bluuebunny/crossref_metadata_2025 huggingface dataset:
Resistance Response of the Ma genes from `Myrobalan' Plum to Meloidogyne hapla and M. mayaguensis
Authors: Rubio-Cabetas Maria-Jose , Minot Jean-Claude , Voisin Roger , Esmenjaud D. , Salesses Georges , Bonnet Abel
Published: February 2019

In `Myrobalan' plum (Prunus cerasifera Ehr.), Ma1 and Ma2 are single major dominant genes that control the resistance to the predominant root-knot nematode (RKN) species Meloidogyne arenaria (Neal) Chitwood, M. incognita (Kofoid & White) Chitwood, and M. javanica (Treub). These genes were evaluated for activity to the northern RKN M. hapla Chitwood and the tropical RKN M. mayaguensis Rammah & Hirschmann, neither of which is controlled by the Mi gene from tomato. This study was conducted under greenhouse conditions using a resistance screening based on high and durable inoculum pressure by the nematodes. Tests were conducted simultaneously for: M. arenaria (as a reference for the Ma genes); M. hapla and M. mayaguensis from crosses segregating for either Ma2 alone or Ma2 and Ma1 and involving the resistant parental clones P.2175 (heterozygous for Ma1) and P.1079 (homozygous for Ma2); and the host parental clone P.2646 (recessive for both Ma genes). Each parental clone and each individual of the segregating progenies reacted in a similar way to M. arenaria and M. mayaguensis, indicating that the Ma genes also control resistance to M. mayaguensis. By contrast, all parental clones and progenies were completely resistant to M. hapla, and, despite high inoculum pressure, no effect of the Ma genes on this species could be established.
Effect of Growth Temperature on Aster Flower Development
Authors: Oren-Shamir M. , Shaked-Sachray L. , Nissim-Levi A. , Weiss D.
Published: February 2019

Little is known about the effect of growth temperature on Aster (Compositae, Asteraceae) flower development. In this study, we report on this effect for two aster lines, `Suntana' and `Sungal'. Growth temperature had a dramatic effect on the duration of flower development, ranging from 22 days for plants growing at 29 °C up to 32 days for plants grown at 17 °C. Flower longevity was ≈40% shorter under the higher temperature for both lines. Growth temperature also affected flowerhead form: `Suntana' flowerhead diameter was 20% larger at 17 °C than at 29 °C. The number of `Sungal' florets per flowerhead was four times greater at the lower temperature. Shading (30%) under temperature-controlled conditions had no effect on any of the parameters measured. For plants grown outdoors, our results suggest that shading plants may increase quality by reducing the growth temperature.
Treatment with Hydrogen Peroxide and Seedcoat Removal or Clipping Improve Germination of `Genesis' Triploid Watermelon
Authors: Duval John R. , NeSmith D. Scott
Published: February 2019

Seeds of triploid watermelons [Citrullus lanatus (Thunb.) Matsum & Nakai] often germinate poorly, which prevents adequate stand establishment in both field and greenhouse environments. Methods of improving germination and emergence of these expensive seeds would reduce overall risk to growers, thus increasing the crop's market prominence. Seeds of `Genesis' triploid watermelon were subjected to three treatments: 1) seedcoat removal; 2) clipping the seedcoat opposite the radicle end; or 3) no seedcoat alteration; and were germinated on agar in the presence of a 0%, 1%, 2%, 4%, or 8% aqueous H2O2 at constant 28 °C in the dark. Seedcoat removal, clipping, and all levels of H2O2 increased final germination percentages relative to the control (no seedcoat alteration, no H2O2) by as much as 70%. Hydrogen peroxide levels >2% resulted in severe injury to germinating seeds. These findings suggest that germination barriers of triploid watermelon are seedcoat related, and that seedcoat alteration and H2O2 can overcome these barriers.
Malus Germplasm Varies in Resistance or Tolerance to Apple Replant Disease in a Mixture of New York Orchard Soils
Authors: Isutsa Dorcas K. , Merwin Ian A.
Published: February 2019

We tested 40 seedling lots and 17 clonal accessions—representing 941 genotypes and 19 species or interspecific hybrids of Malus—for their resistance or tolerance to apple replant disease (ARD) in a mixture of five New York soils with known replant problems. Total plant biomass, root necrosis, root-infesting fungi, and root-lesion nematode (RLN; Pratylenchus penetrans Cobb) or dagger nematode (DN; Xiphinema americanum Cobb) populations were evaluated in apple seedlings and clones grown for ≈60 days in the composite soil. In addition to phytophagous nematodes, various Pythium, Cylindrocarpon, Fusarium, Rhizoctonia and Phytophthora species were isolated from roots grown in the test soil. Plant growth response was categorized by a relative biomass index (RBI), calculated as total plant dry weight in the pasteurized field soil (PS) minus that in an unpasteurized field soil (FS), divided by PS. Nematode reproduction on each genotype was defined by a relative reproduction index (RRI), calculated as final nematode populations in roots and soil (Pf) minus initial soil populations (Pi), divided by Pi. The RBI, RRI, and other responses of accessions to ARD soil were used to rate their resistance, tolerance, or susceptibility to apple replant disease. None of the accessions was completely resistant to ARD pathogens in our test soil. Seedling accessions of M. sieversii Roem. and M. kirghisorum Ponom. appeared to have some tolerance to ARD, based upon their low RRIs and RBIs. Three clonal rootstock accessions (G.65, CG.6210, and G.30), and four other clones (M. baccata Borkh.—1883.h, M. xanthocarpa Langenf.—Xan, M. spectabilis Borkh.— PI589404, and M. mandshurica Schneid.—364.s) were categorized as tolerant to ARD. The disease response of other accessions was rated as susceptible or too variable to classify. We concluded that sources of genetic tolerance to ARD exist in Malus germplasm collections and could be used in breeding and selecting clonal rootstocks for improved control of orchard replant pathogens.
Resistance of Hybrid Citrus Rootstocks to a Mediterranean Biotype of Tylenchulus semipenetrans Cobb
Authors: Verdejo-Lucas S. , Sorribas F.J. , Forner J.B. , Alcaide A.
Published: February 2019

The response of 52 citrus hybrid rootstocks to a Mediterranean biotype of Tylenchulus semipenetrans Cobb was determined in greenhouse tests. Seven selections of the cross `Cleopatra' mandarin [Citrus reshni Hort. × Poncirus trifoliata (L.) Raf], and one of Citrus volkameriana Pasq. × P. trifoliata did not support nematode reproduction and were considered as highly resistant to the citrus nematode. The nematode showed very low infectivity and reproductive potential on seven additional selections of `Cleopatra' mandarin × P. trifoliata, one of `King' mandarin × P. trifoliata, and two C. volkameriana × P. trifoliata. These selections were considered as nematode resistant. All the selections with `Troyer' citrange [Citrus sinensis (L). Osbeck × P. trifoliata (L.) Raf] in their parentage supported nematode reproduction but showed different levels of susceptibility.
Evaluation of Pumpkin Cultivars for Powdery and Downy Mildew Resistance, Virus Tolerance, and Yield
Authors: Keinath Anthony P. , DuBose Virginia B.
Published: February 2019

Twenty-six cultivars and two numbered selections of Cucurbita pepo L. pumpkin and four cultivars of C. maxima Duchesne pumpkin were evaluated in field experiments in 1996 and 1997 in Charleston, S.C. The four C. maxima cultivars (`Mammoth Gold', `Big Max', `Rouge Vif d'Etamps', and `Lumina') and three C. pepo cultigens (HMX 6686, HMX 6688, and Magic Lantern) had lower powdery mildew [Sphaerotheca fuliginea (Schlechtend.:Fr.) Pollacci] severities than did the other C. pepo cultivars. Overall, C. maxima cultivars also had less foliage showing virus symptoms and less downy mildew [Pseudoperonospora cubensis (Berk.& M.A. Curtis) Rostovzev] than did C. pepo cultigens. Mid- and long-season cultigens of both species (≥100 days to maturity) produced a greater number of marketable-quality fruit than did short-season cultigens. Cucurbita maxima and C. pepo produced similar numbers of marketable fruit; however, more potential marketable yield was possible in C. maxima since most fruit were affected by virus. The C. pepo cultigens Spookie, HMX 6686, and Spooktacular produced the greatest numbers of marketable fruit. In general, no cultigens were well-adapted to the growing conditions of the humid coastal plain of the southeastern United States.
076 Determining Gene Numbers and the Potential for Transferring Long Postharvest Longevity of Antirrhinum majus L. Cut Flowers to Short-lived Colored Lines
Authors: Schroeder Kenneth R. , Stimart Dennis P.
Published: February 2019

Postharvest longevity (PHL) is important in determining quality and consumer preference of cut flowers; thus, it remains a pressing problem for the florist industry. Information on genetics and heritability of cut flower PHL is lacking. This study focused on determining gene numbers and inheritance of Antirrhinum majus L. cut flower PHL. An inbred backcross population was generated from a yellow short-lived (YS; 6d PHL) and a white long-lived (WL; 14 d PHL) inbred. F1 hybrids were backcrossed reciprocally three times to each parent. Parental backcross (BC) populations contained 55 to 65 lines. Lines within each BC generation were self-fertilized three generations by single-seed descent without selection to produce BC1S3, BC2S3, and BC3S3 generations. Cut flowers from all generations were evaluated together for PHL in deionized water. Gene numbers were estimated using confidence intervals and the proportion of non-parental BC lines. Continuous variation, estimates of a minimum of two to four genes controlling PHL, and significant environmental variation suggest selection for increased PHL would be successfu,l but slow. A negative correlation between PHL and yellow flower color was detected in this study. In spite of that fact, mean PHL of the yellow flowered inbred lines improved 1 to 2 d when backcrossing to YS and 3 to 4 d when backcrossing to WL without selection. Thus, inbred backcrossing to a long-lived parent with selection for flower color should make acquisition of longlived colored lines attainable.
078 New Dwarf Cultivar, `Andong', of Hibiscus syriacus L.
Authors: Shim Kyung-Ku , Ha Yoo-Mi , Ha Jae-Ho
Published: February 2019

This cultivar originated from a grafting mutant in grafted plants of a selected 100-year-old seedling of Hibiscus syriacus L. for 5 years. In 1999, the plant is named H. syriacus `Andong'. Hibiscus syriacus `Andong' is a deciduous, erect-growing, multiple-stemmed, dwarf type that, in 7 years, has grown 120 cm high and 65 cm wide, with dense branching to the base. It has more than 200 flowers in a 7-year-old tree. The alternate, leathery, waxy, dark green leaves are 5.3 cm long, 3.8 cm wide. But it is 0.48 mm thick and 34.42 mg/cm2 of fresh weight and then is thickier and heavier than that of other cultivars. Therefore, the plant is rarely damaged by aphids and is reliably hardy to -20 °C. The flowers are white with a prominent dark red eye spot that radiates along the veins to midpetal, 5-7 cm in diameter, and blooms profusely from July to October. Total flowering time of `Andong' was 36 h in both 1998 and 1999. It sets very little fruit. AIt does not only germinate by pollen, but also by seeds. This cultivar can be readily propagated by softwood (on 24 July with 7000 ppm IBA in the mist) or hardwood cutting (1000 ppm IBA) and by grafting on seedling H. syriacus understock.
160 Light Conversion Efficiency in Peach Training Systems
Authors: Corelli-Grappadelli Luca , Ravaglia Gianfranco , Magnanini Eugenio
Published: February 2019

Training system efficiency may be defined as the ratio of fruit produced to the amount of light intercepted by the canopy. In apple, a positive, linear relationship between yield and light intercepted is generally found, but in peach similar data are hard to come by. This paper reports data from an ongoing training systems trial now in the 7th year, with trees trained as Y, palmette, and delayed vase. During the life of the orchard, light interception has been measured for the different tree shapes, the yields have been recorded, and, in some years, whole-canopy gas exchanges of cropping trees have been measured. In general, the trees have been intercepting light in amounts proportional to canopy shape and tree density, with the Y (planted at higher density) intercepting more light than the other two systems, which appear more comparable to each other, despite the fact that they intercept light during the day in different ways, with the delayed vase exposing more or less the same leaves to incoming light during most of the day. Cropping has followed the amounts of light intercepted, with higher yields for the Y, without appreciable differences in fruit quality traits. The data accumulated so far indicate furthermore that the palmette and the delayed vase, despite slightly different light interception potentials (lower for the palmette), have similar yields. This might depend in part on the fact that these two systems intercept light according to different patterns during the day, with the palmette—which distributes the light intercepted in a more even fashion between the two sides—perhaps at an advantage over the vase in terms of managing the stress of excessive light (heat) loads during the central hours of the day. Whole canopy Carbon exchange data have been found to be in agreement with the patterns of light interception.
164 Combinations of Chemical Thinners for Bloom and Post-bloom Apple Thinning
Authors: Byers R.E. , Carbaugh D.H. , Combs L.D.
Published: February 2019

Effectiveness of pollination/fertilization inhibitors for flower thinning depends highly on the precise timing of sprays within 24 to 36 h after flower opening. In 1999, cool weather delayed the application of hormone-type thinners, which were intended for at bloom comparison with pollination/fertilization. Pollination inhibitors applied in bloom and hormone thinners applied at petal fall or 8 mm fruit diameter caused good fruit thinning. Ethephon applied in bloom did not cause thinning of `Empire' fruit, but Sevin + Accel + Oil caused good fruit thinning when applied in bloom. Sevin + Accel + Oil increase fruit diameter and did not affect fruit russet. Ethephon applied at 22 mm fruit diameter at water rates of 935 L/ha or 3741 L/ha and chemical rates of 21.5 L/ha or 42.9 L/ha did not cause significant fruit thinning. In 1998, pollination inhibitors and hormone-type growth regulators caused flower and fruit thinning of `Starkrimson'/MM111/106 trees. Good thinning occurred with both pollination inhibitors and ethephon treatments; but Sevin + Accel + oil was not as effective. Thinex caused the most side russet. Treatments that thinned generally caused increased fruit diameter. In 1999, return bloom was promoted by early thinning, but ethephon did not appear to promote return bloom beyond the thinning effect. In 1998, endothall caused good thinning of `York'/MM.111 with a minimum of foliage injury. Fruit diameter was increased. Thinning with endothall in 1998 greatly increased return bloom in 1999, but trees were slightly over thinned. Fruit injury caused by carbaryl was almost non-existant in 1999 in two tests having over 25 carbaryl treatments that compared different formulations and adjuvants for thinning and injury. Some very slight, non-significant injury, may have occurred with three of nine formulations tested when trees were shaded. Shading trees for 1 day in conjunction with carbaryl sprays also did not promote injury. In a previous year, shading trees promoted carbaryl injury. A tank mix of Oil with either 50WP, 80WP, XLR, or 4L formulations caused 3 to 8% of the fruit to show injury at a very low intensity. However, in an adjoining block, Sevin + Accel + Regulaid caused injury to >50% of the fruit when applied the same day as the other experiments. Further investigations on this problem are in progress.
193 Fine Root Turnover and Mycorrhizal Morphotypes in Loblolly Pine (Pinus taeda L.)
Authors: Yang Wei Qiang , Dunbar Amy K. , Topa Mary A.
Published: February 2019

Loblolly pine (Pinus taeda L.) is the most widely planted tree species in the Atlantic Coastal Plain. To maximize its aboveground yield, it is vital to understand how root production, particularly fine root production, affects root carbon allocation to its root systems under various environmental conditions. Over a 2-year period (1998-99), we conducted a field study using minirhizotron technology to investigate fine root production and turn over in four families of a 6-year-old loblolly pine stand in Scotland County, N.C. A total of 144 minirhizotron tubes were installed to examine potential genetic differences in fertilizer effects on fine root turnover. Data analyses indicated an interaction between these families and fertilizer treatments for total fine root length and total fine root number. The effect of treatment on total root length was less clear in the faster-growing families. However, fertilization increased total root length in a slow-growing family but decreased total root length in a faster-growing family. Total root number was decreased by fertilizer treatment in the two fastest-growing families, but increased in the two slowest-growing families. Because ectomycorrhizae are significant carbon sinks in pine root systems and more than 90% of short roots in these loblolly pine families were colonized, ectomycorrhizal short roots (clusters) were classified into nine different morphotypes. No treatment and family interactions were found. Fertilizer treatment decreased the number of mycorrhizal clusters per unit root length. Dark and brown morphotypes were dominant mycorrhizal morphotypes among all the families. Our results suggest possible genetic differences and treatment effects on root system carbon demands of loblolly pine.
603 Phenology of Flowering and Leafing in Florida Cultivated Blueberries
Authors: Lyrene Paul
Published: February 2019

The best time to harvest fresh blueberries in Florida is 1 April to 15 May. Weather during this period is normally favorable for harvest: low rainfall, low humidity, warm, sunny days, and cool nights, and supplies of fresh blueberries from other producing areas are low. To ripen high-quality blueberries in April, the plants must flower in February and must have a full canopy of leaves to support the developing crop in March and April. Observations of thousands of blueberry seedlings and selections over the past 25 years in Florida have indicated that blooming and leafing time are affected by the chilling requirement and heat requirement of the variety and also by environmental factors. Factors that increase plant vigor (high soil fertility, ample moisture, and young plants) cause the plants to flower earlier in the spring. Flower buds that do not open by 15 Mar. in north Florida frequently abort. The timing and extent of this physiological bud abortion varies with cultivar. Some southern highbush cultivars leaf before they flower. Others flower before they leaf. The ideal blueberry variety for north Florida would have a very low chill requirement, a high heat requirement to prevent January flowering, and a short flowering-to-ripening interval.
610 Growth and Cutting Production Rates of Sweetpotato as Affected by CO2 Concentration
Authors: Kubota Chieri , Maruko Haruna , Kozai Toyoki
Published: February 2019

For vegetative propagation of sweetpotato, single or multi-node leafy cuttings are used as propagules. A quantitative understanding of leaf development is important for predicting the number of propagules produced after a given production period under various environmental conditions. For plant production in a relatively closed structure, controlling CO2 concentration is necessary, but effects of CO2 concentration on cutting production rates of sweetpotato are not well-investigated. Single-node cuttings each with a fully expanded leaf (the initial leaf blade length was 66 mm) were grown under one of three levels of CO2 concentration (400, 800, and 1200 μmol·mol-1), 250 μmol·m-2·s-1 PPF, 16 h/day photoperiod, and 29 °C air temperature. The plant dry weight increased faster in the higher CO2 concentrations. Changes in the number of harvestable cuttings during the production period was defined by changes in the number of leaves reaching a leaf blade length (LBL) longer than a given standard length (LS). The number of harvestable cuttings increased almost linearly with time after the LBL of the first leaf reached the LS, regardless of CO2 concentration. The effect of CO2 concentration on cutting production rate (number of harvestable cuttings per day) was varied with different LS. For example, at LS = 20, 30, and 40 mm, the cutting production rate increased slightly at higher CO2 concentrations, while at LS = 60 mm, it decreased significantly at higher CO2 concentrations. This indicates that, under the present experimental conditions, increasing CO2 concentration increased the number of small leaves that might not be usable as cuttings (propagules). Environmental control is necessary in vegetative propagation to increase the number of propagules and the biomass usable as propagules, thereby minimizing energy and resources needed for the propagule/transplant production process.
695 Weed Control in Minor Crops After the Loss of Methyl Bromide
Authors: Hutchinson Chad
Published: February 2019

The economics of pesticide production and registration has limited the number of pesticides registered for use in minor crops relative to agronomic crops. Current regulations such as the Food Quality Protection Act may further reduce the number of efficacious compounds registered for use on minor crops. Traditionally, the lack of registered pesticides for minor crops has been offset by soil fumigation. However, methyl bromide use is scheduled for phase-out in the United States by 2005, leaving a pest control vacuum in some crops. Loss of methyl bromide has stimulated research into the use of other soil fumigants for weed control. Methyl bromide, methyl iodide, propargyl bromide, 1,3-dichloropropene, and metham sodium have been tested alone and in combination with chloropicrin in laboratory experiments to determine their efficacy against Cyperus esculentus L (yellow nutsedge) tubers. All the fumigants controlled nutsedge equal to or better than methyl bromide and resulted in synergistic control when combined with chloropicrin. Although excellent weed control can be achieved with all the fumigants in the laboratory, weed control in the field with the same fumigant may result in poor or no control. Further research is necessary to optimize the field application of the remaining fumigants to maximize pest control. In the near future, to achieve the broad-spectrum pest control obtained with methyl bromide, growers will need to rely on multiple control strategies. The most promising replacement program for broad-spectrum pest control includes dichloropropene/chloropicrin fumigation followed by a herbicide program or mechanical weed control. To control problem weeds that are not controlled with the in-season herbicide program, a chemical fallow program should be instituted in the off-season to reduce weed pressure during the cropping season.
Effect of Mulch and Shading on Bell Pepper Production in Alabama
Authors: Boozer Robert , Simonne Eric , Pitts Jim
Published: February 2019

In 1999, two studies were conducted using bell pepper (Capsicum annuum L.) Study one evaluated the effect of three different mulch systems and bare soil (BS) on day and night temperatures encountered during the early growth, flowering, and fruit set period. Mulch systems were black plastic (BP), black plastic over white plastic (BOW), and minimum tilled rye (MTR). Study two evaluated the use of a 30% shade fabric on black plastic produced bell pepper. In study one, maximum daytime temperatures during the pre-flowering phase was significantly higher for MTR, 35.9 °C, compared to, 33.3, 32.5, and 32.1 °C for BOW, BP, and BS respectively. During early fruit set and fruit development, MTR was 36.9 °C, compared to 35.6, 34.9, 34.9 °C for BWP, BS, and BP respectively. Minimum nighttime temperatures were not significantly different between treatments. Bloom numbers and fruit set were adversely affected by MRT and were significantly lower than other treatments 23 and 15 days prior to harvest. Marketable weight and number of fruit per plot were significantly lower at harvest for MRT, 2.5 kg compared to 15.7, 14.5, and 11.6 kg for BWP, BP, and BS respectively. In study two, 30% shading 15 days prior to harvest resulted in 40% increase in number, 101 and 72, and weight, 21 and 15 kg, of marketable fruit for shaded area compared to nonshaded area respectively. Numbers of culls per plot, predominately sunburned fruit in non-shaded area, were reduced 72% by shading. The potential for developing systems to improve bell pepper production in Alabama are feasible based on these studies.
Evaluation of Poultry Manure and Fertilizer N for Corn in a Strip Test
Authors: Downes John D.
Published: February 2019

Animal waste disposal from large operations is an increasing problem, and its value as a fertilizer needs to be determined. Strip tests often are unreplicated creating problems in analysis. In an unreplicated Georgia farm test involving a three manure (0, 1, 2 loads/acre) × 3 N (0, 70, 90 lb/acre) factorial on corn yield from the control plot was not included, making n = 8, and precluding the usual ANOVA and means comparisons. Partial budget analysis is compared to regression analysis and economic evaluation at varying input costs and corn prices. Best estimates were obtained by finding the N equivalent of manure [(56.4 lb N)/load] and regressing yield on sum of N (Nf + Nm), which estimated Y = –14.0 + 1.1724N – 0.00324NN, RR = .982, F = 136.38, P > F =.000, sye = 3.0 bushel/acre, from which Nmax = 181, Ymax = 92.1 bushel/acre. Nopt varied from 139 to 172 bushel/acre with cost N varying from $0.14/lb (manure cost) to $0.40/lb, and corn prices from $1.50 to $2.50/bushel. Manure thus valued at 16.92 per load when costing $8.00, assuming 56.4 lbs/load N. Major point was estimation N equivalent of manure from yield effects and then regression yield on N. Equation easily converted to one in M.
Germinating Triploid Watermelon Seeds—The Basics
Authors: Maloney Bob
Published: February 2019

The successful germination of triploid watermelon seeds depends largely upon three factors; moisture control, planting depth, and temperature control. The planting medium must be moistened until it is humid, but not wet enough for free water to be squeezed from a handful. This level of humidity must be maintained until germination is complete. The planting depth should be 1.25 to 2.5 cm. This reduces the number of seeds that “push” themselves from the medium and also facilitates correct moisture maintenance. Seeded trays should be placed in a germination room and held 48–72 hours at a temperature of 30 to 32 °C and a relative humidity of 90% to 95% until germination begins. When germination is complete, the plants can be watered normally.
Applications of 2,4,5-TP, 3,5,6-TPA, and Combinations Thereof Increase Lychee Fruit Size and Yield
Authors: Stern Raphael A. , Stern Daniel , Harpaz Moshe , Gazit Shmuel
Published: February 2019

Application of TP as Tipimon® or TPA as Maxim® at the young fruitlet stage significantly increased yield in three lychee (Litchi chinensis Sonn.) cultivars: `Mauritius', `Floridian', and `Kaimana'. Application of TP followed by TPA a week later increased yield more than did either substance alone. In all experiments, TPA increased fruit size and weight, relative to both controls and TP-treated trees. The increased yield did not prevent the increase in fruit size. Use of sprays of TPA may be an effective way of satisfying the market demand for large lychee fruit. Chemical names used: 2,4,5-trichlorophenoxypropionic acid (TP); 3,5,6-trichloro-2-pyridyloxyacetic acid (TPA).
Disease Reaction among Selected Cucurbitaceae to an Acremonium cucurbitacearum Isolate from Texas
Authors: Bruton B.D. , Popham T.W. , García-Jiménez J. , Armengol J. , Miller M.E.
Published: February 2019

Thirty-seven species within Cucurbitaceae representing the genera Citrullus, Cucumis, Cucurbita, Lagenaria, and Luffa were evaluated for disease reaction to an Acremonium cucurbitacearum A. Alfaro-Garcia, W. Gams, and Garcia-Jimenez, isolate (TX 941022) from the Lower Rio Grande Valley of Texas. After 28 days in the greenhouse, seedling disease ratings were made on the hypocotyl, stem-root junction, primary root, and secondary roots. An additional disease measure was derived by averaging the four root disease ratings to establish a disease severity index (DSI). Vine and root dry weight were poor measures of plant damage caused by A. cucurbitacearum. According to the DSI, all species within Cucurbita, Lagenaria, Luffa, and three Cucumis sativus L. cultigens were rated as highly resistant to A. cucurbitacearum. Cucumis melo L. and Citrullus lanatus (Thunb.) Matsum. & Nakai cultigens were the only cucurbits receiving DSI ratings of moderately resistant to susceptible.
Usefulness of Apogee® for the PA Apple Industry
Authors: Greene George M.
Published: February 2019

Excessive tree vigor is a significant production problem for the PA apple industry. A series of experiments were conducted from 1994 to 1999, which indicated that Apogee® could effectively reduce vegetative shoot growth. Results from 1994 to 1996 have previously been reported (HortScience 31:598, 32:558). In 1997, 16 treatments composed of four rates (0, 63, 125, and 250 ppm) and four timings (22 May; 4, 11, and 24 June) in various combinations, were applied as dilute handgun sprays. These treatments were applied to sixth leaf `York Imperial' apple trees. Ten peripheral shoots, at a height of 2 m, were tagged and measured on 21 May, 9 and 30 June, 16 July, 12 Aug., and on 10 Oct. Shoots treated with 63, 125, or 250 ppm on 22 May followed by 0, 63, or 125 ppm on 4, 11, or 24 June were from 65% to 76% of the length of the controls (25.5 cm). Treated shoots were from 69% to 78% of the length of the controls following sprays with 63 ppm on 22 May followed by 0, 63, or 125 ppm on 4, 11, or 24 June. Shoots treated with 125 ppm on 22 May followed by 0 or 63 ppm on 4, 11, or 24 June were from 69% to 73% of the length of the controls. The later applications (11 and 24 June) of 250 ppm gave no growth control but the 22 May treatment gave a 30% reduction in growth. In 1999, dilute handgun sprays of 125, 125, 83, and 83 ppm were made on 22 May and on 4, 11, and 24 June, respectively. Cultivars treated were `Spartan', `Delicious', `York Imperial', `Gala', and `Mutsu'. The length of 10 peripheral shoots at 2 and 3 m were measured on 28 July and on 12 Aug. All cultivars responded and on 12 Aug. treated terminal shoot lengths ranged from 33% to 55% of the controls. With reduced vegetative tree vigor many horticultural factors will be improved. In addition, the severity of shoot fire blight can be reduced and the control of all pests that prosper on young succulent leaves will be easier, especially apple aphids and obliquebanded leafrollers. Major factors to be considered in developing an efficacious Apogee® program appear to be initial tree vigor, length of growing season, and crop load. An initial application at 1 to 3 inches of terminal growth is probably the most critical factor.
Interaction of Potassium Form and Nitrogen Rate: High K Is Not a Cure for Excessive N
Authors: DeMoranville Carolyn J. , Davenport Joan R.
Published: February 2019

It has been speculated that cranberries are susceptible to chloride injury. If this is the case, it is possible that applications of high rates of 0-0-60 (KCl) fertilizer as a K source could be detrimental to cranberry productivity. Grower anecdotes of using 0-0-60 to “shut down the plants” persist. Supposedly, using 225+ kg·ha-1 of this material slows or arrests vegetative growth. In fact, growers have claimed it can overcome the production of rank vegetation that results when too much N fertilizer has been applied. Field plots were initiated to determine the suitability of KCl and to determine if high K rates could overcome the deleterious effects of excess applied N. Plots were set up in a split-block plot design with N doses [three each “normal” (28-34 kg·ha-1 N) vs. “high” (56-67 lb N/A)] in one direction and potassium/chloride treatments in the other direction (KCl or K2SO4 at 115 or 225 kg K2O; CaCl2 to give the equivalent Cl as in the high-rate KCl treatment, and a nontreated control) for a total of 36 2 × 2-m plots per each of three cultivar locations. Plots were treated and evaluated for three consecutive years. There were no significant differences in yield among the K2SO4 and KCl treatments, indicating that at rates as high as 225 kg·ha-1 K2O, 0-0-60 and 0-0-50 perform similarly. Further, treatment with CaCl2 had no significant effect on yield. In the third year, plots receiving no K treatment had significantly lower yield than those receiving either rate or form of K (single degree of freedom comparison, significant at 0.03). These results indicate that at the rates used in this study, KCl is an adequate K source. The effect of N rate was more pronounced than that of the K treatments. In years two and three, the low N rate strips had significantly greater yield compared to that in the high N rate strips. By year two, the high N strips were visually different, with rank overgrowth. There was no significant interaction of N rate and the K treatments. While there was a trend for greater difference between the 0 K and 115 kg K rates in the high N plots compared to the moderate N plots, the addition of K never entirely overcame the negative yield effects of high N rate.
Peach Tree Growth, Yield, and Profitability as Influenced by Tree Form and Tree Density
Authors: Marini Richard P. , Sowers Donald S.
Published: February 2019

`Norman' peach [Prunus persica (L.) Batsch] trees were trained to the central-leader or open-vase form and were planted at high (740 trees/ha), or low (370 trees/ha) density. A third density treatment was a HIGH → LOW density, where alternate trees in high-density plots were removed after 6 years to produce a low-density treatment. From 3 to 5 years after planting, trunk cross-sectional areas (TCA) increased most for low-density trees. After 9 years, TCA was greatest for low-density and least for high-density trees. Because of differences in tree training, central-leader trees were taller than open-vase trees and tree spread was greater for low-density than for high-density trees. Annual yield per hectare was 15% to 40% greater for high-density treatments than for low-density treatments, but tree form had little influence on yield. Average fruit weight tended to be greater for low-density than for high-density treatments, but cumulative marketable yield was greatest for high-density and lowest for HIGH → LOW treatments. Income minus costs for 9 years was nearly $4200/ha higher, and net present value was about $2200/ha higher, for open-vase than for central-leader trees (P = 0.08). Cumulative net present value for the 9 years was about $2660/ha higher for high-than for low-density trees (P = 0.36).
Nitrogen Increases Fresh Weight and Retail Value of Fraser Fir Christmas Trees
Authors: Hinesley L. Eric , Snelling Layne K. , Campbell C. Ray , Roten D.K. , Hartzog Jeff
Published: February 2019

Abies fraseri (Pursh) Poir. Christmas trees were fertilized for 5 years with four levels of N (0, 56, 113, or 170 kg·ha–1 per year) in spring, fall, or equally split between spring and fall. Nitrogen did not affect leader length, number of leaders, or bud frequency on the upper (distal) portion of the leader. Nitrogen increased bud frequency on the lower (proximal) 20 cm of the leader in only 1 of 3 years of measurement. All application schedules increased the number of apical buds on branches, whereas the number of lateral buds was increased only by spring applications. Nitrogen increased tree fresh weight and retail value as well as weight, length, and surface area of needles. Foliar N concentrations in the fall varied with fertilization schedule, and were higher in November than in October.
Condition of Curry Leaves Exposed to Quarantine Treatments of Cold, Gamma Irradiation, or Methyl Bromide Fumigation
Authors: McGuire Raymond G.
Published: February 2019

In separate treatments, leaves of the curry leaf tree [Murraya koenigii (L.) Sprengel] were subjected to 15 days at 1 °C, to gamma irradiation from a 60Co source at dosages from 100 to 1000 Gy, or to fumigation with methyl bromide from 16 to 64 g·m–3. Cold-treated leaves retained their fresh appearance with minimal weight loss when stored in sealed plastic bags; although color intensity of the underside of leaves was measurably reduced, the change was not visually perceptible. Similarly, irradiation was associated with a darkening of leaves and a loss of color intensity, but these changes were not visibly apparent even at the highest dosage. Methyl bromide fumigation, however, greatly increased susceptibility of leaves to postharvest decay. Cold or gamma irradiation treatments should be tolerated by this commodity when treated for pests such as the Asian citrus psyllid (Diaphorina citri Kuwayama) prior to export.
Classification of Kentucky Bluegrass Genotypes Grown as Spaced-plants
Authors: Bonos Stacy A. , Meyer William A. , Murphy James A.
Published: February 2019

The apomictic breeding behavior of Poa pratensis L. provides an opportunity to study many unique genotypes that can vary dramatically in characteristics such as disease resistance, stress tolerance and growth habit. The classification of Kentucky bluegrass into types is based on common growth and stress performance characteristics gathered from field turf trials. These classification types include the Compact, Bellevue, Mid-Atlantic, BVMG (`Baron, `Victa', `Merit', and `Gnome'), Common, and Aggressive types. A spaced-plant nursery trial was established in May 1996 to quantify morphological and growth characteristics of 45 cultivars and selections representing the major types of Kentucky bluegrass. Plant height, panicle height, flag leaf height and length, subtending leaf length and width, rhizome spread, and longest extending rhizome were measured 10 days after anthesis. Compact type cultivars had a lower, more prostrate growth habit than the Common, Mid-Atlantic, and Bellevue types. Mid-Atlantic type cultivars had a wider rhizome spread than Compact type cultivars. Principal component analysis of morphological measurements made on spaced-plants supports the classification types of the Common, Compact, Bellevue, Mid-Atlantic, and BVMG, but not necessarily the Aggressive type.
Tolerance of Four Festuca Species to Ethofumesate and Prodiamine
Authors: Dernoeden Peter H.
Published: February 2019

Festuca species are being seeded into golf course roughs and natural or out-of-bound areas as alternative turfgrasses to replace perennial ryegrass (Lolium perenne L.) in the mid-Atlantic region. The tolerance of fine-leaf fescues to herbicides targeted for annual bluegrass (Poa annua L.) control, such as ethofumesate and prodiamine, is unknown. The objectives of this field study, therefore, were to assess the tolerance of `Rebel II' tall fescue (Festuca arundinacea Schreb.), and the fine-leaf fescue species `Reliant' hard fescue (Festuca longifolia Thuill.), `Jamestown II' Chewings fescue (Festuca rubra L. ssp. commutata Gaud.), and `MX 86' blue sheep fescue (Festuca glauca L.) to various rates, combinations, and times of application of ethofumesate and prodiamine. `Rebel II' was most tolerant of ethofumesate; however, sequential rates ≥0.84 + 0.84 kg·ha-1 reduced quality for 1 or more weeks and 2.24 + 2.24 kg·ha-1 caused unacceptable injury. Single applications of ethofumesate at rates of 0.56, 0.84, and 1.12 kg·ha-1, and sequential treatments of 0.56 + 0.56 and 0.84 + 0.84 kg·ha-1 reduced `Reliant' quality temporarily. Sequential treatments of high rates (i.e., 1.12 + 1.12 and 2.24 + 2.24 kg·ha-1), however, significantly reduced `Reliant' cover. `Jamestown II' was very sensitive to ethofumesate, but recovered from single applications of 0.56, 0.84, and 1.12 kg·ha-1; sequential applications (≥0.84 + 0.84 kg·ha-1) caused unacceptable injury, and rates ≥1.12 + 1.12 kg·ha-1 caused significant loss of cover. The cultivar MX 86 tolerated single applications of 0.56 to 2.24 kg·ha-1 of ethofumesate, but sequential treatments generally reduced quality to unacceptable levels. In one study, `Jamestown II' and `MX 86' were more severely injured when ethofumesate (1.12 or 2.24 kg·ha-1) was applied in October rather than in November. The fescues generally best tolerated a single, November application of ethofumesate at ≤1.12 kg·ha-1. Prodiamine (0.73 kg·ha-1) caused only short-term reductions in quality of `Jamestown II', but was generally noninjurious to the other fescues. Ethofumesate tank-mixed with prodiamine (0.84 + 0.36 or 1.12 + 0.73 kg·ha-1) elicited some short-term reduction in quality, but the level of injury was generally acceptable and injured fescues had recovered by spring. Chemical names used: [±]2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate (ethofumesate); N3,N3-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine); S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridine-dicarbothioate (dithiopyr).
Improved Detection of Petunia Vein Clearing Caulimovirus
Authors: Zeidan M. , Sikron Noga , Cohen J. , Gera A.
Published: February 2019

Petunia vein clearing virus (PVCV), a possible member of the caulimovirus group, was detected in several cultivars of vegetatively propagated petunias (Petunia ×hybrida Hort. Volm.-Andr.) grown in commercial nurseries. Leaf dip preparations and ultrathin sections of leaf tissue were analyzed by transmission electron microscopy (TEM). Spherical virus particles, 45-50 nm in diameter, were observed in samples taken from symptomatic petunia plants. The virus was purified and a polyclonal antiserum was prepared. In immuno-specific electron microscopy (ISEM), the PVCV antiserum-treated samples reacted with a distinct decoration on the virus suspect particles. A polymerase chain reaction (PCR)-based assay was used to detect PVCV in total nucleic acid extracts derived from infected petunia plants. Two primer pairs were designed to flank a 736-base-pair sequence located in the RNA-dependent RNA polymerase gene of the PVCV genome. A DNA fragment of predicted size was visualized in agarose gels. The authenticity of the amplified DNA fragment was confirmed by restriction analysis and by hybridization with the virus-specific PVCV DNA probe. The virus could be detected efficiently in high dilutions of sap extracted from infected petunia plants.
The Biochemical Basis for Flower Color in Calibrachoa
Authors: Waterworth Rebeccah A. , Griesbach Robert J.
Published: February 2019

Recently, several new Calibrachoa La Llave & Lexarza (Solanaceae Juss.) cultivars have been developed with novel red and blue flowers. Most wild species of Calibrachoa have purple flowers. The differences in color were not due to anthocyanin composition, but rather to vacuolar pH. The pH of the red-flowered cultivar was 4.8 while that of the blue-flowered cultivar was 5.6. The wild purple-flowered species had an intermediate pH of 5.0. These data suggest that different pH and pigment genes may be introgressed into other Calibrachoa species to increase cultivar diversity.
Self- and Cross-fertility in Recently Released Highbush Blueberry Cultivars
Authors: Ehlenfeldt Mark K.
Published: February 2019

Self- and cross-fertility were evaluated in the highbush blueberry (Vaccinium corymbosum L.) cultivars Bluegold, Duke, Legacy, Nelson, Sierra, Sunrise, and Toro, all of which have been released since 1985, by comparing them with `Bluecrop' and `Rubel', which were used as standards. Cross-pollination increased fruit set in all cultivars except `Bluecrop', in which set was reduced 13%. The average increase among recently released cultivars was 43%. Cross-pollination also increased fruit weight for all cultivars except `Rubel'. Average increase in fruit weight with cross-pollination of the recently released cultivars was 27%. Fruit set and fruit weight measurements suggest that `Duke', `Legacy', and `Nelson' would perform satisfactorily in solid stands, and that `Sierra' and `Toro' probably need cross-pollination for maximum yields.
Relative Performance of Strawberry Cultivars and Native Hybrids on Fumigated and Nonfumigated Soil in Michigan
Authors: Hancock James F. , Callow Peter W. , Serçe Sedat , Schilder Annemiek C.
Published: February 2019

The performance of four California and 11 eastern cultivars of Fragaria×ananassa Duchesne in Lamarck, and 12 elite F1 hybrids of Fragaria×ananassa with F. virginiana Miller in their immediate background was evaluated in a producer's field with and without methyl bromide-chloropicrin fumigation. Averaged across all genotypes, plants in nonfumigated soils had 43% fewer runners, 18% smaller fruit, and 46% lower yields than did plants on fumigated soil. They also had an average of 27% fewer crowns, 49% more root discoloration, significantly fewer fine roots, and showed symptoms of the black root rot syndrome. The most commonly isolated pathogens from discolored roots were Pythium sp., Rhizoctonia sp., Idriella lunata P.E. Nelson & K. Wilh., and the root-knot nematode (Meloidogyne hapla Chitwood). The performance of all genotypes was enhanced by fumigation, although the F. virginiana hybrids performed comparatively better than the other cultivars on nonfumigated soils.
Rough Bluegrass Germination Varies with Temperature and Cultivar/Seed Lot
Authors: Liu Chunhua , Camberato James J. , Martin S. Bruce , Turner Amy V.
Published: February 2019

Rough bluegrass (Poa trivialis L.) is being utilized more frequently to overseed bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] putting greens and rapid seed germination is necessary for successful establishment. Cultivar and seed lot differences in germination rate and sensitivity to cold may exist. Germination of 10 rough bluegrass cultivars/seed lots was examined in growth chambers at 12-hour day/12-hour night temperatures of 25/15, 20/10, 15/5, and 10/0 °C, and on a bermudagrass putting green at three overseeding dates. Differences in germination among cultivars and seed lots were minimal at 25/15 or 20/10 °C, but substantial at lower temperatures. When seeded on the bermudagrass putting green, differences in germination among cultivars/seed lots were greater at the last seeding date (average daily max./min. of 16/2.7 °C), than at the first seeding dates (average daily max./min. of 21/6.1 °C). Use of blends of several cultivars or seed lots is suggested to ensure the successful establishment of rough bluegrass when overseeding at low temperatures.
Early Performance of 'Conference' Pear on Four Training Systems
Authors: Kappel Frank , Brownlee Rob
Published: February 2019

To determine how different training systems affected early growth and fruiting (first 5 years), `Conference' pear (Pyrus communis L.) trees on Quince A (Cydonia oblonga L.) rootstock were trained to angled trellis, slender spindle, vertical axe, or Y-trellis. The trees of the Y-trellis had the greatest spread after 5 years, and the vertical axe and slender spindle trees were the tallest. The Y-trellis trees had the highest light interception and had significantly higher yields in 1997 than the other training systems. Average fruit weight was inversely related to crop load.