bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of Fruit Load Affects Early Fruit Growth in Apple by Enhancing Carbohydrate Availability, Altering the Expression of Cell Production-related Genes, and Increasing Cell Production
Authors: Dash Madhumita , Johnson Lisa Klima , Malladi Anish
Published: January 2019

Carbohydrate availability is a key factor determining fruit growth in apple (Malus ×domestica) and other fruits. However, the molecular mechanisms regulating fleshy fruit growth in response to changes in carbohydrate availability are not well understood. In this study, carbohydrate availability was manipulated by reducing fruit load, and its effects on apple fruit growth, cell production and expansion, and the expression of genes associated with these processes was investigated. Reduction of fruit load during early fruit development led to a rapid increase in early fruit growth. The increase in fruit growth was associated with a transient increase in sorbitol and fructose concentrations and altered expression of sorbitol dehydrogenase and sucrose synthase genes. Increase in early fruit growth was mediated primarily by an increase in cell production. The aintegumenta gene, MdANT1, an AP2-domain transcription factor associated with the regulation of cell production and fruit growth, displayed an increase in expression by up to 5-fold during early fruit development in response to the reduction in fruit load. Additionally, multiple cell cycle genes positively associated with cell production such as the cyclins, MdCYCA2;1, MdCYCA2;3, MdCYCB1;1, and MdCYCB2;2, and the B-type cyclin-dependent kinases, MdCDKB1;1, MdCDKB1;2, and MdCDKB2;2, displayed higher expression by up to 5-fold under reduced fruit load conditions during early fruit growth. These data indicate that carbohydrate availability affects the expression of key transcription factors and cell proliferation genes, thereby regulating cell production during early fruit growth. Several genes associated with cell expansion such as the expansins, and cobra and cobra-like genes, also displayed altered expression in response to the reduction in fruit load. The expression of three expansin genes was higher under reduced fruit load conditions at maturity, a stage at which a minor increase in cell size was apparent. Together, data from this study indicate that fruit load reduction induces changes in carbohydrate availability and metabolism, which in turn affect cell production-related mechanisms, thereby enhancing early fruit growth.
Bermudagrass Drought Tolerance Associated with Dehydrin Protein Expression during Drought Stress
Authors: Su Kemin , Moss Justin Q. , Zhang Guolong , Martin Dennis L. , Wu Yanqi
Published: January 2019

Drought stress is a major limiting factor for warm-season turfgrass growth during the summer in the U.S. transition zone. Genotypic variation in drought resistance exists among bermudagrasses (Cynodon sp.), but the mechanisms of drought resistance are poorly understood. Our objectives were to investigate physiological changes in three bermudagrass cultivars under a well-watered condition and drought stress. to determine expression differences in soluble protein and dehydrin of the three cultivars under well-watered and drought stress conditions, and to identify the association between dehydrin proteins and drought tolerance. Grasses included a high drought-resistant cultivar, Celebration, a low drought-resistant cultivar, Premier, and a newly released cultivar, Latitude 36. In both well-watered and drought treatments, ‘Latitude 36’ had the highest visual quality and lower or medium electrolyte leakage among three cultivars. In the drought treatment, 16- and 23-kDa dehydrin proteins were observed in ‘Latitude 36’ but not in ‘Celebration’ or ‘Premier’. Our results indicate that the 16- and 23-kDa dehydrin expressions could be associated with drought tolerance and contribute to drought tolerance in bermudagrass.
Single Nucleotide Polymorphisms in Linkage Disequilibrium with the Male-fertility Restoration (Ms) Locus in Open-pollinated and Inbred Populations of Onion
Authors: Havey Michael J.
Published: January 2019

Maintainer lines are used to seed propagate male-sterile lines for the development of hybrid onion (Allium cepa L.) cultivars. The identification of maintainer lines would be more efficient with molecular markers distinguishing genotypes at the nuclear male-fertility restoration (Ms) locus. Ms has been mapped to chromosome 2 of onion and linked genetic markers identified. However, linkages between these markers and Ms were detected using F2 or BC1 families at maximum linkage disequilibrium and, for many markers, their efficacy to predict genotypes at Ms in onion populations at or near linkage equilibrium remains unknown. In this research, near isogenic lines homozygous-dominant and -recessive at Ms were developed and screened for 930 single nucleotide polymorphisms (SNPs). Three SNPs tightly linked on chromosome 2 remained in linkage disequilibrium with genotypes at Ms among randomly selected plants from three open-pollinated populations of onion as well as among a collection of inbred lines. These SNPs should be useful for selection of the recessive ms allele to aid in the development of maintainer lines for hybrid onion development.
Combining Ability and Acceptability of Temperate Sweet Corn Inbreds Derived from Exotic Germplasm
Authors: Rice Reid R. , Tracy William F.
Published: January 2019

Excellent table quality is an essential characteristic of commercial sweet corn (Zea mays) and commonly held paramount as a selection criterion. As a consequence, breeding for improved agronomic performance in sweet corn has been limited in comparison with United States dent corn breeding efforts. The narrowness of genetic diversity within modern sweet corn germplasm suggests potential exists for yield enhancement through new heterotic combinations and introgression of sources of improved agronomic performance. The objective of this study was to examine the results of incorporating nonsweet germplasm in the development of improved temperate sweet corn cultivars. Five inbreds derived from crosses between nonsweet germplasm and temperate supersweet (shrunken2, sh2) inbreds were crossed with three temperate sh2 testers to make 15 experimental hybrids. The hybrids were evaluated in four environments with three replications per environments. Experimental entry Wh04038V × Tester2 yielded 18.1 Mg·ha−1 in 2009 and 16.6 Mg·ha−1 in 2010, significantly out-yielding the top producing commercial control, ‘Overland’, in both years. An additional six entries derived from exotic-by-temperate crosses yielded significantly more than all commercial checks in 2009. Four specific experimental entries consistently exhibited superior resistance to root lodging, northern corn leaf blight (Exserohilum turcicum), and Maize dwarf mosaic virus (MDMV) compared with ‘Marvel’ and ‘Supersweet Jubilee Plus’. Ten of the 15 experimental entries exhibited similar quality for flavor relative to ‘Marvel’ and ‘Overland’, however ‘Supersweet Jubilee Plus’ outperformed all entries for both flavor and tenderness, suggesting that while incorporation of nonsweet germplasm in sweet corn breeding programs may provide valuable contributions for yield and agronomic performance, flavor and tenderness must be carefully regarded.
Short-read DNA Sequencing Yields Microsatellite Markers for Rheum
Authors: Gilmore Barbara S. , Bassil Nahla V. , Barney Danny L. , Knaus Brian J. , Hummer Kim E.
Published: January 2019

Identifying and evaluating genetic diversity of culinary rhubarb (Rheum ×rhababarum) cultivars using morphological characteristics is challenging given the existence of synonyms and nomenclatural inconsistencies. Some cultivars with similar names are morphologically different, and seedlings may grow and become associated with the parental name. Morphological traits of one cultivar may vary when measured under different environmental conditions. Molecular markers are consistent for unique genotypes across environments and provide genetic fingerprints to assist in resolving identity issues. Microsatellite repeats, also called simple sequence repeats (SSRs), are commonly used for fingerprinting fruit and nut crops, but only 10 SSRs have previously been reported in rhubarb. The objectives of this study were to use short-read DNA sequences to develop new di-nucleotide-containing SSR markers for rhubarb and to determine if the markers were useful for cultivar identification. A total of 97 new SSR primer pairs were designed from the short-read DNA sequences. The amplification success rate of these SSRs was 77%, whereas polymorphism of those reached 76% in a test panel of four or eight rhubarb individuals. From the 57 potentially polymorphic primer pairs obtained, 25 SSRs were evaluated in 58 Rheum accessions preserved in the U.S. Department of Agriculture, National Plant Germplasm System. The primer pairs generated 314 fragments with an average of 12.6 fragments per pair. The clustering of many accessions in well-supported groups supported previous findings based on amplified fragment length polymorphisms (AFLPs). Cluster analysis, using the proportion of shared allele distance among the 25 SSRs, distinguished each of the 58 accessions including individuals that had similar names or the same name. Accessions that grouped in well-supported clusters previously belonged to similar clusters with high bootstrap support based on AFLP. In summary, our technique of mining short-read sequencing data was successful in identifying 97 di-nucleotide-containing SSR sequences. Of those tested, the 25 most polymorphic and easy-to-score primer pairs proved useful in fingerprinting rhubarb cultivars. We recommend the use of short-read sequencing for the development of SSR markers in the identification of horticultural crops.
Karyotype Analysis of Wild Rosa Species in Xinjiang, Northwestern China
Authors: Yu Chao , Luo Le , Pan Hui-tang , Sui Yun-ji , Guo Run-hua , Wang Jin-yao , Zhang Qi-xiang
Published: January 2019

Wild Rosa species, which are highly variable and locally adapted, are widely distributed in the Xinjiang Uygur autonomous region of China. These species possess many important horticultural traits that are not found in the gene pool of modern cultivated roses. However, little is known about their cytological characteristics, because few of them have been karyologically analyzed. Karyological data of 13 samples of seven wild Rosa taxa, including R. berberifolia, two botanical varieties of R. spinosissima, R. platyacantha, R. beggeriana, R. acicularis, and R. laxa, were investigated by means of squashes of shoot tips. The results showed that seven samples were diploid (2n = 2x = 14), whereas the other six samples were tetraploid (2n = 4x = 28). The karyotypes of all the test samples were composed of m and sm chromosomes, which include 1A, 2A, 1B, and 2B. There were differences in asymmetry index, centromere index, and distribution of relative lengths. The karyotype of the tetraploid R. laxa var. laxa sample from Aksu easily distinguished from the other R. laxa var. laxa samples tested in having the highest asymmetry index and the most evolved karyotype. This Aksu population merits recognition as a new botanical variety of R. laxa. The karyological data, most of which are first reports for their taxa, provide a comprehensive cytogenetic resource that can be used to better understand the taxonomy, evolution, and speciation in the genus Rosa and to identify candidate species for breeding programs.
Identification of the Paternal Parent of ‘Bing’ Sweet Cherry and Confirmation of Descendants Using Single Nucleotide Polymorphism Markers
Authors: Rosyara Umesh R. , Sebolt Audrey M. , Peace Cameron , Iezzoni Amy F.
Published: January 2019

‘Bing’ is an iconic sweet cherry (Prunus avium L.) cultivar in the United States that even after more than 130 years of cultivation remains the most highly regarded dark sweet cherry and is the standard by which new sweet cherries are judged. ‘Bing’ has been repeatedly used as a parent in North American breeding programs and is found in the lineages of several important modern cultivars. The maternal parent of ‘Bing’ is reported to be ‘Black Republican’, an old cultivar commercially grown for fruit in the Willamette Valley, OR, after ≈1860 and now is usually only grown as a pollenizer cultivar; however, the paternal parent of ‘Bing’ is unknown. The objective of this study was to deduce the paternal parent of ‘Bing’ and validate the pedigree records for the relatives of ‘Bing’ using statistical algorithms that use genomewide single nucleotide polymorphism (SNP) data. With a high probability, it was determined that the sweet cherry cultivar Napoleon, also known as Royal Ann in the Pacific northwestern United States, a large, firm, blush-type, light-fleshed, and productive cherry, is the paternal parent of ‘Bing’. This parentage deduction results in an increase in the known relatedness among U.S. cultivated sweet cherry breeding germplasm because ‘Napoleon’ is an important founder previously known to be present in the ancestry of every self-compatible sweet cherry cultivar bred to date, directly and through ‘Bing’ and its descendants.
Morphological Characteristics and In Situ Auxin Production during the Histogenesis of Staminate Flowers in Precocious Walnut
Authors: Gao Ying , Liu Hao , Pei Dong
Published: January 2019

Monoclonal anti-indole acetic acid antibodies were used to monitor the temporal and spatial pattern of auxin during staminate flower differentiation in walnut (Juglans regia) cultivars Liaoning 1 and Liaoning 3. The relationship between morphological characteristics and histological structure was established. Seven stages of differentiation were recognized based on the visibility and color of the squama, bract, perianth, and rachis as follows: Stage 1, several bract primordia were present in the squama with catkins protruding from the squama as the only externally visible portion of the floret (Stage 1); the bract became externally visible, and the floret, perianth, and stamen primordia formed basipetally (Stage 2); the length of catkins were elongated, only bracts visible and getting brown (Stage 3); the bracts were brown and wrapped tightly, cellular specialization occurred to form a central core containing reproductive cells and tapetal cells that differentiated (Stage 4); the perianth became visible externally, reproductive cells and tapetal cells separated from the exterior layers of the anther wall (Stage 5); the anther walls were reduced to two cell layers (epidermis and endothecium) as the anthers became visible and matured (Stage 6); and the anther turned black, dehisced, and released its pollen grains (Stage 7). The histological differentiation of the flowers was related to auxin. The auxin signal was strongest in the shoot apical meristem (SAM) during bract primordia differentiation; thus, the SAM may be a site of auxin production. When the floral organs began centralized differentiation, auxin was distributed mainly in the differentiating tissues. Our findings indicate that a high level of auxin may strongly affect morphogenesis. Additionally, the tapetal and reproductive cells that arise during cellular specialization may be important for auxin production. The distribution of auxin was centralized in germ pores at the pollen grain surface, indicating that a high level of auxin induces pollen germination.
Impact of Interspecific Introgression on Anthocyanin Profiles of Southern Highbush Blueberry
Authors: Yousef Gad G. , Lila Mary A. , Guzman Ivette , Ballington James R. , Brown Allan F.
Published: January 2019

Blueberry (Vaccinium L. section Cyanococcus Gray), a rich source of polyphenolics with important implications for human health and chronic diseases, has become a major fruit commodity in the United States. This study was designed to assess the impact of introgression through interspecific hybridization on anthocyanin (ANC) profiles among blueberry species. Southern highbush blueberry (V. corymbosum L.) and rabbiteye blueberry (V. virgatum Ait.) commercial cultivars, North Carolina blueberry breeding selections, and blueberry breeding populations with varying degrees of introgression from multiple species were used to address this question. The breeding selections and populations were created and selected for traits not directly related to their ANC profiles and are therefore likely representative of the current selection objectives of most public and private breeding programs. Ripe fruit at a uniform stage of maturity were evaluated for ANC concentration and profile in 2 consecutive years (2010 and 2011) from all plants. Total ANC ranged from 189 to 464, 74 to 421, and 227 to 537 mg/100 g (frozen fruit) in the commercial cultivars, breeding selections, and breeding populations, respectively. Significant increases in total ANC were observed among material that represents an expanded gene pool in southern highbush blueberry (introgression from V. angustifolium Ait., V. elliottii Chap., V. myrsinites Lam., V. pallidum Ait., V. tenellum Ait., V. fuscatum Ait., V. constablaei Gray, and V. arboreum Mar.). Differences in acylation and glycosylation patterns were also observed in the same material, which may condition relative stability, absorption, and bioavailability of ANC. Results suggest that the expansion of the gene base through interspecific hybridization can have both a positive and negative impact on ANC accumulation and that breeders need to be aware of these issues early in the breeding program.
Time-dependent Changes in the Longitudinal Sugar and Respiratory Profiles of Asparagus Spears During Storage at 0 °C
Authors: Verlinden Sven , Silva Silvanda M. , Herner Robert C. , Beaudry Randolph M.
Published: January 2019

The rate of respiration and the concentrations of sucrose, glucose, and fructose were measured along the length of intact asparagus (Asparagus officinalis cv. Jersey Giant) spears during storage at 0 °C. Carbon dioxide production by each of five sections along the spear was initially high but underwent a rapid and extensive decline within the first 24 hours after harvest with the rate of decline slowing thereafter. The respiration rate was highest at the tip (Section 1), decreasing as the distance from the tip increased (Sections 2 through 5 with Section 5 being more basal). Initially, the respiration rate of the tip was approximately four times that of the base, but after 23 days at 0 °C, the respiration rate of the tip was only twice that of the base. Sugar levels were measured in Sections 1 through 4. Sugar levels declined with time, but increased, unlike respiration, with distance from the tip. Sucrose underwent a rapid decline within the first 24 hours of storage in the tip and Sections 3 and 4. Sucrose depletion was most extensive in the tip, reaching more than 95% by Day 23. Glucose underwent the most rapid decline in Section 2. The relatively higher rate of glucose depletion in Section 2, the zone of rapid cell elongation, may have been to support a relatively higher rate of cell wall biosynthesis in this section. For the first day after harvest, sugar depletion far outstripped hexose equivalents respired as CO2. Afterward, however, the rate of respiration (as hexose equivalents) was similar to the rate of sugar depletion for all sections except the most basipetal, which lost carbohydrate faster than could be accounted for by respired CO2. The data suggest that hexoses were exported from more basipetal tissues to support the metabolic activity of more acropetal sections.
Variation for Epicuticular Waxes on Onion Foliage and Impacts on Numbers of Onion Thrips
Authors: Damon Steven J. , Groves Russell L. , Havey Michael J.
Published: January 2019

Natural variation exists in onion (Allium cepa L.) for amounts of epicuticular waxes on foliage, and plants with lower amounts of these waxes suffer less feeding damage from onion thrips (Thrips tabaci Lind.). Wild-type onion possesses copious amounts of epicuticular waxes and is often referred to as “waxy.” The recessively inherited “glossy” phenotype has significantly less wax relative to waxy types and shows resistance to onion thrips but is vulnerable to spray damage, foliar pathogens, and excessive transpiration. Phenotypes visually intermediate between waxy and glossy also exist in onion, which we refer to as “semiglossy.” Epicuticular waxes on the leaves of glossy, semiglossy, and waxy onions were evaluated for appearance using scanning electron microscopy (SEM) and amounts and types were analyzed using gas chromatography/mass spectrometry. Wax crystals were clearly visible on the surface of waxy foliage with decreasing amounts on semiglossy and none on glossy leaves. The ketone hentriacontanone-16 was the most prevalent wax on leaves of waxy onion and was significantly (P < 0.01) less on semiglossy relative to waxy plants and on glossy relative to waxy and semiglossy plants. Numbers of adult and immature onion thrips were significantly reduced (P < 0.05) on glossy and/or semiglossy accessions relative to waxy in field and greenhouse cage experiments. These results indicate that semiglossy plants possess intermediate amounts of epicuticular waxes that may protect leaves from diseases or environmental stresses while still conferring resistance to onion thrips. Therefore, the semiglossy phenotype should be useful in integrated programs managing this important onion pest.
Development and Application of Genic Simple Sequence Repeat Markers from the Transcriptome of Loquat
Authors: Li Xiaoying , Xu Hongxia , Feng Jianjun , Chen Junwei
Published: January 2019

Deep transcriptome sequencing allows for the acquisition of large-scale microsatellite information, and it is especially useful for genetic diversity analysis and mapping in plants without reference genome sequences. In this study, a total of 14,004 simple sequence repeats (SSRs) were mined from 10,511 unigenes screening of 63,608 nonredundant transcriptome unigenes in loquat (Eriobotrya japonica) with a frequency of 22 SSR loci distributed over 100 unigenes. Dinucleotide and trinucleotide repeat SSRs were dominant, accounting for 20.62%, and 42.1% of the total, respectively. Seventy primer pairs were designed from partial SSRs and used for polymerase chain reaction (PCR) amplification. Of these primer pairs, 54 exhibited amplification and 33 were polymorphic. The number of alleles at these loci ranged from two to 17, and the polymorphism information content values ranged from 0.24 to 0.89. We tested the transferability of 33 SSR polymorphic primer pairs in apple and pear, and the transferability rates in these two species were 90.9% and 87.9%, respectively. A high level of marker polymorphism was observed in apple [Malus ×domestica (66.7%)], whereas a low level was observed in pear [Pyrus sp. (51.5%)]. In addition, the PCR products from seven SSR primer pairs were selected for sequence analysis, and 89.2% of the fragments were found to contain SSRs. SSR motifs were conserved among loquat, apple, and pear. According to our sequencing results for real SSR loci, ≈12,490 SSR loci were present in these loquat unigenes. The cluster dendrogram showed a distinct separation into different groups for these three species, indicating that these SSR markers were useful in the evaluation of genetic relationships and diversity between and within the species of Maloideae in the Rosaceae. The results of our identified SSRs should be useful for genetic linkage map construction, quantitative trait locus mapping, and molecular marker-assisted breeding of loquat and related species.
Inheritance of Dwarfiness and Erect Growth Habit in Progenies of Jatropha curcas × Jatropha integerrima
Authors: One Khin Thida , Muakrong Narathid , Phetcharat Chamnanr , Tanya Patcharin , Srinives Peerasak
Published: January 2019

Jatropha (Jatropha curcas) is one of the most popular tree crops for seed production as a source of oil for biodiesel. However, currently grown cultivars are too large in canopy size and thus have very low harvest index. Alteration of canopy height and size can lead to identification of a desirable plant architecture for jatropha. A study was conducted to determine genetic control of dwarfiness and erect growth habit in jatropha populations derived from an interspecific cross between J. curcas with tall-erect (TL-ER) plant type and J. integerrima with dwarf-spreading (DW-SP) plant type. Crosses were made between both species to develop F1, F2, BC1F1, and BC1F2 generations. The F2 plants segregated at a 1:2:1 ratio for tall (TL), intermediate (ID), and dwarf (DW) plant types as well as for spreading (SP), upright (UP), and erect (ER) canopy angles. Both characters segregated independently producing nine phenotypes including TL-ER, TL-UP, TL-SP, ID-ER, ID-UP, ID-SP, DW-ER, DW-UP, and DW-SP at a 1:2:1:2:4:2:1:2:1 ratio. The BC1F1 (J. curcas × F1) plant segregated into TL-ER, TL-UP, ID-ER, and ID-UP at a 1:1:1:1 expected ratio. Six BC1F2 lines were also evaluated to confirm the results by selfing two trees each of BC1F1 showing TL-ER, TL-UP, and ID-ER growth habits. The progenies of TL-ER trees were all TL-ER; the progenies of TL-UP trees segregated into TL-ER, TL-UP, and TL-SP at an expected 1:2:1 ratio, whereas the progenies of ID-ER trees segregated into TL-ER, ID-ER, and DW-ER at an expected 1:2:1 ratio. The results indicated that dwarfiness and erect growth habit were each controlled by independent genes with incomplete dominant action. The knowledge and progenies obtained from this study can be used in breeding jatropha for desirable canopy size and shape.
Quantitative Trait Loci Controlling Amounts and Types of Epicuticular Waxes in Onion
Authors: Damon Steven J. , Havey Michael J.
Published: January 2019

Natural variation exists in onion (Allium cepa L.) for amounts and types of epicuticular waxes on leaves. Wild-type waxy onion possesses copious amounts of these waxes, whereas the foliage of semiglossy and glossy phenotypes accumulates significantly less wax. Reduced amounts of epicuticular waxes have been associated with resistance to onion thrips (Thrips tabaci Lindeman), an important insect pest of onion. A segregating family from the cross of waxy and semiglossy onions was used to map single nucleotide polymorphisms (SNPs) and identify chromosome regions affecting amounts and types of epicuticular waxes as measured by gas chromatography–mass spectrometry. The amount of the primary epicuticular wax on onion leaves, hentriacontanone-16, was controlled by one region on chromosome 5. One region on chromosome 2 affected concentrations of several primary fatty alcohols. Results indicate that the region on chromosome 2 may be associated with the acyl reduction pathway, and the region on chromosome 5 may affect the decarbonylation pathway of epicuticular wax biosynthesis. Because lower amounts of epicuticular waxes are recessively inherited, SNPs tagging regions on chromosomes 2 and 5 will be useful for marker-assisted breeding to vary amounts and types of epicuticular waxes on onion foliage with the goal to develop cultivars resistant to onion thrips.
Fine Root Hydraulic Conductance Is Related to Post-transplant Recovery of Two Quercus Tree Species
Authors: Yin Jingjing , Bassuk Nina L. , Olberg Madeline W. , Bauerle Taryn L.
Published: January 2019

In our study, we investigated whether root hydraulic conductance is related to post-transplant recovery. We used two Quercus species that differ in their transplant ability, Q. bicolor and Q. macrocarpa. Q. bicolor easily survives transplanting, whereas Q. macrocarpa often does not. We compared root hydraulic conductance after transplanting between control (without root pruning) and root-pruned, 1-year-old, small-caliper trees. We also examined the effects of transplant timing on post-transplant recovery of large-caliper trees. Hydraulic conductance in fine roots was correlated with recovery of the two Quercus species after transplanting. Six months after transplanting, small-caliper Q. bicolor trees had similar specific hydraulic conductance (KS) in fine roots compared with the KS before root-pruning, whereas fine root KS in small-caliper Q. macrocarpa trees decreased. Lower pre-dawn and midday xylem water potential in root-pruned Q. macrocarpa 6 weeks after transplanting indicates that root-pruned Q. macrocarpa experienced transplanting-induced water stress. For large-caliper trees, all Q. macrocarpa trees exhibited typical symptoms of transplant shock regardless of transplant timing, which was the result of higher vulnerability to mild water stress compared with Q. bicolor, resulting in a large reduction in fine root KS. Fine root KS in spring-transplanted Q. bicolor trees was much higher than that in fall-transplanted trees, implying spring transplanting is optimal for Q. bicolor. Other intrinsic characteristics of the species should be considered in the future when making better decisions on transplant timing such as xylem anatomy, carbon storage, rhizosphere conditions, and plant growth.
Anatomy of Petal Drop in Sunflowers
Authors: Tata Joyous Suiyigheh , Wien Hans Christian
Published: January 2019

The petals of some sunflower (Helianthus annuus) cultivars used as cut flowers are easily knocked off the flower; this ruins its appearance and destroys its market value. The objectives of this study were to characterize an abscission zone, if present, at the base of petals of sunflower florets in cultivars that differ with respect to petal drop and to determine if differences in the nature and/or development of the abscission zone among cultivars were correlated with differences in timing with respect to petal drop. In the first experiment, we measured the force required to pull petals from the flower head; in the second we investigated changes in the anatomy of the petal–achene juncture. Anatomical analysis revealed a differentiated region (the abscission zone) at the junction of the petal and achene consisting of cells with a different morphology from those above and below it. Cell division at the abscission zone of the short-lived cultivar occurred earlier than in the long-lived cultivar. These differences indicate that whereas the anatomical nature of the abscission zone is similar in the two cultivars, Procut Yellow Lite (PYL) and Procut Bicolor (PBC), the tempo of development differed. Specifically, the abscission layer reached full differentiation, or maturity, sooner in PBC, hence its earlier petal drop, than in PYL.
Inflorescence Bud Initiation, Development, and Bloom in Two Southern Highbush Blueberry Cultivars
Authors: Kovaleski Alisson P. , Williamson Jeffrey G. , Olmstead James W. , Darnell Rebecca L.
Published: January 2019

Blueberry (Vaccinium spp.) production is increasing worldwide, particularly in subtropical growing regions, but information on timing and extent of inflorescence bud development during summer and fall and effects on bloom the next season are limited. The objectives of this study were to determine time of inflorescence bud initiation, describe internal inflorescence bud development, and determine the relationship between internal inflorescence bud development and bloom period the next spring in two southern highbush blueberry [SHB (Vaccinium corymbosum interspecific hybrids)] cultivars. ‘Emerald’ and ‘Jewel’ SHB buds were collected beginning in late summer until shoot growth cessation in late fall for dissection and identification of organ development. Inflorescence bud frequency and number, vegetative and inflorescence bud length and width throughout development, and bloom were also assessed. Inflorescence bud initiation occurred earlier in ‘Emerald’ compared with ‘Jewel’. Five stages of internal inflorescence bud development were defined throughout fall in both cultivars, ranging from a vegetative meristem to early expansion of the inflorescence bud in late fall. ‘Emerald’ inflorescence buds were larger and bloomed earlier, reflecting the earlier inflorescence bud initiation and development. Although inflorescence bud initiation occurred earlier in ‘Emerald’ compared with ‘Jewel’, the pattern of development was not different. Timing of inflorescence bud initiation influenced timing of bloom with earlier initiation resulting in earlier bloom.
Selection of Reference Genes for Real-time Quantitative Polymerase Chain Reaction Analysis of Light-dependent Anthocyanin Biosynthesis in Chrysanthemum
Authors: Hong Yan , Dai SiLan
Published: January 2019

The light-dependent coloration of the vital organs of horticultural crops affects multiple parts of production and sales. The simplicity of the metabolic pathways of anthocyanins and the characteristics of light-dependent coloration make chrysanthemum (Chrysanthemum ×morifolium) an ideal subject for studying the mechanism of light-regulated anthocyanin biosynthesis. In this study, real-time quantitative reverse transcription–polymerase chain reaction (PCR) was used in the analysis of the expression levels of anthocyanin biosynthesis genes in C. ×morifolium ‘Reagan’. The reference genes selected were those assumed to remain at constant levels in three flower color lines at five floral developmental stages and at two light conditions. Using digital gene expression technology, we selected nine reference genes with moderate expression in the chrysanthemum ray florets at various floral developmental stages under illuminated and dark conditions as the candidate reference genes for further study. After comprehensively analyzing the stability of gene expression with three distinct statistical algorithms, geNorm, NormFinder, and qBase plus, we found that F-box and PP2A were the most stable genes in all of the samples. In addition, we analyzed the relative expression level of the CmF3H gene in different samples to verify the reference genes that we selected. This study provides a consensus list of validated reference genes that will benefit future studies of the expression of chrysanthemum genes involved in anthocyanin biosynthesis and floral development under various light conditions. Moreover, this information will also promote the molecular breeding of horticultural crops for their color modification.
Pedicel Transpiration in Sweet Cherry Fruit: Mechanisms, Pathways, and Factors
Authors: Athoo Thomas O. , Winkler Andreas , Knoche Moritz
Published: January 2019

Pedicel appearance is a good indicator of freshness in sweet cherries (Prunus avium L.). Fruit with shriveled, discolored pedicels have reduced market value. Shriveled pedicels are thought to result from postharvest water loss due to transpiration. The objectives of our study were to 1) quantify the transpiration permeances of fruit and pedicel surfaces; 2) determine the role of the fruit in pedicel transpiration; and 3) identify the effects of selected factors on pedicel transpiration. Fruit with and without pedicels were incubated under controlled conditions [usually 22 °C, 75% relative humidity (RH)] and their mass losses determined gravimetrically. Pedicel transpiration was calculated by subtracting measured transpiration of fruit without pedicels from that of fruit with pedicels. Cumulative pedicel transpiration increased with time. Rates of pedicel transpiration were essentially constant over the first 0 to 1.5 hours but declined thereafter, approaching an asymptote over the subsequent period of 1.5 to 96 hours over which measurements were made. Cumulative pedicel transpiration exceeded the amount of water in the pedicel, indicating that at least some of the transpired water originated from the fruit. There was no significant effect of steam girdling on pedicel transpiration suggesting that water moved from the fruit to the pedicel through the xylem (steaming prevents phloem conduction). Abrading the cuticular membrane (CM) from a pedicel surface or extracting the cuticular wax by dipping pedicels once or five times in chloroform/methanol (1:1 v/v) increased rates of transpiration 12-, 3-, and 5-fold, respectively. The water vapor permeance of the pedicel surface determined under steady-state conditions (8.7 ± 0.4 × 10−4 m·s−1) exceeded that of the fruit (2.1 ± 0.1 × 10−4 m·s−1), possibly because of a more permeable CM and/or a higher stomatal density (38.5 ± 1.3 stomata/mm2 for pedicels vs. 1.1 ± 0.0 stomata/mm2 for fruit). Treatments known to affect stomatal opening (incubation in buffered abscisic acid at 0.1 mm or in CO2- or N2-atmospheres) had no effects on pedicel transpiration. Rates of transpiration were negatively correlated with RH but positively with temperature. There was no effect of RH and/or temperature on the permeances of pedicel or fruit surfaces. From our results it is inferred that 1) pedicel transpiration is a physical process governed by Fick’s law of diffusion, where cuticle and wax in particular represent the major rate-limiting barriers; 2) the permeances of pedicel surfaces exceed those of fruit surfaces; and 3) pedicel transpiration can be minimized by minimizing the driving force (difference in water vapor concentration) during postharvest handling and storage.
Growth and Enzymatic Activity of Four Warm-season Turfgrass Species Exposed to Waterlogging
Authors: Zong Junqin , Gao Yanzhi , Chen Jingbo , Guo Hailin , Wang Yi , Meng Fan , Jiang Yiwei , Liu Jianxiu
Published: January 2019

Waterlogging (WL) negatively affects plant growth and development, but the physiological responses of turfgrass species to WL are not well understood. The objective of this study was to examine growth and physiological mechanisms of WL tolerance in warm-season turfgrass species. Knotgrass (Paspalum paspaloides), spiny mudgrass (Pseudoraphis spinescens), seashore paspalum (Paspalum vaginatum), and centipedegrass (Eremochloa ophiuroides) were subjected to 30 days of WL. At the end of the treatment, knotgrass and spiny mudgrass maintained the shoot and root biomass while seashore paspalum and centipedegrass showed reductions in biomass under WL. Root oxidase activity (ROA) was unaffected until after 12 or 18 days of WL but decreased by 14.3%, 17.8%, 32.0%, and 68.7% at 30 days of WL for knotgrass, spiny mudgrass, seashore paspalum, and centipedegrass, respectively. Waterlogging increased root activities of lactate dehydrogenase and alcohol dehydrogenase, but generally to a lesser extent in knotgrass and spiny mudgrass. The leaf and root activities of superoxide dismutase (SOD) and peroxidase (POD) were induced after 6 or 12 days of WL, but to a greater extent for knotgrass and spiny mudgrass. At 30 days of WL, the increased leaf and root activities of SOD and POD were higher in knotgrass and spiny mudgrass than that of seashore paspalum and centipedegrass; while centipedegrass showed 37.8% reduction in root SOD activity. The total soluble protein (TSP) concentration remained unchanged in both leaves and roots during the entire WL treatment for knotgrass, while a decreased leaf TSP was found in the other three species after 12 or 24 days of WL as well as in the roots of seashore paspalum and centipedegrass. More reductions in leaf or root TSP were observed in seashore paspalum and centipedegrass than in knotgrass and spiny mudgrass at 30 days of WL. The results indicated that higher ROA, activities of antioxidant enzymes and TSP contributed to WL tolerance of warm-season turfgrass species.
Anthocyanin, Carotenoid, Tocopherol, and Ellagitannin Content of Red Raspberry Cultivars Grown under Field or High Tunnel Cultivation in the Southeastern United States
Authors: Bradish Christine M. , Yousef Gad G. , Ma Guoying , Perkins-Veazie Penelope , Fernandez Gina E.
Published: January 2019

High tunnels have been widely adopted for red raspberry (Rubus idaeus) production in the United States to extend the harvest season and increase yields. In this study, effects of high tunnel production on contents of plant secondary metabolites (anthocyanins, carotenoids, tocopherols, and ellagitannins) in red raspberry fruit were determined for three fall-fruiting cultivars (Autumn Britten, Caroline, and Nantahala) grown at three locations in North Carolina under field and high tunnel cultivation systems. Cultivar was the primary contributing factor to variation in phytochemicals, with minor effects of location and production system. The anthocyanin cyanidin-3-glucoside and the carotenoids α-carotene, β-carotene, lutein, and zeaxanthin were higher in fruit produced in field compared with tunnel cultivation (P < 0.01). Accumulation of total anthocyanins and tocopherols in fruit were unaffected by high tunnel cultivation in comparison with traditional field cultivation. Carotenoid content varied by genotype and production system. ‘Autumn Britten’ and ‘Caroline’ showed no difference, but were higher than ‘Nantahala’ for α-carotene, β-carotene, 9-cis-β-carotene, and lutein + zeaxanthin (P < 0.0001). Phytochemical differences among field and tunnel produced fruit have important implications for breeding with increased nutritional value in mind, and also the understanding of the relationships of plant pigments to light and temperature.
Grafting of Genetically Engineered Plants
Authors: Song Guo-qing , Walworth Aaron E. , Loescher Wayne H.
Published: January 2019

Grafting is a well-established agricultural practice, and it now has implications for the commercialization of transgenic plants. In transgrafted plants, only one part (scion or rootstock) is transgenic with the other part untransformed. However, transgenes may affect both mobile and immobile endogenous metabolites (e.g., RNAs, proteins, and phytohormones) and mobility has implications for transgrafting. In the phloem, long-distance transport of mobile metabolites can play important roles in plant development and signaling. In a transgrafted plant, an immobile transgene product (ITP) is not likely to be translocated across the graft union. In contrast, mobile transgene products (MTP) may be translocated across the graft. Regardless of the mobility of transgene products (TP), interaction of transgenic and nontransgenic parts in transgrafted plants through either the MTP or ITP has been demonstrated to be effective in facilitating changes in nontransgenic portions of the plant. Consequently, and particularly in fruit crops, transgrafting provides the potential for improving products from their nontransgenic parts with the possibility of minimizing the controversy over transgenic crops. This review focuses mainly on the mobility of TP and effects on the whole transgrafted plant.
Genome-wide Identification and Characterization of the DELLA Subfamily in Prunus mume
Authors: Lu Jiuxing , Yang Weiru , Zhang Qixiang
Published: January 2019

Control of development is an important issue in the production of ornamental plants. Gibberellins (GAs) play a key role in regulating plant growth and development. DELLA is nuclear negative regulators of GA signaling. We identified two DELLA homologous genes, PmDELLA1 and PmDELLA2, in the genome of mei (Prunus mume) genome. We analyzed the structure, expression patterns and molecular functions of both genes. Tissue expression analysis showed that both genes were transcriptionally active. PmDELLA1 showed higher expression in seeds than PmDELLA2. This indicated that PmDELLA2 plays different roles from PmDELLA1 in seed germination. The expressions of both genes at various flowering stages were relatively low. We speculated that PmDELLAs might be positive regulators of flowering by releasing the repression of GA during floral blooming. Transgenic arabidopsis (Arabidopsis thaliana) lines overexpressing the two genes showed dwarf and delayed flowering. We confirmed that the two PmDELLAs were partially conserved with genes encoding DELLA proteins in arabidopsis. Our bioinformatics and functional analyses provide information that may be valuable to improve the economic, agronomic and ecological properties of mei and other Rosaceae fruit trees.
Development and Transferability of Black and Red Raspberry Microsatellite Markers from Short-Read Sequences
Authors: Dossett Michael , Bushakra Jill M. , Gilmore Barbara , Koch Carol A. , Kempler Chaim , Finn Chad E. , Bassil Nahla V.
Published: January 2019

The advent of next-generation, or massively parallel sequencing technologies has been a boon to the cost-effective development of molecular markers, particularly in nonmodel species. Here, we demonstrate the efficiency of microsatellite or simple sequence repeat (SSR) marker development from short-read sequences in black and red raspberry (Rubus occidentalis L. and R. idaeus L., respectively), compare transferability of markers across species, and test whether the rate of polymorphism in the recovered markers can be improved upon by how marker sequences are chosen. From 28,536,412 black raspberry reads and 27,430,159 reads in red raspberry, we identified more than 6000 SSR sequences in each species and selected 288 of these (144 from each species), for testing in black and red raspberry. A total of 166 SSR primer pairs were identified with informative polymorphism in one or both species. SSRs selected based on different percentages (90% to 97% as compared with ≥98%) of read cluster similarity did not differ in polymorphism rates from each other or from those originating from singletons. Efficiency of polymorphic SSR recovery was nearly twice as high in black raspberry from black raspberry-derived sequences as from red raspberry-derived sequences, while efficiency of polymorphic SSR recovery in red raspberry was unaffected by the source of the primer sequences. Development of SSR markers that are transferable between red and black raspberry for marker-assisted selection, evaluation of genome collinearity and to facilitate comparative studies in Rubus L. will be more efficient using SSR markers developed from black raspberry sequences.
Malic Acid Promotes Cracking of Sweet Cherry Fruit
Authors: Winkler Andreas , Ossenbrink Max , Knoche Moritz
Published: January 2019

When mature sweet cherries (Prunus avium L.) came into contact with sweet cherry juice, cracking dramatically increased. The objectives of our study were: 1) to quantify the cracking of fruit in cherry juice, 2) to determine which constituent(s) of the juice especially promote cracking and, 3) to establish its/their mode of action in promoting cracking. Artificial juice was made up as an aqueous solution of the same five pure chemicals and at the same relative concentrations as the five major osmolytes of real sweet cherry juice. Artificial and real juice was used at half-isotonic concentrations as the real juice from that batch of fruit. Cracking of sweet cherries placed in either artificial or real juice was more rapid and occurred for lower net water uptakes than of fruit placed in half-isotonic polyethylene glycol 6000. The crack-promoting component in sweet cherry juice was malic acid. Further tests with malic acid, and other organic acids, and with different concentrations of malic acid, with and without pH control, and with the enantiomers of malic acid, showed the effects were primarily related to the pH of the incubation solution. Leakage of anthocyanin from discs of flesh was increased in the presence of malic acid and greater in hypotonic than hypertonic solutions, suggesting that malic acid increases the permeability of the plasma membrane and tonoplast and weakens the cell walls. Malic acid may be an important link (amplifier) in a reaction chain that begins with the bursting of individual epidermal cells and ends with the formation of macroscopic skin cracks.