bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Analysis of Strawberry Root System Traits in Fumigated and Nonfumigated Soils I. Inheritance Patterns of Strawberry Root System Characteristics
Authors: Fort Sean B. , Shaw Douglas V.
Published: January 2019

Seedling offspring of crosses among 10 selected strawberry genotypes (Fragari ×ananassa Duch.) from the University of California strawberry improvement program were established in annual hill culture. Soil treatments consisted of 1) preplant fumigation using a mixture of methyl bromide and chloropicrin or 2) no fumigation. Root systems of individual plants were sampled with a soil probe in January, April, and July 1994 to determine root mass (RM), secondary root mass (SRM), and a subjective root appearance score (RAS). For each trait, genetic analyses of partial diallels were performed to quantify sources of genetic, environmental, and interaction variance. Root trait values differed significantly between soil treatments only for the April sampling date, with all trait values greater in fumigated soils than in nonfumigated soils. For RM and SRM, variance due to general combining ability (GCA) was significant in April and July. Narrow-sense heritabilities (h2) for RM increased between January (0.14) and July (0.40); SRM showed a similar trend with a higher h2 on each sampling date. GCA variances were nonsignificant for RAS, however, significant fumigation × GCA interaction variance was detected for RAS in January. Specific combining ability (SCA) variances were nonsignificant for all traits. To further quantify the extent of interactions, correlations (rg) between genotypic expressions in fumigated soils and nonfumigated soils were calculated for each root trait. These rg values were at or near unity (> 0.85) for RM and SRM on all sampling dates, implying that genetic variability for these traits is conditioned by genes with identical effects within each soil environment. Conversely, rg between soil environments was 0.52, 0.62, and -0.18, for January, April, and July RAS, respectively. These findings suggest that genetic variability exists within this germplasm base for strawberry root mass characteristics. Genetic variation also exists for January root appearance score, but it is not conditioned identically across fumigation treatments.
Development of SCAR Markers Linked to a Phytophthora fragariae Resistance Gene and Their Assessment in European and North American Strawberry Genotypes
Authors: Haymes K.M. , Van de Weg W.E. , Arens P. , Maas J.L. , Vosman B. , Nijs A.P.M. Den
Published: January 2019

Two dominant sequence characterized amplified region (SCAR) markers (linked at 3.0 cM, coupling phase) were constructed for the strawberry (Fragaria ×ananassa Duch.) gene Rpf1. This gene confers resistance to red stele root rot, caused by the soil-born fungus Phytophthora fragariae Hickman var. fragariae. The SCAR markers were developed originally from the sequence of RAPD OPO-16C(438) that is linked in repulsion phase to the Rpf1 allele. This SCAR primer set produced multiple bands in the resistant test progeny and in some of the susceptible progeny; therefore, new SCARs were developed based on the sequence differences among these bands. These new SCARs were linked in coupling phase to the Rpf allele and mapped to the same location as the original RAPD OPO-16C(438). The SCAR markers, as well as some additional RAPD markers known to be linked to Rpf1, were shown to be highly conserved in linkage to the gene based on examination of 133 European and North American Fragaria L. sp. cultivars and breeding selections. These flanking RAPD and SCAR-PCR markers can be used in breeding programs for the selection of red stele (Rpf1) resistance.
Cuticular Phenolics and Scald Development in `Delicious' Apples
Authors: Ju Zhiguo , Bramlage William J.
Published: January 2019

Influences of fruit maturity, AVG and ethephon preharvest treatments, and storage conditions on cuticular phenolic concentration, α-farnesene accumulation and oxidation, and scald development of `Delicious' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] were studied. Advanced maturity and ethephon treatment increased free phenolics in fruit cuticle at harvest, while AVG treatment caused a reduction. Free cuticular phenolics increased during early storage in ethephon-treated and nontreated fruit but not in AVG-treated apples. Advanced maturity and ethephon did not alter α-farnesene accumulation overall, but reduced conjugated triene (CT281) formation and scald development. When stored in a low-ethylene room (<1 μL·L-1), AVG-treated fruit accumulated very low levels of α-farnesene and CT281 and did not develop scald after 6 months at 0 °C. When stored in a commercial room (ambient ethylene >5 μL·L-1), the AVG-treated and control fruit accumulated similar amounts of α-farnesene and CT281 and developed similar percentages of scald. In general, free phenolic concentrations in fruit cuticle were negatively correlated with CT281 formation and scald development of apples. Chemical names used: aminoethoxyvinylglycine (AVG); 2-chloroethylphosphonic acid (ethephon).
Identification and Characterization of Storage Proteins in Zygotic and Somatic Embryos of Geranium (Pelargonium ×hortorum)
Authors: Madakadze R.M. , Krochko J.E. , Senaratna T.
Published: January 2019

Storage proteins in zygotic and somatic embryos of `Scarlet Orbit Improved', zonal geranium (Pelargonium hortorum L.H. Bail.) were identified and characterized using gel electrophoresis. The major seed storage proteins in zygotic embryos were an 11S globulin and two low molecular weight (LMW1-2) proteins. The 11S globulin consisted of four distinct subunits (53-74 ku), with each subunit being composed of an acidic polypeptide (A1-A4; 28-44 ku) linked via disulphide bonds to a basic polypeptide (B1-B4; 20-25 ku) and was named pelargin. The LMW (15.5 and 12,5 ku) albumins were not linked with disulphide bonds. Mature somatic embryos contained 80% of the proteins in zygotic embryos. Although protein profiles were more distinct in mature somatic embryos compared to nonmature, none of the zygotic embryo storage protein was present in the somatic embryos, indicating lack of complete maturity of somatic embryos. This study identified zygotic embryo proteins and demonstrated that maturation of somatic embryos improves protein content and types of proteins.
Citrus Fruit Abscission Induced by Methyl-jasmonate
Authors: Hartmond Ulrich , Yuan Rongcai , Burns Jacqueline K. , Grant Angela , Kender Walter J.
Published: January 2019

Methyl jasmonate (MJ) was tested as a potential abscission chemical to enhance mechanical harvest of `Hamlin' and `Valenica' orange [Citrus sinensis (L.) Osb.]. In field experiments, a solution of 1, 5, 10, 20, or 100 mm MJ was applied either as a stem wrap to individual fruit or as a spray to entire trees or canopy sectors. Solutions of 10, 20, and 100 mm MJ resulted in significant and consistent reduction of fruit detachment force and caused fruit drop within 7 to 10 days. Fruit loosening was preceded by an increase in the internal ethylene concentration of fruit similar to that of other experimental abscission compounds. While concentrations of 10 mm and less caused no or negligible phytotoxicity, solutions exceeding 10 mm MJ induced unacceptable levels of leaf abscission.
Photoperiod and the Difference between Day and Night Temperature Influence Stem Elongation Kinetics in Verbena bonariensis
Authors: Shimizu Hiroshi , Heins Royal D.
Published: January 2019

The effects of photoperiod and the difference between day temperature (DT) and night temperature (NT) (DIF) on stem elongation in Verbena bonariensis L. (tall verbena) were investigated. Plants were exposed to nine treatment combinations of -10, 0, or 10 °C DIF and 8-, 12-, or 16-hour photoperiods. Stem elongation was measured and analyzed by a noncontact computer-vision-based system. Total daily elongation increased as DIF increased; it also increased as photoperiod increased under positive DIF (DT > NT) and zero DIF (DT = NT), but not under negative DIF. Under positive DIF, daily elongation was 90% greater under the 16-hour photoperiod than under the 8-hour photoperiod. DIF affected elongation rate during the daily light span but not during the daily dark span. Total light-span elongation increased as DIF or photoperiod increased. Total dark-span elongation was not influenced by DIF or photoperiod. Elongation rates per hour in the light and dark were not significantly affected by photoperiod but increased in the light as DIF increased. Therefore, for a particular DIF, total elongation during 16-hour photoperiods (long days) was greater than that under 8-hour photoperiods (short days) because there were more hours of light under long days.
Light Absorption and Partitioning in Relation to Nitrogen Content in `Fuji' Apple Leaves
Authors: Cheng Lailiang , Fuchigami Leslie H. , Breen Patrick J.
Published: January 2019

Bench-grafted `Fuji' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] trees on Malling 26 (M.26) rootstocks were fertigated for 6 weeks with N concentrations ranging from 0 to 20 mm. These treatments produced levels of leaf N ranging from 0.9 to 4.3 g·m-2. Over this range, leaf absorptance increased curvilinearly from 74.8% to 92.5%. The light saturation point for CO2 assimilation expressed on the basis of absorbed light increased linearly at first with increasing leaf N, then reached a plateau at a leaf N content of ≈3 g·m-2. Under high light conditions (photosynthetic photon flux of 1500 μmol·m-2·s-1), the amount of absorbed light in excess of that required to saturate CO2 assimilation decreased with increasing leaf N. Chlorophyll fluorescence measurements revealed that the maximum photosystem II (PSII) efficiency of dark-adapted leaves was relatively constant over the leaf N range, except for a slight decrease at the lower end. As leaf N increased, nonphotochemical quenching declined under high light, and there was an increase in the efficiency with which the absorbed photons were delivered to open PSII centers. The photochemical quenching coefficient remained high except for a decrease at the lower end of the leaf N range. Actual PSII efficiency increased curvilinearly with increasing leaf N, and was highly correlated with light-saturated CO2 assimilation. The fraction of absorbed light potentially going into singlet oxygen formation was estimated to be ≈10%, regardless of leaf N status. It was concluded that there was more excess absorbed light in low N leaves than in high N leaves under high light conditions. Nonphotochemical quenching was enhanced with decreasing leaf N to reduce both the PSII efficiency and the probability of damage from photooxidation by excess absorbed light.
Lovastatin Inhibits α-Farnesene Biosynthesis and Scald Development in `Delicious' and `Granny Smith' Apples and `d'Anjou' Pears
Authors: Ju Zhiguo , Curry Eric A.
Published: January 2019

Effects of Lovastatin treatment on ethylene production, α-farnesene biosynthesis, and scald development were studied using `Delicious' and `Granny Smith' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] and `d'Anjou' pears (Pyrus communis L.) stored in air at 0 °C. During 6 months storage, Lovastatin did not affect internal ethylene concentration but reduced α-farnesene production in a concentration dependent manner in both apples and pears. Lovastatin reduced scald at 0.63 mmol·L-1 and inhibited scald completely at 1.25 or 2.50 mmol·L-1 in `Delicious' and `Granny Smith' apples. In `d'Anjou' pears, Lovastatin at concentrations from 0.25 to 1.25 mmol·L-1 inhibited scald completely. After 8 months storage, inhibition of scald in both apples and pears by Lovastatin was concentration-dependent but none of the concentrations totally eliminated scald. Compared with 11.8 mmol·L-1 diphenylamine, Lovastatin treatment reduced scald to the same level at 1.25 mmol·L-1 in `d'Anjou' pear and 2.50 mmol·L-1 in `Delicious' and `Granny Smith' apples. Lovastatin did not affect apple or pear fruit color, firmness, soluble solids content, or titratable acidity during storage in either apple or pear compared with the controls. Chemical name used: [1S-[1a (R °), 3α, 7β, 8β (2S °, 4S °), 8αβ]]-1,2,3,7,8,8α-hexahydro-3,7-dimethyl-8-[2-(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1-naphthaienyl 2-methylbutanoate (Lovastatin).
Water Relations during Ripening for Fruit of Well-watered versus Water-stressed Opuntia ficus-indica
Authors: Nerd Avinoam , Nobel Park S.
Published: January 2019

Water relations and fruit development were studied for up to 100 days after anthesis for potted plants of Opuntia ficus-indica (L.) Mill. (a prickly pear) that were either well-watered or water-stressed, each plant consisting of a medium-sized cladode bearing two or three fruit. Even though cladodes of water-stressed plants lost up to 50% of their thickness, their fruit continued to gain water and to develop; at ripening such fruit had only 16% less water than fruit of watered plants. Maturation indicated by the decrease in fractional peel content and increases in pulp weight and in pulp soluble sugar content was hastened by water stress, leading to ripening ≈88 days after anthesis for water-stressed plants, which was 10 days earlier than for watered plants. Fruit had a lower stomatal frequency than the cladodes but both exhibited Crassulacean acid metabolism behavior. Transpiration occurred mainly at night, and the daily amount of water transpired per unit fruit surface area decreased with time, especially for fruit of water-stressed plants. This decrease was related to fruit expansion (leading to decreased stomatal frequency) for watered plants and to both fruit expansion and water stress for water-stressed plants. At 75 days after anthesis, daily diameter changes of fruit were correlated with transpiration, contraction occurring at night and expansion during the daytime, and changes were greater for watered plants for which daily transpiration was higher.
Analysis of Salt Tolerance in Nine Leafy Vegetables Irrigated with Saline Drainage Water
Authors: Shannon Michael C. , Grieve Catherine M. , Lesch Scott M. , Draper John H.
Published: January 2019

Saline agricultural drainage water may be used as a resource to grow high value horticultural crops and reduce the volume of drainage for eventual disposal. To explore reuse options the effects of salinity and timing of application were tested on selected leafy vegetables grown in 24 sand culture plots in Riverside, Calif. The leafy winter vegetables included `Ruby Red Chard' Swiss chard [Beta vulgaris L. var. flavescens (Lam.) Lam.], `Space' spinach (Spinacia oleracea L.), `Vitamin Green' salad greens [Brassica rapa L. (Narinosa Group)], `Red Giant' mustard greens [Brassica juncea L. (Czerniak)], pac choi [Brassica rapa L. (Chinensis Group)], `Winterbor' kale [Brassica oleracea L. (Acephala Group)], tatsoi [Brassica rapa L. (Narinosa Group)], `Salad King' curly endive (Cichorium endivia L.), and `Red Preco No. 1' radicchio (Cichorium intybus L.). All vegetables were planted at the same time and irrigated initially with tap water and nutrients. At 3 and 7 weeks after seeding (application times), six salinity treatments were initiated by adding salts to the irrigation water to represent the chemical compositions of drainage waters found typically in the San Joaquin Valley, Calif. The six salinity treatments had electrical conductivities of 3 (control), 7, 11, 15, 19, or 23 dS·m-1. A randomized complete block design was used with (6 salinities × 2 application times × 2 replications). Within each plot a 1.5-m row of each of the nine vegetables was grown as split plots. Salinity reduced fresh weight (FW) yields of all species. Salt stress applied at 3 weeks after seeding reduced FWs for seven of the nine vegetables compared to salination at 7 weeks. Analyses of salt tolerance curves, maximum yields, and the point of 50% yield reduction (C50) were conducted. Greens produced the highest biomass at 874 g/plant, but was the most affected by application time. Swiss chard and radicchio were not significantly affected by timing of salinity application, and Swiss chard was the most salt tolerant overall. Greens, kale, pac choi, and to a lesser extent, tatsoi, have potential as winter-grown, leafy vegetables in drainage water reuse systems.
Intracanopy Lighting Influences Radiation Capture, Productivity, and Leaf Senescence in Cowpea Canopies
Authors: Frantz Jonathan M. , Joly Robert J. , Mitchell Cary A.
Published: January 2019

Traditional overhead lighting of dense crop stands in controlled environments favors development of upper leaf layers to maximize interception of light incident at the top of the foliar canopy. The resultant mutual shading of lower leaves in the understory of the canopy can severely limit productivity and yield of planophile crops. Intracanopy lighting alleviated the effects of mutual shading in dense, vegetative stands of cowpea [Vigna unguiculata (L.) Walp ssp. unguiculata] growing in a controlled environment by sustaining irradiance within the understory throughout development of this edible-foliage crop. For an overhead lighting system, photosynthetic photon flux (PPF) in the understory was reduced to 1% of its initial value by 35 days of growth. PPF in an intracanopy-lighted stand remained within 30 μmol·m-2·s-1 of initial values throughout the 50-day cropping period. Spectral distribution of radiation within the intracanopy-lighted stand also remained relatively constant throughout canopy development. In the overhead-lighted stand, violet and blue radiation in the understory decreased as much as 60% from initial values. Stability of the radiation environment within the intracanopy-lighted stand delayed leaf senescence 27 days beyond when interior leaves of the overhead-lighted canopy began to turn yellow on day 16. The intracanopy-lighted stand produced twice as much edible biomass per unit electrical energy consumed by lamps as for the overhead-lighted system. The treatment differences were due to the continuous presence of understory irradiation when using intracanopy lighting but not when using overhead lighting, and they underscore the importance of the entire foliar canopy in realizing the full productivity potential of dense crop stands in controlled environments.
Characterization of Changes in `Gala' Apple Aroma during Storage Using Osme Analysis, a Gas Chromatography-Olfactometry Technique
Authors: Plotto Anne , McDaniel Mina R. , Mattheis James P.
Published: January 2019

Changes in the odor-active volatile compounds produced by `Gala' apples [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Gala'] were measured after 4, 10, and 20 weeks storage at 1 °C in regular atmosphere (RA) or controlled atmosphere (CA), and 16 weeks in CA followed by 4 weeks in RA. Aroma was evaluated using the gas chromatography-olfactometry method Osme. Production of volatile esters decreased along with corresponding fruity aromas during CA storage. Hexyl acetate, butyl acetate, and 2-methylbutyl acetate were emitted in the largest amounts and perceived with the strongest intensities from RA-stored fruit. While hexyl acetate and butyl acetate concentrations and aroma intensities decreased during CA storage, 2-methylbutyl acetate remained at the RA concentration until apples had been stored 16 weeks in CA. Perception intensities of methylbutyrate esters with apple or berrylike odors decreased less than straight chain esters in CA-stored fruit. 4-Allylanisole, ß-damascenone, and 1-octen-3-ol, as well as an unknown compound with a watermelon descriptor, were perceived more in RA-stored fruit than in CA-stored apples. Factor analysis indicated the importance of these compounds in `Gala' apples stored 4 weeks in RA. Even though these compounds do not have an apple odor, they contribute to fresh `Gala' aroma.
Mealiness and Pectolytic Activity in Peaches and Nectarines in Response to Heat Treatment and Cold Storage
Authors: Obenland David M. , Carroll Tanya R.
Published: January 2019

`Elegant Lady', `O'Henry' and `September Sun' peaches [(Prunus persica (L.) Batsch (Peach Group)] and `Summer Bright' and `Summer Grand' nectarines [(Prunus persica (L.) Batsch f. nucipersica (Nectarine Group)] heated to a seed surface temperature of 47.2 °C over a period of 4 hours developed mealy flesh sooner and to a much greater extent than nonheated fruit following cold storage at 5 °C for 1 to 3 weeks. Exo- and endopolygalacturonase activities were reduced following 3 to 4 hours of heating and may have been responsible for the increased mealiness. Mealiness often developed in defined regions rather than throughout the entire fruit. Comparison of juicy and mealy regions within individual fruit revealed that mealy regions contained 65% and 86% less exo- and endopolygalacturonase activity, respectively, than juicy regions, whereas pectinmethylesterase activity was unchanged. Extractable protein was reduced by >50% in the mealy regions of the fruit. Intermittent warming periods of 24 hours at 20 °C at weekly intervals during storage at 5 °C were less effective in reducing mealiness in heat-treated than in control fruit. It is important that future work with heat treatments and stone fruit closely monitor potential effects on this disorder to avoid loss of market quality following treatment.
Chitosan Effects on Blackmold Rot and Pathogenic Factors Produced by Alternaria alternata in Postharvest Tomatoes
Authors: Reddy M.V. Bhaskara , Angers Paul , Castaigne Francois , Arul Joseph
Published: January 2019

Stem scar application of chitosan inhibited growth and production of pathogenic factors by blackmold rot [Alternaria alternata (Fr.:Fr.) Keissl.] in challenged tomato (Lycopersicon esculentum Mill.) fruit stored at 20 °C for 28 days. Blackmold lesions were visible within 4 days of inoculation in control fruit, compared with >7 days in chitosantreated fruit. Macerating enzyme activity (polygalacturonase, pectate lyase, and cellulase) in the tissue in the vicinity of the lesions was <50% in chitosan-treated fruit compared with control fruit. Chitosan also inhibited production of oxalic and fumaric acids (chelating agents) and host-specific toxins such as alternariol and alternariol monomethylether by the fungus. The pH of the infected tissue decreased from 4.7 to 4.0 in the control fruit, the optimum for polygalacturonase activity, while the pH of chitosan-treated fruit remained at 4.6. In addition, chitosan also induced production of rishitin (a phytoalexin) in tomato tissue. Such chitosan-pathogen-host interactions may be exploited in the control of postharvest pathogens of fresh fruit and vegetables.
Phosphate and Potassium Retention and Release during Chrysanthemum Production from Precharged Materials: I. Alumina
Authors: Williams Kimberly A. , Nelson Paul V. , Hesterberg Dean
Published: January 2019

Soilless root media have little capacity to retain PO4 or K, and this contributes to leaching of these nutrients during greenhouse crop production. The objective of this research was to evaluate the suitability of precharged alumina as a sole source of PO4 and K during greenhouse production of potted chrysanthemum [Dendranthema ×grandiflora Kitam. (syn. Chrysanthemum ×morifolium Ramat.)]. Phosphate and K adsorption and desorption curves were created at 25 °C for two particle sizes (0.5 to 0.9 and 1.8 to 3.2 mm) of alumina (Al2O3; acid-washed and unwashed), and a medium of 7 peat: 3 perlite (v/v) using solutions of KH2 PO4 (P at 0 to 20,000 mg.L-1). Based on these curves, 1.8 to 3.2 mm, unwashed alumina was selected for use in the studies. Precharged alumina was tested in two greenhouse studies at 10% and 30% (v/v) of a peat-perlite medium used to produce `Sunny Mandalay' chrysanthemum. Phosphate, K, and pH were determined on unaltered root medium solutions collected throughout the 10-week cropping cycle, and foliar analyses were conducted on tissue collected at the middle and end of the cycle. Potassium release was adequate to meet chrysanthemum demand for 4 weeks, but inadequate for the remainder of the production cycle. Precharged alumina retained and released PO4 at sustained concentrations (P at <2 mg·L-1) over the course of a 10-week cropping cycle. Growth of plants receiving PO4 from precharged alumina was not significantly different from the controls receiving liquid fertilizer (P at 46.5 mg·L-1) at each watering when precharged alumina comprised 30% of the medium, and only slightly less when precharged alumina comprised 10% of the medium. A phosphorus budget showed that while 36% (103 mg) of the applied PO4-P was lost in the leachate of the controls, only 0.1% (2 mg) was lost from plants produced with alumina-P. This research demonstrates that in a soilless medium with physical properties similar to standard commercial mixes, low but adequate PO4 concentrations can be achieved and sustained using current production practices.
Diallel Analysis of High Carotenoid Content in Cucumbers
Authors: Navazio John P. , Simon Philipp W.
Published: January 2019

Three orange-mesocarp derivatives of the xishuangbannan cucumber (Cucumis sativus L. var. xishuangbannanesis Qi et Yuan), P100, P101, and P104; and NPI (P105), an unrelated cucumber (Cucumis sativus L.) reported to have orange flesh, were selected as parents for a diallel experiment to evaluate inheritance of orange cucumber mesocarp pigment over 3 years. Visual color intensity and carotenoid content were closely related. A preponderance of additive genetic effects for cucumber mesocarp pigmentation was observed in grade size 2 fruit (immature fruit used for pickling). Both additive and nonadditive genetic effects were important in grade size 4 fruit (mature). Years and yea× genotype interactions were highly significant for pigmentation of size 2 fruit, indicating the importance of environment on the expression of pigmentation in this size class. In contrast, color development was stable among years for size 4 fruit. P104 exhibited high general combining ability (GCA) estimates for size 4 fruit pigmentation across years, while P101 had high GCA estimates for size 2 fruit. The diallel analysis illustrated high fruit carotene content of parents per se. However, most hybrid combinations of the diallel reduced carotenoid content relative to parents, indicating both dominance for low carotenoid content for both fruit sizes and lack of genetic complementation among parents to enhance fruit color. Genetic control of pigmentation in size 2 fruit appeared to be independent of that for size 4 fruit.
Heat Shocks Applied either before or after Wounding Reduce Browning of Lettuce Leaf Tissue
Authors: Loaiza-Velarde Julio G. , Saltveit Mikal E.
Published: January 2019

Wounds and injuries incurred during preparation of fresh-cut lettuce (Lactuca sativa L.) stimulate phenolic metabolism, which leads to tissue browning. Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5.) is the first committed enzyme in the phenylpropanoid pathway and regulates its overall activity. Maximum activity of wound-induced PAL occurred sooner as the storage temperature increased from 0 to 25 °C, but the maximums were lower. A heat shock at 50 °C for 90 seconds protected fresh-cut lettuce tissue against browning, helped retain greenness, and decreased subsequent production of phenolics when applied either after or before wounding. Browning was reduced when the heat shock was applied up to 36 hours after wounding, while the maximum effect occurs around 6 hours before cutting. Like the heat-shock treatment, the protein synthesis inhibitor cycloheximide reduced wound-induced PAL activity, but it did not prevent tissue browning. When cycloheximide was applied in combination with heat-shock treatments, browning did not occur. Heat shocks may control tissue browning by more than just interfering with protein synthesis.
Plant Oil Emulsions Prevent Senescent Scald and Core Breakdown and Reduce Fungal Decay in `Bartlett' Pears
Authors: Ju Zhiguo , Curry Eric A. , Duan Yousheng , Ju Zhiqiang , Guo Aixin
Published: January 2019

Preclimacteric `Bartlett' pears (Pyrus communis L.) were dipped for 3 min in either corn (Zea mays L.) or soybean [(Glycine max (L.) Merrill] oil emulsion immediately after harvest and stored at 0 °C. Untreated control fruit developed higher percentages of senescent scald, core breakdown, and decay after 15 weeks storage. Both treatments inhibited senescent scald, core breakdown, and decay in a similar and concentration dependent manner. Complete control of senescent scald and core breakdown was achieved by emulsions at 5% and 10%, and of decay by emulsion at 10%. Compared with controls, emulsion treatments delayed and reduced internal ethylene accumulation and volatile production in early storage and increased them in late storage. Compared with controls, fruit treated with oil contained similar levels of internal O2 and CO2 in early storage and higher CO2 and lower O2 in late storage. While control fruit lost commercial value after 15 weeks at 0 °C plus 5 days at 20 °C, oil-treated fruit exhibited normal color change, and had higher soluble solids, titratable acidity, and volatile production. Microscopic examination revealed that emulsion-treated fruit had a continuous surface film conforming to the contour of the fruit.
Developmental Consequences of Cold Temperature Stress at Transplanting on Seedling and Field Growth and Yield. II. Muskmelon
Authors: Korkmaz Ahmet , Dufault Robert J.
Published: January 2019

For the earliest yields of spring melons, muskmelon [Cucumis melo L. (Reticulatus Group)] fields in the southeast United States may be transplanted in late winter before the last frost date. Seedlings may be exposed to cold temperatures cycling between almost freezing and optimal for weeks before warm weather predominates and such exposure may reduce later growth and yields. To test whether cold stress may reduce growth and yield, `Athena' muskmelon seedlings were subjected to cold stress at 2 ± 1 °C then transferred to a greenhouse at 29 ± 5 °C before field transplanting. In 1997, cold exposure durations were 3, 6, or 9 h and were repeated (frequency) for 1, 3, 6, or 9 d before transplanting. In 1998, duration levels were not changed but frequencies were 3, 6, or 9 d. In 1997, as cold stress increased, seedling shoot and root fresh and dry weights, height, leaf area, and leaf chlorophyll content decreased linearly, but shoot carbohydrates decreased curvilinearly and stabilized with ≈54 hours cold stress. In 1998, all seedling growth characteristics except leaf chlorophyll content decreased linearly as cold stress exposure increased. Leaf chlorophyll content decreased curvilinearly as cold stress increased to 36 h, but leveled off with more hours of cold stress. Even 1 week after transplanting, plants exposed to cold stress for up to 81 h continued to transpire more than control plants. In both years, vining (date first runner touched the ground) and male and female flowering were delayed significantly with increasing cold stress, but fruit set was affected only in 1998. Cold stress in 1998 delayed earliness with early fruit weight and number per plot decreasing as cold stress exposure increased. Total yields decreased linearly in both years as cold stress increased with 21 to 32 hours causing 10% yield reduction in 1997 and 1998, respectively. Results indicate a potential risk exists for yield reduction if `Athena' muskmelon is planted weeks before last frost dates.
Inheritance of Resistance in Tomato to Race T3 of the Bacterial Spot Pathogen
Authors: Scott J.W. , Jones J.B. , Somodi G.C.
Published: January 2019

Hawaii 7981 tomato (Lycopersicon esculentum Mill.), resistant to race T3 of the bacterial spot pathogen [Xanthomonas campestris pv. vesicatoria (Doidge) Dye], was crossed to the susceptible tomato inbred, Fla. 7060, and subsequently F2 and backcross seed were obtained. These generations were planted in the field, inoculated with the race T3 pathogen and evaluated for disease severity over two summer seasons. Data were tested for goodness-of-fit to a model based on control by the incompletely dominant gene Xv3 that confers hypersensitivity. The F1 was intermediate in disease severity to the parents for both seasons. When data were combined over both seasons, the backcrosses fit the expected 1:1 ratios although each deviated from the expected ratio in one of the 2 years tested. The F2 did not fit the expected 1:2:1 ratio in either year or when data from the two years were combined due to a deficiency of resistant plants. Thirty-three F2 plants representing an array of disease severities and hypersensitivity reactions were selected in the second season and their F3 progeny were inoculated and evaluated for disease severity. Hawaii 7981 was significantly more resistant than the 12 most resistant F3 selections even though all expressed hypersensitivity. A hypersensitive F3 with intermediate field resistance was crossed to Hawaii 7981 and subsequently, F2 and backcross generations were obtained. These generations were field inoculated with the race T3 pathogen and evaluated for disease severity. Hawaii 7981 was significantly more resistant than the F3 parent as in the previous year. The data did not fit an additive-dominance model and epistatic interactions were significant. Thus, it appears that field resistance to race T3 of bacterial spot found in Hawaii 7981 is conferred quantitatively by Xv3 and other resistance genes. Breeding implications are discussed.
Genetic Relationships among Cultivated Diploid Plums and Their Progenitors as Determined by RAPD Markers
Authors: Boonprakob Unaroj , Byrne David H. , Graham Charles J. , Okie W.R. , Beckman Thomas , Smith Brian R.
Published: January 2019

Diploid plums (Prunus L. sp.) and their progenitor species were characterized for randomly amplified polymorphic DNA polymorphisms. Bootstrap analysis indicated the variance of genetic similarities differed little when the sample size was >80 markers. Two species from China (Prunus salicina Lindl. and P. simonii Carr.) and one species from Europe (P. cerasifera Ehrh.) contributed the bulk (72% to 90%) of the genetic background to the cultivated diploid plum. The southeastern plum gene pool was more diverse than those from California, Florida, or South Africa because of the greater contribution of P. cerasifera and P. angustifolia Marsh. to its genetic background.
Response of Nicotiana alata to Insertion of an Autoregulated Senescence- inhibition Gene
Authors: Schroeder Kenneth R. , Stimart Dennis P. , Nordheim Erik V.
Published: January 2019

Nicotiana alata Link and Otto (Jasmine tobacco) was transformed with an autoregulated senescence-inhibition gene construct PSAG12-IPT encoding isopentenyl transferase via Agrobacterium-mediated transformation. Transformation was confirmed by polymerase chain reaction. Transgenic plants exhibited up to 2- to 4-fold fewer senesced leaves, 29% longer in situ flower life, 26% more shoot dry weight, and a 32% to 50% reduction in flowers per branch. Additionally, transgenics were 28% shorter and had up to 174% more branches, indicative of cytokinin overproduction and a lack of tight autoregulation of PSAG12-IPT. Variation among independent transgenics suggests selection for enhanced PSAG12-IPT is feasible. Our observations of increased branching and in situ flower longevity, as well as reduced plant height and flowers per branch provide new information on PSAG12-IPT and its potential value for biological study and horticultural application.
Properly Timed Soil-applied Nitrogen Fertilizer Increases Yield and Fruit Size of `Hass' Avocado
Authors: Lovatt Carol J.
Published: January 2019

To protect groundwater from potential nitrate pollution, `Hass' avocado (Persea americana Mill.) growers in California divide the total annual soil-applied nitrogen (N) fertilizer (N at 56 to 168 kg·ha-1) into small applications made during the period from late January to early November. However, no research had been conducted to test the efficacy of this fertilization practice, and there was concern that the amount of N in the individual applications may be too little to meet the demand of the tree at some stages of its phenology. The research presented herein addressed the question of whether yield of `Hass' avocado could be increased by doubling the amount of N currently applied during specific stages of tree phenology. The control in this experiment was the practice of annually applying N as NH4NO3 at 168 kg·ha-1 (168 trees/ha) in six small doses of N at 28 kg·ha-1 in January, February, April, June, July, and November. From these six application times, five were selected on the basis of tree phenology and additional N as NH4NO3 at 28 kg·ha-1 was applied at each time for total annual N of 196 kg·ha-1. Two phenological stages were identified for which N application at 56 kg·ha-1 in a single application (double dose of N) significantly increased the 4-year cumulative yield (kilograms fruit per tree) 30% and 39%, respectively, compared to control trees (P ≤ 0.01). In each case, more than 70% of the net increase in yield was commercially valuable large size fruit (178 to 325 g/fruit). The two phenological stages were when shoot apical buds have four or more secondary axis inflorescence meristems present (mid-November); and during anthesis to early fruit set and initiation of the vegetative shoot flush at the apex of indeterminate floral shoots (about mid-April). When the double dose of N was applied at either of these two stages, the kilograms and number of large size fruit averaged across the 4 years of the study was significantly greater than the control trees (P ≤ 0.01). Averaged across the 4 years of the study, only the November treatment increased yield compared to the control trees (P ≤ 0.05). Application of the double dose of N at flower initiation (January), during early-stage gynoecium development (February), or during June drop had no significant effect on average or cumulative yield or fruit size compared to control trees. Application of the double dose of N in April significantly reduced the severity of alternate bearing (P ≤ 0.05). Yield was not significantly correlated with leaf N concentration. Time and rate of N application are factors that can be optimized to increase yield, fruit size, and annual cropping of `Hass' avocado. When the amounts of N applied were equal (196 kg·ha-1), time of application was the more important factor.
Pyridine Nucleotide Charge Reduces Photosynthesis under Short-term Oxygen Deficiency
Authors: Zude-Sasse Manuela , Hartmond Ulrich , Ebert Georg , Lüdders Peter
Published: January 2019

Soil flooding reduces partial pressure of oxygen (pO2) in the root zone and often results in a reduction in photosynthesis and growth. In greenhouse studies, rooted stem cuttings of the mango (Mangifera indica L.) rootstock selection 13/1 were exposed to anoxia by saturating the root zone with N2 for up to 52 h. Reduced pO2 in the root zone affected the energy status of the roots and particularly enhanced the phosphorylated and nonphosphorylated pyridine nucleotide charges—the ratio of reduced Nicotinamide-adenine-dinucleotides [NAD(P)H] to total Nicotinamide-adenine-dinucleotide content [oxidized NAD(P)+ plus NAD(P)H]—that drive the redox reaction rates in cell metabolism. Also, the pyridine nucleotide charges in leaves were enhanced, while the photosynthetic rate decreased following reduction in pO2 in the root zone. During up to 4 h of reduced pO2, the ratio of internal CO2 concentration in the mesophyll to ambient CO2 concentration was unchanged. This implies a nonstomatal influence on photosynthesis. In addition, light saturation of photosystem II occurred at lower irradiance (470 μmol·m-2·s-1) resulting in reduced maximum photochemical efficiency below that of the high pO2 controls. After 28 h of reduced pO2, NAD(P) charges in the leaves returned to normal, diminishing its potential effect on net photosynthetic rate.
Carotenoid Content and Color in Diploid Potatoes
Authors: Lu Wenhe , Haynes Kathleen , Wiley Eugene , Clevidence Beverly
Published: January 2019

The yellow pigment in potato (Solanum L. sp.) tuber flesh is caused by various carotenoids that may protect against cancer, cardiovascular disease, and macular eye degeneration. The objectives of this research were to 1) identify and quantify the carotenoids present in 11 diploid clones from a hybrid population of Solanum phureja ssp. phureja Juz. & Bukasov-S. stenotomum ssp. stenotomum Juz. & Bukasov and two tetraploid potato cultivars (the yellow-fleshed `Yukon Gold' and the white-fleshed `Superior'), and 2) determine the relationship between tuber yellow intensity and carotenoid content. Yellow intensity was measured by a colorimeter programmed to calculate a yellowness index, YI E-313. Carotenoid analyses were performed on an automated high-performance liquid chromatography system with software for integration and quantitation with detection at 450 nm using a diode array detector. Six major carotenoids were detected: neoxanthin, violaxanthin, lutein-5,6-epoxide, lutein, zeaxanthin, and an unknown carotenoid. Total carotenoid content in the yellow-fleshed diploid clones was 3 to 13 times higher than `Yukon Gold' and 4 to 22 times higher than `Superior'. Both total and individual carotenoid contents were positively correlated with tuber yellow intensity. There was an exponential relationship between total carotenoid content and tuber yellow intensity. This suggests that selecting for more intense yellow flesh will result in higher levels of carotenoids. These specific diploid clones were selected for this study because they produced at least five percent 2n pollen; they have the potential to make significant contributions to improving the nutritional status of tetraploid potatoes through 4x-2x hybridizations.
Early Growth of Muskmelon in Mulched Minitunnels Containing a Thermal Water Tube. I. Carbon Dioxide Concentrations in the Tunnel
Authors: Aziz Fahrurrozi , Stewart Katrine A. , Jenni Sylvie
Published: January 2019

Temperature modification is the most investigated environmental factor considered to affect muskmelon (Cucumis melo L. Reticulatus Group) growth in a mulched minitunnel production system. Until now, effects on CO2 concentrations within the tunnel have been ignored. Experiments on production of `Earligold' netted muskmelon were conducted in 1997, 1998, and 1999 to determine daily CO2 concentrations for 10 mulched minitunnel and thermal water tube combinations. Carbon dioxide concentrations under nonperforated (clear or infrared-blocking polyethylene) tunnels were significantly higher (three to four times) than that of ambient air. Soil respiration under the plastic mulch was primarily responsible for increased CO2 levels in the tunnel. Daily CO2 concentrations in the tunnels varied little during early muskmelon growth, but fluctuated widely as the plants developed. Ventilation significantly decreased CO2 concentrations in the tunnels but levels remained significantly above the control and perforated tunnel treatments. When using mulched minitunnels for muskmelon production, daily CO2 concentrations should be recognized as a significant factor influencing growth.
Postulated Physiological Roles of the Seven-carbon Sugars, Mannoheptulose, and Perseitol in Avocado
Authors: Liu Xuan , Sievert James , Arpaia Mary Lu , Madore Monica A.
Published: January 2019

Avocado (Persea americana Mill.) tissues contain high levels of the seven-carbon (C7) ketosugar mannoheptulose and its polyol form, perseitol. Radiolabeling of intact leaves of `Hass' avocado on `Duke 7' rootstock indicated that both perseitol and mannoheptulose are not only primary products of photosynthetic CO2 fixation but are also exported in the phloem. In cell-free extracts from mature source leaves, formation of the C7 backbone occurred by condensation of a three-carbon metabolite (dihydroxyacetone-P) with a four-carbon metabolite (erythrose-4-P) to form sedoheptulose-1,7-bis-P, followed by isomerization to a phosphorylated d-mannoheptulose derivative. A transketolase reaction was also observed which converted five-carbon metabolites (ribose-5-P and xylulose-5-P) to form the C7 metabolite, sedoheptulose-7-P, but this compound was not metabolized further to mannoheptulose. This suggests that C7 sugars are formed from the Calvin Cycle, not oxidative pentose phosphate pathway, reactions in avocado leaves. In avocado fruit, C7 sugars were present in substantial quantities and the normal ripening processes (fruit softening, ethylene production, and climacteric respiration rise), which occurs several days after the fruit is picked, did not occur until levels of C7 sugars dropped below an apparent threshold concentration of ≈20 mg·g-1 fresh weight. The effect of picking could be mimicked by girdling the fruit stalks, which resulted in ripening on the tree. Again, ripening followed a decline in C7 sugars to below an apparent threshold level. Taken together, these data indicate that the C7 sugars play important roles in carbon allocation processes in the avocado tree, including a possible novel role as phloem-mobile ripening inhibitors.
Long-term Exposure to Ethylene Affects Polyamine Levels and Sprout Development in `Russet Burbank' and `Shepody' Potatoes
Authors: Jeong Jin-Cheol , Prange Robert K. , Daniels-Lake Barbara J.
Published: January 2019

Potato (Solanum tuberosum L. `Russet Burbank' and `Shepody') tubers were exposed to continuous 4 μL·L-1 (166 μmol·m-3) ethylene in air. Treatment started after 8 weeks in storage and continued up to 33 weeks of storage at 9 °C over one (`Russet Burbank') or two (`Shepody') storage seasons. Tubers were sampled at 3 week (`Shepody') or 5 week (`Russet Burbank') intervals for polyamine content [putrescine, (PUT); spermidine, (SPD); and spermine, (SPM)] and sprout number and fresh weight per tuber. During the storage period, `Shepody' had higher concentrations of all three polyamines and a higher PUT/(SPD + SPM) ratio, compared with `Russet Burbank'. All three polyamines in both cultivars increased during storage, and the increase was more rapid in `Shepody' than in `Russet Burbank'. Regardless of cultivar and year, exposure to ethylene induced higher spermidine (SPD) content and a lower PUT/(SPD + SPM) ratio, compared with the air treatment. Sprouts appeared later and were smaller on ethylene-treated tubers and were more numerous in `Russet Burbank'. These long-term ethylene effects may be due, in part, to enhanced transformation of PUT to SPD.
Indian Mustard and Allyl Isothiocyanate Inhibit Sclerotium rolfsii
Authors: Harvey Stephanie G. , Hannahan Heather N. , Sams Carl E.
Published: January 2019

Allyl isothiocyanate (AITC) is the predominant isothiocyanate produced by damaged tissues of Indian mustard (Brassica juncea (L) Czerniak). This study investigated Indian mustard and AITC mediated suppression of mycelial growth and sclerotial germination of Sclerotium rolfsii Saccardo, a common soilborne pathogen. Indian mustard (IM) treatments of 0, 0.1, 0.2, 0.6, 1.0, 2.0, 4.1, 5.1, 10.2, 20.4, 40.8, 81.6, and 163.3 g·L-1 (weight of reconstituted mustard per liter of air) were evaluated for suppression of mycelial growth. Treatment effect was evaluated by measuring the radial growth of mycelia. Sclerotia were placed in culture tubes containing 18 g autoclaved soil and covered with an additional 5 g soil. AITC at concentrations of 0, 4.0, 16.0, 64.0, 256.0, 1024.0, or 4096.0 μmol·L-1 was injected into the tubes. Treated sclerotia were removed from tubes and plated on potato dextrose agar to determine viability. Mycelial growth was inhibited with IM treatments (P < 0.01). Inhibiting concentrations (IC) of IM for mycelial growth inhibition of 50% and 90% were 0.7 and 1.0 g·L-1, respectively, with death resulting with >2 g·L-1. Inhibition attributable to AITC alone was lower than that achieved by IM producing equivalent amounts of AITC. Germination of sclerotia was negatively correlated with AITC concentration (r = 0.96; P < 0.01). The IC50 and IC90, of AITC were 249.0 and 528.8 μmol·L-1, respectively, at 42 hours. The lethal concentration for sclerotia was not reached; only suppression occurred at the highest treatment concentrations. Sclerotium rolfsii mycelia were sensitive to the IM volatiles and were suppressed at low concentrations. Sclerotia were more resistant than the mycelia and required higher concentrations of AITC to suppress germination.