheres. PDC enzyme activity was higher in CO2-treated fruit than their air-treated control at 2 °C but not at 20 °C. ADH activity and ADH mRNA accumulation of the CO2-treated berries were higher than in air at 20 °C but not 2 °C. The results, overall, indicate that patterns of change among gene expression, enzyme activities, and fermentation product accumulation were not consistent.
Genetic Variation and Response to Selection for Early Season Fruit Production in California Strawberry Seedling (Fragaria ×ananassa Duch.) Populations
Authors: Shaw Douglas V. , Larson Kirk D.
Published: January 2019

The genetic opportunity for selection of early fruiting strawberry cultivars was evaluated using seedling populations from the Univ. of California (UC) breeding program in three years. Narrow-sense heritabilities for early season yield and for the proportion of an individual's total yield expressed early were moderate (h2 = 0.24-0.53) and broad-sense heritabilities were slightly larger (H2 = 0.31-0.70), suggesting the presence of some nonadditive genetic variance for these traits. These two traits were genetically correlated with each other (rg = 0.78-0.98), but only early yield was consistently genetically correlated with seasonal yield (rg = 0.52-0.82). Selection was performed for each trait using an index on full-sib family means and individual phenotypic values in two of the three years, and predicted response was compared with that obtained using vegetatively propagated runner plants from selected genotypes in the subsequent fruiting season. Statistically significant (P < 0.05) selection response was obtained in one of two years for each trait, and combined analysis demonstrated highly significant (P < 0.01) response for both traits. However, realized response over all traits and years was just 27.3% of that predicted based on the estimated heritabilities and applied selection intensities. These results suggest that selection for early yield should be based at least in part on runner plant evaluations rather than exclusively on seedling performance.
Vegetative Phase Transition and Corn Borer Resistance of shrunken2 versus sugary1 Sweet Corn Near-isogenic Inbred Lines
Authors: Revilla Pedro , Tracy William F. , Soengas Pilar , Ordás Bernardo , Ordás Amando , Malvar Rosa Ana
Published: January 2019

The genes sugary1 (su1) and shrunken2 (sh2) are commonly used to produce sweet and super-sweet corn (Zea mays L.), respectively. In this work we compare corn borer [european corn borer (ECB) (Ostrinia nubilalis Hbn.) and pink stem borer (PSB) (Sesamia nonagrioides Lef.)] susceptibility in seven pairs of su1 and sh2 near-isogenic sweet corn inbreds (101t, C23, C40, C68, Ia453, Ia5125, and P39) and the relationship between corn borer resistance and vegetative phase transition. The seven pairs of near-isogenic inbreds were evaluated under corn borer infestation during 3 years in northwestern Spain. Differences among inbreds were significant for most of the traits, although resistance was partial. Ia5125su1 and C40su1 were the most resistant inbreds. Differences between a few pairs of near-isogenic su1 and sh2 strains were significant for some vegetative phase change and corn borer damage-related traits. Generally su1 strains flowered earlier, had a shorter juvenile phase, fewer PSB, and more ECB larvae than sh2 strains. However su1 and sh2 strains did not differ significantly for most traits related to phase transition and corn borer damage; notably ear damage was not significantly different between su1 and sh2 strains. These results suggest that theoretical and practical results of sweet corn (sugary1) breeding for corn borer resistance could be capitalized for super-sweet corn (shrunken2) breeding.
The Effect of Crop Load on Tree Water Consumption of `Golden Delicious' Apples in Relation to Fruit Size: An Operative Model
Authors: Naschitz Shaul , Naor Amos
Published: January 2019

Water availability and crop load (number of fruit per tree) affect the fruit size of apple (Malus ×domestica Borkh.), but their interaction in relation to fruit size is not well understood. The objective of the present study was to explore the effect of crop load on water consumption of `Golden Delicious' apple in relation to fruit size. A wide range of irrigation rates and crop loads was applied to mature, field-grown `Golden Delicious' apple trees for two consecutive years, 1995 and 1996. The number of fruit, crop yield, and average fruit diameter were determined for each tree. A model was proposed to describe the combined effect of crop yield and irrigation rate on fruit size. In the model, irrigation waters were divided between two uses: vegetative water use (UV), which enables the tree to produce a steady, long-term yield; and reproductive water use (UR), which supports the production of the dry mass of commercial-size fruit. Potential fruit diameters were 77.1 and 72.2 mm for 1995 and 1996, respectively. Calculated vegetative use values were 300.2 and 323.4 mm for 1995 and 1996, respectively. The response of fruit diameter to reproductive water use per ton fresh weight (specific reproductive water use; URT) was fitted by a hyperbolic model in which the fruit diameter increases with increasing specific reproductive water use and approaches the yearly potential diameter at 60 to 70 m3·t-1, irrespective of the potential fruit diameter. In both years, fruit diameter showed a closer correlation with the specific reproductive water use than with either crop load or irrigation rate. In conclusion, the crop yield and the potential fruit size determine the irrigation rate required to achieve a certain average fruit diameter. The year's potential fruit diameter does not affect the total tree water use or its components. The proposed model can be used by growers for supporting decisions on irrigation and thinning strategies in commercial orchards.
Inheritance of Phytophthora Stem Blight Resistance as Compared to Phytophthora Root Rot and Phytophthora Foliar Blight Resistance in Capsicum annuum L.
Authors: Sy Ousmane , Bosland Paul W. , Steiner Robert
Published: January 2019

The pathogen Phytophthora capsici Leon. is known to be a limiting factor of chile pepper (Capsicum L.) production around the world. The genetics of the resistance is becoming better understood due to the specific nature of the host-pathogen interaction, i.e., all plant organs are subject to infection. It has been shown that phytophthora root rot resistance and phytophthora foliar blight resistance are under different genetic mechanisms. This study aimed at understanding the inheritance of resistance of phytophthora stem blight and to determine whether phytophthora stem blight was the same disease syndrome as phytophthora root rot and phytophthora foliar blight. Stem cuttings of a segregating F2 population and testcross progeny facilitated the ability to screen for two disease syndromes concurrently. When the three disease syndromes were compared separately, the F2 populations fit a 3 resistant (R): 1 susceptible (S) ratio and the testcross progenies fit a 1R:1S ratio. When comparative studies were performed (stem vs. foliar and stem vs. root), the F2 populations fit a 9R/R:3R/S:3S/R:1S/S ratio and the testcross fit a 1R/R:1R/S:1S/R:1S/S ratio. These ratios are consistent of a single gene controlling the resistance of each system. Therefore, phytophthora stem blight, root rot, and foliar blight are three separate disease syndromes.
Linkage of an Alternaria Disease Resistance Gene in Mandarin Hybrids with RAPD Fragments
Authors: Dalkilic Zeynel , Timmer L.W. , Gmitter Frederick G.
Published: January 2019

The inheritance of resistance to a host-specific isolate (Shinn) of Alternaria alternata (Fr.:Fr.) Keissl. from `Minneola' tangelo (a cross between Citrus paradisi Macf. `Duncan' and C. reticulata Blanco `Dancy') was shown to be controlled by a single recessive allele, aaM1, within the citrus genome. A backcross between resistant `Clementine' mandarin (C. reticulata) and susceptible LB#8-10 (a hybrid of `Clementine' mandarin and `Minneola' tangelo) resulted in 61 resistant (R) and 58 susceptible (S) plants (χ2 = 0.0756, P ≥ 0.05), but the reciprocal cross deviated from the expected 1R:1S ratio (87 R and 36 S plants (χ2 = 21.1463, P ≥ 0.05). A dominant allele, AaM1, of this resistance gene was found in a loose coupling phase linkage with two RAPD markers, P12850 (15.3 cM) and AL31250 (36.7 cM), after JOINMAP computer analysis.
Sorbitol Transporter Expression in Apple Sink Tissues: Implications for Fruit Sugar Accumulation and Watercore Development
Authors: Gao Zhifang , Jayanty Sastry , Beaudry Randolph , Loescher Wayne
Published: January 2019

In apple (Malus ×domestica Borkh.), where sorbitol is a primary photosynthetic product that is translocated throughout the plant, accumulation of sorbitol in sink cells appears to require an active carrier-mediated membrane transport step. Recent progress in isolation and characterization of genes for sorbitol transporters in sour cherry (Prunus cerasus L.) and mannitol transporters in celery (Apium graveolens L.) suggested that similar transporters may be present in apple tissues. A defect in these transporters could also explain the occurrence of the fruit disorder watercore, characterized by the accumulation of fluids and sorbitol in the apoplasmic free space. Our objectives therefore included isolation and characterization of genes for sorbitol transporters in apple tissues and comparisons of expression of transporter genes, especially in various sink tissues including watercored and non-watercored fruit tissues. We have isolated and characterized two sorbitol transporter genes, MdSOT1 and MdSOT2. Sequence analyses indicated that these are members of the major facilitator transporter superfamily that gives rise to highly hydrophobic integral membrane proteins. Heterologous expression and measurement of sorbitol uptake in yeast indicated that these are specific and with high affinities for sorbitol, with Kms for sorbitol of 1.0 and 7.8 mm for MdSOT1 and MdSOT2, respectively. Sorbitol transporter expression was evident in all sink tissues tested with the exception of watercore-affected fruit tissues. Sorbitol accumulation in apple sink tissues thus involves an apoplasmic active membrane transport step and watercore results from a defect in that process.
AFLP Markers Linked to Eastern Filbert Blight Resistance from OSU 408.040 Hazelnut
Authors: Chen Honglin , Mehlenbacher Shawn A. , Smith David C.
Published: January 2019

Eastern filbert blight (EFB), caused by Anisogramma anomala (Peck) E. Müller, is a devastating disease to european hazelnut (Corylus avellana L.) orchards in the Willamette Valley of Oregon. Selection OSU 408.040 showed no symptoms or signs of the fungus following greenhouse inoculations, and enzyme-linked immunosorbant assays (ELISAs) were negative. Segregation ratios in three progenies indicate that a single dominant gene controls the resistance. A total of 64 amplified fragment length polymorphism (AFLP) primer combinations were screened using three resistant and three susceptible individuals as well as the parents of the cross OSU 245.098 × OSU 408.040. Primer combinations that showed no more than one recombinant in these six seedlings were investigated in 30 additional seedlings. Markers that showed <15% recombination with resistance were amplified in the remaining seedlings of the population. Five AFLP markers linked in coupling to resistance were identified. B2-125 was located on one side of the resistance locus at a distance of 4.1 centimorgans (cM), while A4-265 (9.2 cM), C2-175 (5.9 cM) and D8-350 (2.5 cM) were on the other side, and A8-150 cosegregated with resistance. Three of these markers (B2-125, C2-175, and D8-350) were also linked in coupling in a similar order in seedlings from a second progeny. These markers may be useful in marker-assisted selection for eastern filbert blight resistance from hazelnut selection OSU 408.040.
Nitrogen Inhibits Nodulation and Reversibly Suppresses Nitrogen Fixation in Nodules of Alnus maritima
Authors: Laws M. Tiffany , Graves William R.
Published: January 2019

Symbiotic associations between Alnus maritima (Marsh.) Muhl. ex Nutt. (seaside alder) and actinomycetes in the genus Frankia Brunchorst result in root nodules in which atmospheric nitrogen (N) is fixed. The economic and environmental benefits of N fixation have led to interest in inducing root nodules during production of A. maritima. Because woody plants produced in nurseries typically are provided N fertilizer, our objectives were to determine how applied N influences nodulation of A. maritima and to characterize how short-term changes in root-zone N affect the function of nodules. Potted seedlings were grown in perlite that was inoculated with 30 mL of soil from the root zones of mature plants in their native habitat on the Delmarva Peninsula. Each pot was drenched once daily for 10 weeks with nutrient solution that contained ammonium nitrate at 10 concentrations from 0 to 8 mm. Plants that received no ammonium nitrate formed the most nodules, and nodulation decreased linearly as ammonium nitrate increased from 0.25 to 4 mm. Plants treated with ammonium nitrate at 4 or 8 mm formed nearly no nodules, while ammonium nitrate at 0.5 mm resulted in vigorous plants with an average nodule count of 70. In a second experiment, a population of nodulated seaside alders was established by irrigating seedlings in inoculated perlite once daily with 0.5-mm ammonium nitrate for 6 weeks. Plants then were provided ammonium nitrate at 0.5, 2, or 4 mm for 2 weeks. Acetylene-reduction assays showed suppressed nodule activity among plants provided 2- and 4-mm ammonium nitrate. Daily irrigation of those plants with N-free solution subsequently led to a rapid depletion of root-zone N and to a concomitant resurgence of nodule activity. These results demonstrate that N fertilization can be managed to promote nodulation of A. maritima and show that decreased nodule activity caused by short-term increases in root-zone N is reversible.
The First Genetic Linkages among Expressed Regions of the Garlic Genome
Authors: Zewdie Yayeh , Havey Michael J. , Prince James P. , Jenderek Maria M.
Published: January 2019

Garlic (Allium sativum L.) has been cultivated by asexual propagation since time immemorial. The discovery of male-fertile garlic accessions has opened a venue for genetic studies and improvement through sexual recombination. An S1 family of 84 plants was generated from a single male-fertile heterozygous plant from the U.S. Dept. of Agriculture Plant Introduction 540316 and used to identify the first genetic linkages in garlic based on single nucleotide polymorphisms, simple sequence repeats, and randomly amplified polymorphic DNAs. Thirty-seven markers formed nine linkage groups covering 415 centimorgans (cM) with average distance of 15 cM between loci; other 16 loci remained unlinked. A male fertility locus was placed on the map. This first genetic map of garlic is a seminal step toward the genetic improvement of garlic and eventual marker-assisted breeding.
DNA Polymorphism and Assessment of Genetic Relationships in Walnut Genotypes Based on AFLP and SAMPL Markers
Authors: Kafkas Salih , Ozkan Hakan , Sutyemez Mehmet
Published: January 2019

Turkey has more than 4 million walnut trees (Juglans regia L.), most of which are derived from seedlings, and are nongrafted trees. This characteristic leads to a huge opportunity to select superior walnut genotypes from natural populations for cultivation and for breeding programs. Several selection studies have been performed in the last decades and few genotypes were selected. The goal of this study was to characterize and determine genetic relationships among 21 walnut genotypes with potential in walnut production using amplified fragment length polymorphism (AFLP) and selective amplification of microsatellite polymorphic loci (SAMPL) techniques. Eight primer combinations (six for AFLP and two for SAMPL) were applied to 21 walnut genotypes and a total of 230 bands of which 50.4% of them were polymorphic were obtained. The SAMPL technique was more effective than AFLP in the separation of very closely related genotypes. Genotypes of the pairs `Maras-18' with `Maras-46', `KSU-5' with `Sutyemez-1', `Maras-12' with `Sutyemez-2,' `Kaman-3' with `Kaman-4', and `KSU-11' with `Maras-10' were the most closely related.
Overexpression of Mannitol-1-Phosphate Dehydrogenase Increases Mannitol Accumulation and Adds Protection Against Chilling Injury in Petunia
Authors: Chiang Yu-Jen , Stushnoff C. , McSay A.E. , Jones M.L. , Bohnert H.J.
Published: January 2019

Petunia ×hybrida (Hook) Vilm. cv. Mitchell was transformed with an E. coli gene encoding mannitol-1-phosphate dehydrogenase (mtlD). Four plant lines that grew on kanamycin and contained the mtlD transgene were identified. Two of these lines contained high levels of mannitol [high-mannitol lines M3 and M8; mean mannitol = 3.39 μmol·g-1 dry weight (DW)] compared to nontransformed wild-type plants (0.86 μmol·g-1 DW), while two lines had mannitol levels similar to wild-type plants (low-mannitol lines M2 and M9; mean mannitol = 1.05 μmol·g-1 DW). Transgenic and control plants were subjected to chilling stress (3 ± 0.5 °C day/0 ± 0.5 °C night, 12-hour photoperiod and 75% relative humidity) to evaluate the role of mannitol in chilling tolerance. Based upon foliage symptoms and membrane leakage after a 3-week chilling treatment, the high-mannitol containing lines, M3 and M8, were more tolerant of chilling stress than the low-mannitol containing transgenic lines, M2 and M9, and wild-type. Under nonchilling conditions mannitol was the only carbohydrate that differed among transgenic lines, but all carbohydrates were present. When subjected to chilling stress, mannitol levels dropped by 75%, sucrose by 52%, and inositol by 54% in the low-mannitol lines (M2 and M9). In M3 and M8, the high-mannitol lines, mannitol levels decreased by 36%, sucrose by 25%, and inositol by 56%, respectively. Raffinose increased 2- to 3-fold in all lines following exposure to low-temperature chilling stress. In the higher mannitol lines only 0.04% to 0.06% of the total osmotic potential generated from all solutes could be attributed to mannitol, thus its action is more like that of an osmoprotectant rather than an osmoregulator. This study demonstrates that metabolic engineering of osmoprotectant synthesis pathways can be used to improve stress tolerance in horticultural crops.
Simple Sequence Repeat (SSR) Markers for Genetic Mapping of Raspberry and Blackberry
Authors: Stafne Eric T. , Clark John R. , Weber Courtney A. , Graham Julie , Lewers Kim S.
Published: January 2019

Interest in molecular markers and genetic maps is growing among researchers developing new cultivars of Rubus L. (raspberry and blackberry). Several traits of interest fail to express in seedlings or reliably in some environments and are candidates for marker-assisted selection. A growing number of simple sequence repeat (SSR) molecular markers derived from Rubus and Fragaria L. (strawberry) are available for use with Rubus mapping populations. The objectives of this study were to test 142 of these SSR markers to screen raspberry and blackberry parental genotypes for potential use in existing mapping populations that segregate for traits of interest, determine the extent of inter-species and inter-genera transferability with amplification, and determine the level of polymorphism among the parents. Up to 32 of the SSR primer pairs tested may be useful for genetic mapping in both the blackberry population and at least one of the raspberry populations. The maximum number of SSR primer pairs found useable for mapping was 60 for the raspberry population and 45 for the blackberry population. Acquisition of many more nucleotide sequences from red raspberry, black raspberry, and blackberry are required to develop useful molecular markers and genetic maps for these species. Rubus, family Rosaceae, is a highly diverse genus that contains hundreds of heterozygous species. The family is one of the most agronomically important plant families in temperate regions of the world, although they also occur in tropical and arctic regions as well. The most important commercial subgenus of Rubus is Idaeobatus Focke, the raspberries, which are primarily diploids. This subgenus contains the european red raspberry R. idaeus ssp. idaeus L., as well as the american black raspberry R. occidentalis L. and the american red raspberry R. idaeus ssp. strigosus Michx. Interspecific hybridization of these, and other raspberry species, has led to greater genetic diversity and allowed for the introgression of superior traits such as large fruit size, fruit firmness and quality, disease resistance, and winter hardiness.
Nutrient Uptake among Subspecies of Cucurbita pepo L. Is Related to Exudation of Citric Acid
Authors: Gent Martin P.N. , Parrish Zakia D. , White Jason C.
Published: January 2019

Exudation of organic acids by roots has been implicated in uptake of minerals from soil. Three cultivars within each of two subspecies of summer squash (Cucurbita pepo ssp. ovifera D. S. Decker var. ovifera and C. pepo ssp. pepo var. pepo) were grown in the field. Plants of ssp. pepo had higher concentrations of K, P, and Zn than those of ssp. ovifera. These same cultivars were grown under P sufficient and depleted conditions in hydroponics, to measure exudation of organic acids from roots. When grown in hydroponics, tissues of ssp. ovifera had similar or higher concentrations of nutrients than ssp. pepo. Therefore, differences in tissue composition of field-grown plants are likely due to differences in nutrient uptake ability, not inherent differences in tissue composition between subspecies. Phosphorus nutrition played a significant role in exudation of organic acids into the hydroponics solution. For both subspecies, P depletion resulted in exudation of more citric and succinic acid, and less oxalic and tartaric acid. Under P depletion, ssp. pepo exuded more citric acid than ssp. ovifera. When soil was eluted with solution containing root exudates, the exudates from ssp. pepo eluted more K, Mg, Fe, and Zn than did those from ssp. ovifera. Among subspecies of C. pepo, exudation of organic acids, particularly exudation of citric acid in response to P depletion, is associated with the plant's ability to accumulate more inorganic nutrients when grown in the field.
The Role of Leaf Pigment and Antioxidant Levels in UV-B Resistance of Dark- and Light-green Kentucky Bluegrass Cultivars
Authors: Zhang Xunzhong , Ervin E.H. , Schmidt R.E.
Published: January 2019

Ultraviolet-B [UV-B (280-320 nm)] radiation is one of the major factors causing quality decline of transplanted sod. Pigments and antioxidants are associated with plant stress resistance, but their roles in turfgrass tolerance to UV-B damage are not well understood. The objectives of this study were to determine if kentucky bluegrass (Poa pratensis L.) cultivars with darker green genetic leaf color possessed greater pigment and antioxidant defense capacities and if such characteristics were associated with greater resistance to UV-B. Two cultivars, `Moonlight' (dark green) and `Limerick' (light green), were selected and subjected to continuous, artificial UV-B radiation (70 μmol·m-2·s-1). UV-B irradiation reduced turf quality by 58% (`Moonlight') and 77% (`Limerick') relative to day 1 when measured 10 days after initiation of UV-B exposure. Higher canopy photochemical efficiency (PEc) was found in `Moonlight' relative to `Limerick' under UV-B stress and during recovery. `Moonlight' contained greater levels of chlorophyll (1.5 to1.6-fold), carotenoids (1.3-fold), superoxide dismutase [SOD (1.0-fold)] and catalase [CAT (1.5-fold)] than `Limerick' when measured at 10 days after UV-B initiation. Turfgrass quality and PEc were positively correlated with pigments (chlorophyll and carotenoids) and antioxidant enzymes (SOD and CAT), and negatively correlated with lipid peroxidation. The results suggest that selecting dark-green cultivars with greater pigment content and antioxidant activity may be an effective approach for turfgrass breeders and sod producers to improve tolerance of newly transplanted sod to environments with higher UV-B radiation.
Changes in Protein Content, Protease Activity, and Amino Acid Content Associated with Heat Injury in Creeping Bentgrass
Authors: He Yali , Liu Xiaozhong , Huang Bingru
Published: January 2019

Various physiological processes may deteriorate in response to increasing temperatures, contributing to the decline in turf quality for cool-season turfgrasses during heat stress. This study was performed to investigate metabolic changes (membrane lipid peroxidation, total protein content, amino acid content, and protease activity) associated with turf quality decline for creeping bentgrass (Agrostis stolonifera Huds.) in response to gradually increasing temperatures for a short duration and prolonged exposure to lethally high temperature. Plants were subjected to increasing temperatures of 20, 25, 30, 35, and 40 °C for 7 days at each level of temperature [gradual heat stress (GHS)] or exposed to high temperature of 40 °C for 28 days [prolonged heat stress (PHS)] in growth chambers. During the GHS treatment, significant decline in turf quality occurred when plants were exposed to 30 °C for 7 days; simultaneously, malondialdehyde (MDA) content increased and total protein content in shoots decreased significantly compared to those at 20 °C. Protease activity increased at 25 °C and then decreased as temperature was elevated from 30 to 40 °C during the GHS treatment. Amino acid content decreased under GHS, beginning at 25 °C. Under the PHS treatment, turf quality declined and MDA content increased significantly, beginning at 14 days of PHS, while total protein content decreased at 7 days of PHS. Protease activity and amino acid content increased at 7 days of PHS, and then declined with longer stress duration. Our results indicated that protease activity, and amino acid and total protein content were more responsive to GHS or PHS than that of lipid peroxidation and turf quality. Changes in metabolic parameters of protease activity, amino acid and total protein content, and lipid peroxidation may contribute to leaf senescence and poor turf performance under severe or prolonged heat stress conditions for creeping bentgrass.
Seed Storage Reserves and Glucosinolates in Brassica rapa L. Grown on the International Space Station
Authors: Musgrave M.E. , Kuang A. , Tuominen L.K. , Levine L.H. , Morrow R.C.
Published: January 2019

Although plants are envisioned to play a central role in life support systems for future long-duration space travel, plant growth in space has been problematic due to horticultural problems of nutrient delivery and gas resupply posed by the weightless environment. Iterative improvement in hardware designed for growth of plants on orbital platforms now provides confidence that plants can perform well in microgravity, enabling investigation of their nutritional characteristics. Plants of B. rapa (cv. Astroplants) were grown in the Biomass Production System on the International Space Station. Flowers were hand-pollinated and seeds were produced prior to harvest at 39 days after planting. The material was frozen or fixed while on orbit and subsequently analyzed in our laboratories. Gross measures of growth, leaf chlorophyll, starch and soluble carbohydrates confirmed comparable performance by the plants in spaceflight and ground control treatments. Analysis of glucosinolate production in the plant stems indicated that 3-butenylglucosinolate concentration was on average 75% greater in flight samples than in ground control samples. Similarly, the biochemical make-up of immature seeds produced during spaceflight and fixed or frozen while in orbit was significantly different from the ground controls. The immature seeds from the spaceflight treatment had higher concentrations of chlorophyll, starch, and soluble carbohydrates than the ground controls. Seed protein was significantly lower in the spaceflight material. Microscopy of immature seeds fixed in flight showed embryos to be at a range of developmental stages, while the ground control embryos had all reached the premature stage of development. Storage reserve deposition was more advanced in the ground control seeds. The spaceflight environment thus influences B. rapa metabolite production in ways that may affect flavor and nutritional quality of potential space produce.