bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth, Gas Exchange, and Chlorophyll Fluorescence of Four Ornamental Herbaceous Perennials during Water Deficit Conditions
Authors: Starman Terri , Lombardini Leonardo
Published: January 2019

A study was conducted to characterize the morphological and physiological responses of four herbaceous perennial species subjected to two subsequent drought cycles. Lantana camara L. `New Gold' (lantana), Lobelia cardinalis L. (cardinal flower), Salvia farinacea Benth. `Henry Duelberg' (mealy sage), and Scaevola aemula R. Br. `New Wonder' (fan flower) were subjected to two consecutive 10-day drought cycles. Growth response, leaf gas exchange, and chlorophyll fluorescence were measured during the experiment. The morphology of L. cardinalis and L. camara was not affected by drought, while S. farinacea had reductions in plant height and leaf area and S. aemula had reductions in dry weight. Overall, plant growth and development continued even when substrate water content was reduced to 0.13 mm3·mm-3, which indicated a level of substrate water below container capacity was sufficient for greenhouse production of these species. The drought treatments had little effect on the photochemical efficiency (Fv/Fm) of Photosystem II. An increase in minimal fluorescence (Fo) was observed in S. aemula on the last day of the second cycle. Drought treatment caused increased leaf-level water use efficiency (WUE) at the end of the first cycle in L. cardinalis and S. aemula, but not in L. camara and S. farinacea. Plants of L. camara, S. farinacea, and S. aemula that had received drought during both cycles became more water use efficient by the end of the second cycle, but L. cardinalis did not.
Attacin A Gene from Tricloplusia ni Reduces Susceptibility to Xanthomonas axonopodis pv. citri in Transgenic Citrus sinensis `Hamlin'
Authors: Boscariol Raquel L. , Monteiro Mariza , Takahashi Elizabete K. , Chabregas Sabrina M. , Vieira Maria Lucia C. , Vieira Luiz G.E. , Pereira Luiz F.P. , Mourão Filho Francisco de A.A. , Cardoso Suane C. , Christiano Rock S.C. , Filho Armando Bergamin , Barbosa Janaynna M. , Azevedo Fernando A. , Mendes Beatriz M.J.
Published: January 2019

Citrus canker, caused by Xanthomonas axonopodis Starr and Garces pv. citri (Hasse) Vauterin et al., is one of the main problems affecting citrus production. In order to obtain resistance to phytopathogenic bacteria, insect genes, coding for antimicrobial proteins, have been used in plant genetic transformation. In this study, transgenic Citrus sinensis (L.) Osb. `Hamlin' plants expressing the antimicrobial insect-derived attacin A gene (attA) were obtained by Agrobacterium tumefaciens (Smith and Towns.) Conn-mediated transformation. Initially, the cDNA clone was used to construct a binary plasmid vector (pCattA 2300). The construction included the native signal peptide (SP) responsible for directing the insect protein to the extracellular space where bacteria is supposed to accumulate in vivo. In order to investigate the native SP effectiveness in a plant model system, onion (Allium cepa L.) epidermal cells were transformed, via biobalistics, using plasmids containing the attA gene with or without SP, fused with the green fluorescent protein gene (pattA 1303 and pSPattA 1303). Fluorescence accumulation surrounding the cells was observed only in tissues transformed with the plasmid containing the gene with SP, indicating the protein secretion to the apoplast. Citrus transformation was confirmed by PCR and Southern blot hybridization analysis in 12 regenerated plants. Transcription of attA gene was detected by Northern blot analysis in all transgenic plants. Eight selected transgenic lines were propagated and inoculated with a 106 cfu/mL suspension of the pathogen X. axonopodis pv. citri. Compared to control (non-transformed plant), seven transgenic lines showed a significant reduction in susceptibility to citrus canker. The results obtained here indicate the potential use of antibacterial proteins to protect citrus from bacterial diseases.
Xylem Vessel Anatomy of Sweet Cherries Grafted onto Dwarfing and Nondwarfing Rootstocks
Authors: Olmstead Mercy A. , Lang N. Suzanne , Ewers Frank W. , Owens Shirley A.
Published: January 2019

Xylem vessel anatomy was examined in tissues surrounding the graft union of sweet cherry (Prunus avium L.) scion (stem) and nondwarfing, semi-dwarfing, or dwarfing rootstock (root) combinations, to characterize potential changes in anatomical features during the initial stages of graft union formation. Vessel element length, frequency, diameter, lumen area (LAV), and mean vessel hydraulic diameter (VDh) were examined in `Rainier' (P. avium) scion wood grafted onto nondwarfing `Colt' (P. pseudocerasus L. × P. avium) or `F 12/1' (P. avium) rootstock and semi-dwarfing `Gisela 6' [`Gi 6' (P. cerasus L. × P. canescens L.)], or dwarfing `Gisela 5' [`Gi 5' (P. cerasus × P. canescens)] rootstock systems in: heterograft combinations (commercial scion-rootstock combinations); homografts (scion and rootstock are the same genetic material); and reciprocal heterografts (rootstock tissue grafted onto scion tissue). Vessel element length was not affected by rootstock, but vessel frequency and lumen area in graft union tissues were smaller in `Rainier'/`Gi 5' (dwarfing combination) than in `Rainier'/`Colt' (nondwarfing combination). The heterograft combination of `Rainier'/`Gi 5' had smaller scion LAV, lower VDh and narrower vessels than homograft or reciprocal heterograft combinations. As callus differentiated into vascular elements, xylem rays in `Rainer'/`Gi 5' tended to develop at an acute angle to the longitudinal axis of the tree and there was an increase in nonfunctional phloem in `Rainer'/`Gi 5' compared to `Rainer'/`F 12/1'. Collectively, the data provides further evidence that a combination of smaller and fewer vessels in the scion and graft union, as well as irregular vessel orientations in the vascular tissue within dwarfing combinations could contribute to hydraulic resistance in the graft union resulting in reduced scion growth (dwarfing).
Genotypic Variation for Resistance to Phytophthora cactorum in a California Strawberry Breeding Population
Authors: Shaw Douglas V. , Hansen John , Browne Greg T.
Published: January 2019

One hundred-eighty six strawberry genotypes from the Univ. of California strawberry (Fragaria ×ananassa Duch.) breeding program were evaluated for resistance to Phytophthora cactorum Schroet. in trials conducted over 6 years; 60 of these genotypes were tested in 2 years or more. Mother plants of each genotype were grown in a propagation nursery beginning in June, and runner plants were set into soil infested with inoculum from a mix of four P. cactorum isolates in August or September of the same year. Runner plants of each genotype were harvested from the inoculated nursery, transferred to a fruiting field location, and evaluated for disease symptoms during the winter and spring following inoculation using a disease severity score. Significant variation for the disease severity score was detected due to years, genotypes, and their interaction. Differences among genotypes were responsible for 60.6% of the phenotypic variance, whereas years and year × genotype interactions contributed relatively little to this variance, 8.2% and 9.3%, respectively. A separate analysis conducted using a balanced subset of six cultivars that were present in all trial years detected variance components due to years and year × genotype interaction slightly smaller than those estimated for the complete trial, 5.0% and 3.9%, respectively. These results highlight the utility of the screening system and suggest that stable resistance to P. cactorum is obtainable in California strawberry breeding populations and production systems.
Fertility and Inheritance of Variegated and Purple Foliage Across a Polyploid Series in Hypericum androsaemum L.
Authors: Olsen Richard T. , Ranney Thomas G. , Werner Dennis J.
Published: January 2019

Inheritance of two mutant foliage types, variegated and purple, was investigated for diploid, triploid, and tetraploid tutsan (Hypericum androsaemum). The fertility of progeny was evaluated by pollen viability tests and reciprocal crosses with diploids, triploids, and tetraploids and germinative capacity of seeds from successful crosses. Segregation ratios were determined for diploid crosses in reciprocal di-hybrid F1, F2, BCP1, and BCP2 families and selfed F2s with the parental phenotypes. F2 tetraploids were derived from induced autotetraploid F1s. Triploid segregation ratios were determined for crosses between tetraploid F2s and diploid F1s. Diploid di-hybrid crosses fit the expected 9: 3: 3: 1 ratio for a single, simple recessive gene for both traits, with no evidence of linkage. A novel phenotype representing a combination of parental phenotypes was recovered. Data from backcrosses and selfing support the recessive model. Both traits behaved as expected at the triploid level; however, at the tetraploid level the number of variegated progeny increased, with segregation ratios falling between random chromosome and random chromatid assortment models. We propose the gene symbol var (variegated) and pl (purple leaf) for the variegated and purple genes, respectively. Triploid pollen stained moderately well (41%), but pollen germination was low (6%). Triploid plants were highly infertile, demonstrating extremely low male fertility and no measurable female fertility (no viable seed production). The present research demonstrates the feasibility of breeding simultaneously for ornamental traits and non-invasiveness.
Flower and Stamen Structures of Male-fertile and Male-sterile Chestnut (Castanea sativa Mill.) Cultivars
Authors: Mert Cevriye , Soylu Arif
Published: January 2019

The flower and stamen structures of four male-fertile (`Firdola', `Karamehmet', `Sariaslama', and `Haciomer') and two male-sterile (`Osmanoglu' and `Vakit Kestanesi') chestnut cultivars were evaluated using scanning electron and light microscopes. Anther dimensions and pollen production capabilities were also determined. Stamens of the male-fertile cultivars showed more distinct flowering habit than male-sterile cultivars, which failed to show visible flowering due to shorter stamens. Flower clusters on the catkins had six to seven flowers while the mean number of stamens per flower varied from 9.50 to 11.95 among the cultivars, except for `Osmanoglu' with 2.60 stamens per flower. Some `Osmanoglu' flowers had no stamens or abnormal stamens (e.g., lacking anthers) or abortive anthers. Stamens of the male-sterile cultivar Vakit Kestanesi had short filaments and small anthers with few or no pollen. The pollen number per anther was significantly lower in the male-sterile than in the male-fertile cultivars. Three different kinds of anther surface morphologies were determined among the cultivars. The surface structure of male-fertile cultivars consisted of polygonal epidermis cells. Male-sterile `Osmanoglu' had long polygonal epidermis cells, which had a thread-like surface appearance. Male-sterile `Vakit Kestanesi' had epidermis cells with hollow middles and swollen edges. In male-sterile cultivars the length of the anthers was significantly less than that of the male-fertile cultivars. The anther wall of the male-fertile cultivars consisted of three clearly different cell layers. However, the anther walls of the male-sterile cultivars were not complete in all cases, and the number of layers varied from one to three.
Ploidy and Genome Segregation in Musa Breeding Populations Assessed by Flow Cytometry and Randomly Amplified Polymorphic DNA Markers
Authors: Oselebe H.O. , Tenkouano A. , Pillay M. , Obi I.U. , Uguru M.I.
Published: January 2019

The majority of edible bananas (Musa L.) are triploid (2n = 3x = 33) cultivars known as dessert, plantain, or cooking bananas with predominant AAA, AAB, and ABB genomes, justifying the aim of breeding programs to develop improved hybrids of the different utilization classes in the triploid background. This usually involves crossing 3x landraces to 2x accessions that are donors of resistance genes, selecting 4x and 2x primary hybrids from the 3x-2x progenies, and crossing 4x-2x hybrids to produce secondary 3x hybrids. Ploidy and genome segregation routinely occurs during this process and constitutes a major hindrance for selection because this is not easily detectable at the morphological level. This study was carried out to assess the potential of early screening for discriminating ploidy and genome classes in 4x (AAAB)-2x (AA) breeding populations, based on flow cytometry and genome-specific RAPD analysis. Results indicate that progenies of 4x-2x crosses produced predominantly 3x progenies (94.1%). RAPD analysis identified seven genomic classes, dominated by AAA and AAB configurations segregating 1:1 (χ2 = 0.21, P = 0.05). Plant size and bunch weight increased with ploidy level, justifying ploidy-based grouping of progenies for homogenous field evaluation. Similarly, genome-based grouping within ploidy classes is recommended to allow proper evaluation of progenies according to targeted postharvest utilization. Thus, ploidy analysis by flow cytometry and genome determination by RAPD open prospects for enhancing breeding efficiency in the development of triploid bananas or plantains.
Identification of Cacao TIR-NBS-LRR Resistance Gene Homologues and Their Use as Genetic Markers
Authors: Kuhn David N. , Narasimhan Giri , Nakamura Kyoko , Brown J. Steven , Schnell Raymond J. , Meerow Alan W.
Published: January 2019

Identifying genetic markers linked to disease resistance in plants is an important goal in marker-assisted selection. Using a candidate-gene approach, we have previously developed genetic markers in cacao (Theobroma cacao L.) for two families of genes involved in disease resistance: non-TIR-NBS-LRR (Toll/Interleukin-1 Receptor-nucleotide binding site-leucine rich repeat) resistance gene homologues and WRKY transcription factor genes; however, we failed to isolate TIR-NBS-LRR genes. Using a novel algorithm to design degenerate primers, we have now isolated TIR-NBS-LRR loci as determined by DNA sequence comparison. These loci have been developed as genetic markers using capillary array electrophoresis (CAE) and single-strand conformational polymorphism (SSCP) analysis. We have mapped three distinct TIR-NBS-LRR loci in an F2 population of cacao and demonstrated that one is located on linkage group 3 and the other two on linkage group 5.
Mycorrhizal Colonization of Cranberry: Effects of Cultivar, Soil Type, and Leaf Litter Composition
Authors: Kosola Kevin R. , Workmaster Beth Ann A.
Published: January 2019

Although ericoid mycorrhizal fungi improve nitrogen (N) nutrition of cranberry (Vaccinium macrocarpon Ait.) and other Ericaceae in their native habitat, the prevalence of ericoid mycorrhizal colonization in cranberry has not been widely examined. The authors measured ericoid mycorrhizal colonization of cranberry root samples from 13 cultivars growing in cranberry beds in Wisconsin. Mycorrhizal colonization was present in all samples. Bed age had a slight but statistically significant negative effect on mycorrhizal colonization. Neither cultivar, bed substratum, nor soil pH had a significant effect on mycorrhizal colonization. Fungicide treatment for fruit diseases did not appear to affect mycorrhizal colonization of cranberry roots. Soil layering in the root zone incited by regular sanding had a significant effect on mycorrhizal colonization; colonization decreased with increasing depth in the root zone soil. Leaf litter was more decomposed in deeper soil layers, with a lower carbon-to-N ratio. Given the consistent presence of ericoid mycorrhizal fungi in cultivated cranberry, it is possible that they may play a role in N nutrition of the cranberry agroecosystem.
Cold Hardiness of Floral Buds of Deciduous Azaleas: Dehardening, Rehardening, and Endodormancy in Late Winter
Authors: Kalberer Scott R. , Arora Rajeev , Leyva-Estrada Norma , Krebs Stephen L.
Published: January 2019

Dehardening resistance and rehardening capacity in late winter and spring are important factors contributing to the winter survival of woody perennials. Previously the authors determined the midwinter hardiness, dehardening resistance, and rehardening capacities in deciduous azalea (Rhododendron L.) floral buds in early winter. The purpose of this study was to investigate how these parameters changed as winter progressed and to compare rehardening response at three treatment temperatures. Experiments were also conducted to measure bud water content during dehardening and chilling accumulation of 10 azalea genotypes. Buds of R. arborescens (Pursh) Torr., R. canadense (L.) Torr., R. canescens (Michx.) Sweet, and R. viscosum (L.) Torr. var. montanum Rehd. were acclimated in the field and were dehardened in the laboratory at controlled warm temperatures for various durations. Dehardened buds were rehardened for 24 hours at 2 to 4 °C, 0 °C, or –2 °C. Bud hardiness (LT50) was determined from visual estimates of freeze injury during a controlled freeze–thaw regime. The midwinter bud hardiness in the current study was ≈4 to 8 °C greater than in early winter. R. canadense and R. viscosum var. montanum dehardened to a larger extent in late winter than in the early winter study whereas R. arborescens and R. canescens did not. The rehardening capacities were larger in early than in late winter. Even though rehardening occurred throughout the first 8 days of dehardening (DOD) in early winter in the previous study, in the current study it was only observed after 10 DOD (R. viscosum var. montanum) or 15 DOD (R. arborescens). There was no difference among the rehardening capacities at the three rehardening temperatures for any genotype. Water content decreased throughout dehardening in all four genotypes examined. R. canadense had the lowest chilling requirement (CR) [450 chilling units (CU)], followed by R. atlanticum (Ashe) Rehd., R. austrinum (Small) Rehd., R. canescens, and R. calendulaceum (Michx.) Torr. with intermediate CR [820, 830, 830, and 1000 CU respectively). The CR of R. arborescens, R. prinophyllum (Small) Millais, R. prunifolium (Small) Millais, R. viscosum var. montanum, and R. viscosum var. serrulatum (Small) Millais exceeded 1180 CU. Results of this study indicate that the dehardening kinetics (magnitude and rate) and the rehardening capacity of azalea buds are influenced by the progression of winter and the depth of endodormancy.
Posttransplant Root and Shoot Growth Periodicity of Sugar Maple
Authors: Richardson-Calfee Lisa E. , Harris J. Roger , Fanelli Jody K.
Published: January 2019

Fundamental information regarding posttransplant root and shoot growth dynamics is needed to better understand transplant establishment. Seasonal patterns of root, shoot, and trunk growth of balled-and-burlapped and pot-in-pot (PIP) sugar maples (Acer saccharum Marsh.) transplanted at leaf drop (Nov. 2000), late fall (Dec. 2000), early spring (Mar. 2001), budbreak (Apr. 2001), or budset (July 2001) were measured and compared with nontransplanted field- and PIP-grown trees. All trees exhibited a pattern of maximum shoot extension, root growth, and trunk expansion in early May, late May, and early June, respectively. Maximum root growth was concurrent with early trunk expansion, both of which began when shoot growth was decreasing. Root growth was characterized by periods of abundant growth in late May and early June and less growth in summer and early fall. Transplanting at fall leaf drop, in late fall or spring, or at budbreak did not appear to radically disrupt the normal growth periodicity of sugar maple. However, transplanting at budset (summer) resulted in abundant root growth 11 weeks later than the period of maximum root growth in all other treatments. Our data indicate that similar amounts of root regeneration can be expected for irrigated July-transplanted trees as for trees transplanted in fall and spring. As well, our study provides evidence of root mortality during the winter and spring after the first posttransplant growing season. Although minimal root mortality was evident in nontransplanted field trees, substantial root mortality was evident in the nontransplanted PIP trees during winter and early spring.
Temperature, Duration in Simulated Shipping, and Thermal Acclimatization on the Development of Chilling Injury and Subsequent Flowering of Phalaenopsis
Authors: Wang Yin-Tung
Published: January 2019

Bare-root Phalaenopsis Blume orchids are frequently shipped by air freight intercontinentally. It was not known how temperature and duration in shipping affect their subsequent performance during greenhouse production. On 15 Sept., container-grown plants of vegetatively propagated Phalaenopsis (Atien Kaala Group) ‘TSC 22’ were removed from pots and individually weighed immediately. These bare-root plants were packed in cartons with shredded newspaper and placed in growth chambers at 15, 20, 25, or 30 °C in darkness. After 4, 7, and 14 days, one-third of the plants were removed from each temperature treatment, weighed, planted in pots, and then placed in a greenhouse. Weight loss increased with increasing air temperature and duration in storage. Chilling injury (CI) was more severe at 15 °C than 20 °C storage temperature and was progressively more severe as storage duration increased from 4 to 14 days. Plants had no sign of CI at 25 °C or 30 °C regardless of storage duration. Leaf loss was most severe on plants stored at 15 °C for 7 days (three leaves) or 14 days (five leaves) or at 30 °C for 14 days (three leaves). Storing plants 14 days or less between 15 °C and 25 °C did not affect the time of spiking (emergence of the flowering shoot), but at 30 °C, spiking was delayed by 5 to 8 days regardless of the duration. Storage resulted in reduced flower count, but not flower size, regardless of temperature and duration. In a second experiment, potted Phalaenopsis plants of the same clone were thermal-acclimatized in growth chambers in mid-September for 10 days at 25 °C followed by another 10 days at 20 °C before being stored in pots or bare-root at 15 °C, 20 °C, 25 °C, or 30 °C for 10 days. Thermal acclimatizing at 25 °C and 20 °C reduced the severity of CI and leaf loss after being stored for 10 days at 15 °C either bare-root or in pots, but did not reduce leaf loss resulting from heat at 30 °C. Repotting or storing bare-root plants did not affect spiking or flowering date under otherwise similar conditions. Nondisturbed plants in pots stored at temperatures between 20 °C and 30 °C for 10 d had higher flower count as compared with bare-root plants that were similarly stored. Spiking of nonacclimatized, bare-root plants was delayed after 10 days at either storage temperature, whereas flowering was delayed by 15 °C and 30 °C only. Bare-root Phalaenopsis orchids should be shipped near 25 °C during the warm period of the year and between 25 °C and 15 °C in the late fall through early spring to avoid CI or heat stress.
Upper and Lower Heritability Estimates in Guayule Based on Mode of Reproduction
Authors: Ray Dennis T. , Veatch-Blohm Maren Elizabeth , Teetor Valerie Hunter , Walsh Bruce
Published: January 2019

Guayule (Parthenium argentatum Gray) has been difficult to improve through classical plant breeding because of its facultative apomictic reproductive system and long growth period to harvest (2–5 years). Attempts have been made to increase rubber concentration and yield by selecting for traits correlated with rubber production. The objective of this study was to estimate heritability values in guayule that more accurately account for the contributions of apomictic and sexual reproduction occurring among populations, using a modified parent–progeny regression. Heritability was calculated using a modified version of the formula for single parent–progeny regression (h
2 = 2b): that is, h
2 = (2 – p)b, where p = proportion of apomixis and b = regression coefficient. Therefore, heritability was estimated as a range of values between the midparent and single parent regression, which correspond to complete apomixis and complete sexuality, respectively. At 2 years of growth, there was a significant regression between each parent trait and the corresponding progeny trait except rubber and guayulin B concentrations, with heritability estimates ranging from moderate to high for most parameters measured. Because apomixis occurs more frequently than sexual reproduction, most heritability estimates should fall closer to the midparent value, resulting in lower heritability. To increase resin and rubber yield in the progeny, selection should focus on plant height and width because these two traits are highly correlated with resin and rubber yield and have the highest heritability of the traits measured.
Effects of Cultivar and Plant Spacing on the Seasonal Water Requirements of Highbush Blueberry
Authors: Bryla David R. , Strik Bernadine C.
Published: January 2019

Plant water requirements were investigated in three northern highbush blueberry (Vaccinium corymbosum L.) cultivars, Duke, Bluecrop, and Elliott, grown either at a high-density spacing of 0.45 m apart within rows or a more traditional spacing of 1.2 m. Spacing between rows was 3.0 m. As is typical for the species, each cultivar was shallow-rooted with most roots located less than 0.4 m deep, and each was sensitive to soil water deficits with plant water potentials declining as low as −1.6 MPa within 5 to 7 days without rain or irrigation. Compared with traditional spacing, planting at high density significantly reduced dry weight and yield of individual plants but significantly increased total dry weight and yield per hectare. High-density planting also significantly increased total canopy cover and water use per hectare. However, although canopy cover (often considered a factor in water use) increased up to 246%, water use never increased more than 10%. Because of more canopy cover at high density, less water penetrated the canopy during rain or irrigation (by overhead sprinklers), reducing both soil water availability and plant water potential in each cultivar and potentially reducing water use. Among cultivars, water use was highest in ‘Duke’, which used 5 to 10 mm·d−1, and lowest in ‘Elliott’, which used 3 to 5 mm·d−1. Peak water use in each cultivar was during fruit development, but water use after harvest declined sharply. Longer irrigation sets (i.e., longer run times) or alternative irrigation methods (e.g., drip) may be required when growing blueberry at high density, especially in cultivars with dense canopies such as ‘Elliott’.
Mechanisms of Low-temperature Tolerance in Cucumber Leaves of Various Ages
Authors: Kuk Yong In , Shin Ji San
Published: January 2019

To determine whether differential tolerance to paraquat among cucumber (Cucumis sativus L.) leaves of various ages correlates with low-temperature tolerance, leaves of three cultivars at the four-leaf stage were exposed to 5 °C. Leaves tolerant to paraquat were also tolerant to low temperature as indicated by electrolyte leakage changes in leaf tissue, lipid peroxidation, and photosynthesis measurements. The youngest leaf (leaves were numbered 1 to 4 with the youngest leaf given 4) on the same plant was more tolerant than older leaves to low temperature. During chilling, lipid peroxidation and H2O2 content increased in the oldest leaf when compared with the three younger leaves. Photosynthetic activity and chlorophyll a fluorescence (Fv/Fm) were significantly lower in leaf 1 than in leaf 4. There was no difference in superoxide dismutase, catalase, ascorbate peroxidase (APX), and glutathione reductase activities among various leaf ages in untreated plants. Induction of antioxidant activity in response to low temperature was higher in the youngest leaf than in the oldest leaf. Expression of APX isozymes increased in response to low temperature, and their expression was the highest in the youngest leaf. Current results support earlier findings that antioxidant protection also was a mechanism for paraquat tolerance.
Inheritance and Characterization of a Glabrous Trait in Summer Squash
Authors: Xiao Qiubin , Loy J. Brent
Published: January 2019

This study was undertaken to determine the inheritance of a glabrous trait discovered in yellow straightneck summer squash (Cucurbita pepo L.) in 1992 and to compare trichome distribution and anatomy and morphologic features that relate to productivity in glabrous and nonglabrous genotypes. Inheritance data from 1994, 2003, and 2004 confirm that the glabrous trait is inherited as a single gene recessive, designated gl-2, but that in some segregating F2 populations with a zucchini or caserta (C. pepo ssp. pepo) background, there is a deficiency of glabrous segregants. Nonglabrous (NG) plants bore numerous trichomes on stems, petioles, leaf blades, and fruit. Trichomes were simple (unbranched), and most were either conical and unicellular or small filiform and multicellular (two to five cells). However, some larger multicellular trichomes with compound feet were found on major leaf blade veins and along vein tracts of petioles. Large, multicellular trichomes with compound feet were only occasionally present on leaf blades and petioles of glabrous (G) plants, and other trichome types were much reduced. This reduction gives fruit and foliage a smooth, waxy feel and largely eliminates trichome damage to fruit and skin irritation to workers during harvesting. Leaf number, staminate to pistillate flower ratios, and fruit size were not significantly different between glabrous (gl-2/gl-2) and nonglabrous (Gl-2/gl-2) backcross (BC) genotypes. In one of two BC populations, pistillate flowering was 2 d earlier in NG as compared with G plants. The glabrous gene reduced the size of leaf blades in two BC populations; however, differences in total leaf areas were not statistically significant at P = 0.05. A comparison of leaf numbers and size among G and NG parental plants and reciprocal F1 hybrids derived from three separate crosses did not reveal a consistent effect of the gl-2 gene on plant morphology. Earliness and productivity of the best glabrous hybrids were similar to that of popular commercial cultivars.
Molecular Analysis of Genetic Diversity and Geographic Origin within an Ex Situ Germplasm Collection of Cherimoya by Using SSRs
Authors: Escribano P. , Viruel M.A. , Hormaza J.I.
Published: January 2019

Cherimoya (Annona cherimola Mill.) is an underused fruit crop with a clear niche for expansion in subtropical climates. In this study, 16 simple sequence repeat (SSR) loci were used to find molecular polymorphisms among 279 cherimoya accessions from a worldwide ex situ field germplasm collection. A total of 79 amplification fragments were amplified with 16 pairs of SSR primers, with an average of 4.9 bands/SSR. Mean expected and observed heterozygosities averaged 0.53 and 0.44, respectively. The total value for the probability of identity was 4.34 × 10−8. The SSRs studied resulted in 267 different fingerprinting profiles, of which 258 were unique genotypes; the rest were putative cases of synonymies or mislabeling errors. Unweighted pair group method with arithmetic averages (UPGMA) cluster analysis indicated the relationships among the analyzed accessions, showing some specific groups related to their geographical origins. Analysis of molecular variance (AMOVA) was performed to examine the distribution of genetic variation of the 148 accessions collected from putative cherimoya origin areas in Ecuador and Peru, showing that the major variations occurred within valleys in each country. The results confirmed the usefulness of microsatellites for identification of genetic diversity and geographic origin of cherimoya and are discussed in terms of their implications for ex situ conservation of cherimoya genetic resources.
Estimation of Geometric Attributes and Masses of Individual Cucumber Organs Using Three-dimensional Digitizing and Allometric Relationships
Authors: Kahlen Katrin , Stützel Hartmut
Published: January 2019

The objective of this study was to estimate geometric attributes and masses of individual cucumber (Cucumis sativus L.) organs in situ. Using three-dimensional (3D) digitizing techniques, geometric data were obtained that were used to establish allometric relationships between geometric organ attribute and organ mass. Moreover, the authors were looking for the effects of ontogeny and the influence of environmental factors on the allometric relationships in cucumber. If such an allometric relationship did not exist, they alternatively tested the relationship between organ dry weight and organ number counted from the top of the plant downward. Lastly, they included allometric relationships based on biomechanical approaches focused on lamina mass and petiole attributes. The digitizing method provided accurate data for the calculation of geometric plant part attributes, such as length, area, and volume. Based on these data it was possible to describe the relationships between plant part dry weight and plant part geometry by allometric functions except for internode length. Apart from this exception, two different kinds of allometric equations were used: a simple power function with two parameters and a linear function without intercept. Information about more than one dimension of the considered plant part (e.g., area or volume) led to a simple linear relationship, whereas knowledge of just one dimension, like plant part length, resulted in more complex nonlinear relationships. Ontogeny led, in general, to a reduction in the scaling exponent or in the scaling factor, whereas changes of the environment distributed these values. Considering these effects makes it possible to determine dry matter partitioning on organ scale nondestructively and investigate long-term processes on intact plants.
Grafted Melons Irrigated with Fresh or Effluent Water Tolerate Excess Boron
Authors: Edelstein Menahem , Ben-Hur Meni , Plaut Zui
Published: January 2019

The effects of boron and effluent (treated sewage water) on vegetative growth, fruit yield, and boron uptake of grafted and nongrafted melons (Cucumis melo L. cv. Arava) were studied. Nongrafted melon plants and melon plants grafted onto the commercial Cucurbita maxima Duchesne × Cucurbita moschata Duchesne rootstock ‘TZ-148’ were grown in pots filled with perlite in a heated greenhouse and were irrigated with fresh water or effluent. The two irrigation waters contained boron in five concentrations ranging from 0.1 to 10.4 mg·L−1. The boron concentration in the plants increased linearly with that in the irrigation water. The highest boron concentrations were found in old leaves, the lowest in the fruit, and intermediate concentrations were noted in the roots. The boron concentrations were, in general, significantly lower in grafted than nongrafted plants, possibly because the root system of the former had higher selectivity and lower boron absorption than that of the latter. Fruit yield and dry weight accumulation in shoots and roots decreased linearly as the boron concentration in the irrigation water increased, the nongrafted plants were more sensitive than grafted ones to the boron level, and both were more sensitive under fresh water irrigation than under effluent irrigation. It is suggested that the higher boron sensitivity of the root systems of the nongrafted plants probably decreased their capability to absorb water and nutrients, which in turn sharply reduced their fruit yields.
Day/Night Temperature Affects Growth and Photosynthesis of Cultivated Salvia Taxa
Authors: Lasseigne F. Todd , Warren Stuart L. , Blazich Frank A. , Ranney Thomas G.
Published: January 2019

Eight taxa of Salvia L., representing broad geographic origin and diversity within the genus, were grown under long day conditions for 36 d at 15-h days of 20, 25, 30, 35, or 40 °C and 9-h nights of 15 or 25 °C. Taxa of European origin displayed broader tolerance to high day temperatures (DTs) with the lowest relative reduction in growth and net photosynthesis (Pn) occurring at DTs 30 °C or greater compared with those native to North and South America. Salvia splendens Sell. ex Roem. & Schult. (scarlet sage) was particularly intolerant of high temperatures with all plants dying at days of 40 °C. All plants of S. nemorosa L.‘Ostfriesland’ (‘Ostfriesland’ wood sage), S. pratensis L. (meadow sage), and S. × sylvestris L. ‘Mainacht’ (‘May Night’ salvia) survived at days of 40 °C with no visual signs of injury, whereas all other taxa except S. splendens exhibited stunted, contorted growth with foliar chlorosis and necrosis at 40 °C. Day temperature exerted the primary effect on top growth, root growth, and Pn of all taxa. Night temperature effects were significant for some taxa but were of less importance than day temperature.
Genetic Structuring and Parentage Analysis for Evolutionary Studies in Grapevine: Kin Group and Origin of the Cultivar Sangiovese Revealed
Authors: Di Vecchi Staraz Manuel , Bandinelli Roberto , Boselli Maurizio , This Patrice , Boursiquot Jean-Michel , Laucou Valérie , Lacombe Thierry , Varès Didier
Published: January 2019

Genetic structuring and parentage analysis were performed on a very large database comprising 2786 unique multilocus genotypes [20 nuclear simple sequence repeats (nSSRs)] of Vitis vinifera L. ssp. sativa (DC.) Hegi with a special focus on Tuscan cultivars to reveal the parentage and history of the cultivar Sangiovese, the most important cultivar of Italy. For this cultivar, the authors also analyzed clones and synonyms, investigating its genetic origin and intracultivar diversity. Known synonyms of ‘Sangiovese’ were confirmed and new ones were revealed with cultivars outside Tuscany. Some synonyms were invalidated, and unexpected homonyms were identified. The absence of true intracultivar variability leads to the rejection of a polyclonal origin for ‘Sangiovese’. The existence of an Italian genetic pool composed of ancient cultivars including Sangiovese was demonstrated by analyzing the entire set of 2786 cultivars. Ten individuals compose the kin group of ‘Sangiovese’, including two offspring: ‘Ciliegiolo’ and ‘Catarratto bianco faux’. Despite the large presence and long history of ‘Sangiovese’ in the Tyrrenian area, its kin group is unexpectedly composed of a majority of ancient cultivars that are largely diffused in far southern Italy, which leads to the hypothesis of a Sicilian origin for ‘Sangiovese’. Analysis of the Tuscan pool revealed large kin groups for cultivars Mammolo and Garganega, demonstrating their contribution to the genetic diversification in the Tyrrenian area. This work contributes to the understanding of grapevine diversification, evolution, and history in Italy and Europe.
Antioxidant Capacity and Flavonoid Content in Wild Strawberries
Authors: Wang Shiow Y. , Lewers Kim S.
Published: January 2019

Fruit of the cultivated strawberry (Fragaria ×ananassa Duchesne ex Rozier) are a good source of natural antioxidants, which play an important role in protecting human health. Antioxidant levels vary considerably among strawberry genotypes. The cultivated strawberry is a hybrid of two very different wild progenitor species: F. virginiana Mill. and F. chiloensis (L.) Mill. The progenitor species are valued by strawberry breeders as sources of novel traits, but have not been evaluated for antioxidant capacity or levels of antioxidant compounds. The objectives of this study are 1) to evaluate the antioxidant contents and antioxidant activities in representatives of F. virginiana and F. chiloensis in comparison with representatives of the cultivated strawberry species (F. ×ananassa), 2) to determine which strawberry compounds are most closely correlated with antioxidant capacity among these three species, and 3) to identify wild strawberry genotypes with high antioxidant activity and bioactive compounds for use in cultivar development. Fruit of 19 accessions from each of the three species, cultivated strawberry plus the two progenitor species (F. ×ananassa, F. virginiana, and F. chiloensis), were evaluated for levels of antioxidant capacity (oxygen radical absorbance capacity), total phenolics, total anthocyanins, ellagic acid, quercetin 3-glucoside plus quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-rutinoside, p-coumaryl–glucose, pelargonidin 3-glucoside, pelargonidin 3-glucoside–succinate, cyanidin 3-glucoside, and cyanidin 3-glucoside–succinate. Fruit of the 13 accessions tested from the wild progenitor species F. virginiana had significantly higher antioxidant capacity, total phenolics, and total anthocyanins than did the fruit of three accessions tested from the cultivated strawberry F. ×ananassa, or the three accessions tested from the other wild progenitor species (F. chiloensis), and will be valuable as a source of parent material for developing more nutritious strawberry cultivars. The high correlation with antioxidant capacity, relative efficiency, and lack of genotype-by-year interaction in this study suggests that the measurement of total phenolics may be the better assay to use for the later selection stages in a strawberry cultivar development program. Of the evaluated F. virginiana accessions, NC 95-19-1, JP 95-1-1, CFRA 0982, NC 96-5-3, and RH 30 fruit were highest in antioxidant capacity and should prove useful toward development of strawberry cultivars with high antioxidant capacities.
Microsatellite Marker for Homozygosity Testing of Putative Doubled Haploids and Characterization of Mimulus Species Derived by a Cross-genera Approach
Authors: Murovec Jana , Stajner Natasa , Jakse Jernej , Javornik Branka
Published: January 2019

A codominant marker for homozygosity testing and species discrimination needed in breeding programs was developed and applied to different Mimulus L. species and cultivars. Degenerative primers used to amplify intron 10 of topoisomerase 6 subunit B (top6B) in distant species also amplified the locus in all analyzed Mimulus species. The sequences obtained revealed the presence of a microsatellite motif and were used to design a specific microsatellite primer pair, Mim-top6B, for Mimulus species. The microsatellite marker showed a high degree of polymorphism in Mimulus species, and the heterozygous nature of most M. aurantiacus Curtis cultivars. The marker was further used to analyze putative doubled haploids of M. aurantiacus and showed that all but one was heterozygous, indicating their hybrid origin.
Quantitative Genetic Analysis of Growth Rate in Avocado
Authors: Chen Haofeng , Ashworth Vanessa E.T.M. , Xu Shizhong , Clegg Michael T.
Published: January 2019

The authors report a quantitative genetic analysis of avocado (Persea americana Mill.) growth rate, flower abundance, and fruit set. The data are based on a total of 204 different genotypes of progeny of ‘Gwen’ avocado. Each was replicated four times, with two replicates planted in each of two locations in southern California (Irvine and Riverside). Data were collected over 4 years (consecutive) on tree height, canopy diameter, and trunk diameter, representing three distinct measures of growth rate. Growth data were found to fit a linear regression over years, so the slope (growth rate) was used in the analyses. In addition, 2 years of data on flower abundance and 1 year on fruit set were also collected. Quantitative genetic analyses of these data showed that broad-sense heritability (H) was 35.5%, 30.3%, and 26.6% for tree height, canopy diameter, and trunk diameter respectively; and 33.8% and 23.0% for flowering abundance and fruit set respectively. No genotype-by-location effect was noted for growth rate; however, flower abundance and fruit set showed a relatively weak genotype-by-location effect (21.9% and 17.1% respectively). The H estimates are low, probably as a result of sources of uncontrolled environmental error associated with variation in initial planting dates, but fall within the range that should permit quantitative trait locus analyses. The authors also found a moderate positive correlation between tree growth rates and fruit set, but none between growth rates and flower abundance. Different pollen parents have significantly different impacts on tree growth rates, flower abundance, and fruit set.
Genotypic Differences in Sweet Cherry Fruit Size are Primarily a Function of Cell Number
Authors: Olmstead James W. , Iezzoni Amy F. , Whiting Matthew D.
Published: January 2019

Understanding the genetic control of fruit size in sweet cherry (Prunus avium L.) is critical for maximizing fruit size and profitable fresh market production. In cherry, coordinated cycles of cell division and expansion of the carpel result in a fleshy mesocarp that adheres to a stony endocarp. How these structural changes are influenced by differing genetics and environments to result in differing fruit sizes is not known. Thus, the authors measured mesocarp cell length and cell number as components of fruit size. To determine the relative genotypic contribution, five sweet cherry cultivars ranging from ≈1 to 13 g fresh weight were evaluated. To determine the relative environmental contribution to fruit size, different-size fruit within the same genotype and from the same genotype grown in different environments were evaluated. Mesocarp cell number was the major contributor to the differences in fruit equatorial diameter among the five sweet cherry cultivars. The cultivars fell into three significantly different cell number classes: ≈28 cells, ≈45 cells, and ≈78 cells per radial mesocarp section. Furthermore, mesocarp cell number was remarkably stable and virtually unaffected by the environment as neither growing location nor physiological factors that reduced final fruit size significantly altered the cell numbers. Cell length was also significantly different among the cultivars, but failed to contribute to the overall difference in fruit size. Cell length was significantly influenced by the environment, indicating that cultural practices that maximize mesocarp cell size should be used to achieve a cultivar's fruit size potential.
Late Blight Resistance of RB Transgenic Potato Lines
Authors: Kuhl Joseph C. , Zarka Kelly , Coombs Joseph , Kirk William W. , Douches David S.
Published: January 2019

Late blight of potato (Solanum tuberosum L.), incited by Phytophthora infestans (Mont.) de Bary, is a devastating disease affecting tuber yield and storage. Recent work has isolated a resistance gene, RB, from the wild species Solanum bulbocastanum Dun. Earlier work in Toluca, Mexico, observed significant levels of field resistance under intense disease pressure in a somatic hybrid containing RB. In this study, five transgenic RB lines were recovered from the late blight susceptible line MSE149-5Y, from the Michigan State University (MSU) potato breeding program. Transgenic lines were molecularly characterized for the RB transgene, RB transcript, and insertion number of the kanamycin resistance gene NPTII. Transgenic lines and the parent line were evaluated for resistance in field and laboratory tests. Molecular characterization alone did not predict which lines were resistant. Three of the RB transformed MSE149-5Y lines showed increased resistance under field conditions at MSU and increased resistance in detached leaf evaluations using multiple isolates individually (US-1, US-1.7, US-8, US-10, and US-14). Transfer of RB into late blight susceptible and resistant lines could provide increased protection to potato late blight. The use of the RB gene for transformation in this way creates a partially cisgenic event in potato because the gene's native promoter and terminator are used. This type of transformation provides a chance to generate greater public acceptance of engineered approaches to trait introgression in food crops.