bluuebunny/crossref_metadata_2025 huggingface dataset:
(383) Effect of Harmony and Freedom Rootstocks on Yield and Quality of `Red Globe' Table Grapes
Authors: Valenzuela-Ruiz Manuelde Jesus , Robles-Contreras Fabián , Grijalva-Contreras Raul Leonel , Macias-Duarte Rubén
Published: February 2019

The region of Caborca, Sonora, Mexico, is one of the main area producers of table grapes, in particular the cultivar Red Globe. However, the main problems in the region include shortage and high cost of water, nematode infestation, and salinity. The objective of the present research was to determine the behavior of `Red Globe' cultivated on the rootstocks Harmony and Freedom. This study was carried out in the INIFAP Caborca research station in the year 2002, and consisted of 10 plants for treatment (on each rootstock). When water was low, a drip irrigation system was used. There was a completely randomized statistical design. We observed no differences among the two rootstocks in the different phonological stages (budbreak, flowering, and harvest time). The results indicated statistical differences between the rootstocks. Yield was higher on Freedom rootstock, with 2120 boxes/ha (boxes of 10 kg), an average of 470 boxes/ha more than on Harmony rootstock. Freedom rootstock also improved the quality of the grape (better color, bigger size of berry, and clusters, and the foliage was also more developed with this rootstock). In both rootstocks, nematode control was 100%, 30% in water consumption, and no fertilizer was used.
(384) Raisin Production of `Fiesta Seedless' on Freedom Rootstock under Different Plantation Densities
Authors: Valenzuela-Ruiz Manuelde Jesus , Grijalva-Contreras Raul Leonel , Robles-Contreras Fabián , Macias-Duarte Rubén
Published: February 2019

Grape is one of the more important crops in northwestern Mexico (Sonora), especially for table grape. Although raisin production is a good option, it must be efficient and productive due to the problems of shortage and high cost of water, salinity, and nematodes. The objective of this research was the evaluation of `Fiesta Seedless' on Freedom rootstock for raisin production with different plantation densities. This study was carried out in the INIFAP Caborca research station in 2002. Four plant separations (1.0, 1.5, 1.7, and 2.0 m) were evaluated on furrows 4 m apart. Plants were grafted on Freedom rootstock in 1999. We also considered a control treatment (4 × 2 m on its own feet) and fertilized it with 80N–60P–80K. All experiments were carried out under the espalier training system with double crossbeam; watering was under a drip-irrigation system; and the statistical design was completely randomized. Statistical differences between the evaluated spacings were not observed, but all densities surpassed the control. Greatest yields were obtained with 1.5- and 1.7-m spacings, at 6.1 and 6.0 t·ha-1 of raisin, respectively, which were 2.2 t·ha-1 more than the control (3.8 t·ha-1). There were no differences in sugar content and harvest time, since all treatmens, including the control, were harvested at 24 °Brix. Freedom rootstock had 100% nematode control, 30% less water consumption, and was not fertilized.
(387) Evaluating the Resistance against Anthracnose by Bioassay using Culture Filtrates from Elsinoe ampelina
Authors: Yun Hae Keun , Park Kyo Sun , Rho Jeong Ho , Jo Hyeon Mo
Published: February 2019

Breeding of cultivars resistant to anthracnose is one of the most important grape-breeding goals in Korea. Culture filtrates produced by E. ampelina were used to determine varietal susceptibility to anthracnose in grape cultivars as a substitute for pathogen inoculation or field screening in this study. Resistance evaluated by bioassay of grape leaves with culture filtrates and their ethyl acetate extracts was compared with ones from pathogen inoculation and field screening. To evaluate the resistance to anthracnose disease in grape germplasm, European grapes, American grapes, and Vitis hybrids were tested. Bioassay with culture filtrates produced by the pathogen showed that `Black Eye', `Mario', `Niunai', `Rizamat', and `Rosario Bianco' were sensitive; and `Campbell Early', `Niagara', and `Honey Red' were tolerant to anthracnose. In the result of anthracnose resistance evaluation by pathogen inoculation, some cultivars, such as `Black Swan','Rizamat', `Rosario Bianco', and `Kaiji', were susceptible; and others, such as `Campbell Early', `Niagara', `Sheridan', and `Izumo Queen', were found to be resistant to anthracnose. Evaluation in the vineyard showed that `Black Eye', `Mario', `Niunai', `Rizamat', and `Rosario Bianco' were susceptible; `Campbell Early', `Niagara', and `Honey Red' were resistant. The results of bioassay with culture filtrates of the pathogen were consistent with ones from the results by pathogen inoculation and screening in the vineyard.
(411) Companion Choice, Crop Density, and Mixture Ratio Affect Polyculture Yield Advantage
Authors: Bomford Michael K.
Published: February 2019

Polycultures are thought to offer yield advantages over monocultures when net competition between plants of different species is less than that between plants of the same species. Planting density and crop ratios may both alter these competitive effects. To observe such effects, dicultures of basil (Ocimumbasilicum L.), brussels sprout (Brassica oleracea L.), and tomato (Lycopersicumesculentum Mill.) were grown organically at a range of ratios and densities (1–47 plants/m2) over two field seasons. Relative land output (RLO) values were calculated from field data and from modeled yield-density-ratio surfaces. Both methods showed yield advantages from polyculture at high planting densities (RLO = 2.20 @ top density), but not at low densities. Dicultures offered a 19% yield advantage, on average. Competition for resources was compared by measuring canopy light interception and soil moisture content, showing tomato to be the most competitive crop, followed by brussels sprout, then basil. Diculture yield advantages were most pronounced when individuals of a less competitive species outnumbered those of a more competitive species. Yield advantages were 36% and 20% for dicultures dominated by basil and brussels sprout, respectively.

Dicultures dominated by tomato offered no yield advantage. The results are discussed in terms of the current ecological understanding of plant interactions, and possible advantages to be derived from small-scale intercropping, popularly termed companion planting.
(219) Nitrogen Relationships to Yield and Quality of Carrots Grown on Mineral and Organic Soil in Ontario
Authors: Westerveld Sean , McKeown Alan , McDonald Mary Ruth
Published: February 2019

In previous work with carrots (Daucus carota L.), little effect of nitrogen could be found on yield, but low nitrogen increased foliar disease. To determine if residual soil nitrate supplies sufficient nitrogen for carrots, plots were located on the same site for 3 years. Two sites were selected, one sand (pH 8.1, 2.6% OM), one organic (pH 6.0, 75% OM). Treatments consisted of 0%, 50%, 100%, 150%, and 200% of recommended levels (kg·ha-1) for organic (60) and mineral soils (110), plots were spilt in half with one fertilized every year, one in 2002 and were arranged in a split plot design with four replications. Foliar and soil samples were taken for nitrate analysis plus levels of Alternariadauci and Cercospora carotae foliar blight were recorded each year. Applied nitrogen had no effect on yield on muck soils. Over 3 years on mineral soils, total yield ranged from 36 to 48 t·ha-1 with no applied N. On mineral soils, yield was maximized at (kg·ha-1) 110, over 165, and 55-165 in 2002, 2003, and 2004, respectively. Stands on mineral soils were reduced at or above recommended rates in 2004. It is possible that carrots obtained considerable nitrogen perhaps deep in the soil profile. As in previous studies, applied nitrogen reduced foliar blights. Thus, nitrogen application is required for pest management purposes even if there is almost sufficient residual nitrogen for yield.
(430) Leaf Gas Exchange of Carrots in Response to Increasing Leaf Temperatures
Authors: Pettipas F. Christine , Lada Rajasekaran R. , Gordon Robert , Astatkie Tess
Published: February 2019

Increasing temperature as a result of global climate change is expected to exert a great influence on agricultural crops, possibly through effects on photosynthesis. Response to temperature of leaf gas exchange parameters of carrot (Daucus carota L. var. sativus) cultivars Cascade, Carson, Oranza, and Red Core Chantenay (RCC) were examined in a controlled growth room experiment. Leaf net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were measured at temperatures ranging from 15 to 35 °C at 370 μmol·mol-1 (CO2) and 450±20 μmol·m-2·s-1 PAR. The cultivars responded similarly to increasing temperature and did not differ in most photosynthetic parameters except gs. The PN increased between 20 and 30 °C, thereafter increasing only slightly to 35 °C. On average, increasing temperature from 20 to 30 °C increased PN by 69%. Carboxylation efficiencies (Ca/Ci ratio) ranged from 1.12–2.33 mmol·mol-1 while maximum PN were 3.25, 3.90, 5.49, 4.19 μmol·m-2·s-1 for Carson, RCC, Cascade, and Oranza, respectively. The E did not reach maximum at 35 °C while gs peaked at 30 °C and then decreased by 93% at 35 °C. The water use efficiency (WUE) decreased with an increase in temperature due to increases in both PN and E. The results indicate that increasing temperatures above the seasonal average (<20 °C) increases both PN and E up to 30–35 °C. An increase in photosynthesis due to an increase in temperature is expected to hasten growth. Carrots may be able to withstand a moderate increase in temperature.
(438) Searching for Cold Hardy Lace-bark Elm (Ulmus parvifolia Jacq.) for Northern Latitudes
Authors: Shirazi A.M. , Ware G.H.
Published: February 2019

The genus Ulmus contains numerous stress-tolerant species, especially those from areas of China with climates similar to various regions of the United States. Lace-bark elm, Ulmus parvifolia, the true Chinese elm, has an extensive temperature distribution range in China and offers great promise as a street tree. The high resistance of this elm to Dutch elm disease and other elm problems makes it an excellent tree for urban landscapes. Two new U. parvifolia cultivars, Athena® and Allee®, are not cold hardy for northern climates and there is a need for new cold hardy lace-bark elms. Screening thousands of seedlings for cold hardiness, upright form, beautiful bark characteristics, and larger leaves will bring the most desirable U. parvifolia cultivars into the green industry. We determined that seed dormancy and the percentage of seed germination of four selected lacebark elms after 2 and 4 weeks were >30% and >50%, respectively. There were significant differences in stem cold hardiness among new lace-bark elms from China (about –32 to –40 °C). Laboratory determination of cold hardiness can provide great advantages over years of field testing. Response to the outdoor temperature in December, January, and February on a seed cold hardiness freezing test showed significant reduction in seed germination, especially at –30 °C. Freezing test of seeds to –40 °C, resulted in lt50 of –3 to –5 °C in December, so, it is less likely that these U. parvifoilia will become invasive in northern latitudes. Invasiveness of these U. parvifolia for higher zones, e.g., 6–8 could be greater and selection of these elms is suitable for zones 5 and lower. Planting these elms in zones 4, 3, and 2 will give us useful information regarding their winter performance.
(440) Flowering and Fruiting in Olives in the Absence of Chilling Temperatures
Authors: Malik Nasir , Bradford Joe M. , Brockington Jim E.
Published: February 2019

Cultivation of olives was not developed in southern and coastal Texas because it was assumed that the winters in this area do not provide enough chilling for flowering. Our initial experiments have demonstrated that olive trees of `Arbequina' could flower and fruit under mild winter conditions; i.e., without the typical chilling conditions (below 7.2 °C are chilling temperatures, but 2–4 °C during the night was considered optimal chilling) that have previously been considered necessary for flowering and fruiting in olives. We propose that lack of flowering in southern Texas is due more to high temperatures during the day (many days reaching 26 °C) than lack of chilling temperatures in the night. Thus, `Arbequina', and perhaps other cultivars of olives, should be able to grow and flower and fruit normally in coastal Texas, where daytime temperature do not rise as high as in southern Texas. A survey of coastal Texas revealed that this is indeed a possibility, because a few trees planted in areas of coastal Texas do flower and fruit. Experiments have now been started at different sites to evaluate the performance of olives in coastal Texas.
(111) Establishment of Root-bound Plumbago auriculata Lam. in a Landscape
Authors: Vyapari Sudeep , Thralls Edmund L. , Scheiber Michele S.
Published: February 2019

A study was conducted to evaluate establishment of root-bound vs. nonroot-bound container-grown Plumbago auriculata Lam. in a landscape. A total of 144 plants were transplanted from #1 containers in a rain-out shelter at Mid-Florida Research and Education Center, Apopka, Fla., in June 2004. The field soil type was amended with composted yard waste. The three treatment types used for the study were: 1) root-bound plants; 2) root-bound plants with a vertical slice made through the root ball at a 90° angle; and 3) nonroot-bound plants. To evaluate the effect of these three treatments during the course of establishment period, harvesting was done once every 2 weeks. Data on growth indices (height × width × width), shoot dry weight, root dry weight, and length of the longest root were recorded. The experimental design was a completely randomized design consisting of three treatments, 12 harvest dates (days after planting), and four replicates per harvest date. Plants were maintained according to the best management practices recommended by the UF/IFAS, and were irrigated once a day using microirrigation. Experimental data were analyzed for significance of correlation among variables using SAS version 9.1. Results of the correlation and regression analysis indicated that the increase in the shoot dry weights (g), root dry weights (g), growth indices (m3), and root: shoot ratio had significant relationship with the harvest dates. Correlation among harvest dates and shoot dry weight, root dry weight, or growth indices was found to be positive. However, results of the study indicated that as the number of days after planting increased, the root to shoot ratio decreased.
(112) Heat and Drought Affect Photosynthesis of Sugar Maple (Acer saccharum) Ecotypes
Authors: Griffin Jason J.
Published: February 2019

Common sugar maple (Acer saccharum Marshall) selections suffer from prolonged drought and constant wind on the southern Great Plains. Nonirrigated plants often have scorched and torn leaves as a result of these environmental stresses. In field studies, a sugar maple ecotype native to western Oklahoma (known as `Caddo' maple) has shown improved tolerance to drought and leaf tatter. A study to examine drought tolerance of seedling `Caddo' maple compared to typical seedling sugar maple was established at the John C. Pair Horticultural Center. One seedling of each type was planted in a single 38-L container. Containers were placed on a greenhouse bench, and once acclimated, irrigation was withheld until predawn leaf water potential indicated a substrate water potential of –1.5 MPa. Containers were weighed, and seedlings were maintained in a prolonged drought condition for 3 weeks by adding water each morning to return the container to the original weight. After 3 weeks, photosynthetic temperature response curves were generated for the drought-stressed and the irrigated control plants. Osmotic potential of expressed sap was also measured on rehydrated leaves. The main effects of species, irrigation, and temperature were all significant. `Caddo' maples were able to maintain a higher rate of net photosynthesis than the typical seedlings when drought stressed and as temperature increased. The optimum temperature for photosynthesis did not significantly differ among treatments (36 °C), whereas the maximum rate of photosynthesis was significantly greater for the `Caddo' maples (41 μmol·m-2·s-1) than the typical sugar maples (16 μmol·m-2·s-1).
(119) Celosia argenteaCan Be Produced Using Saline Wastewaters
Authors: Carter Christy T. , Grieve Catherine M. , Poss James A.
Published: February 2019

Salinity tolerance of two cultivars of Celosiaargentea (`Chief Rose' and `Chief Gold') was investigated using a completely randomized design with three replications. Seedlings grown in greenhouse sand tanks were exposed to six salinity levels (2.5, 4, 6, 8, 10, and 12 dS·m–1) and two water ionic compositions mimicking sea water and drainage waters from the Imperial and Coachella valleys. Phenotypic measurements were made when plants were harvested during flowering, and concentrations of Ca2+, Mg2+, Na+, K+, Cl-, total-S, and total-P were also determined from leaf tissues. Overall, phenotypic measurements (including stem length, stem weight, stem diameter, inflorescence length, inflorescence weight, and number of leaves) tended to decrease as salinity increased, yet stem lengths were still above the minimum stem length recommended for marketability (41 cm). Significant interactions were found for salinity and water ionic composition for all mineral analyses for both cultivars. As salinity increased, Ca2+, K+, and total-P decreased as Mg2+, Na+, and Cl- increased for both cultivars. `Chief Gold' can be produced commercially in either water composition up to 12 dS·m–1. `Chief Rose' can be produced up to 8 dS·m–1 in sea water and 10 dS·m–1 in water ionic compositions similar to those of the Imperial and Coachella valleys. Saline waters dominated by chloride and sulphate salts can be used to produce Celosiaargentea commercially.
(122) Simulation of Poor Quality Irrigation Waters in Subirrigation and Top-watering using Mixture Experiments
Authors: Kent Matthew W. , Reed David W.
Published: February 2019

The effects of cations vs. anions in salinity studies cannot be separated by traditional means. Analysis of mixture experiments allows ionic ef-fects to be analyzed individually by varying proportions of ions without changing their total concentrations. A series of mixture experiments were performed in the greenhouse to determine the effects of the anions bicarbonate, chloride, and sulfate, given a constant and equal concentration of the cation sodium, on vinca `Pacifica Red' grown with different irrigation systems and leaching fractions. In subirrigation, increasing total ion concentrations from 30 to 60 meq/L total ion concentrations (TIC) caused a general decrease in shoot fresh and dry weights, with bicarbonate contributing to the greatest degree of reduction, and sulfate the least. Root dry weight was similarly decreased with increasing TIC, but the differences between individual ion effects were more subtle. SPAD data, an indication of chlorophyll concentration, showed a sharp decrease with increase in bicarbonate, but not with sulfate or chloride. Medium pH increased as TIC increased, being influenced primarily by bicarbonate. Conversely, growing medium EC was influenced most by sulfate and chloride, and least by bicarbonate with increasing TIC. At 30 meq/L TIC, top-watered treatments with a leaching fraction (LF) of 5% generally had reduced shoot and root dry weight without regard to ion species, while a leaching fraction of 35% produced results more similar to those of subirrigation. While medium EC and pH varied with layer and irrigation method, bicarbonate generally affected EC least and pH most.
(126) Response of Six Begonia Species to Different Substrate EC
Authors: Jeong Ka Yeon , Pasian Claudio , Tay David
Published: February 2019

There is limited information on optimal substrate EC level for begonia species (noncultivated hybrids). The objective of this study was to evaluate the response of six species to different substrate EC in a greenhouse. Begonia albopicta, B. cucullata var. cucullata, B. echinosepala var. elongatifolia, B. holtonis, B. fuchsioides (red) and B. fuchsioides (pink) plants were propagated by stem cuttings, and transplanted into plastic pots using a soilless mix. Five concentrations (20, 80, 200, 400, and 600 mg·L-1 N) of 17–5–17 fertilizer were applied as irrigation water to derive the five substrate EC levels. This experiment was a factorial randomized complete-block design. Substrate EC was measured weekly using the PourThru method and averaged for each treatment of each species. Inflorescence number, the longest stem length, SPAD readings, leaf area, and dry weight of each plant were measured as growth parameters. There were significant responses to substrate EC level and species on begonia growth parameters. The highest growth parameters of B. albopicta and B. cucullata were obtained at EC 5.7 and 6.6 mS·cm-1, respectively. The maximum growth of B. echinosepala and B. holtonis was observed at 2.6 and 3.0 mS·cm-1, respectively. B. fuchsioides, grown at 1.2 mS·cm-1, had the best growth parameter values. As EC level increased, SPAD value for B. fuchsioides (pink) and B. holtonis also increased. The highest SPAD reading was observed at EC 3.7 mS·cm-1 for B. albopicta, EC 6.6 mS·cm-1 for B. cucullata, EC 2.6 mS·cm-1 for B. echinosepala, and EC 4.1 mS·cm-1 for B. fuchsioides (red). Plant mortality of several begonia species was observed when grown at EC value above 6.4 or below 4.4 mS·cm-1.
(258) Differential Response of Colored Carrots to Cavity Spot
Authors: McDonald Mary Ruth , Kooi Kevin Vander , Simon Philipp
Published: February 2019

Cavity spot of carrot, caused by several species of Pythium, is endemic in many carrot production areas of the world, including the Holland/Bradford Marsh region of Ontario, Canada. Field trials were conducted from 2002–04 to determine if carrots with different pigments varied in susceptibility to the disease. Carrots from the USDA breeding program at the University of Wisconsin were seeded in muck soil (pH 6.4, 60% organic matter) on 28, 30, and 27 May, harvested 22, 22, and 23 Oct., and assessed for disease on 5, 8, and 10 Dec. 2002, 2003, and 2004, respectively. The carrots were white (W 105-7), yellow (W 102-1), dark orange (W 101-23), red (W 104-3), and purple (W 106-3). Cultivar `Cellobunch' was included in 2003 and 2004. Twenty-five carrots of each of four replicate plots were assessed in 2002 and 2003, and 50 carrots were assessed in 2004, for disease incidence and severity [disease severity index (DSI), based on the size of the largest lesion per carrot]. Disease incidence was moderate in 2002 and 2003 (34%, 33%), and high in 2004 (60%). Consistent differences in susceptibility to cavity spot were identified over the three years of trials. The purple carrot had the lowest incidence (12%) and severity (7 DSI) of cavity spot, followed by the dark orange carrot (39%, 22 DSI) as compared to the susceptible yellow carrot (58%, 41 DSI). There was no difference in disease reaction between the yellow and white carrots. `Cellobunch' had the same reaction as the dark orange carrot. Studies are needed to determine whether the pigments themselves cause differences in the disease response.
Physiological Responses of Apple Trees to Different Irrigation Practices
Authors: Valenzuela Luis R. , Neilsen Denise , Neilsen Gerry , Eissenstat David
Published: February 2019

New irrigation practices using controlled soil water deficits offer the opportunity of reducing tree vegetative growth and enhancing fruit quality without decreasing fruit size or yield. We tested partial root zone drying (PRD) and deficit irrigation in `Golden Delicious' trees on M9 rootstock, at Summerland, B.C., Canada. There were four treatments: full irrigation (100% daily ET replacement), both sides irrigation (50%daily ET replacement), deficit irrigation (1 side, 50% daily ET replacement) and PRD (alternating sides, 50% daily ET replacement). The purpose of this study was to determine how deficit irrigation and PRD affect above- and below-ground physiology of apple trees where the amount of irrigation was the same. Soil water content, stem water potential, stomatal conductance and transpiration were significantly higher for deficit irrigation than PRD irrigation (P < 0.05) for both years (2003 and 2004). Root dynamics varied among years. For both years, root production was higher in trees under PRD than in trees under deficit irrigation. Root survivorship was significantly higher for trees exposed to PRD treatment than those exposed to deficit irrigation treatment in 2003 (P < 0.0003), but not in 2004 (P > 0.662). Stem growth, fruit yield, and fruit quality were generally not affected by treatments in 2003. In 2004, however, fruit yield was 37% higher in deficit irrigation than in PRD (P < 0.05). Soluble solids and sugar: acid ratio did not differ between these two treatments. For conditions where the amount of irrigation applied was the same, our results suggest that PRD may be less effective than deficit irrigation.
Effect of Fertigation Strategy on Nitrogen Availability and Nitrate Leaching using Microirrigation
Authors: Hanson Blaine R. , Hopmans Jan , Simunek Jirka
Published: February 2019

Injection during the middle one-third or the middle one-half of the irrigation is recommended for fertigation using microirrigation. However, short fertigation events are commonly used by growers. This project investigated the effect of fertigation practices on nitrate availability and leaching. The first phase of the project (completed) determined nitrate distributions in the root zone for four microirrigation systems, three soil types, and five fertigation strategies using the HYDRUS-2D computer simulation model. Fertigation strategies included injecting for short time periods at the beginning, middle, and end of the irrigation cycle, respectively; injecting during the middle 50% of the irrigation cycle, and continuous injection. The second phase (ongoing) is investigating the distribution of nitrate, ammonium, urea, phosphate, and potassium around the drip line for selected Phase 1 scenarios. Phase 1 results showed less nitrate leached from the root zone for a 2-h injection time at the end of a long irrigation event compared to injection at the beginning and middle of a long irrigation event for surface drip irrigation. A more continuous fertigation resulted in a more uniform distribution of nitrate in the soil. The results were less conclusive for subsurface drip lines, due to upward movement of nitrate above the drip line. Little difference in nitrate leaching occurred for short irrigation events, regardless of fertigation strategy. Data analysis of the Phase 2 modeling is under way. The HYDRUS-2D model included partition coefficients for ammonium, phosphate, and potassium, and parameters for hydrolysis (conversion of urea to ammonium), nitrification, and denitrification.
Xanthophyll Cycle-dependent Thermal Dissipation and the Antioxidant System of `Gala' Apple Peel in Response to Nitrogen Supply
Authors: Xia Guohai , Cheng Lailiang
Published: February 2019

Four-year-old `Gala'/M.26 trees were grown under low (2.5 mm), medium (12.5 mm), or high (25 mm) N supply with balanced nutrients in sand culture and the cropload was adjusted to 5 fruit/cm2 trunk cross-sectional area at 10 mm king fruit. At about 100 days after bloom, exposed fruit on the south side of the canopy were chosen for monitoring chlorophyll fluorescence and fruit peel samples were taken for measuring xanthophyll cycle pigments, antioxidant enzymes, and metabolites. At noon, the efficiency of excitation transfer (Fv'/Fm') of the sun-exposed peel was higher in the low N treatment than in the medium or high N treatments. Photochemical quenching coefficient did not differ between fruits in different N treatments. The Photosystem II operating efficiency was higher in the peel of low N fruit compared with medium N or high N fruit. However, maximum quantum efficiency (Fv/Fm) of fruit peel after overnight dark adaptation was similar across the N treatments. The xanthophyll cycle pool size expressed on peel area basis was larger in the high N fruit than in the low N fruit. This corresponds well with the thermal dissipation capacity, as indicated by efficiency of excitation transfer. Over 95% of the xanthophyll cycle pool in the sun-exposed side was present in the form of zeaxanthin and antheraxanthin at noon regardless of N treatments. Activities of superoxide dismutase and all the antioxidant enzymes and metabolites in the ascorbate-glutathione cycle were higher in the high N fruit than in low N fruit. The results indicate that apple fruit with a good N status have a higher photoprotective capacity in terms of xanthophyll cycle-dependent thermal dissipation and detoxification of reactive oxygen species compared with low N fruit.
Genetic Study of Leaflet Number and Prickles in Roses
Authors: Shupert David , Byrne David H. , Pemberton H. Brent
Published: February 2019

Research with the Basye Rose Breeding and Genetic Program at Texas A&M University has developed rose populations to use to study the genetic nature of leaf, stem, and several other rose traits. The rose populations are from the backcross of Rosachinensis`Old Blush' to WOB (interspecific hybridization of the diploid parents Rosawichuariana `Basye's Thornless' and `Old Blush'). The qualitative trait of presence of stem prickles and the quantitative traits of stem prickle density and leaflet number were observed in three field locations. Two locations are in College Station, Texas, and one location in Overton, Texas. The qualitative trait of presence of stem prickles supports the reported monogenic modes of inheritance. The presence of stem prickles (dominant) had a segregation ratio of 1:1 for prickles: no prickles. Prickle density and leaflet number demonstrated a quantitative mode of inheritance. For prickle density the genotype was significant and environment was nonsignificant. For leaflet number the genotype/generation was significant and environment was nonsignificant. This shows that genotype influences prickle density and leaflet number expression. The genotype by environment interaction was nonsignificant for all traits.
Improving IPM Decision Support in Vegetable Crops through Weather-based Disease Advisories
Authors: Sutherland Albert , Damicone John , Jabrzemski Rafal , Blackburn Stdrovia
Published: February 2019

Weather-based disease advisories have allowed vegetable producers to optimize their fungicide applications. These models typically use only past weather data to identify times of potential disease outbreak. The Oklahoma Mesonet has developed a new Spinach White Rust Advisory that improves grower disease decision support by combining forecast, current, and past weather data in calculating infection periods. The decision-support component issues initial spray advisories, based on infection hour accumulation from the first true-leaf stage or from a previous fungicide application date for subsequent sprays. The advancement in this model in relation to traditional weather-based disease advisories are: incorporation of an 84-hour forecast, hourly model recalculation, cultural practice customization, user site selection from any of 110+ statewide sites, and immediate access to detailed historical data. The model is available on the Oklahoma Mesonet AgWeather website (http://agweather.mesonet.org).
Use of Compost as an Alternative to Methyl Bromide for Vegetables
Authors: Sanders Doug , Reyes Luz M. , Monks David , Louws Frank , Driver James
Published: February 2019

We evaluated the influence of three compost sources and compost amended with T382 with fumigant Telone C-35 and various combinations of compost and Telone C-35 on the yield and pest management of cucumber, pepper, tomato, collard, southern pea, and summer squash in a multicrop rotational system. In the first year, there were few differences between the compost treatments and Telone C-35, but all treatments resulted in more yield than the control. In the second year, all compost treatments and/or Telone C-35 improved total and marketable yield of cucumber, pepper, tomato, southern pea, and summer squash. Furthermore, in the second year, Telone C-35 treat-ments produced more yield than some of the compost treatments in tomatoes. Combining Telone C-35 with compost did not differ from either treatment alone. Nematode and disease assessments were not consistent and will be discussed in further detail.
Whole-plant Photosynthesis of Containerized Hydrangeas and Abelias as Affected by Substrate Moisture Content
Authors: van Iersel Marc W. , Dove Sue
Published: February 2019

Efficient water use in nurseries is increasingly important. In recent years, new soil moisture sensors (ECH2O probes) have become available, making it possible to monitor the moisture content of the growing medium in containers. One piece of information that is lacking for fully-automated irrigation systems is how much water actually needs to be present in the growing medium to prevent detrimental effects of drought on plants. We determined the effect of substrate moisture on photosynthesis and plant water relations of hydrangea and abelia. Growth rates of these species were measured during two subsequent drying cycles to determine how drought affects the growth rate of these species. Whole-plant photosynthesis, an indicator of growth rate, of both species remained stable as the volumetric moisture content of the substrate dropped from 25% to 15%, with pronounced decreases in photosynthesis at lower substrate moisture levels. Abelias and hydrangeas wilted when the substrate moisture level dropped to 6.3% and 8.3%, respectively. At wilting, abelias had lower leaf water potential (–3.7 MPa) than hydrangeas (–1.8 MPa). After the plants were watered at the end of the first drying cycle, the photosynthesis of the plants did not recover to pre-stress rates, indicating that the drought stress caused a long-term reduction in photosynthesis. Despite the more severe drought stress in the abelias (both a lower substrate water content and lower water potential at wilting), abelias recovered better from drought than hydrangeas. After the plants were watered at the end of the first drying cycle, the photosynthetic rate of abelias recovered to ≈70%, while the photosynthetic rate of the hydrangeas recovered to only 62% of the pre-stress rate.
Development of Water Need Indices for Irrigation Permits for Three Container Sizes of Ligustrum japonicum Thumb.
Authors: Beeson Richard
Published: February 2019

In Florida, ornamental nurseries and other agricultural entities have been required to obtain volume-limited permits for irrigation water since 1992. Since then, volumes permitted for nurseries have declined. This project set out to establish maximum annual irrigation quantities for Ligustrum japonicum Thumb. grown in three common container sizes. Plants were scheduled and grown such that every 4 months, beginning 1 Jan., plants 2 months from marketable size would be available to place in suspension lysimeters with accompanying border plants. Once in lysimeters, plant weights were recorded every half-hour for 4 months. At that point, plants were 2 months larger than marketable size, thus averaging marketable size over the 4-month period. Data were collected through six 4-month cycles (2 years), along with daily calculation of reference evapotranspiration and monthly canopy measurements. Irrigation was applied overhead and based on a minimum 30% reduction in plant available water within a container. Daily actual evapotranspiration was used to calculate a water need index for each plant. These water need indices, normalized by different surface areas, will be discussed, along with comparisons of cumulative actual evapotranspiration to irrigation depth applied.
Quantifying the Thermal Tolerance of Nonrooted Petunia Cuttings and Their Subsequent Performance
Authors: Lopez Roberto G. , Runkle Erik S.
Published: February 2019

In 2003, commercial greenhouse growers in the United States imported 724 million nonrooted cuttings valued at $53 million. During transit and storage, cuttings can be exposed to environmental stresses (e.g., low or high temperature), which can consequently decrease quality, rooting, and subsequent plant performance. We performed experiments to quantify how temperature and storage duration of cuttings influence root initiation, root number, lateral branch count and length, and time to flower of Tiny Tunia `Violet Ice' petunia (Petunia × hybrida hort. Vilm. -Andr.). Dry or wet cuttings were harvested and packaged into perforated bags within small, ventilated boxes and then into traditional shipping boxes. The boxes were placed in environmental chambers with temperature setpoints of 0, 5, 10, 15, 20, 25, or 30 °C for 0, 1, 2, 3, 4, or 5 d. Cuttings were then rooted in a propagation house at 26 °C with a vapor pressure deficit of 0.3 kPa under ambient photo-periods. The visual quality rating of dry packaged cuttings decreased with increasing temperature and shipping duration. After 2 d at ≥25 °C, cuttings were horticulturally unacceptable due to water stress and chlorophyll degradation and they never fully recovered. Dry- or wet-packaged cuttings held at temperatures of 0 to 30 °C formed significantly fewer roots and lateral branches as duration increased from 1–5 d. Although cuttings held for 5 d at 0 °C produced 60% fewer lateral branches, they subsequently flowered 5 d earlier than plants held at 0 °C for 1 d. Therefore, exposure to temperatures >15 °C for ≥3 d can reduce petunia cutting quality, delay rooting, and decrease plant size at flowering.
Water Requirements and Drought Tolerance of Bedding Plants
Authors: Nemali Krishna S. , van Iersel Marc W.
Published: February 2019

Optimal substrate volumetric water content (θ) and drought tolerance of impatiens, petunia, salvia, and vinca were investigated by growing plants under four constant levels of θ (0.09, 0.15, 0.22, and 0.32 m3·m-3). Gas exchange, quantum efficiency (ΦPSII), electron transport rate (ETR), non-photochemical quenching (NPQ), and leaf water potential (ϒ) were measured for all species, and response of photosynthesis (Pn) to internal CO2 concentration (Ci) was studied in petunia and salvia. Leaf photosynthesis (Pmax) was highest at a θ of 0.22 m3·m-3 for all species and did not differ between a θ of 0.15 and 0.22 m3·m-3 for vinca and petunia. The Pn-Ci response curves for petunia were almost identical at a θ of 0.22 and 0.15 m3·m-3. Regardless of species, ETR and ΦPSII were highest and NPQ was lowest at a θ of 0.22 m3·m-3. Based on these results, a θ of 0.22 m3·m-3 for salvia and impatiens and a slightly lower θ of 0.15 m3·m-3 for vinca and petunia, is optimal. Mean osmotic potential in all treatments was lower in vinca and salvia and resulted in higher turgor potential in these species than other species. Analysis of Pn-Ci response curves indicated that Pn at a θ of 0.09 m3·m-3 was limited by both gas phase (stomatal and boundary layer) and non-gas phase (mesophyll) resistance to CO2 transfer in salvia. At the lowest θ level, Pn in petunia was only limited by gas phase resistance, indicating that absence of mesophyll resistance during drought may play a role in the drought tolerance of petunia.
Effect of Drought Stress on Growth and Ginsenoside Content of American Ginseng
Authors: Lee Jin Wook , Mudge Kenneth W. , Lardner Joseph
Published: February 2019

American ginseng (Panax quinquefolium L.) contains pharmacologically active secondary compounds known as ginsenosides, which have been shown to be affected by both genetic and environmental factors. In this greenhouse experiment, we tested the hypothesis that ginsenosides would behave as “stress metabolites” and be associated with osmoregulation in response to drought stress. Two year-old seedlings, grown in 5-inch pots, were well watered for 40 days prior to the initiation of treatments. Plants in the drought stress treatment were watered every 20 days while the controls were watered every 10 days, and the experiment was terminated after 4 and 8 dry down cycles (80 days), respectively. Predawn leaf water potential and relative water content (RWC) of drought-stressed plants during a typical dry down cycle were lower than control plants. The diameter and weight of primary storage roots were decreased in the stressed treatment. The length of the main storage root and the longest secondary (fibrous) root were significantly increased by the drought stress treatment. Leaf chlorophyll content of drought-stressed plants was lower than controls. The osmotic potential of the drought-stressed ginseng was not lower than the control, indicating that ginsenoside is not involved in osmoregulation in response to drought stress. Furthermore, ginsenosides Rb1 and Rd, and total ginsenosides were significantly lower in primary roots of drought-stressed plants compared to control plants.
Photoassimilate Regulation of Sorbitol and Sucrose Metabolism in Peach Fruit
Authors: Bianco Riccardo Lo , Morandi Brunella , Rieger Mark
Published: February 2019

Along with sucrose, sorbitol represents the major photosynthetic product and the main form of translocated carbon in peach. The objective of the present study was to determine whether in peach fruit, sorbitol and sucrose enzyme activities are source-regulated, and more specifically modulated by sorbitol or sucrose availability. In two separate trials, peach fruit relative growth rate (RGR), enzyme activities, and carbohydrates were measured 1) at cell division stage before and after girdling of the shoot subtending the fruit; and 2) on 14 shoots with different leaf to fruit ratio (L:F) at cell division and cell expansion stages. Fruit RGR and sorbitol dehydrogenase (SDH) activity were significantly reduced by girdling, whereas sucrose synthase (SS), acid invertase (AI), and neutral invertase (NI) where equally active in girdled and control fruits on the fourth day after girdling. All major carbohydrates (sorbitol, sucrose, glucose, fructose and starch) were reduced on the fourth day after girdling. SDH activity was the only enzyme activity proportional to L:F in both fruit developmental stages. Peach fruit incubation in sorbitol for 24 hours also resulted in SDH activities higher than those of fruits incubated in buffer and similar to those of freshly extracted samples. Overall, our data provide some evidence for regulation of sorbitol metabolism, but not sucrose metabolism, by photoassimilate availability in peach fruit. In particular, sorbitol translocated to the fruit may function as a signal for modulating SDH activity.
Nitrogen Level and Form Influence Kale Growth and Leaf Pigment Concentrations
Authors: Kopsell Dean A. , Kopsell David E. , Curran-Celentano Joanne
Published: February 2019

Kale (Brassica oleracea L.) ranks highest among vegetable crops for lutein and beta-carotene carotenoids, which function as antioxidants in disease prevention. Nitrogen (N) rate and N form influence plant growth and alter pigment composition and accumulation. The objectives of these experiments were to investigate the effect of N rate and form on biomass and accumulation of plant pigments in the leaf tissues of kale. Three kale cultivars were grown using nutrient solution culture. In the first study, N treatment rates were 6, 13, 26, 52, and 105 mg·L–1, at a constant NH4-N:NO3-N ratio. Kale biomass increased linearly in response to increasing N rate. On a fresh weight basis, lutein and beta-carotene were not affected by N rate. However, carotenoids calculated on a dry weight basis increased linearly in response to increasing N rate. In a second study, kale was grown under: 100% NH4-N:0% NO3-N, 75% NH4-N:25% NO3-N, 50% NH4-N:50% NO3-N, 25% NH4-N:75% NO3-N, and 0% NH4-N:100% NO3-N, at a N rate of 105 mg·L–1. Linear increases in biomass were observed for each kale cultivar as percentage of NO3-N increased. Lutein concentrations increased 155%, 73%, and 39% for `Toscano', `Winterbor', and `Redbor' kale, respectively, as N form changed 0% NO3-N to 100% NO3-N. Concentration of leaf beta-carotene increased linearly in response to increasing NO3-N in each cultivar tested. Nitrogen management should be considered in crop production programs designed to increase the concentrations of nutritionally important carotenoids.
Severity of Leaf Removal Affects Regrowth of American Mayapple
Authors: Cushman Kent , Maqbool Muhammad , Bedir Ebru , Lata Hemant , Khan Ikhlas , Moraes Rita
Published: February 2019

Podophyllotoxin is a pharmaceutical compound extracted from rhizomes of Indian mayapple (Podophyllumemodi). Leaves of American mayapple (P. peltatum) also contain podophyllotoxin, and the species is being investigated as a domestic, renewable, and alternative source of the compound. The objective of this study was to explore strategies of leaf removal that would not adversely affect regrowth of American mayapple shoots in subsequent years. Plots were established in two locations among naturally occurring populations in the wild, one in full sun and one in partial shade. Plots were 1.0 m2 and leaves were removed from plants every spring, every other spring, or every third spring. In addition, leaves were removed in early spring, soon after shoots emerged and leaves had fully expanded, or in late spring, when leaves first showed evidence of yellowing and beginning to senesce. Sexual and asexual leaves were harvested separately. Leaf number, leaf area, and dry weight were recorded. Subsamples of leaf material were extracted to determine podophyllotoxin, α-peltatin, and β-peltatin contents. Results clearly showed that leaf removal every year, in combination with early harvest, was too severe and plants lost vigor over the 4-year period of this study. Plants subjected to this treatment combination produced significantly less leaf area and dry weight than any of the other treatment combinations. Results were similar for both sun and shade locations. Lignan content was not affected by treatment. Our results indicate that leaves can be removed from mayapple plants as often as every year provided harvests are not scheduled too soon after shoot emergence.
Confirmation of `Medjool' Date Palm (Phoenix dactylifera L.) as a Landrace Variety by a Study of `Medjool' Accessions from Morocco Using AFLP Markers
Authors: Elhoumaizi Mohammed Aziz , Devanand Panchanoor S. , Fang Jinggui , Chao Chih Cheng T.
Published: February 2019

Six date varieties from Egypt, one `Deglet Noor' and four `Medjool' date accessions from California, and 66 accessions of `Medjool' date from Morocco, the country of origin of `Medjool' date, were examined using four sets of fluorescent labeled amplified fragment length polymorphism (AFLP) markers. A total of 402 AFLP bands were generated and 160 were polymorphic (39.8%). The 66 `Medjool' accessions from Morocco shared minimum 79% of genetic similarity. These results support the hypothesis that `Medjool' date is a landrace variety and not a genetically uniform variety. `Medjool' is the first confirmed landrace variety of date palm worldwide. This raises the possibility that other landrace varieties of date palm may exist in different date-growing areas and in centers of diversity. The confirmation of a landrace variety of date palm also has significant impact on future date palm germplasm collection and preservation. The mechanism(s) creating the genetic variation within `Medjool' accessions remains unknown. One possible mechanism is that spontaneous genetic changes could occur frequently within vegetative tissues of date palm like offshoots under high temperature and drought stresses.