bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Photosynthesis and Carbohydrate Metabolism in Mature Apple Leaves in Response to Whole Plant Source-Sink Manipulation
Authors: Zhou Rui , Quebedeaux Bruno
Published: January 2019

Photosynthesis and carbohydrate metabolism in apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] source leaves were monitored during a 7-day period after source-sink manipulations by girdling or partial defoliation treatments. In the girdling treatment, sorbitol, sucrose, glucose, and starch accumulated in leaves, and net photosynthetic rates (Pn) at 350 μL·L-1 CO2 decreased during a 7-day period. Pn measured at 1000 μL·L-1 [CO2] was also decreased but the changes were less. Stomatal conductance and intracellular CO2 concentration decreased markedly in leaves of girdled shoots. When shoots were partially defoliated, starch and glucose concentrations in remaining source leaves declined steadily during the 7-day study period. Sorbitol and sucrose concentrations decreased during the first 2 days after defoliation, then increased the following 5 days. Pn of the remaining leaves measured at ambient and elevated CO2 levels were enhanced markedly. Aldose-6-phosphate reductase activity in source leaves increased markedly from 27.5 to 39.2 μmol·h-1·g-1 fresh weight (FW) after partial defoliation but remained unchanged in leaves after girdling. Selective and maximum sucrose phosphate synthase (SPS) activities increased following partial defoliation and decreased following girdling. ADP-glucose pyrophosphorylase activity remained relatively unchanged in the partial defoliation treatments but increased markedly in the girdled-shoot leaves. These results suggested that girdling-induced photosynthetic inhibition is mainly due to stomatal limitation, however, the photosynthesis enhancement by partial defoliation may be due primarily to acceleration of photosynthetic capacity per se. These studies showed that the metabolism of sorbitol, sucrose and starch, three photosynthetic end products in mature apple leaves, was coordinately regulated in source leaves in response to source-sink manipulations.
Inheritance of Resistance in Strawberry to Bacterial Angular Leafspot Disease Caused by Xanthomonas fragariae
Authors: Lewers K.S. , Maas J.L. , Hokanson S.C. , Gouin C. , Hartung J.S.
Published: January 2019

Bacterial angular leafspot disease (Xanthomonas fragariae Kennedy and King) of strawberry (Fragaria species and F. ×ananassa Duch. cultivars) has become increasingly important to strawberry fruit and plant production. Strawberry cultivars and species vary in susceptibility to infection. However, little is known regarding epidemiology of the disease and resistance to infection. Two octoploid genotypes, a native F. virginiana (US 4808, tested as SG-89) and a F. virginiana (SG 26) × F. ×ananassa (`Earliglow') hybrid (US 4809, tested as 80-4-38), previously were found to be highly resistant to two differentially pathogenic strains of X. fragariae representing two of four genotypic strain groups. Our objective was to determine the number of genes involved with resistance for these two strawberry genotypes, whether strawberry resistance is conferred by dominant or recessive alleles, and whether or not the heritability is high enough for breeders to reliably make selections of resistant individuals in breeding populations. About 120 F1 seedlings from crosses of susceptible `Sweet Charlie' with each of the two resistant genotypes were clonally propagated and challenged with each of four X. fragariae strains. These strains were selected to represent four genotypes of X. fragariae defined by repetitive element based PCR: ATCC 33239, Xf-3, Xf-6, and Xf-1425. Plants were quantitatively rated on a scale of 0 (resistant) to 5 (susceptible) in replicated evaluations. High estimates for broad sense heritability support the conversion of the quantitative disease scores to qualitative scores and the classification of genotypes as resistant or susceptible. The qualitative ratings were used to estimate the number of genes involved with resistance. Some segregation ratios fit a 7S:1R ratio, and others fit a 15S:1R ratio, indicating that three or four unlinked loci could explain the inheritance of resistance in these populations. The high estimates for broad sense heritability show that resistant progeny can be selected with confidence, though large populations will be needed to identify enough resistant progeny from which to select for other important traits.
Comparative Vegetative Growth Responses of Two Peach Cultivars Grown on Size-controlling versus Standard Rootstocks
Authors: Weibel Antonio , Johnson R. Scott , DeJong Theodore M.
Published: January 2019

Vegetative growth of two peach (Prunus persica L. Batsch) cultivars Flavorcrest and Loadel growing on six different rootstocks (`Nemaguard', `Hiawatha', K-146-43, K-146-44, P-30-135, and K-119-50) was analyzed during the third season of growth in an experimental orchard at the University of California Kearney Agricultural Center near Parlier, California. Seasonal trunk cross-sectional area, shoot and internode growth, diurnal stem extension growth rate and summer and dormant pruning weights were measured to determine extent of size-control imparted by the experimental rootstocks compared to the trees on the `Nemaguard' control and to characterize the nature of the sizecontrolling response. Trunk cross-sectional area growth of trees on the two smallest rootstocks (K-146-43 and K-146-44) was only 25% to 37% of the growth of trees on `Nemaguard', while trees on the other three rootstocks provided an intermediate level of size control. Generally, the seasonal patterns of shoot growth did not vary substantially among trees on the different rootstocks, but average shoot and internode lengths did correspond with tree size. Vigorous watersprout growth was decreased by more than 80% in the trees on the least vigorous rootstocks compared to trees on `Nemaguard' resulting in major reductions in the extent of summer and winter pruning weights. Variations in vegetative shoot growth appeared to correspond to variations in daily shoot extension growth rates but more research is needed to explore these relationships.
Assessment of Genetic Diversity of Pawpaw (Asimina triloba) Cultivars with Intersimple Sequence Repeat Markers
Authors: Pomper Kirk W. , Crabtree Sheri B. , Brown Shawn P. , Jones Snake C. , Bonney Tera M. , Layne Desmond R.
Published: January 2019

The pawpaw [Asimina triloba (L.) Dunal.] is a tree fruit native to many areas of the southeastern and mid-western United States. Kentucky State University (KSU) is designated as a satellite repository for Asimina for the U.S. Department of Agriculture (USDA), National Plant Germplasm System (NPGS). An assessment of the level of genetic diversity in cultivated pawpaw would assist in development of the future germplasm repository collection strategies for cultivar improvement. The objectives of this study were to identify intersimple sequence repeat (ISSR) markers that segregate in a simple Mendelian fashion and to use these markers to assess genetic diversity in 19 pawpaw cultivars. Leaf samples from the 34 progeny of controlled crosses (1-7-1 × 2-54 and reciprocal) and the parents were collected, DNA was extracted, and subjected to the ISSR methodology using the University of British Columbia microsatellite primer set #9. Seven primers yielded 11 Mendelian markers with either a 3:1 or 1:1 ratio that was confirmed by chi-square analysis. Analysis of genetic diversity using 10 of the ISSR markers from 19 pawpaw cultivars revealed a moderate to high level of genetic diversity, with a percent polymorphic loci P = 80 and an expected heterozygosity He = 0.358. These diversity values are higher than those reported for cultivated pawpaw using isozyme or randomly amplified polymorphic DNA (RAPD) markers, indicating that the ISSR marker methodolgy has a higher level of discrimination in evaluating genetic diversity in pawpaw and/or pawpaw has greater levels of genetic diversity than previously found.
A Resistance to Systemic Symptom Expression of Melon Necrotic Spot Virus in Melon
Authors: Mallor Cristina , Álvarez José María , Luis-Arteaga Marisol
Published: January 2019

Melon necrotic spot virus (MNSV) has been found affecting melon (Cucumis melo L.) crops. At present the only known resistance in melon is controlled by a single recessive gene, nsv. The presence of nsv in a melon genotype has been correlated with the lack of necrotic lesions on the mechanically inoculated cotyledons. Thus, in a screening program for MNSV resistance, melon genotypes that developed necrotic lesions in the inoculated cotyledons were discarded. However, in this paper we show that some melon accessions mechanically inoculated with MNSV do develop local necrotic lesions, therefore showing the absence of the gene nsv, but fail to develop the systemic symptoms typical of diseased plants under the screening conditions. In some of these accessions the influence of the temperature on the development of systemic symptoms was studied. The results showed that, depending on the accession, temperatures under 25 or 20 °C enhanced the systemic development of the disease. One of the tested varieties, `Doublon', did not develop systemic symptom at any of the tested temperatures (15, 17.5, 20, 22.5, 25, 27.5, and 30 °C). In this variety, the lack of systemic symptoms was correlated to the lack of virus infection of these tissues based upon ELISA results. MNSV was not detected in the uninoculated parts of the plant, and seems to remain confined to the local lesions produced on the cotyledons following the mechanical inoculation. Restriction of viral multiplication and/or cell-to-cell movement could explain the pattern of viral distribution in this variety. This reaction was observed in the `Doublon' plants mechanically inoculated with each of five isolates of MNSV tested, including an isolate that overcomes the nsv gene resistance.
Allelism between the P and Stp Genes for Seedcoat Color and Pattern in Common Bean
Authors: Bassett Mark J.
Published: January 2019

The P locus in common bean (Phaseolus vulgaris L.) can express complete absence of color (white) in seedcoats and flowers with p (with B V) or a pale grayish white seedcoat and nearly white flower with pgri, but P has never been considered a seedcoat pattern locus. Genes controlling seedcoat colors and patterns have been backcrossed into the recurrent parent 5-593 with black seedcoats and violet flowers. The cross, p BC3 5-593 × t stpmic BC3 5-593 (black seeds with a long white micropyle stripe and fibula arcs), failed to show evidence of genetic complementation in either F1 or F2 progeny, leading to the hypothesis that P and Stp are allelic. Five cross combinations between two recessive P alleles (p BC3 5-593 and pgri BC3 5-593) and three recessive alleles at the stippled seedcoat gene Stp (stp BC3 5-593, stphbw BC3 5-593, and stpmic BC3 5-593) expressed no genetic complementation in seedcoats and flowers of F1 progeny and confirmed the allelism hypothesis. New gene symbols are proposed for the recessive alleles at Stp, viz., pstp for stp, phbw for stphbw and pmic for stpmic. The dominance order at P is P > pmic > phbw > pstp > pgri > p. Crosses were made between t self-colored BC3 5-593 and three other parents—pstp BC3 5-593, phbw BC3 5-593, and pmic BC3 5-593—to explore interactions between the pattern genes T and P; and segregation for seedcoat patterns in F2 was discussed. The hypothesis was proposed that the T locus regulates expression at P, or the biosynthetic step regulated by P.
Relationships of Cold Acclimation and Antioxidative Enzymes with Chilling Tolerance in Cucumber (Cucumis sativus L.)
Authors: Kuk Yong In , Lee Jae Hong , Kim Han Yong , Chung Soon Ju , Chung Gap Chae , Guh Ja Ock , Lee Hee Jae , Burgos Nilda R.
Published: January 2019

To determine whether chilling tolerance is related to cold acclimation, changes in physiological responses and activity of antioxidative enzymes were investigated in leaves of cucumber (Cucumis sativus L.) grown in controlled environments. Plants were exposed to 15 °C (cold-acclimated) or 25 °C (nonacclimated) for 3 days, under 50 μmol·m-2·s-1 photosynthetic photon flux and 70% relative humidity. Plants were then exposed to 8 °C chilling temperature for 3 days, and allowed to recover in a growth chamber at 25 °C for 3 days. Measurements of leaf water content, cellular leakage, lipid peroxidation, chlorophyll a fluorescence, and quantum yield showed that cold-acclimated leaves were less affected by chilling compared to nonacclimated leaves. Cold-acclimated leaves recovered faster than nonacclimated leaves with regard to all variables examined. Catalase and ascorbate peroxidase activities were induced in cold-acclimated leaves, but not in nonacclimated leaves. These data indicate that cold acclimation increased chilling tolerance of cucumber in association with antioxidative enzymes.
Using Amplified Fragment-length Polymorphisms (AFLPs) to Identify Peach Cultivars
Authors: Aranzana Maria José , Carbó Joaquim , Arús Pere
Published: January 2019

A sample of 210 cultivars of Prunus persica (L.) Batsch, with a wide range of fruit and plant characteristics, was studied for variability using nine polymorphic amplified fragment length polymorphism (AFLP) primer combinations. Forty-seven AFLPs allowed identification of 196 (93%) different genotypes, 187 of which could be distinguished with three primer combinations. Eleven cultivars with the same AFLP phenotype corresponded to known somatic mutations (sports), but from the four sports of the `Springcrest' group, two (`Maycrest' and `Queencrest') differed at three AFLPs from the others (`Starcrest' and `Early Maycrest'). Cluster analysis allowed differentiation of most cultivars with nonmelting fruit flesh, generally used for canning, from the melting-flesh peach and nectarine cultivars used for fresh consumption.
Intergeneric Hybridizaton between Schlumbergera Lem. and Hatiora Britt. & Rose (Cactaceae)
Authors: Boyle Thomas H. , Idnurm Alexander
Published: January 2019

Post-pollination barriers to intergeneric hybridization between Easter cactus [Hatiora gaertneri (Regel) Barthlott, H. rosea (Lagerheim) Barthlott, and H. ×graeseri Barthlott ex D. Hunt] and holiday cactus [Schlumbergera truncata (Haworth) Moran and S. ×buckleyi (Buckley) Tjaden] were determined and procedures were devised for circumventing these barriers. Examination of Hatiora and Schlumbergera pistils at 72 hours after intergeneric crosses indicated no abnormalities in pollen germination or pollen tube growth in the upper style. Pollen tubes of Hatiora were arrested in the lower half of Schlumbergera styles and failed to enter the ovary. Schlumbergera pollen tubes exhibited normal growth in Hatiora styles but most tubes lost directionality, burst, or failed to penetrate the micropyles after reaching the ovary. Three growth regulators (BA, GA3 and NAAm) were applied individually to ovaries of `Crimson Giant' Easter cactus after intergeneric crosses. GA3 and NAAm increased fruit set compared to the control (lanolin alone) or BA but none of the fruit harvested 160 days after pollination contained mature embryos. Four progeny were obtained when a short-styled S. ×buckleyi clone was crossed as a female parent with H. ×graeseri. Isozyme patterns and morphological characteristics confirmed that the four progeny were intergeneric hybrids. This is the first report of successful intergeneric hybridization between Hatiora and Schlumbergera. Chemical names used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)]; gibberellic acid (GA3); α-naphthaleneacetamide (NAAm).
Firmness Decline in `Gala' Apple during Fruit Development
Authors: Volz Richard K. , Harker F. Roger , Lang Sandy
Published: January 2019

Puncture force was measured in `Gala'apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit from 16 to 175 days after full bloom over 2 years using a range of circular flat-tipped probes (1 to 11 mm diameter) to test the firmness of each fruit. The area-dependent (Ka) and perimeter-dependent (Kp) coefficients of puncture force were determined and were used to calculate the indicative puncture force approximating a standard 11.1-mm-diameter Effegi/Magness-Taylor probe for even the smallest fruit. Ka declined exponentially throughout fruit development with much greater changes occurring closer to bloom. In contrast, maximum Kp occurred at 107 to 119 days after full bloom before declining progressively. Estimated firmness (using a 11.1-mm-diameter probe) declined constantly from 16 days after full bloom. Ka was associated with developmental changes in cortical tissue intercellular air space, cell volume and cell packing density although relationships changed throughout fruit growth. However seasonal change in Kp was not associated with any obvious anatomical change in the cortex.
Temperature and Irradiance Effects on Flowering of Two Species of Leucocoryne
Authors: Catley J.L.
Published: January 2019

The influences of temperature and irradiance on flowering of two species of Leucocoryne [L. coquimbensis F. Phil and L. ixioides (Hook.) Lindl.] were examined in controlled environment growth rooms. Growing environments had day/night temperatures of 10/5, 15/10, or 20/15 °C, providing mean temperatures of 7.5, 12.5, or 17.5 °C, and photosynthetic photon fluxes (PPF) of 497 or 710 μmol·m-2·s-1. Inflorescence emergence data were recorded up to three times a week, measurements of floral development were made twice weekly and destructive harvests were carried out every 2 weeks. Both species of Leucocoryne flowered most quickly when grown at a mean temperature of 17.5 °C. Leucocoryne coquimbensis flowered first in all temperature regimes (means of 7.5, 12.5, or 17.5 °C), taking an average of 7.1, 5.1, or 4.5 months to flower, whereas plants of L. ixioides took 7.6, 5.4, or 4.7 months to flower. Although taking longer to flower, L. ixioides produced better quality flowers (taller scapes and more florets per inflorescence). Plants of L. coquimbensis grown in the two highest temperature regimes produced up to four inflorescences per bulb. As mean temperature decreased, the number of inflorescences produced by each bulb together with the number of florets in each inflorescence and the number of leaves produced before emergence of the inflorescence decreased. Decreases in these attributes were much greater with a 5 °C mean temperature drop from 12.5 °C, than a drop from 17.5 to 12.5 °C. At least half the florets in an inflorescence opened before the first floret began to senesce. The onset of senescence was delayed as mean temperature decreased. The highest irradiance level promoted development of further inflorescences of L. ixioides at all mean temperatures, and at a mean temperature of 17.5 °C for L. coquimbensis. Flower stem heights of L. coquimbensis increased as mean temperature increased and irradiance level decreased. An increase in irradiance level also promoted scape heights of L. ixioides, although maximum scape heights were attained at a mean temperature of 12.5 °C. Regardless of mean temperature or irradiance level, all cut stems were able to stand without support. These findings suggest days to flowering, inflorescence number and floral quality may be improved by growing these two species of Leucocoryne at mean temperatures greater than 17.5 °C, whereas mean temperatures below 12.5 °C will be detrimental to these floral attributes.
Identifying Lychee (Litchi chinensis Sonn.) Cultivars and their Genetic Relationships Using Intersimple Sequence Repeat (ISSR) Markers
Authors: Degani Chemda , Deng Jiusheng , Beiles Avigdor , El-Batsri Ruth , Goren Moshe , Gazit Shmuel
Published: January 2019

There is widespread confusion and uncertainty concerning the identity of lychee cultivars: the same cultivar may be known under different names and different cultivars may appear under the same name. In the present study, the potential of intersimple sequence repeat (ISSR) for the identification of 66 lychee cultivars and accessions and a determination of their genetic relationships was evaluated, using 32 primers containing different simple sequence repeat motifs. Of the 194 bands produced, 124 (64%) were polymorphic. A set of six ISSR primers was sufficient to distinguish all cultivars and accessions. Thus, cultivars which are morphologically very similar and have identical isozyme profiles can be distinguished by ISSR analysis. However, seven pairs of accessions, each considered to be the same cultivar, were found to be identical by ISSR analysis. Nei and Li band-sharing distances and Nei genetic distances were calculated among the cultivars and two similarity dendrograms were generated using the neighbor-joining algorithm. Results showed that the ISSR technique is a valuable tool for identification of lychee cultivars and analysis of their genetic relationships.
Cultivar Decline in Sweetpotato: II. Impact of Virus Infection on Yield and Storage Root Quality in `Beauregard' and `Hernandez'
Authors: Bryan A.D. , Schultheis J.R. , Pesic-VanEsbroeck Z. , Yencho G.C.
Published: January 2019

To determine the effects of Sweet potato feathery mottle virus (SPFMV), and possibly other newly described potyviruses, on sweetpotato yield and storage root appearance, virus-indexed `Beauregard' and `Hernandez' mericlones testing free of known viruses were compared with virus-infected mericlones in two separate experiments over two years. The experiments were arranged in a split-plot, randomized, complete-block design with the initial presence (VI+) or absence (VI-) of SPFMV as the whole plot factor and mericlone as the subplot factor. Plants were monitored weekly for symptoms of SPFMV and vine samples were taken for virus-indexing on Ipomoea setosa. Additional testing for selected sweetpotato viruses was done using a nitrocellulose membrane enzyme-linked immunosorbant assay. SPFMV was the only virus detected in the study, using available testing methodologies. Field monitoring indicated that §100% of the VI-plants were reinfected with SPFMV by 9 weeks after planting. The presence of virus before planting reduced yields of No. 1 roots by 26% and decreased overall appearance ratings for the three `Beauregard' mericlones. In addition, VI+ planting materials resulted in increased storage root length and reduced storage root width of both cultivars leading to increased storage root length/diameter ratios, further detracting from overall storage root appearance. The results of this study demonstrate that SPFMV contributes to cultivar decline in sweetpotato. However, the interaction of SPFMV with other newly described potyviruses, which may result in synergistic negative effects on sweetpotato yield and quality, needs further research.
Analysis of Sweet Cherry (Prunus avium L.) Cultivars Using SSR and AFLP Markers
Authors: Struss Darush , Ahmad Riaz , Southwick Stephen M. , Boritzki Manuela
Published: January 2019

Simple sequence repeats (SSRs) and amplified fragment-length polymorphisms (AFLPs) were used to evaluate sweet cherry (Prunus avium L.) cultivars using quality DNA extracted from fruit flesh and leaves. SSR markers were developed from a phage library using genomic DNA of the sweet cherry cultivar Valerij Tschkalov. Microsatellite containing clones were sequenced and 15 specific PCR primers were selected for identification of cultivars in sweet cherry and for cross-species amplification in Prunus. In total, 48 alleles were detected by 15 SSR primer pairs, with an average of 3.2 putative alleles per primer combination. The number of putative alleles ranged from one to five in the tested cherry cultivars. Forty polymorphic fragments were scored in the tested cherry cultivars by 15 SSRs. All sweet cherry cultivars were identified by SSRs from their unique fingerprints. We also demonstrated that the technique of using DNA from fruit flesh for analysis can be used to maintain product purity in the market place by comparing DNA fingerprints from 12 samples of `Bing' fruit collected from different grocery stores in the United States to that of a standard `Bing' cultivar. Results indicated that, with one exception, all `Bing'samples were similar to the standard. Amplification of more than 80% of the sweet cherry primer pairs in plum (P. salicina), apricot (P. armeniaca) and peach (P. persica L.) showed a congeneric relationship within Prunus species. A total of 63 (21%) polymorphic fragments were recorded in 15 sweet cherry cultivars using four EcoRI-MseI AFLP primer combinations. AFLP markers generated unique fingerprints for all sweet cherry cultivars. SSRs and AFLP polymorphic fragments were used to calculate a similarity matrix and to perform UPGMA cluster analysis. Most of the cultivars were grouped according to their pedigree. The SSR and AFLP molecular markers can be used for the grouping and identification of sweet cherry cultivars as a complement to pomological studies. The new SSRs developed here could be used in cherry as well as in other Prunus species for linkage mapping, evolutionary and taxonomic study.
Inhibiting Tomato Ripening with 1-Methylcyclopropene
Authors: Mir Nazir , Canoles Mauricio , Beaudry Randolph , Baldwin Elizabeth , Mehla Chhatar Pal
Published: January 2019

The capacity for 1-methylcyclopropene (1-MCP) to inhibit color change and firmness loss and alter aroma profiles for tomato (Lycopersicon esculentum Mill.) fruit was evaluated as a function of 1-MCP concentration, multiple and continuous applications, and stage of ripeness. In addition, the relationship between external and internal fruit color and firmness was determined. 1-MCP reduced the rate of red color development in fruit of all stages of ripeness. A single application of 1-MCP delayed color development by ≈ days. A second application of 1-MCP 10 days after first treatment additionally delayed color development of mature green fruit by another 8 to 10 days. Continuous 1-MCP application completely inhibited color development of breaker and half-ripe fruit for the duration (34 days) of application, but only partially inhibited firmness loss. When fruit at 50% color development were treated with 1-MCP, gel color development tended to lag behind the external fruit color change compared to nontreated fruit. Some aroma volatiles were affected by 1-MCP applied at the mature green and breaker stages, but the effect was relatively minor; 1-MCP did not affect sugar or titratable acid levels in these fruit. Collectively, the data indicate 1-MCP caused minor shifts in the quality attributes of locule color, aroma, and firmness relative to external color, which may reduce the value of this treatment, but benefits accrued by slowed firmness loss and color development may afford sufficient compensation to make 1-MCP application commercially feasible.
Abscisic Acid Synthesis in Acer rubrum L. Leaves—A Vapor-pressure-deficit-mediated Response
Authors: Bauerle W.L. , Whitlow T.H. , Setter T.L. , Vermeylen F.M.
Published: January 2019

Quantitative differences in leaf abscisic acid (ABA) among Acer rubrum L. (red maple) ecotypes were investigated. This study tested the hypothesis that seedlings from wet and dry maternal sites display distinctly different capacities to synthesize ABA in response to atmospheric vapor pressure deficits. The increased levels of ABA in leaf tissue in the red maple ecotypes were associated with atmospheric vapor pressure deficit (VPD). Leaves on well-watered plants responded to VPD by increasing their ABA levels and reducing their photosynthesis (Anet) and stomatal conductance (gs). Both ecotypes appear to accumulate ABA at about the same rate as VPD increased. Despite the similar accumulation rates between ecotypes, wet site ecotypes consistently had a higher level of ABA present in leaf tissue under both low and high VPD conditions. Furthermore, wet site provenances appear to reduce Anet and gs in response to ABA accumulation, whereas dry sites do not present as clear an ABA/gs relationship. This study shows variation between wet and dry site red maple populations in physiological response to atmospheric vapor pressure deficits, indicating that natural ecotypic variation in stomatal responsiveness to air humidity is likely mediated by ABA accumulation in leaf tissue. This research demonstrates that ecotypes of red maple may be selected for atmospheric drought tolerance based on site moisture conditions.
Endogenous Free Polyamines of Mangos in Relation to Development and Ripening
Authors: Malik Aman Ullah , Singh Zora
Published: January 2019

Changes in endogenous free polyamines (putrescine, spermidine, spermine) were monitored from fruit set (fruit diameter 4.6 ± 0.5 mm, wt 0.09 ± 0.05 g) until 1 week before the expected harvest time in `Kensington Pride' and `Glen' to examine their role during mango (Mangifera indica L.) fruit development. Polyamines (PAs) in the pericarp tissues (exocarp and mesocarp) were estimated throughout the fruit development period, while estimations from growing ovules were started from 41 days after fruit set (DAFS). During fruit ripening, ethylene production and endogenous free PAs in skin and pulp of `Kensington Pride' mango were also monitored. PA contents of pericarp declined between fruit set and maturity from 788 to 101 nmol·g-1 fresh weight (FW) in `Kensington Pride' and from 736.6 to 89.6 nmol·g-1 FW in `Glen' during fruit development. Spermidine (SPD) and spermine (SPM) were higher than putrescine (PUT) during the initial phase of fruit growth. The highest levels of free PAs, especially SPD and SPM, at the initial stages of fruit growth suggest a potential role during the cell division phase and not in subsequent fruit development. Ovule seems to be a rich source of PAs as evident from 2.3- and 2.7-fold higher total PAs than pericarp tissues in `Kensington Pride' and `Glen', respectively. During fruit ripening of `Kensington Pride', total PAs increased in skin and pulp tissues along with the climacteric rise of ethylene, and reached maximum levels (skin 796, pulp 314 nmol·g-1 FW) on day 4 of ripening. Skin exhibited 55.8% higher mean free PAs than the pulp. PUT dominated both in skin and pulp tissues. The simultaneous increase of ethylene and free PAs during fruit ripening suggests that their biosynthesis may not be competitive, and free PAs may have evolved as a response to increased biosynthesis of ethylene.
Is There Such a Thing as Kalmia × Rhododendron?
Authors: Grant Mike L. , Toomey Nicola H. , Culham Alastair
Published: January 2019

Two putative hybrids between Kalmia and Rhododendron, their suspected progenitor species and related taxa were submitted to DNA sequencing of cpDNA trnL-F and nrDNA ITS regions in order to test whether there was DNA sequence evidence both for hybridization per se and for the direction of the cross should one be evident. Comparison of eight DNA sequences from these putative hybrids with Rhododendron and Kalmia species showed clear evidence of origin within Rhododendron. No evidence of Kalmia DNA was detected. These putative intergeneric hybrids appear to be mutants of Rhododendron and not of hybrid origin.
ISSR and AFLP Markers Differ among American Watermelon Cultivars with Limited Genetic Diversity
Authors: Levi Amnon , Thomas Claude E. , Newman M. , Reddy O.U. K. , Zhang X. , Xu Y.
Published: January 2019

Wide phenotypic diversity exists among American heirloom cultivars of watermelon (Citrullus lanatus var. lanatus). However, in published studies, low or no polymorphism was revealed among those heirlooms using isozyme or randomly amplified polymorphic DNA (RAPD) markers. In this study, experiments with inter-simple sequence repeat (ISSR) [also known as simple sequence repeat-(SSR-) anchored primers] and amplified fragment-length polymorphism (AFLP) markers produced high polymorphisms among watermelon heirloom cultivars. ISSR (111) and AFLP (118) markers (229 total) identified 80.2% to 97.8% genetic similarity among heirloom cultivars. The phylogenetic relations based on ISSR and AFLP markers are highly consistent with the parental records available for some of the heirloom cultivars, providing confidence in the dendogram constructed for heirlooms based on similarity values. As compared with RAPD markers, ISSRs and AFLPs are highly effective in differentiating among watermelon cultivars or elite lines with limited genetic diversity.
Pectin Ultra-degradation Decreases the Force Required to Detach Ripe Fruit from the Calyx in Tabasco Pepper
Authors: Arancibia Ramón A. , Motsenbocker Carl E.
Published: January 2019

Pectin metabolism was analyzed in tabasco pepper (Capsicum frutescens L.) to determine the metabolic process associated with the ease of fruit detachment from the calyx. The ease of fruit detachment (deciduous fruit) is a desirable trait in peppers that facilitates mechanical harvest. Two genotypes that differ in the fruit detachment force were used: `Easy Pick' (EZ), which requires a low force, and `Hard Pick' (HP), which requires higher force. Pectin dissolution in water from fresh-ripe EZ tissue was 20 times higher than from HP tissue. EDTA-soluble uronide from inactivated EZ cell wall, however, was only 1.8 times higher. Pectin dissolution was inversely correlated to the fruit detachment force and followed a sigmoidal curve during fruit ripening. Size-exclusion chromatography of EDTA-soluble polyuronides indicated that pectin was degraded in ripe fruit tissue from both genotypes. The degree of depolymerization, however, was more extensive in EZ fruit. Consequently, the ease of fruit detachment was attributed to pectin ultra-degradation. Total pectin content in dry tissue and ethanol/acetone-extracted cell wall was similar in both genotypes. Pectin content in dry tissue was maintained throughout ripening, while extracted cell wall pectin increased slightly. In contrast, the degree of pectin esterification of extracted cell wall decreased only in ripe EZ fruit. These results suggest that pectin de-esterification may have a role in the enhanced pectin depolymerization and consequently in the ease of fruit detachment of the EZ genotype.
Inheritance of the Flower Types of Gerbera hybrida
Authors: Kloos Wesley E. , George Carol G. , Sorge Laurie K.
Published: January 2019

Cultivated gerbera daisies [Gerbera hybrida (G. jamesonii Bolus ex Adlam × G. viridifolia Schultz-Bip)] have several different flower types. They include single and crested cultivars that have normal florets with elliptical (ligulate) outer corolla lips and spider cultivars that have florets with laciniated (split) outer corolla lips appearing as several pointed lobes. The objective of this investigation was to determine the mode of inheritance of the major flower types of gerberas in the North Carolina State Univ. collection. The collection contained parents and four generations of progeny representing a wide range of single and crested cultivars and some spider cultivars. Genotypes of parents used in crosses were determined by testcrosses to single-flowered, ligulate floret cultivars similar in phenotype to the wild, parental gerbera species. Testcrosses indicated that the wild type was recessive to the crested and spider flower types and given the genotype crcrspsp. For each of the types, a series of crosses were made to produce PA, PB, F1, F2, BC1A, and BC1B progeny. Allelism was tested operationally by crossing genotypes in all possible combinations and observing single-gene-pair ratios. Linkage relationships among the crested and spider loci were tested using dihybrid crosses and testcrosses. Phenotypic segregation ratios suggested the presence of two dominant alleles, Crd and Cr, determining the enlarged disk and trans floret, male-sterile and enlarged trans floret, male-fertile crested types, respectively, and an unlinked dominant gene, Sp, determining the spider type. Dominance appeared to be incomplete due to the reduction of trans floret length in most Crdcr and Crcr heterozygotes compared to crested homozygotes and the appearance of the quasi-spider type (spider trans and disk florets and ligulate and/or slightly notched ray florets) among certain crested Spsp heterozygotes.
Identification and Confirmation of RAPD and SCAR Markers Linked to the ms-3 Gene Controlling Male Sterility in Melon (Cucumis melo L.)
Authors: Park Soon O. , Crosby Kevin M. , Huang Rongfeng , Mirkov T. Erik
Published: January 2019

Male sterility is an important trait of melon in F1 hybrid seed production. Molecular markers linked to a male-sterile gene would be useful in transferring male sterility into fertile melon cultivars and breeding lines. However, markers linked to the ms-3 gene for male sterility present in melon have not been reported. Our objectives were to identify randomly amplified polymorphic DNA (RAPD) markers linked to the ms-3 gene controlling male sterility using bulked segregant analysis in an F2 population from the melon cross of line ms-3 (male-sterile) × `TAM Dulce' (male-fertile), convert the most tightly linked RAPD marker to the ms-3 gene into a sequence characterized amplified region (SCAR) marker based on a specific forward and reverse 20-mer primer pair, and confirm the linkage of the RAPD and SCAR markers with the ms-3 gene in an F2 population from the cross of line ms-3 × `Mission' (male-fertile). A single recessive gene controlling male sterility was found in F2 individuals and confirmed in F3 families. Two RAPD markers that displayed an amplified DNA fragment in the male-sterile bulk were detected to be linked to the ms-3 gene in the F2 population from the cross of line ms-3 × `TAM Dulce'. RAPD marker OAM08.650 was closely linked to the ms-3 gene at 2.1 cM. SCAR marker SOAM08.644 was developed on the basis of the specific primer pair designed from the sequence of the RAPD marker OAM08.650. The linked RAPD and SCAR markers were confirmed in the F2 population from the cross of line ms-3 × `Mission' to be consistently linked to the ms-3 gene at 5.2 cM. These markers were also present in 22 heterozygous fertile F1 plants having the ms-3 gene. The RAPD and SCAR markers linked to the ms-3 gene identified, and confirmed here could be utilized for backcrossing of male sterility into elite melon cultivars and lines for use as parents for F1 hybrid seed production.
Calcium Uptake and Whole-plant Water Use Influence Pod Calcium Concentration in Snap Bean Plants
Authors: Pomper Kirk W. , Grusak Michael A.
Published: January 2019

Understanding the mechanisms that regulate xylem transport of calcium (Ca) to snap bean (Phaseolus vulgaris L.) pods could allow approaches to increase pod Ca concentration and enhance the nutritional value of edible pods. Using the snap bean cultivars Hystyle and Labrador, which exhibit high and low pod Ca levels, respectively, we wished to determine whether there were differences between the two cultivars in stem xylem-sap Ca concentration and whether any differences in sap Ca concentration were related to differences in whole-plant water uptake or Ca import between the cultivars. Well-watered greenhouse-grown plants were placed in a growth chamber at a constant light intensity for an equilibration period. Pot weight loss was measured to determine whole-plant water use and stem xylem exudate was subsequently collected from the severed base of the shoot at flowering and at two stages of pod development. `Hystyle' displayed an exudate Ca concentration that was 50% higher than `Labrador' during pod development. `Labrador' showed 35% greater total water transport through the stem than `Hystyle'. `Labrador' plants also showed a significantly larger leaf area than `Hystyle' plants. Additional plants were used to determine total, long-term Ca influx. No difference was observed between cultivars in total Ca influx into the aerial portion of the plant. With whole-shoot Ca influx being equivalent and pod transpiration rate identical in the two cultivars, our results suggest that the higher whole-plant water uptake in `Labrador' led to a dilution of Ca concentration in the xylem stream and thus less total Ca was transported to developing pods, relative to that in `Hystyle'. Increased transpiration efficiency, enhanced root uptake of Ca, or reduced Ca sequestration in the xylem pathway of the stem could lead to an enhancement in pod Ca concentration in future cultivars of snap bean.
Delayed Modified Atmosphere Packaging of Fresh-cut Romaine Lettuce: Effects on Quality Maintenance and Shelf-life
Authors: Kim Ji Gang , Luo Yaguang , Saftner Robert A. , Gross Kenneth C.
Published: January 2019

Fresh-cut tissues are subjected to severe injury during preparation that leads to increased respiratory activity and quality deterioration. Modified atmosphere packaging (MAP) has been used to maintain quality of fresh-cut produce, but O2 depletion and excessive CO2 accumulation can be injurious. This study was conducted to evaluate the effect of delayed packaging and MAP using two different oxygen transmission rate (OTR) films on quality maintenance and shelf stability of fresh-cut romaine lettuce (Lactuca sativa L.). Romaine lettuce leaves were cut, washed, dried, and placed for 0, 4, 8, and 12 hours at 5 °C in ambient air before packaging. Fresh-cut samples were placed into packages prepared from films having OTRs of 8.0 and 16.6 pmol·s-1·m-2·Pa-1, flushed with N2 to reach an initial headspace O2 level of 1.5 kPa O2, and stored at 5 °C for up to 14 days. Delayed packaging affected gas composition, fermentative volatile production, off-odor development, color, CO2 injury, and tissue electrolyte leakage. With increasing delay before packaging, fermentative volatile production, off-odor development, and CO2 injury progressively decreased and discoloration increased. The modified atmospheres obtained with 16.6 OTR film increased discoloration when present, and generally had less off-odor development and CO2 injury compared to MAP with 8.0 OTR film. Delayed packaging affected overall quality of fresh-cut romaine lettuce packaged with both films. A 12-hour delayed packaging into packages prepared from 8.0 OTR film maintained quality by inhibiting CO2 injury, off-odor development, and tissue electrolyte leakage. However, an 8-hour delayed packaging into packages prepared from 16.6 OTR film was better at maintaining the quality of fresh-cut romaine lettuce at 5 °C for 14 days. The results indicated that delayed packaging could be an alternative method to optimize or balance package O2 during suboptimal OTR film packaging conditions.
Interspecific Hybridization of Fragaria vesca subspecies with F. nilgerrensis, F. nubicola, F. pentaphylla, and F. viridis
Authors: Bors R.H. , Sullivan J.A.
Published: January 2019

The potential of using Fragaria vesca L. as a bridge species for interspecific hybridization to F. nilgerrensis Schlect, F. nubicola Lindl., F. pentaphylla Losinsk, and F. viridis Duch. was investigated using a wide germplasm base of 40 F. vesca accessions. This study was successful in producing many hybrids between F. vesca and other diploid species indicating its value as a bridge species. Of the species used as males, F. nubicola, F. pentaphylla, and F. viridis accessions were more successful, averaging 8 to 16 fruit and 16 to 25 seeds/fruit. It was most difficult to obtain hybrids with F. nilgerrensis, which had only three seeds per fruit. Differences among pollen donors were minimal when hybrid seeds were germinated in vitro. For different species combinations, 75% to 99% of seeds had embryos and 77% to 89% of these embryos germinated. The lack of significant differences in crossability variables among the four F. vesca subspecies [i.e., ssp. americana (Porter) Staudt, ssp. bracteata (Heller) Staudt, ssp. vesca L., and ssp. vesca var. semper-florens L.] demonstrated the similarity between these species and the strong potential for gene flow between F. vesca and other diploid species. As European and North American F. vesca subspecies are not sufficiently divergent to differ in interspecific hybridization, F. vesca may be a younger species rather than an older progenitor species.
Genotypic and Environmental Variation in Antioxidant Activity and Total Phenolic Content among Blackberry and Hybridberry Cultivars
Authors: Connor Ann Marie , Finn Chad E. , Alspach Peter A.
Published: January 2019

Antioxidant compounds absorbed from our diet are thought to have a role in preventing chronic diseases that result from oxidative damage. Berry fruit have high levels of antioxidants, and further increases in antioxidant activity (AA) might be possible through breeding. We determined the AA, total phenolic content (TPH), and fruit weight in 16 blackberry and hybridberry (Rubus L.) cultivars harvested in New Zealand and Oregon in 2002 and 2003, to assess genetic and environmental variation. Both AA and TPH varied significantly between years within location, but not among cultivars or between locations per se. However, cultivar interactions with both location and year within location contributed to variation in both variates. In contrast, both cultivar and location contributed to variation in fruit weight, but years within location did not. However, the cultivar × year within location interaction was significant for this trait. Variance component distributions confirmed that cultivar and location effects together contributed little (<20%) to the total variation in either AA or TPH, while cultivar × environment interactions accounted for >50% of total variation in these traits. Cultivar and location effects together contributed ≈70% of the total variation observed in fruit weight. Phenotypic correlations were significant between AA and fruit weight (r = -0.44), and between TPH and fruit weight (r = -0.51). When adjusted for fruit weight, analyses for AA and TPH demonstrated that cultivar effects approached significance (P = 0.06) and accounted for ≈25% of total variance, while location effects accounted for none. Although the cultivars in this study had diverse interspecific backgrounds, utilization of various Rubus species in blackberry and hybridberry breeding is not uncommon, and our results demonstrating significant cultivar × environment interaction for AA and TPH should be applicable to breeding for high AA genotypes.