bluuebunny/crossref_metadata_2025 huggingface dataset:
Bunch Shading During Different Developmental Stages Affects the Phenolic Biosynthesis in Berry Skins of ‘Cabernet Sauvignon’ Grapes
Authors: Koyama Kazuya , Goto-Yamamoto Nami
Published: January 2019

The effect of bunch shading during early development (before the onset of ripening) and/or during ripening on the phenolic composition of grape skins (Vitis vinifera L. cv. Cabernet Sauvignon) as well as on the mRNA levels of the biosynthetic genes on the flavonoid pathway was examined. Shading during early development resulted in decreased proanthocyanidin (PA) concentrations. The PA concentrations decreased during ripening, and the decrease of the concentrations was lower in berries shaded during early development than that in the exposed berries. Thus, no significant effect of shading during early development was observed at harvest. Shading during ripening did not influence this decline in the PAs. On the other hand, shading during early development induced changes in the composition such as a decrease of the trihydroxylated subunits within PAs, which agreed with the relative decrease of VvF3′5′H expression. The anthocyanin concentrations were remarkably reduced when the bunches were shaded during ripening, which was in accordance with the decreased transcription of several anthocyanin biosynthetic genes and transcriptional factors. Shading during early development did not influence the anthocyanin concentrations at harvest; however, it decreased the proportion of trihydroxylated anthocyanins. Thus, shading during early development also had an influence on the compounds biosynthesized during ripening.
Comparative Growth, Morphology, and Anatomy of Easy- and Difficult-to-acclimatize Sea Oats (Uniola paniculata) Genotypes During In Vitro Culture and Ex Vitro Acclimatization
Authors: Aracama Carmen Valero , Kane Michael E. , Wilson Sandra B. , Philman Nancy L.
Published: January 2019

Growth and development of two sea oats (Uniola paniculata L.) genotypes with differing acclimatization capacities when transferred from in vitro to ex vitro greenhouse conditions were compared as a function of the duration of shoot multiplication and rooting stages. Anatomical and morphological development differed between genotypes in vitro. After 4, 8, and 12 weeks of Stage II culture, leaf length and shoot number were significantly greater for the easy-to-acclimatize genotype (EK 16-3) than the difficult-to-acclimatize genotype (EK 11-1). Shoot dry weights in both genotypes were greatest after 4 weeks culture. Browning and dying of tissue steadily increased with time. Shoot number per plantlet increased from Week 4 to 8 in both genotypes but decreased after 12 weeks. Once transferred to Stage III culture for 6 weeks, significant differences in root architecture and morphology were observed between the two genotypes. EK 16-3 plantlets developed short but numerous roots and “grass-like” leaves with fully expanded blades. Conversely, EK 11-1 plantlets developed few long roots and “lance-like” leaves, which were short, thick, and without expanded blades. Anatomical and morphological development during Stage III differed between culture duration and genotypes. Shoot and root dry weights of both genotypes increased during 3, 6, and 9 weeks of culture. Shoot dry weights of EK 16-3 plantlets were lower at 3 weeks but higher at 9 weeks than EK 11-1. Conversely, root dry weights were higher for EK 11-1 than for EK 16-3 plantlets throughout Stage III culture. Anatomical observations of EK 11-1 plantlets using light and electron microscopy correlated poor ex vitro acclimatization and poor survival with abnormal tissue organization, stomatal aperture blockage, and thylakoid membrane disruption.
Detection of Quantitative Trait Loci and Inheritance of Root-knot Nematode Resistance in Sweetpotato
Authors: Cervantes-Flores Jim C. , Yencho G. Craig , Pecota Kenneth V. , Sosinski Bryon , Mwanga Robert O.M.
Published: January 2019

Resistance to root-knot nematodes [Meloidogyne incognita (Kofoid & White) Chitwood] in sweetpotato [Ipomoea batatas (L.) Lam.] was studied in a mapping population consisting of 240 progeny derived from a cross between ‘Beauregard’, the predominant cultivar in the United States, and ‘Tanzania’, an African landrace. Quantitative trait loci (QTL) analyses to locate markers associated with resistance to root-knot nematodes (RKN) were performed using genetic maps based on parental segregation in ‘Beauregard’ and ‘Tanzania’ consisting of 726 and 947 single-dose amplified fragment length polymorphism (AFLP) markers, respectively. RKN resistance in the progeny was highly skewed with most of the progeny exhibiting medium to high levels of resistance. Single-point analysis of variance and interval mapping revealed seven consistently significant QTL in ‘Tanzania’ and two significant QTL in ‘Beauregard’. In ‘Tanzania’, three QTL were associated with reduction in resistance as measured by the number of RKN egg masses and explained ≈20% of the variation. Another four QTL had positive effects on resistance and explained ≈21% of the variation. Other minor QTL explained ≈2% or less of the variation but were not always consistent across geographical locations. In ‘Beauregard’, two QTL had positive effects on RKN resistance and explained ≈6% of the observed variation. Based on molecular and phenotypic data, RKN resistance in sweetpotato is hypothesized to be conferred by several genes, but at least nine AFLP markers (seven from ‘Tanzania’ and two from ‘Beauregard’) are associated with genomic regions that have the biggest effect in the number of egg masses of RKN produced in the root system.
Antioxidative Responses and Candidate Gene Expression in Prairie Junegrass under Drought Stress
Authors: Jiang Yiwei , Watkins Eric , Liu Shuwei , Yu Xiaoqing , Luo Na
Published: January 2019

Prairie junegrass (Koeleria macrantha) is a native cool-season C3 grass that has shown potential as a low-input turfgrass. An increased understanding of the physiological and molecular responses of prairie junegrass to water-deficit conditions is important for developing cultivars with enhanced drought tolerance. The objective of this study was to characterize the antioxidative responses and candidate gene expression in prairie junegrass subjected to drought stress. Two drought-tolerant (TOL-1 and TOL-2) and two drought-susceptible (SUS-1 and SUS-2) genotypes of prairie junegrass were subjected to 7 days of drought stress. Leaf relative water content (RWC) of SUS-1 and SUS-2 was 72.1% and 73.8% and RWC of TOL-1 and TOL-2 was 90.1% and 85.4% in drought-stressed plants, respectively. Drought stress did not affect chlorophyll fluorescence, lipid peroxidation, and antioxidative enzyme activities of superoxide dismutase (SOD), catalase (CAT), peroxidase, ascorbate peroxidase (APX), or glutathione reductase for tolerant or susceptible genotypes. The TOL-2 and SUS-2 genotypes were further examined for candidate gene expression. Drought stress did not alter expression levels of CAT and chloroplastic copper/zinc SOD (Cu/ZnSOD), but increased levels of APX in either genotype, compared with their relative controls. Expression of P5CS encoding Δ1-pyrroline-5-carboxylate synthetase and P5CR encoding Δ1-pyrroline-5-carboxylate reductase for proline biosynthesis were up-regulated under drought stress for both genotypes; however, expression of P5CR was more strongly induced under drought stress for TOL-2, compared with its control. The expression of 1-FFT encoding fructan:fructan 1-fructosyltransferase, which is involved in fructan biosynthesis, was strongly induced under drought stress for TOL-2 but not detected under either control or drought stress conditions for SUS-2. These results indicate that the genes involved in proline and fructan biosynthesis may play an important role in drought tolerance in prairie junegrass.
Osmotic Potential, Sucrose Level, and Activity of Sucrose Metabolic Enzymes in Tall Fescue in Response to Deficit Irrigation
Authors: Fu Jinmin , Huang Bingru , Fry Jack
Published: January 2019

Effects of deficit irrigation applied to home lawns, used as means of water conservation, are an important issue. However, the impact of deficit irrigation on sucrose metabolism in tall fescue (Festuca arundinacea) is unknown and important because sucrose is the dominant form of carbohydrate transported to developing plant organs. The objectives of this study were to investigate the effects of deficit irrigation on leaf water content, osmotic potential (ψS), sucrose level, and the activity of sucrose phosphate synthase (SPS; EC 2.4.1.14), sucrose synthase (SS; EC 2.4.1.13), and acid invertase (AI; EC 3.2.1.26) in tall fescue leaves. Sods of ‘Falcon II’ tall fescue were established in polyvinylchloride (PVC) tubes (10 cm diameter × 40 cm long) filled with a mixture of sand and fritted clay [9:1 (v:v)] and then placed in growth chambers. Reference evapotranspiration rate [ETo (millimeters of water per day)] was determined by weighing the PVC tubes containing well-watered turfgrass every 3 days to determine water loss on a daily basis as ETo. Deficit irrigation treatments were applied as follows: well-watered control, mild drought stress (60% ETo), and severe drought stress (20% ETo). Leaf water content was lower at 6, 12, and 20 days of treatment for the 20% ETo treatment and 20 days after treatment began for the 60% ETo treatment. Compared with the well-watered control, ψS was lower in the 60% ETo treatment on all three measurement dates. Sucrose was higher at 8 and 14 days after treatment began in the 60% ETo treatment and on all three measurement dates in the 20% ETo treatment relative to the well-watered control. No difference in sucrose level was observed between the 20% ETo and 60% ETo irrigation regimes at 8 and 14 days of treatment. Beginning 14 days after treatment, tall fescue had a higher level of SPS in the 60% ETo and 20% ETo treatments compared with the well-watered treatment. Tall fescue receiving 60% or 20% ETo had a lower level of AI activity on all measurement dates. Results suggest that the decrease in ψS was accompanied by higher sucrose levels, which were the result of the increased level of SPS and SS activity and a decline in AI activity.
Differences in Cell Number Facilitate Fruit Size Variation in Rabbiteye Blueberry Genotypes
Authors: Johnson Lisa Klima , Malladi Anish , NeSmith D. Scott
Published: January 2019

Fruit size is a valuable commercial trait in blueberry. The cellular basis of variation in fruit size among rabbiteye blueberry (Vaccinium ashei) genotypes was investigated. Twenty genotypes, including cultivars and advanced selections from the University of Georgia blueberry breeding program, were analyzed. Among the 20 genotypes, fruit weight and fruit diameter varied by over threefold and 1.6-fold, respectively. Regression analysis indicated a linear relationship between fruit weight and fruit diameter (R2 = 0.97, P < 0.001), suggesting that fruit diameter is a good predictor of fruit weight. Among the 20 genotypes, mesocarp cell number and cell area varied by almost 2.5-fold and 1.5-fold, respectively. Although fruit diameter and cell number were significantly related (R2 = 0.79, P < 0.001), no relationship could be established between fruit diameter and cell area. These data indicate that variation in fruit size among rabbiteye blueberry genotypes is primarily facilitated by variation in cell number. Two small and two large fruit size genotypes were further analyzed. Differences in cell number among some of these genotypes were apparent at bloom suggesting that cell production before bloom is an important mechanism contributing to variation in final cell number. Differences in final cell number among other genotypes were manifested during fruit development, indicating that cell production during fruit development was also instrumental in determining variation in final cell number. This study suggests that fruit size variation in rabbiteye blueberry genotypes is determined by mechanisms that regulate cell production before bloom and during fruit development.
Comparative Analysis of Chilling Response in Cucumber Through Plastidic and Nuclear Genetic Effects Component Analysis
Authors: Gordon Vanessa S. , Staub Jack E.
Published: January 2019

Chilling damage can cause major reductions in cucumber (Cucumis sativus L.) yield. Cucumber plants can withstand a chilling event (i.e., tolerance and susceptibility), in which response is dictated primarily by maternally inherited plastid genomes or by the biparental contribution of a nuclear factor. To examine the modes of inheritance, exact reciprocal backcross cucumber populations (BC1–5), were created by crossing ‘Chipper’ (chilling-tolerant plastid, susceptible nucleus) and line North Carolina State University (NCSU) M29 (chilling-susceptible plastid, susceptible nucleus). These progeny and their parents were subjected to chilling stress [5.5 h at 4 °C in 270 μmol·m−2·s−1 photosynthetic photon flux (PPF) cool white lighting] at the first true-leaf stage. The chilling response of individuals possessing either NCSU M29 or ‘Chipper’ cytoplasm in any generational comparison was not significantly different (P > 0.05) from that of the maternal plastid source (susceptible or tolerant). Moreover, lines within a plastid type did not differ significantly (P > 0.05) in chilling response despite unequal nuclear contributions demonstrating the absence of nuclear additive or dosage effects originating in ‘Chipper’ or NCSU M29. Additionally, line NC-76, previously identified as a nuclear source of chilling tolerance, performed intermediate to ‘Chipper’ and NCSU M29 in chilling response under these stress conditions. The F1 progeny derived from crossing both BC5 plastidic response types (susceptible and tolerant) with NC-76 (paternal parent) performed comparable to their plastid donors and were significantly different (P < 0.0001) from one another despite their heterozygous nuclear nature resulting from the contribution of the nuclear chilling-tolerant factor contributed by NC-76. The response of tolerant and susceptible BC5 lines (i.e., ‘Chipper’ plastid in the NCSU M29 background and NCSU M29 plastid in ‘Chipper’ background, respectively) was reversible by crossing BC progeny with an alternate chilling-response plastid type. It is concluded that under these chilling conditions, plastid effects determine tolerance or susceptibility in the cucumber germplasms examined.
Exogenous Spermidine Alleviates the Oxidative Damage in Cucumber Seedlings Subjected to High Temperatures
Authors: Tian Jing , Wang Li-Ping , Yang Yan-Juan , Sun Jin , Guo Shi-Rong
Published: January 2019

Heat tolerance is considered to be an essential feature for cucumber (Cucumis sativus) production, and it has been suggested that higher antioxidant ability could prevent the oxidative damage in plants caused by high-temperature stress. We aimed to investigate whether the application of exogenous spermidine (Spd) increases antioxidant activities and, therefore, elevates the heat tolerance of cucumber. Cucumber seedlings (cv. Jinchun No. 4) showing moderate heat tolerance were grown in climate chambers to investigate the effects of exogenous Spd (1 mm) foliar spray treatment on the activities and isozyme levels of antioxidative enzymes under both high-temperature stress 42/32 °C (day/night) and normal temperature 28/18 °C (day/night). On high-temperature stress, the activities of superoxide dismutase and ascorbate peroxidase were significantly reduced; the catalase activity was initially lower and then increased, whereas the peroxidase activity was initially higher and then decreased. The levels of these isozymes also changed differently. On treatment with exogenous Spd, the activities of these antioxidant enzymes were noticeably enhanced, and the isozyme zymogram expression had some changes. It was concluded that foliar spray with Spd effectively improved the total antioxidant ability of cucumber seedlings and, therefore, enhanced the tolerance of the plants to high-temperature stress.
Genetic Diversity of 41 Apple Rootstocks Based on Simple Sequence Repeat Markers
Authors: Jin Wanmei , Zhang Qiang , Liu Sunzhong , Wei Qinping , Jin Wanmei , Cheng Zongming , Xue Xiaohui , Yang Tingzhen
Published: January 2019

Molecular markers are valuable tools in evaluating genetic diversity and fingerprinting plant germplasm. In this report, simple sequence repeat (SSR) markers were used for assessing genetic diversity in 41 dwarf and semidwarf and early flowering apple (Malus sp.) rootstocks. Sixty-two of 112 pairs of SSR primers generated multiple, scorable fragments. The total number of scored bands was 4138 with the polymorphic frequency ranging from 22.0% to 68.6% with a mean value of 58.5% in 737 alleles. The number of alleles per locus ranged from 6 to 19 with an average of 11.9 alleles. Polymorphic information content per locus was ranged from 0.176 to 0.885 with an average value of 0.606. These results suggested a complex genetic background and genetic diversity in these apple rootstocks. Based on three principal components and unweighted pair group mean average (UPGMA) of SSR data, the 41 apple rootstocks were divided into five groups. Group I contained M. xiaojinensis ‘Xiaojinhaitang'. Group II consisted of M. hupehensis var. pingyiensis ‘Pingyitiancha'. Group III contained M. baccata ‘Shandingzi' and its offspring. Group IV was composed of 16 apple rootstocks, including Malling and Malling Merton series from Great Britain; ‘Budagovski 9' from Russia; ‘Polish 22' from Poland; ‘Cornell-Geneva 24' from the United States; and ‘GM.256', ‘Nei Meng 11', ‘MD.001', ‘7734', and ‘7848' from China. Group V consisted of 16 Shao series rootstocks, which were offspring of M. honanensis × M. domestica ‘Ralls Genet'. This research suggests that the breeding can achieve best performance with more robust rootstock if crosses were performed among these five major groups of germplasms rather than within the major groups.
Cultivar Identification, Pedigree Verification, and Diversity Analysis among Peach Cultivars Based on Simple Sequence Repeat Markers
Authors: Sitther Viji , Zhang Dapeng , Dhekney Sadanand A. , Harris Donna L. , Yadav Anand K. , Okie William R.
Published: January 2019

Information on genetic relationships and pedigree structure in germplasm collections is vital to breeders in crop improvement programs. In this study, we assessed genetic identity, kinship distance, and parentage–sibship relationships among 37 peach (Prunus persica) accessions and breeding lines using simple sequence repeat (SSR) markers. Pairwise comparisons based on multilocus SSR profiles led to the identification of two synonymous groups including five accessions. Two pairs of parent–offspring and one full sibling relationships were identified using the likelihood method, and Bayesian cluster analysis partitioned the accessions into groups that were partially compatible with the known pedigree, origin, and flesh color. The 37 accessions were grouped into four clusters, which were largely supported by the known pedigree and origin of these accessions. Although the observed mean heterozygosity was 0.219, mean inbreeding coefficient was 0.635, indicating a high degree of inbreeding among the accessions. Eleven of the 15 SSR markers (73.3%) tested were transferable to nine related Prunus species. Results of the study demonstrate that these SSRs could facilitate the assessment of genetic identity and pedigree structure.
Antioxidant Enzyme Activity and Gene Expression in Response to Lead Stress in Perennial Ryegrass
Authors: Li Huiying , Luo Hongji , Li Deying , Hu Tao , Fu Jinmin
Published: January 2019

Lead pollution is an important issue in the world. Perennial ryegrass (Lolium perenne), as one of the widely used turfgrass and forage species, has a potential for bioremediation. The objective of this study was to investigate how antioxidant enzymes and their gene transcripts respond to Pb stress in perennial ryegrass. Ryegrass seedlings were subjected to 0, 0.5, and 3.2 mm of Pb(NO3)2 for 7 days in a hydroponic system maintained in a greenhouse. Both root and shoot growths were inhibited by Pb compared with the control. However, contents of chlorophyll (Chl) a and total Chl were unaffected by Pb treatment. Results from this study showed a substantial increase of malondialdehyde (MDA) content in leaf tissues when perennial ryegrass was exposed to Pb at 3.2 mm. The MDA content from plants in the 0.5 mm Pb treatment was lower than the control, indicating that an effective defense mechanism existed. Circumstantial evidence came also from the content of soluble protein in 0.5 mm Pb treatment, which was not different from the control. Furthermore, the activity of catalase (CAT) increased at 0.5 mm Pb compared with the control, indicating that CAT might play an important role in scavenging reactive oxygen species (ROS). The expression profiles of eight genes encoding antioxidative enzymes were upregulated within 24 hours of Pb treatment. In conclusion, antioxidant enzymes responded to Pb at an early stage of exposure and their gene expression profiles provided more details in time courses of the activation of those systems.
Growth Response and Gene Expression in Antioxidant-related Enzymes in Two Bermudagrass Genotypes Differing in Salt Tolerance
Authors: Hu Longxing , Huang Zehui , Liu Shuqian , Fu Jinmin
Published: January 2019

Plant adaptation to salt stress may be associated with morphological, physiological, and gene expression alterations. The objective of this study was to investigate the effect of salt stress on morphological and antioxidant enzyme changes and its gene expressions in bermudagrass (Cynodon dactylon). Salt-tolerant ‘C43’ and salt-sensitive ‘C198’, previously determined in our preliminary study, were subjected to four salinity levels: 0 mm (control), 100 mm (low), 200 mm (moderate), and 400 mm (high) NaCl for 21 days. Salt stress decreased turf quality and canopy height, especially in ‘C198’. Salt stress increased root length, root number, root fresh weight, and root/shoot length ratio, to a greater extent in salt-tolerant genotype. Salt stress increased Na+ and decreased K+ content, which resulted in a higher Na+/K+ ratio in bermudagrass, to a great extent in shoot and root of ‘C198’. Moderate (200 mm) and high (400 mm) salt concentration increased malondialdehyde and hydrogen peroxide content in old leaves of ‘C198’. ‘C43’ exhibited a greater activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and dehydro-ascorbate reductase (DHAR) than ‘C198’ in old leaves subjected to 200 and 400 mm NaCl. Antioxidant gene expressions were upregulated in new leaves and downregulated in old leaves with increasing salinity levels for both genotypes. Salt-tolerant genotypes exhibited a relatively greater antioxidant gene expression than salt-sensitive ones when exposed to the same level of salt stress. These results suggested that SOD, CAT, APX, and DHAR might be involved in scavenging salt stress-induced reactive oxygen species in bermudagrass at the level of gene expression. Salt tolerance might be attributed to the development and maintenance of a more extensive root system under saline conditions and induced antioxidant gene expressions, leading to more efficient enzyme stimulation and protection in bermudagrass.
Genetic Parameters and Breeding for Yield in Red Raspberry
Authors: Stephens M. Joseph , Alspach Peter A. , Beatson Ron A. , Winefield Chris , Buck Emily J.
Published: January 2019

For most small fruit-breeding programs, high yield is a key objective and breeders face a number of challenges breeding for high yield, including interaction of environmental influences and the high cost of yield measurements. Red raspberry (Rubus idaeus) yield is determined by a number of yield components (YC), including cane number, cane length, number of fruiting laterals, fruit numbers, and fruit size. The ultimate goal for breeders would be to be able to select for high-yield genotypes using key YC as early in the life of the plant as possible. In this study we set out to determine how individual components of yield are inherited, determine which components contribute the most to total yield, and investigate whether it is possible using key components to make selections for high-yielding genotypes on 1- and 2-year-old plants. We estimated variance components, heritabilities, phenotypic and genotypic correlations, and breeding values for yield and YC from 1008 genotypes based on 85 families derived from 45 parents harvested over three seasons in Washington state. Narrow-sense heritability estimates varied from moderately low [0.2 for number of canes (NCAN)] to moderately high [0.69 for berry weight (BWT)]. In general, all YCs were positively correlated with total yield (TYLD). The highest genetic correlation with TYLD was found for BWT (0.8), followed by cane length (CLEN) (0.54) and number of fruit per lateral (NFRT) (0.5). NCAN had the lowest genetic correlation with TYLD (–0.03). Genotype × year (G×Y) interaction was higher for some YCs than others. Berry weight, lateral length (LLEN), and NFRT were found to be the most stable overall seasons and the interaction was higher between the first and second years than between the second and third years of the study. To determine the most important YC, we calculated the correlations between the product of all combinations of subsets of the YC breeding values and TYLD. Berry weight, CLEN, and cane diameter (CDIA) were found to be the most important for 2009, 2010, and 2011, respectively. The two most important YCs were LLEN and BWT and this was consistent overall seasons. We demonstrate that it is possible to select high-yielding genotypes by measuring key components such as LLEN, CLEN, and BWT in the first and second fruiting seasons.
Genetic Parameters and Development of a Selection Index for Breeding Red Raspberries for Processing
Authors: Stephens M. Joseph , Alspach Peter A. , Beatson Ron A. , Winefield Chris , Buck Emily J.
Published: January 2019

New commercial red raspberry (Rubus idaeus) cultivars suited to machine-harvesting and processing markets need to be high-yielding and have good fruit quality attributes, including fruit firmness, sugar content, acidity, flavor, and health properties. Combining many traits in one genotype is a challenge for breeders, especially for traits negatively correlated with yield. Despite its potential, the use of multiple-trait selection through selection indices has had limited application in fruit breeding. In this study, we estimated variance components, heritabilities, phenotypic and genetic correlations and breeding values for total yield (TYLD), harvest span, mid-harvest day and fruit quality traits, firmness (FIRM), soluble solids (SS), acidity (ACID), total anthocyanins (TACY), and total ellagitannins (TELG) from 1008 seedling genotypes based on 85 families derived from 45 parents harvested over three seasons in Washington state. Narrow-sense heritability estimates ranged from moderately low (0.22 for TYLD) to moderately high (0.73 for SS). All traits measured had positive genetic correlations with TYLD except for ACID (–0.35) and TACY (–0.28). Genotype × year (G×Y) interaction was high for TYLD and low for fruit quality attributes FIRM, SS, ACID, TACY, and TELG, and interactions were higher between the first (2009) and second (2010) seasons than between the second (2010) and third (2011) seasons. Using economic weights and breeding values derived from multivariate analysis for TYLD, FIRM, SS, and TACY, we constructed a selection index designed to assist with multiple-trait selection for population improvement and the development of commercial raspberry cultivars.
Genetic Differences and Environmental Variations in Carotenoid Contents of Fruit Flesh in Parental Population Used in Citrus Breeding in Japan
Authors: Nonaka Keisuke , Kita Masayuki , Ikoma Yoshinori , Fukamachi Hiroshi , Imai Atsushi , Yoshioka Terutaka , Yamada Masahiko
Published: January 2019

To aid the breeding of citrus (Citrus sp.) for high carotenoid content, we assayed the fruit flesh of 48 cultivars and selections within a parental population consisting of both old and new cultivars and selections at two locations in Japan. The mean total carotenoid (CAR) content across all 48 cultivars and selections over the two locations was 26.59 μg·g−1 fresh weight (FW). The most prominent carotenoid was β-cryptoxanthin [BCR (12.09 μg·g−1 FW)] followed by violaxanthin [VIO (8.04 μg·g−1 FW)], ζ-carotene (2.27 μg·g−1 FW), phytoene (1.86 μg·g−1 FW), and β-carotene (0.96 μg·g−1 FW). Broad-sense heritabilities of CAR, BCR, and VIO were 0.80 or greater based on a sample of five fruit on one tree per location in one time sampling for 1 year in a location, which were revealed to be large enough for gauging the genetic variation. The mean CAR and BCR contents in a cultivar and selection group in advanced generations were nearly the same as in the initial population, suggesting no or little selection pressure on carotenoid content in the citrus breeding so far. High carotenoid contents in cultivars and selections released or selected recently, which have high fruit qualities, suggest their high potential for combining high fruit quality and high carotenoid content in breeding. We showed that the critical phenotypic value used in selecting hybrid seedlings can be determined from the estimate of environmental variance.
Genetic Structure and Phylogenetic Relationships of Capsicum chinense
Authors: Moses Marissa , Umaharan Pathmanathan
Published: January 2019

Capsicum chinense is commercially the most important pepper species grown in the Caribbean. It is popularly used to impart pungency and flavor to Caribbean cuisine. However, unlike Capsicum annuum, which is the most commercially exploited domesticated species internationally, C. chinense has not been methodically collected or characterized for systematic improvement through plant breeding. The objectives of the study were to assess the diversity of C. chinense and its structure within the Caribbean basin and to determine its phylogenetic relationship to groups within South America. DNA isolated from 201 accessions of C. chinense, representing geographical regions where the species is found, were amplified using arbitrary primers to generate 138 polymorphic and reproducible random amplification of polymorphic DNA (RAPD) markers. Nei’s and Shannon’s diversity indices for C. chinense (0.28 and 0.419, respectively) were higher in South America compared with Central America or the Caribbean, corresponding to its putative center of diversity. The study showed the existence of three phylogenetic clusters within C. chinense. The largest cluster consisted of accessions from the Upper Amazon region, the Guianas including Venezuela, and the Lesser Antilles of the Caribbean. The other major cluster was represented by accessions principally from the Lower Amazon region. Another distinct but small cluster consisted of samples solely from the Greater Antilles of the Caribbean. The discovery of the three phylogenetic clusters within C. chinense may have potential for exploiting heterosis in breeding. The implications of the findings to the understanding of the phylogenetic origin and distribution of C. chinense are discussed.
Optimization of an Agrobacterium-mediated Transient Assay for Gene Expression Studies in Anthurium andraeanum
Authors: Hosein Fazeeda N. , Lennon Adrian M. , Umaharan Pathmanathan
Published: January 2019

Gene function studies in anthurium (Anthurium andraeanum) have been hindered by the low efficiency of stable transformation, the long regeneration time required as well as the genotype-dependent nature of Agrobacterium (Agrobacterium tumemaciens)-mediated transformation protocols. Agrobacterium-mediated transient expression assays can serve as an attractive alternative for investigating gene function once such assays are optimized. The effects of host factors (genotype, explant type, and developmental maturity of explants), Agrobacterium factors (strain, growth phase, and its concentration), media conditions (infiltration medium used, acetosyringone concentration, type of surfactant, and its concentration), and other experimental factors (infiltration time, cocultivation time, and vacuum infiltration) were investigated on the efficiency of Agrobacterium transient transformation, with replications, using transient expression of β-glucuronidase as an indicator. Although the efficiency of transient transformation was initially found to be highly host genotype-dependent, the genotypic differences in transient transformation efficiency diminished as the protocol was optimized. Agrobacterium strain GV3101 grown to an optical density at 600 nM (OD600) of 1.5 and resuspended to a final OD600 of 0.8 in infiltration medium [0.5% glucose, 10 mm 2-(N-morpholino) ethanesulfonic acid] supplemented with 100 μM acetosyringone and 0.05% of a non-ionic surfactant (S240), for an infiltration period of 16 hours and a cocultivation timeframe of 2 days yielded transient transformation efficiencies as high as 100%.
Temporal and Spatial Pattern of Indole-3-acetic Acid Occurrence during Walnut Pistillate Flower Bud Differentiation as Revealed by Immunohistochemistry
Authors: Gao Ying , Liu Hao , Dong Ningguang , Pei Dong
Published: January 2019

We used anti-indole-3-acetic acid (IAA) monoclonal antibodies to monitor the temporal and spatial pattern of IAA during pistillate flower bud differentiation in the walnut (Juglans regia) cultivar Liaoning 1. Based on morphological changes, the process of pistillate flower bud differentiation was divided into five stages. The flower induction stage, which includes the early phase, midphase, and late phase, persisted from 25 Apr. to the end of May. The pedicel differentiation stage began on 5 June. The bract primordium stage began on 25 June and persisted through mid-March of the next year. Both the perianth and pistil differentiation stages persisted for nearly 2 weeks. During the floral induction period, little IAA was present in the shoot apical meristem (SAM); hence, the SAM may not always be a site of IAA production. IAA was obviously concentrated in cells of the first several layers of the SAM during pedicel primordium formation. High levels of IAA were also noted in the phyllome, young leaf tips, and vascular bundle of leaves and gemmae. This direct evidence indicates that no close relationship exists between IAA and physiological differentiation; instead, IAA may strongly affect morphogenesis. These findings comprise a first step toward elucidating the walnut flowering mechanism.
Changes in Photosynthetic Characteristics and Antioxidative Protection in Male and Female Ginkgo during Natural Senescence
Authors: Shi Dawei , Wei Xiaodong , Chen Guoxiang , Xu Yanli
Published: January 2019

Ginkgo (Ginkgo biloba), a dioecious tree species, is widely distributed throughout the world, yet little is known about sex-related responses to autumnal senescence in ginkgo. The aim of this study was to investigate changes in photosynthetic activities, concentration of oxidative stress parameters [malondialdehyde (MDA) and H2O2] and antioxidant systems, and ultrastructure of chloroplasts in the naturally senescing leaves of two ginkgo sexes and to examine whether progression of senescence is sex-specific in ginkgo. Photosynthesis in ginkgo leaves of both sexes was not limited by stomatal factors, but rather non-stomatal factors such as decreased photosynthetic pigments and photochemical activities that became more important during autumnal senescence. The responses of antioxidative enzymes were different from those of antioxidants to leaf senescence. Correlation analysis revealed that autumnal leaf senescence was significantly correlated to antioxidative enzymes changes but not to antioxidants such as ascorbate (ASA) and glutathione (GSH). Guaiacol peroxidase (POD) became more important in senescing leaves and played a major protective role, especially at the late stage of senescence. The shape of chloroplasts of both sexes changed from oblong to round, and there was an increase in the number and size of osmiophilic granules during senescence; swollen thylakoid membranes in the stroma and grana with a significant increase in MDA content were also observed. During autumnal senescence, female ginkgo plants showed smaller decreases in net photosynthetic rates, photosynthetic pigments, photochemical activities, superoxide dismutase, ascorbate peroxidase and catalase activities, higher POD activity, ASA and GSH contents, and smaller increases in H2O2 and MDA contents than did males. In addition, female plants had a later senescence of chloroplasts, a smaller accumulation of osmiophilic granules, and a slower rate of membrane damage. These results show that female ginkgo exhibit slower leaf senescence, which may be related to increased reproductive costs.
Composition and Emission Rhythm of Floral Scent Volatiles from Eight Lily Cut Flowers
Authors: Kong Ying , Sun Ming , Pan Hui-tang , Zhang Qi-xiang
Published: January 2019

Floral scents emitted from eight cultivars of cut lily flowers (Lilium) were analyzed. Floral volatiles were collected by headspace adsorption on sorbent tubes and analyzed by gas chromatography–mass spectrometry (GC/MS) using a direct thermal desorption. Fifty volatile compounds were identified. Nine compounds were detected in all lilies, whereas 20 compounds were detected in all scented lilies. The results revealed that non-scented lilies emitted trace amounts of volatile compounds, whereas scented lilies emitted high levels of volatile compounds. Monoterpenoids and benzenoids were the dominant compound classes of volatiles emitted from scented lilies. Myrcene, (E)-β-ocimene, linalool, methyl benzoate, and ethyl benzoate were the major compounds of the aroma of scented lilies; 1,8-cineole was also a major compound in the two scented oriental × trumpet hybrid lilies. Scent emissions occurred in a circadian rhythm with higher levels of volatiles emitted during the night. Lilium ‘Siberia’ was selected as a model to investigate the source of the emissions. GC/MS analysis of four flower parts and neutral red staining revealed that tepals were the source of floral scent.
Stress and Strain in the Sweet Cherry Skin
Authors: Grimm Eckhard , Peschel Stefanie , Becker Tobias , Knoche Moritz
Published: January 2019

Rain-cracking of sweet cherry (Prunus avium L.) fruit involves failure of the exocarp caused by excessive stress and strain. The objective of our study was to quantify exocarp strain in developing cherries. The release of linear elastic strain was followed in vivo using a gaping assay, whereas the release of biaxial elastic strain was followed in vitro after excision of small exocarp segments (ESs) that were submerged in silicone oil and strain release quantified by image analysis. When mature sweet cherry fruit were cut (by making two or more deep, longitudinal incisions parallel to the stylar/pedicel axis and on opposing sides of the fruit down to the pit), the incisions rapidly “gaped.” The gaping wounds continued to widen as they progressively released the linear elastic strain in the skin. By 24 hours the combined widths of two gapes represented 8.8% ± 0.1% of the fruit circumference. Increasing the number of cuts from two to 12 increased the cumulative gape widths to 14.9% ± 0.2%. In ES, monitoring the time course of relaxation after excision revealed a rapid release of biaxial strain, having a half-time of ≈2.7 minutes. Relaxation continued, but at a decreasing rate, for up to 48 hours. Across eight cherry cultivars, the biaxial strain in the exocarp at maturity ranged from 18.7% ± 1.9% in ‘Lapins’ to 36.0% ± 1.8% in ‘Katalin’. Elastic strain in the ES was always lower than that measured in an isolated cuticular membrane (CM). Increasing the temperature from 2 to 35 °C increased the rate of strain release and also the total percent strain released at 96 hours. In developing ‘Hedelfinger’ sweet cherry fruit, there was essentially no elastic strain in the exocarp at 45 days after full bloom (DAFB). Thereafter, significant elastic strain developed, reaching a maximum of 47.6% ± 2.5% at 87 DAFB. The effect of exocarp cell turgor on strain in the ES (evidenced by the difference in the reversible strain between ES with and without turgor) was closely and positively related to the relative area growth rate of the skin (r2 = 0.957). Strain release peaked at ≈59 DAFB, and there was no effect of turgor on strain release in mature fruit. Our data demonstrated the following: 1) the exocarp is a viscoelastic material composite; 2) at maturity, plastic and elastic strain components make up 66% and 34% of the total percent strain, respectively; 3) elastic strain in the exocarp increases during Stage III development; and 4) the strain in the exocarp is unaffected by strain in the CM. Thus, the epidermis and hypodermis layers must represent the main, load-bearing structure in sweet cherry fruit with the cuticle making a mechanically insignificant contribution.
Metabolic Responses of Hybrid Bermudagrass to Short-term and Long-term Drought Stress
Authors: Du Hongmei , Wang Zhaolong , Yu Wenjuan , Huang Bingru
Published: January 2019

The accumulation of different types of metabolites may reflect variations in plant adaptation to different severities or durations of drought stress. The objectives of this project are to examine changes in metabolomic profiles and determine predominant metabolites in response to short-term (6 days) and long-term (18 days) drought stress with gas chromatography–mass spectrometry analysis in a C4 perennial grass species. Plants of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis cv. Tifdwarf) were unirrigated for 18 days to induce drought stress in growth chambers. Physiological responses to drought stress were evaluated by visual rating of grass quality, relative water content, photochemical efficiency, and electrolyte leakage (EL). All parameters decreased significantly at 6 and 18 days of drought stress, except EL, which increased with the duration of drought stress. Under short-term drought stress (6 days), the content did not change significantly for most metabolites, except methionine, serine, γ-aminobutyric acid (GABA), isoleucine, and mannose. Most metabolites showed higher accumulation under long-term drought stress compared with that under the well-watered conditions, including three organic acids (malic acid, galacturonic acid, and succinic acid), 10 amino acids (proline, asparagine, phenylalanine, methionine, serine, 5-hydroxynorvaline, GABA, glycine, theorine, valine), seven sugars (sucrose, glucose, galactose, fructose, mannose, maltose, xylose), one nitrogen compound (ethanolamine), and two-sugar alcohol (myo-inositol). The accumulation of those metabolites, especially malic acid, proline, and sucrose, could be associated with drought adaptation of C4 hybrid bermudagrass to long-term or severe drought stress.
Main and Epistatic Quantitative Trait Loci Associated with Seed Size in Watermelon
Authors: Prothro Jason , Sandlin Katherine , Abdel-Haleem Hussein , Bachlava Eleni , White Victoria , Knapp Steven , McGregor Cecilia
Published: January 2019

Watermelon (Citrullus lanatus) is an important crop grown for both its edible flesh and seeds. Seed size is an important trait in watermelon breeding, with large seeds preferred for planting and edible seeds but small seeds preferred in fruit sold for consumption. Large, medium, and small seed sizes are thought to be controlled by two genes with epistatic interaction. A ‘Klondike Black Seeded’ × ‘New Hampshire Midget’ (KBS × NHM) recombinant inbred line population and a ZWRM 50 × PI 244019 (ZWRM × Citroides) F2 population were used to identify main effect quantitative trait loci (M-QTL) and epistatic QTL (E-QTL) associated with 100 seed weight (100SWT), seed length (SL), and seed width (SWD). Thirteen M-QTL were identified on four linkage groups (LGs) for the three traits in the two populations. Major M-QTL (R2 = 26.9% to 73.6%) were identified at the same location on LG 2 in both populations for all three traits. M-QTL for all three traits also colocalized on LG 9 in the ZWRM × Citroides population and on LG 4 for 100SWT and SL in the KBS × NHM population. Significant epistatic effects were found between the M-QTL on LG 2 and LG 4 in the KBS × NHM population and between LG 2 and LG 9 in the ZWRM × Citroides population. The phenotypic variance explained by the E-QTL was generally small. The stable, major M-QTL on LG 2 is a candidate for marker-assisted selection for seed size in watermelon.
Photosynthetic Light Requirements and Effects of Low Irradiance and Daylength on Phalaenopsis amabilis
Authors: Guo Woei-Jiun , Lin Yu-Zu , Lee Nean
Published: January 2019

Phalaenopsis has become one of the most important potted plants around the world. Thus, we used a key commercial Phalaenopsis amabilis cultivar, TS97, as a model to determine the light requirements for maximal carbon fixation and photosystem II (PSII) efficiency in its leaves and to investigate the effects of low irradiance and daylength on photosynthesis and flower development. In mature ‘TS97’ leaves, the daily total CO2 uptake capacity and net acid fixation increased with increasing photosynthetic photon flux (PPF) and saturated at ≈200 μmol·m−2·s−1, whereas the fluorescence ratio values were significantly reduced to 0.68 to 0.75 above 325 μmol·m−2·s−1 PPF, indicating photoinhibition of PSII. Positive assimilation of the nocturnal CO2 uptake occurred at a very low PPF (less than 5 μmol·m−2·s−1), suggesting highly efficient use of light energy by ‘TS97’ plants. Leaves developed under 30 μmol·m−2·s−1 PPF exhibited lower light requirement of 125 μmol·m−2·s−1 PPF to reach maximal CO2 uptake, below which the daytime CO2 uptake declined dramatically. Under a 12-hour daylength, exposing the leaves to a low PPF for 4 hours at any time during the day did not affect the photosynthetic capacity in ‘TS97’ leaves, suggesting that 8 hours of optimal irradiance is required for high-level photosynthesis, whereas the 12-hour daylength resulted in a higher CO2 uptake rate and the daily total CO2 uptake than the 8-hour daylength. Moreover, the 12-hour daylength promoted earlier flower formation and higher flower count compared with the 6- to 8-hour daylengths. Longer daylengths neither accelerated flowering formation nor enhanced total flower count. In conclusion, 8 hours of saturating PPF at 200 μmol·m−2·s−1 and a 12-hour daylength are sufficient for maximizing photosynthesis and flower production in ‘TS97’ plants.
Beneficial Role of Exogenous Spermidine on Nitrogen Metabolism in Tomato Seedlings Exposed to Saline-alkaline Stress
Authors: Zhang Yi , Hu Xiao-Hui , Shi Yu , Zou Zhi-Rong , Yan Fei , Zhao Yan-Yan , Zhang Hao , Zhao Jiu-Zhou
Published: January 2019

We studied the effects of exogenous spermidine (Spd) on plant growth and nitrogen metabolism in two cultivars of tomato (Solanum lycopersicum) that have differential sensitivity to mixed salinity-alkalinity stress: ‘Jinpeng Chaoguan’ (salt-tolerant) and ‘Zhongza No. 9’ (salt-sensitive). Seedling growth of both tomato cultivars was inhibited by salinity-alkalinity stress, but Spd treatment alleviated the growth reduction to some extent, especially in ‘Zhongza No. 9’. Exogenous Spd may help reduce stress-induced increases in free amino acids, ammonium (NH4+) contents, and NADH-dependent glutamate dehydrogenase (NADH-GDH) activities; depress stress-induced decreases in soluble protein and nitrate content; and depress nitrate reductase, nitrite reductase, glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT), glutamate oxaloacetate transaminase (GOT), and glutamate pyruvate transaminase (GPT) activities, especially for ‘Zhongza No. 9’. Based on our results, we suggest that exogenous Spd promotes the assimilation of excess toxic NH4+ by coordinating and strengthening the synergistic action of NADH-GDH, GS/NADH-GOGAT, and transamination pathways, all during saline-alkaline stress. Subsequently, NH4+ and its related enzymes (GDH, GS, GOGAT, GOT, and GPT), in vivo, are maintained in a proper and balanced state to enable mitigation of stress-resulted damages. These results suggest that exogenous Spd treatment can relieve nitrogen metabolic disturbances caused by salinity-alkalinity stress and eventually promote plant growth.