bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and Characterization of LEAFY and APETALA1 Homologues from Citrus sinensis L. Osbeck `Washington'
Authors: Pillitteri Lynn Jo , Lovatt Carol J. , Walling Linda L.
Published: January 2019

Homologues of the floral meristem identity genes LEAFY (LFY) and APETALA1 (AP1) were isolated from the hybrid perennial tree crop `Washington' navel orange (Citrus sinensis) and designated CsLFY and CsAP1, respectively. Citrus has an extended juvenile period unlike herbaceous plants and responds to different floral stimuli than herbaceous plants or deciduous tree species. Despite these differences, the deduced amino acid sequences of CsLFY and CsAP1 genes are at least 65% identical with their Arabidopsis thaliana L. Heynh counterparts and share even greater sequence similarity to LFY and AP1 from the deciduous woody perennials, Populus balsamifera Bradshaw and Populus tremuloides Michaux, respectively. Like A. thaliana LFY (AtLFY) and AP1 (AtAP1), CsLFY and CsAP1 expression was restricted almost exclusively to reproductive tissues, but observed expression of CsAP1 in the fourth whorl carpel tissue of mature flowers was distinct from other plant AP1 genes. Transgenic A. thaliana plants ectopically expressing CsLFY or CsAP1 showed early-flowering phenotypes similar to those described for overexpression of AtLFY and AtAP1. In addition, the 35S:CsLFY and 35S:CsAP1 transgenes partially complemented the lfy-10 and ap1-3 mutants, respectively. The severity of the overexpression phenotypes correlated with the accumulation of CsLFY or CsAP1 transcripts. LFY is a single-copy gene in flowering plants but consistent with its hybrid origin, the genome of C. sinensis `Washington' has two easily distinguishable CsLFY and CsAP1 alleles derived from it's parental genotypes, C. maxima L. Osbeck (pummelo) and C. reticulata Blanco (mandarin). Allelic polymorphism at both the CsLFY and CsAP1 loci was restricted to the 5′- and 3′-flanking regions.
Germination and Embryo Anatomy of Osmotically Primed Parsley Schizocarps
Authors: Olszewski Michael W. , Pill Wallace G. , Pizzolato Thompson D.
Published: January 2019

`Moss Curled' parsley [Petroselinum crispum (Mill.) Nyman ex. A.W. Hill] schizocarps were osmotically primed in polyethylene glycol at -1.0 MPa for 7 days at 20 °C. The smaller of the two mericarps within a parsley schizocarp had lower germination percentage, but similar rate and synchrony of germination. Osmotic priming increased germination percentage, rate, and synchrony, irrespective of mericarp half. This promotive effect of priming on germination was associated with embryonic advancement as indicated by a doubling of radicle and cotyledon volumes, without changes in lengths of these organs. Periclinal divisions of the lateral expansion meristem, distinct in primed radicles but indistinct in nonprimed radicles, led to radial alignment of the cortical cells and a doubling of cortical volume and thereby increased radicle volume. Each embryonic cotyledon of primed mericarps had three distinct procambial bundles that differentiated along most of the cotyledon length, while nonprimed cotyledons had from zero to three that differentiated only a short way into the cotyledon. Priming increased coyledonary procambium length by 5-fold and volume by 11-fold. Increased embryonic growth due to priming was associated with greater endosperm depletion adjacent to the embryo. The schizocarps frequently separated or partially separated into component mericarps during priming, indicating a weakening of pericarp tissue along the commissural suture and possibly elsewhere.
Rootstocks and Plant Water Relations Affect Sugar Accumulation of Citrus Fruit Via Osmotic Adjustment
Authors: Barry Graham H. , Castle William S. , Davies Frederick S.
Published: January 2019

Citrus rootstocks have well-known effects on tree size, crop load, fruit size, and various fruit quality factors. Fruit from trees budded on invigorating rootstocks are generally larger with lower soluble solids concentration (SSC) and titratable acidity compared to fruit from trees budded on less invigorating rootstocks. Although it is unclear how rootstocks exert their influence on juice quality of Citrus L. species, plant water relations are thought to play a central role. In addition, the larger fruit size associated with invigorating rootstocks and the inverse relationship between SSC and fruit size implies that fruit borne on trees on invigorating rootstocks have lower SSC due to dilution effects in larger fruit. To determine how rootstock type affects sugar accumulation in fruit of Citrus species, controlled water-deficit stress was applied to mature `Valencia' sweet orange [C. sinensis (L.) Osb.] trees on Carrizo citrange [C. sinensis × Poncirus trifoliata (L.) Raf.] or rough lemon (C. jambhiri Lush.) rootstocks. Withholding water from the root zone of citrus trees during stage II of fruit development decreased midday stem water potential and increased the concentrations of primary osmotica, fructose and glucose. Sucrose concentration was not affected, suggesting that sucrose hydrolysis took place. Increased concentrations of sugars and SSC in fruit from moderately water-stressed trees occurred independently of fruit size and juice content. Thus, passive dehydration of juice sacs, and concentration of soluble solids, was not the primary cause of differences in sugar accumulation. Controlled water-deficit stress caused active osmotic adjustment in fruit of `Valencia' sweet orange. However, when water-deficit stress was applied later in fruit development (e.g., stage III) there was no increase in sugars or SSC. The evidence presented supports the hypothesis that differential sugar accumulation of citrus fruit from trees on rootstocks of contrasting vigor and, hence, plant water relations, is caused by differences in tree water status and the enhancement of sucrose hydrolysis into component hexose sugars resulting in osmotic adjustment. Therefore, inherent rootstock differences affecting plant water relations are proposed as a primary cause of differences in sugar accumulation and SSC among citrus rootstocks.
Prolonged Somatic Transposition in Citrus: The Autonomous Ac Transposable Element Remains Active in the Citrus Genome for Several Years
Authors: Trainin Taly , Lipsky Alexander , Levy Avraham A. , Holland Doron
Published: January 2019

The maize transposable element Activator (Ac) has been shown to be active in a number of dicots, including arabidopsis [Arabidopsis thaliana (L.) Heynh.], tobacco (Nicotiana tabacum L.), tomato (Lycopersicon esculentum Mill.), potato (Solanum tuberosum L.), and aspen (Populus tremuloides Michx.). However, no information is available on somatic transposition in any plant during several years of growth and development. It is not known how transposition affects genetic variability among vegetative parts that have developed during a long period of growth. In order to explore the possibility of using somatic Ac transposition for gene tagging and mutagenesis in fruit trees, a derivative of the maize Ac transposable element was introduced into `Duncan' grapefruit (Citrus paradisi Macf.) by Agrobacterium tumefaciens (Smith & Towns.) Conn.-mediated stable transformation. Genetically identical 4-year-old sibling trees were established by grafting one of the transformants on Troyer citrange [Citrus sinensis (L.) Osbec. × Poncirus trifoliate (L.) Ras.] rootstocks. We demonstrated that the Ac element was active upon transformation in citrus (Citrus L.) trees and that transposition can create genetic variability among tree siblings and among leaves collected from different parts of the same tree. Ac was still active among propagated plants 4 years after transformation, clearly indicating that it is capable of maintaining itself in citrus trees for a long period of time. The observation of different integration patterns in different parts of the same tree and within tree siblings originating from the same transformant suggests that an Ac-based mutagenesis system could be very useful in creating somatic mutations in citrus trees.
Growth Environment and Leaf Anatomy Affect Nondestructive Estimates of Chlorophyll and Nitrogen in Citrus sp. Leaves
Authors: Jifon John L. , Syvertsen James P. , Whaley Eric
Published: January 2019

Correlations between extractable leaf chlorophyll (Chl) concentration and portable, nondestructive leaf “greenness” meter readings imply that such estimates can be used as surrogate measurements of leaf nitrogen (N) status. However, few studies have actually found a direct relationship between Chl meter readings and leaf N. We evaluated the utility of two handheld transmittance-based Chl content meters (SPAD-502, Minolta Corp. and CCM-200, Opti-Sciences) and one reflectance-based meter (Observer, Spectrum Technologies), in estimating Chl and N concentrations in intact leaves of several citrus cultivars. Total Chl determined analytically, correlated well with nondestructive Chl meter readings (r2: 0.72 to 0.97; P < 0.0001), but regression models differed among cultivars using the same meter and also among meters for a given cultivar. The relationships were generally more linear and stronger at low Chl concentrations (<0.5 mmol·m-2) than at higher Chl concentrations, reflecting increased variability in Chl meter readings with increasing leaf Chl. Significant relationships between Chl meter readings and measured leaf N concentrations were also found in all the cultivars tested (r2: 0.23 to 0.69; P < 0.01), but the data were more variable than those for Chl. Field-grown leaves were significantly thicker and had higher Chl meter readings than greenhouse-grown leaves of similar Chl or N concentrations. The results suggest that nondestructive Chl content meters can overestimate Chl and N in thicker leaves and/or leaves with high Chl concentrations. A single prediction equation derived from a wide range of Chl or N concentrations could be applicable across the range of citrus cultivars when grown in the same environment. Potential limitations associated with leaf thickness as influenced by environmental factors may necessitate the development of more specific calibration equations.
Plant Age, Fertilization, and Biological Control Affect Damage Caused by Twospotted Spider Mites on Ivy Geranium: Development of an Action Threshold
Authors: Opit George P. , Chen Yan , Williams Kimberly A. , Nechols James R. , Margolies David C.
Published: January 2019

In three experiments, damage caused by twospotted spider mite (TSSM; Tetranychus urticae Koch) was correlated with the quality of ivy geranium [Pelargonium peltatum (L.) L'Her ex Aiton], and the action threshold for TSSM on ivy geranium was developed. Ivy geranium quality was measured as overall plant quality—plant size and form, and leaf greenness and glossiness—leaf browning, and leaf distortion. Young plants with high initial TSSM numbers (30 TSSM/plant) exhibited the greatest damage, suggesting that monitoring for TSSM early in the plant production cycle is necessary to prevent extensive damage. The leaf distortion index and overall plant quality were correlated with cumulative TSSM density and marketability in 4-week-old plants infested with 30 TSSM, whereas leaf browning was not correlated with either. Thus, either leaf distortion or overall plant quality can be used to measure economic damage resulting from TSSM. The action threshold for TSSM on ivy geranium was determined using overall plant quality. When the predatory mite, Phytoseiulus persimilis Athias-Henriot, is used to control TSSM, the action threshold was found to be 2 TSSM/leaf. Results also showed that fertilizer combinations of 8 or 24 mm nitrogen and 0.32, 0.64, or 1.28 mm phosphorus had no effect on cumulative TSSM density. When P. persimilis was released at predator: prey ratios of 1:60, 1:20, and 1:4, TSSM damage, measured as both leaf distortion and overall plant quality, was significantly reduced at 1:4 and 1:20, but not at 1:60. A 1:4 rate resulted in the most marketable plants. These results suggest that P. persimilis should be released at a rate of 1:4 when the TSSM action threshold is reached.
Pathogen-derived Resistance to Tomato Spotted Wilt Virus in Transgenic Tomato and Tobacco Plants
Authors: Fedorowicz Olga , Bartoszewski Grzegorz , Kamińska Maria , Stoeva Pravda , Niemirowicz-Szczytt Katarzyna
Published: January 2019

This study was undertaken to remedy significant yield losses in commercial tomato (Lycopersicon esculentum Mill.) and tobacco (Nicotiana tabacum L.) production caused by tomato spotted wilt virus (TSWV). One of the possible sources of resistance can be incorporation into the host plant of a viral nucleoprotein (N) gene by Agrobacterium-mediated transformation. Twelve primary transformants of tomato and 141 of tobacco were analyzed for the expression of the N gene and for resistance to the TSWV infection. The tests have demonstrated that transgenic plants were protected against virus infection irrespective of whether or not they contained detectable levels of the translational product.
Transpiration Capacity in Poinsettia Cuttings at Different Rooting Stages and the Development of a Cutting Coefficient for Scheduling Mist
Authors: Wilkerson Erin G. , Gates Richard S. , Zolnier Sérgio , Kester Sharon T. , Geneve Robert L.
Published: January 2019

Rooting stage, transpiration capacity, and relative water content were measured in cuttings every 5 days for 25 days. Cell divisions in phloem parenchyma were evident between 5 and 10 days after sticking, organized subcuticular root primordia were present between 10 and 12 days, and roots emerged between 12 and 15 days. Transpiration was measured in poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch `Freedom Dark Red') cuttings under light or dark conditions at increasing vapor pressure deficit (VPDair) levels during different stages of rooting. Transpiration capacity did not increase until roots emerged on the cuttings. Light had a significant impact on transpiration rates only after roots emerged. Light was more significant than VPDair for determining actual transpiration. Between visible rooting (15 days) and 25 days, increase in total root length was linear (r2 = 0.92) and significantly correlated with transpiration (r2 = 0.98). Transpiration capacity increased after visible rooting, but did not significantly increase under non-misted conditions until cuttings were well-rooted and had a total root length >50 cm (18 days after sticking). Relative water content measured before and after entering the transpiration chamber confirmed that cuttings were only able to take enough water from the medium to continue sustained transpiration after 18 days. A cutting coefficient was developed from transpiration data to modify the misting interval for dynamic controlled misting. Greenhouse studies showed a 55% or greater reduction in water use with dynamic control compared to constant static or stepped down static control. Rooting performance was unaffected by misting interval. Foliar nutrition was significantly reduced in all cuttings after 7 days in the mist bench, but changes in foliar elemental content were not correlated with misting interval.
Predicting Rooting Stages in Poinsettia Cuttings Using Root Zone Temperature-based Models
Authors: Wilkerson Erin G. , Gates Richard S. , Zolnier Sérgio , Kester Sharon T. , Geneve Robert L.
Published: January 2019

Root zone temperature optima for root initiation and root elongation stages for rooting in poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch `Freedom Dark Red') cuttings was determined to be 28 and 26 °C, respectively. Threshold temperatures where rooting development was slow (>24 days) or did not occur were ≤20 and ≥32 °C. Time to visible rooting and postemergent root elongation was modeled based on cumulative daily mean root zone temperatures in growth chamber studies using a thermogradient table to provide simultaneous temperatures between 19 to 34 °C. Time to root emergence at different root zone temperatures was best described using a nonlinear growth rate derived mathematical model, while postemergent root elongation up to 100 cm could be described using either a linear thermal time model or a nonlinear equation based on elongation rate. These temperature-based mathematical models were used to predict rooting in six greenhouse experiments. Using a root zone base temperature of 21 °C, observed vs. predicted time to visible root emergence was highly correlated (r2 = 0.98) with a mean prediction error (MPE) of 1.6 d. Observed vs. predicted root length using the linear thermal time model had a r2 = 0.69 and an MPE of 14.6 cm, which was comparable to the nonlinear model with an r2 = 0.82 and an MPE of 14.8 cm.
Determination of Endodormancy Break in Almond Flower Buds by a Correlation Model Using the Average Temperature of Different Day Intervals and its Application to the Estimation of Chill and Heat Requirements and Blooming Date
Authors: Alonso J.M. , Ansón J.M. , Espiau M.T. , Company R. Socias i
Published: January 2019

Almond (Prunus amygdalus Batsch.) blooming date is determined by the temperatures during the dormancy period, from the onset of endodormancy to just before blooming. In this work we have developed a model, based on several years data, to estimate the mean transition date from endodormancy to ecodormancy in 44 almond cultivars covering the whole range of almond bloom, through the significance of correlation coefficients between the temperatures occurring during dormancy and the date of full bloom. The estimation of this date for each cultivar has allowed the calculation of its chill and heat requirements. It was found that most cultivars have chilling requirements between 400 and 600 chill units, whereas the span of heat requirements was wider, from 5500 to 9300 growing degree hours Celsius. Some cultivars show high chilling requirements and low heat requirements whereas others show opposite requirements. These differences confirm the wide almond adaptability to different climatic conditions and offer the possibility of being utilized in breeding programs. The good fit shown by the application of this model in the prediction of bloom time may sustain its application in chilling and heat requirement estimation in other fruit species if blooming dates and climatic data for several years are available.
Prolonged High Temperature Exposure and Daily Light Integral Impact Growth and Flowering of Five Herbaceous Ornamental Species
Authors: Warner Ryan M. , Erwin John. E.
Published: January 2019

Flowering of many herbaceous ornamentals is reduced or eliminated under high temperatures. On warm, sunny days, greenhouse growers often cover crops with light-reducing screening materials to reduce air and plant temperature. However, low irradiance can also reduce flowering on many species. To examine the impacts of temperature and irradiance on herbaceous ornamental flowering and to select a model to study high temperature-reduced flowering, Antirrhinum majus L. (snapdragon) `Rocket Rose', Calendula officinalis L. (calendula) `Calypso Orange', Impatiens wallerana Hook.f. (impatiens) `Super Elfin White', Mimulus ×hybridus Hort. ex Siebert & Voss (mimulus) `Mystic Yellow', and Torenia fournieri Linden ex E. Fourn (torenia) `Clown Burgundy' were grown at constant 32 ± 1 °C or 20 ± 1.5 °C under a 16-hour photoperiod with daily light integrals (DLI) of 10.5, 17.5, or 21.8 mol·m-2·d-1. Flower bud number per plant (all flower buds ≥1 mm in length when the first flower opened) of all species was lower at 32 than 20 °C. Reduction in flower bud number per plant at 32 compared to 20 °C varied from 30% (impatiens) to 95% (torenia) under a DLI of 10.5 mol·m-2·d-1. Flower diameter of all species except snapdragon was less at 32 than 20 °C. Decreasing DLI from 21.8 to 10.5 mol·m-2·d-1 decreased flower diameter of all species except snapdragon. Calendula, impatiens, and torenia leaf number below the first flower was greater at 32 than 20 °C, regardless of DLI. Increasing DLI from 10.5 to 17.5 mol·m-2·d-1 increased shoot dry mass gain rate of all species, regardless of temperature. Further increasing DLI from 17.5 to 21.8 mol·m-2·d-1 at 20 °C increased shoot dry mass gain rate of all species except snapdragon and mimulus, indicating that these species may be light saturated below 21.8 mol·m-2·d-1. Under DLIs of 17.5 and 21.8 mol·m-2·d-1 shoot dry mass gain rate was lower at 32 than 20 °C for all species except torenia. Torenia shoot dry mass gain rate was 129 mg·d-1 at 20 °C compared to 252 mg·d-1 at 32 °C under a DLI of 17.5 mol·m-2·d-1. We suggest torenia may be a good model to study the basis for inhibition of flowering under high temperatures as flowering, but not dry mass gain, was reduced at 32 °C.
Effect of Elevated CO2 Levels and Leaf Area Removal on Sorbitol, Sucrose, and Phloridzin Content in `Gala'/Malling 9 Apple Leaves
Authors: Kelm Mark A. , Flore James A. , Beninger Clifford W.
Published: January 2019

Apple seedlings (Malus domestica Borkh.) were grown under ambient (370), 700, and 1400 μmol·mol-1 CO2 regimes and artificially damaged by removal of leaf area (0%, 15%, and 30%). Increased CO2 concentration had a highly significant effect on the concentrations of sucrose, sorbitol and phloridzin, however there were no significant interactions between CO2 concentration and leaf damage. As CO2 concentration increased there was an increase in levels of sucrose and phloridzin, whereas sorbitol concentration decreased. These findings are discussed in relation to the carbon nutrient balance hypothesis as well as other hypotheses regarding the production of plant primary and secondary compounds in response to elevated levels of CO2 and mechanical damage and/or herbivory.
Characterization of 14 Microsatellite Markers for Genetic Analysis and Cultivar Identification of Walnut
Authors: Dangl Gerald S. , Woeste Keith , Aradhya Mallikarjuna K. , Koehmstedt Anne , Simon Chuck , Potter Daniel , Leslie Charles A. , McGranahan Gale
Published: January 2019

One hundred and forty-seven primer pairs originally designed to amplify microsatellites, also known as simple sequence repeats (SSR), in black walnut (Juglans nigra L.) were screened for utility in persian walnut (J. regia L.). Based on scorability and number of informative polymorphisms, the best 14 loci were selected to analyze a diverse group of 47 persian walnut accessions and one J. hindsii (Jepson) Jepson ex R.E. Sm × J. regia hybrid (Paradox) rootstock. Among the 48 accessions, there were 44 unique multi-locus profiles; the accessions with identical profiles appeared to be synonyms. The pairwise genetic distance based on proportion of shared alleles was calculated for all accessions and a UPGMA (unweighted pair group method with arithmetic mean) dendrogram constructed. The results agree well with what is known about the pedigree and/or origins of the genotypes. The SSR markers distinguished pairs of closely related cultivars and should be able to uniquely characterize all walnut cultivars with the exception of budsports. They provide a more powerful and reliable system for the molecular characterization of walnut germplasm than those previously tested. These markers have numerous applications for the walnut industry, including cultivar identification, verification of pedigrees for cultivar and rootstock breeding programs, paternity analysis, and understanding the genetic diversity of germplasm collections.
Associating Molecular Markers with Virus Resistance to Classify Sweetpotato Genotypes
Authors: Mcharo M. , LaBonte D. , Mwanga R.O.M. , Kriegner A.
Published: January 2019

Molecular markers linked to resistance to sweetpotato chlorotic stunt closterovirus [SPCSV (genus Crinivirus, family Closteroviridae)] and sweetpotato feathery mottle virus [SPFMV (genus Potyvirus, family Potyviridae)] were selected using quantitative trait loci (QTL) analysis, discriminant analysis and logistic regression. Eighty-seven F1 sweetpotato [Ipomoea batatas (L.) Lam.] genotypes from a cross of `Tanzania' and `Wagabolige' landraces were used to generate DNA marker profiles for this study. Forty-five of the clones were resistant to SPCSV while 37 were resistant to SPFMV. A combination of 232 amplified fragment length polymorphism (AFLP) markers and 37 random amplified polymorphic DNA (RAPD) markers obtained were analyzed to determine the most informative markers. All three statistical procedures revealed that AFLP marker e41m33.a contributed the greatest variation in SPCSV resistance and RAPD marker S13.1130 accounted for most of the variation in SPFMV resistance. The power of discriminant and logistic analyses is that you do not need a parent-progeny population. An evaluation of these two models indicated a classification and prediction accuracy rates of 96% with as few as four markers in a model. Both multivariate techniques identified one important discriminatory marker (e44m41.j) for SPCSV and two markers (e41m37.a and e44m36.d) for SPFMV that were not identified by QTL analysis.
Acid Citrus Fruit Improvement via Interploid Hybridization Using Allotetraploid Somatic Hybrid and Autotetraploid Breeding Parents
Authors: Viloria Zenaida , Grosser Jude W.
Published: January 2019

Interploid hybridization was conducted using `Key' lime [Citrus aurantifolia (Cristm.) Swing.], `Lakeland' limequat hybrid [C. aurantifolia × Fortunella japonica (Thumb.) Swing.], Palestine sweet lime (C. limettioides Tan.), `Etrog' citron (C. medica L.), and seven lemon [C. limon (L.) Burm. F.] varieties as female progenitors and five allotetraploid somatic hybrids {`Hamlin' sweet orange [C. sinensis (L.) Osbeck] × `Femminello' lemon (C. limon)]; `Key' lime × `Valencia' sweet orange (C. sinensis); `Valencia' sweet orange × rough lemon (C. jambhiri Lush); Milam lemon (purported C. jambhiri hybrid) × `Femminello' lemon (C. limon); and `Valencia' sweet orange × `Femminello' lemon} and two autotetraploids [`Giant Key' lime (C. aurantifolia) and `Femminello' lemon] as pollen progenitors. A few tetraploid × diploid crosses were also performed. Thirty-five parental cross combinations were accomplished in 2000, 2001, and 2002. The breeding targets were seedlessness, cold-tolerance, and disease resistance. Triploid hybrids were recovered through embryo culture. Generation of triploid citrus hybrids was affected by several factors including sexual compatibility, cross direction, embryo developmental stage, pollen viability, as well as horticultural practices and climatic conditions. Efficiency of triploid hybrid production was higher in diploid × tetraploid crosses than the reciprocal. Many more triploid hybrids were generated from lemon seed progenitors compared to the other acid citrus fruit progenitors. `Todo el Año', `Lisbon', and `Limonero Fino 49' showed the highest sexual compatibility. Embryo germination rate and normal plant recovery were also higher in lemons as compared to the other seed progenitors. Low winter temperatures might have affected the hybrid production efficiency from tropical acid fruit progenitors. A total of 650 hybrids (mostly triploid) were transferred to soil. The novel genetic combinations of these progenies should be valuable for the genetic improvement of acid citrus fruit (lemons and limes).
Variation and Heritabilities of Antioxidant Activity and Total Phenolic Content Estimated from a Red Raspberry Factorial Experiment
Authors: Connor Ann Marie , Stephens M. Joseph , Hall Harvey K. , Alspach Peter A.
Published: January 2019

Variance components and narrow-sense heritabilities were estimated for antioxidant activity (AA), total phenolic content (TPH), and fruit weight in red raspberry (Rubus idaeus L.) fruit from offspring of a factorial mating design. Forty-two full-sib families utilizing seven female and six male parents were evaluated in each of two years in Motueka, New Zealand. In a single year, values within individual half-sib families ranged as widely as 25.3-79.4 μg·g-1 fruit for AA, 205-597 mg/100 g fruit for TPH, and 1.06-7.69 g for fruit weight. Analyses of variance for these three variates demonstrated significant parental source variation in both individual and combined year analyses. For AA and TPH, female parental effects accounted for ≈7% to 19% of total variation, while male effects accounted for ≈6% to 8%. A partially pigment deficient R. parvifolius L. derivative female parent accounted for some of these differences. Female × male parent interaction was not significant for AA and TPH and was marginally significant for fruit weight in combined year analysis. Year had a significant effect on the overall mean AA and TPH, but contributed less than genetic effects to the overall variation in all three traits. Interactions of year with genetic effects were not statistically significant for AA or TPH, indicating that between-year rank or scale changes among families were negligible. The largest proportion of variation was found within rather than among full-sib families. However, variation among plots within full-sib families accounted for 12% to 19% of total variation, indicating environmental differences accounted for some of the observed within-family variation in AA and TPH. Antioxidant activity and TPH were highly phenotypically correlated (r = 0.93); their genetic correlation (r = 0.59) implies that substantial additive genetic factors underlie the phenotypic correlation, but that nonadditive genetic or environmental influences are also important. Both AA and TPH were weakly negatively phenotypically correlated with fruit weight (r = -0.34 and -0.33, respectively), but the corresponding genetic correlations were close to zero. Thus, selection for both high AA or TPH and high fruit weight is possible. Narrow-sense heritability estimates based on variance components from combined year data were h2 = 0.54, 0.48, and 0.77 for AA, TPH, and fruit weight, respectively. These estimates imply a rapid response to selection is possible.
Additional Genes Controlling Flowering Time in Lactuca sativa and L. serriola
Authors: Ryder Edward J. , Milligan David C.
Published: January 2019

Six genes controlling flowering time or bolting time in Lactuca L. have been reported. Several crosses between parents differing in time to opening of first flower were made to ascertain the inheritance of additional flowering time traits in Lactuca species. The parents in the crosses were of five flowering classes: very late (VL), late (L), early (E), very early (VE), and very, very early (VVE). Segregation from a cross between C-2-1-1 (VL) (L. sativa L.) and `Vanguard 75' (L) confirmed that `Vanguard 75' flowering was controlled by the previously identified gene Ef-2ef-2. Mutant line 87-41M-7 (VVE) was crossed by D-3-22M (VE) and segregated 3VVE:1 VE, indicating a dominant allele, Ef-3, that decreased flowering time an additional 7 days. Cos-like line 796 (VE) was crossed to cultivars Salinas (VL) and Vanguard 75. Segregation indicated a gene Ef-4ef-4, with lateness dominant. PI 175735 (E) (L. serriola L.), crossed with C-2-1-1 produced an F2 population with a bimodal distribution, segregating 3 E:1 VL, indicating a single gene Ef-5ef-5. PI 236396 (E) and PI 250020 (E) were crossed to `Salinas' and `Vanguard 75'. Segregation and morphological similarity indicated the same gene in both PI lines, Ef-6ef-6, with earliness dominant.
How to Investigate Four-way Nutrient Interactions in Plants: A New Look at Response Surface Methods
Authors: Paparozzi Ellen T. , Stroup Walter W. , Conley M. Elizabeth
Published: January 2019

Response surface methods refer to a set of experimental design and analysis methods to study the effect of quantitative treatments on a response of interest. In theory, these methods have a broad range of applicability. While they have gained widespread acceptance and application in manufacturing and quality improvement research, they have never caught on in the agricultural sciences. We propose that this is because there has not been specific research demonstrating their usage. In this paper, two 34 factorial experiments were performed using 100 poinsettia plants (Euphorbia pulcherrima Willd. ex Klotzsch) to measure nutrient element concentrations in leaves at three rates each of nitrogen (N), sulfur (S), iron (Fe), and manganese (Mn). Three different methods of analysis were compared—the standard analysis of variance with no regression model, the quadratic regression model commonly assumed for most standard response surface methods and the Hoerl model regression, a nonlinear alternative to quadratic response. Actual nutrient element values were compared with the values predicted by each regression model and then also evaluated to see if the visual symptomology of yellowing related to those nutrient concentrations in leaves. The Hoerl model demonstrated better ability to detect biologically relevant nonlinear two-, three-, and four-way nutrient interactions. Though there was minimal replication this model characterized the treatment effects while keeping the size of the experiment manageable both in terms of time (labor) and cost of plant analyses. Additionally, it was shown that when S, Fe, and/or Mn were deficient along with N, their visual deficiency symptoms were masked by the overall yellowing associated with N deficiency. This model is recommended as the initial experiment in a series where scientists are looking to expand information already determined for two factors. Other treatment systems that this can be used with include: levels of irrigation, pesticides, and plant growth regulators.
A Temperature Index Model to Estimate Long-term Freeze-risk of Satsuma Mandarins Grown on the Northern Coast of the Gulf of Mexico
Authors: Ebel R.C. , Campbell B.L. , Nesbitt M.L. , Dozier W.A. , Lindsey J.K. , Wilkins B.S.
Published: January 2019

Estimates of long-term freeze-risk aid decisions regarding crop, cultivar, and rootstock selection, cultural management practices that promote cold hardiness, and methods of freeze protection. Citrus cold hardiness is mostly a function of air temperature, but historical weather records typically contain only daily maximum (Tmax) and minimum (Tmin) air temperatures. A mathematical model was developed that used Tmax and Tmin to estimate air temperature every hour during the diurnal cycle; a cold-hardiness index (CHI500) was calculated by summing the hours ≤10°C for the 500 h before each day; and the CHI500 was regressed against critical temperatures (Tc) that cause injury. The CHI500 was calculated from a weather station located within 0.1 km of an experimental grove and in the middle of the satsuma mandarin (Citrus unshiu Marc.) industry in southern Alabama. Calculation of CHI500 was verified by regressing a predicted CHI500 using Tmax and Tmin, to a measured CHI500 calculated using air temperatures measured every hour for 4 winter seasons (1999-2003). Predicted CHI500 was linearly related to measured CHI500 (r2 = 0.982). However, the slope was a little low such that trees with a CHI500 = 400, near the maximum cold-hardiness level achieved in this study, had predicted Tc that was 0.5 °C lower than measured Tc. Predicted and measured Tc were similar for nonhardened trees (CHI500 = 0). The ability of predicted Tc to estimate freeze injury was determined in 18 winter seasons where freeze injury was recorded. During injurious freeze events, predicted Tc was higher than Tmin except for a freeze on 8 Mar. 1996. In some freezes where the difference in Tc and Tmin was <0.5 °C there were no visible injury symptoms. Injury by the freeze on 8 Mar. 1996 was due, in part, to abnormally rapid deacclimation because of defoliation by an earlier freeze on 4-6 Feb. the same year. A freeze rating scale was developed that related the difference in Tc and Tmin to the extent of injury. Severe freezes were characterized by tree death (Tc - Tmin > 3.0 °C), moderate freezes by foliage kill and some stem dieback (1.0 °C ≤ Tc - Tmin ≤ 3.0 °C), and slight freezes by slight to no visible leaf injury (Tc - Tmin < 1.0 °C). The model was applied to Tmax and Tmin recorded daily from 1948 through 2004 to estimate long-term freeze-risk for economically damaging freezes (severe and moderate freeze ratings). Economically damaging freezes occurred 1 out of 4 years in the 56-year study, although 8 of the 14 freeze years occurred in two clusters, the first 5 years in the 1960s and 1980s. Potential modification of freeze-risk using within-tree microsprinkler irrigation and more cold-hardy cultivars was discussed.
Protein Changes in Response to Heat Stress in Acclimated and Nonacclimated Creeping Bentgrass
Authors: He Yali , Liu Xiaozhong , Huang Bingru
Published: January 2019

The acclimation of plants to moderately high temperature plays an important role in inducing plant tolerance to subsequent lethal high temperatures. This study was performed to investigate the effects of heat acclimation and sudden heat stress on protein synthesis and degradation in creeping bentgrass (Agrostis palustris Huds.). Plants of the cultivar Penncross were subjected to two temperature regimes in growth chambers: 1) heat acclimation—plants were exposed to a gradual increase in temperatures from 20 to 25, 30, and 35 °C for 7 days at each temperature level before being exposed to 40 °C for 28 days; and 2) sudden heat stress (nonacclimation)—plants were directly exposed to 40 °C for 28 days from 20 °C without acclimation through the gradual increase in temperatures. Heat acclimation increased plant tolerance to subsequent heat stress, as demonstrated by lower electrolyte leakage (relative EL) in leaves of heat-acclimated plants compared to nonacclimated plants at 40 °C. Heat acclimation induced expression of some heat shock proteins (HSPs), 57 and 54 kDa, detected in a salt-soluble form (cystoplasmic proteins), which were not present in unacclimated plants under heat stress. However, HSPs of 23, 36, and 66 kDa were induced by both sudden and gradual exposure to heat stress. In general, total protein content decreased under both heat acclimation and sudden heat stress. Cystoplasmic proteins was more sensitive to increasing temperatures, with a significant decline initiated at 25 °C, while sodium dodecyl sulphate (SDS)-soluble (membrane) protein content did not decrease significantly until temperature was elevated to 30 °C. The results demonstrated that both a gradual increase in temperature and sudden heat stress caused protein degradation and also induced expression of newly synthesized HSPs. Our results suggested that the induction of new HSPs during heat acclimation might be associated with the enhanced thermotolerance of creeping bentgrass, although direct correlation of these two factors is yet to be determined. This study also indicated that protein degradation could be associated with heat injury during either gradual increases in temperature or sudden heat stress.
Microsatellite Markers in Hazelnut: Isolation, Characterization, and Cross-species Amplification
Authors: Bassil Nahla V. , Botta R. , Mehlenbacher S.A.
Published: January 2019

Three microsatellite-enriched libraries of the european hazelnut (Corylus avellana L.) were constructed: library A for CA repeats, library B for GA repeats, and library C for GAA repeats. Twenty-five primer pairs amplified easy-to-score single loci and were used to investigate polymorphism among 20 C. avellana genotypes and to evaluate cross-species amplification in seven Corylus L. species. Microsatellite alleles were estimated by fluorescent capillary electrophoresis fragment sizing. The number of alleles per locus ranged from 2 to 12 (average = 7.16) in C. avellana and from 5 to 22 overall (average = 13.32). With the exception of CAC-B110, di-nucleotide SSRs were characterized by a relatively large number of alleles per locus (≥5), high average observed and expected heterozygosity (Ho and He > 0.6), and a high mean polymorphic information content (PIC ≥ 0.6) in C. avellana. In contrast, tri-nucleotide microsatellites were more homozygous (Ho = 0.4 on average) and less informative than di-nucleotide simple sequence repeats (SSRs) as indicated by a lower mean number of alleles per locus (4.5), He (0.59), and PIC (0.54). Cross-species amplification in Corylus was demonstrated. These microsatellite markers were highly heterozygous and polymorphic and differentiated among genotypes of C. avellana irrespective of geographical origin. They will aid in fingerprinting genotypes of the european hazelnut and other Corylus species, genome mapping, and genetic diversity assessments.
Optimization of Cucumber Doubled Haploid Line Production Using In Vitro Rescue of In Vivo Induced Parthenogenic Embryos
Authors: Claveria Elisabet , Garcia-Mas Jordi , Dolcet-Sanjuan Ramon
Published: January 2019

Homozygous doubled haploid lines (DHLs) from new cucumber (Cucumis sativus L.) accessions could be useful to accelerate breeding for resistant varieties. DHLs have been generated by in vitro rescue of in vivo induced parthenogenic embryos. The protocol developed involves the following: 1) induction of parthenogenic embryos by pollinating with pollen irradiated with a Co60 γ-ray source at 500 Gy; 2) in vitro rescue of putative parthenogenic embryos identified by their morphology and localized using a dissecting scope or X-ray radiography; 3) discrimination of undesirable zygotic individuals from the homozygous plants using cucumber and melon SSR markers; 4) determination of ploidy level from homozygous plants by flow cytometry; 5) in vitro chromosome doubling of haploids; and 6) acclimation and selfing of selected lines. Codominant markers and flow cytometry confirmed the gametophytic origin of plants regenerated by parthenogenesis, since all homozygous lines were haploids. No spontaneous doubled haploid plants were rescued. Chromosome doubling of haploid plants was accomplished by an in vitro treatment with 500 μm colchicine. Rescue of diploid or chimeric plants was shown by flow cytometry, prior to their acclimation and planting in the greenhouse. Selfing of colchicine-treated haploid plants allowed for the perpetuation by seed of homozygous lines. The high rate of seed set, 90% of the lines produced seed, facilitated the recovery of inbred lines. Despite some limiting factors, parthenogenesis is routinely used in a cucumber-breeding program to achieve complete homozygosity in one generation. Breeding for new commercial hybrid cultivars will be accelerated. DHLs are ideal resources for genomic analyses.
Inheritance of AFLP Markers and Their Use for Genetic Diversity Analysis in Wild and Domesticated Pawpaw [Asimina triloba (L.) Dunal]
Authors: Wang Ying , Reighard Gregory L. , Layne Desmond R. , Abbott Albert G. , Huang Hongwen
Published: January 2019

Pawpaw (Asimina triloba) produces the largest fruit native to the United States. Six linkage groups were identified for A. triloba using the interspecific cross [PPF1-5 (A. triloba) × RET (A. reticulata Shuttlw. ex Chapman)], covering 206 centimorgans (cM). A total of 134 dominant amplification fragment length polymorphism (AFLP) markers (37 polymorphic and 97 monomorphic) were employed for estimating the genetic diversity of eight wild populations and 31 cultivars and advanced selections. For the wild populations, the percentage of polymorphic loci over all populations was 28.1% for dominant markers and Nei's genetic diversity (He) were 0.077 estimated by 134 dominant markers. Genetic diversity and the percentage of polymorphic loci estimated using only polymorphic dominant AFLPs were 0.245 and 79%, respectively, which are comparable with other plant species having the same characteristics. Estimated genetic diversity within populations accounted for 81.3% of the total genetic diversity. For cultivars and advanced selections, genetic diversity estimated by 134 dominant markers was similar to that of wild pawpaw populations (He = 0.071). Thirty-one cultivars and advanced selections were delineated by as few as nine polymorphic AFLP dominant loci. Genetic relationships among wild populations, cultivars and advanced selections were further examined by unweighted pair group method with arithmetic mean (UPGMA) of Nei's unbiased genetic distance. The genetic diversity estimated for wild populations using the clustered polymorphic markers was lower than the result estimated using the nonclustered polymorphic markers. Therefore, this study indicates that the number of sampled genomic regions, instead of the number of markers, plays an important role for the genetic diversity estimates.
Inheritance of Day-neutrality in Octoploid Species of Fragaria
Authors: Serçe Sedat , Hancock James F.
Published: January 2019

The inheritance of day-neutrality in octoploid Fragaria L. was investigated in crosses between day-neutral (DN) × short day (SD) and DN × DN types using F. ×ananassa Duchesne in Lamarck cultivars and elite selections of F. virginiana Miller and F. chiloensis (L.) Miller. Genotypes were considered as DN if they flowered under both the SDs of spring before 30 May (<14 hours) and the long days of summer after 24 July (>15 hours). Wide ranges in the percentage of DN progeny were found among the families regardless of species background (30% to 87% in DN × SD and 22% to 93% in DN × DN crosses). None of the families fit the segregation ratios expected if DN was regulated by recessive alleles at one locus, and only about half of the families fit the segregation ratios expected if a single dominant allele regulated DN. Several two-gene models fit the segregation data better than the single locus ones, but none of the genetic models tested fit the DN segregation ratios at the ends of the distribution range. The wide range observed in the percentage of DN progeny across all the families is most consistent with a polygenic model. Several other kinds of observations supported the multigenic regulation of DN: 1) Different DN parents crossed to the same SD genotype often produced different percentages of DN progeny, 2) Some of the day-neutrality sources were more powerful than others in producing of DNs, and 3) None of the DN parents produced 100% DN progeny, which would be expected if there were homozygous dominant DN individuals. Specific combining abilities for DN and flowering strength were significant, while general combining abilities for these traits were not. Our results suggest that parental combinations can be selected that will generate very high proportions of DN progeny that bloom for long periods of time.
Cloning and Characterization of Two Anthocyanin Biosynthetic Genes from Dendrobium Orchid
Authors: Mudalige-Jayawickrama Rasika G. , Champagne Michele M. , Hieber A. David , Kuehnle Adelheid R.
Published: January 2019

Two full-length cDNA clones, Den-CHS-4 and Den-DFR-1, encoding chalcone synthase (CHS) and dihydroflavonol 4-reductase (DFR) were obtained from flower bud RNA of a lavender cyanidin-accumulating Dendrobium Sw. hybrid using reverse transcription-polymerase chain reaction (RT-PCR). Northern analyses indicated that both genes are expressed in all developmental stages of buds, with highest expression in the medium-sized buds. RT-PCR analyses showed that DFR expression was confined to floral tissue while CHS was expressed in floral and vegetative tissues but not in pseudobulbs. The nucleotide sequence of a DFR clone isolated from a pale orange pelargonidin-accumulating Dendrobium hybrid was exactly the same as Den-DFR-1, ruling out the substrate specificity of DFR as a possible cause of the color difference.