Severe Curl Research Articles

A new species of Aceria (Acari: Eriophyidae) damaging sowthistles, Sonchus spp. (Asteraceae), in Australia with notes on Aceria sonchi (Nalepa, 1902)

A new species of eriophyoid mite from Australia is described and illustrated. Aceria thalgi sp. n. causes severe curling and rolling of leaves of common introduced sowthistle, Sonchus oleraceus L. It also affects introduced Sonchus asper (L.) Hill and native Sonchus hydrophilus Boulos. The native species may be the original host for this mite. Aceria thalgi sp. n. is shown to be a separate species to Aceria sonchi (Nalepa), which forms distinctive leaf galls on Sonchus spp. in southern Europe. English translations of past descriptions of A. sonchi are included for comparison. Historical observations and records from New South Wales suggest that A. thalgi sp. n. has been known for at least 80 years prior to its recent rediscovery in Western Australia. This implies that the newly described species may be widespread across the continent. There is also a past record of similar damage symptoms occurring on sowthistles in New Zealand. Aceria thalgi sp. n. has the potential to be a useful biological control agent in Australia and Canada, where sowthistles are major weeds of agriculture.

Isolation and molecular characterization of Xylella fastidiosa from coffee plants in Costa Rica

Coffee plants exhibiting a range of symptoms including mild to severe curling of leaf margins, chlorosis and deformation of leaves, stunting of plants, shortening of internodes, and dieback of branches have been reported since 1995 in several regions of Costa Rica's Central Valley. The symptoms are referred to by coffee producers in Costa Rica as "crespera" disease and have been associated with the presence of the bacterium Xylella fastidiosa. Coffee plants determined to be infected by the bacterium by enzyme linked immunosorbent assay (ELISA), were used for both transmission electron microscopy (TEM) and for isolation of the bacterium in PW broth or agar. Petioles examined by TEM contained rod-shaped bacteria inside the xylem vessels. The bacteria measured 0.3 to 0.5 microm in width and 1.5 to 3.0 microm in length, and had rippled cell walls 10 to 40 nm in thickness, typical of X. fastidiosa. Small, circular, dome-shaped colonies were observed 7 to 26 days after plating of plant extracts on PW agar. The colonies were comprised of Gram-negative rods of variable length and a characteristic slight longitudinal bending. TEM of the isolated bacteria showed characteristic rippled cell walls, similar to those observed in plant tissue. ELISA and PCR with specific primer pairs 272-l-int/272-2-int and RST31/RST33 confirmed the identity of the isolated bacteria as X. fastidiosa. RFLP analysis of the amplification products revealed diversity within X. fastidiosa strains from Costa Rica and suggest closer genetic proximity to strains from the United States of America than to other coffee or citrus strains from Brazil.

Regulation of AUXIN RESPONSE FACTOR3 by TAS3 ta-siRNA Affects Developmental Timing and Patterning in Arabidopsis

MicroRNAs (miRNAs) and trans-acting siRNAs (ta-siRNAs) in plants form through distinct pathways, although they function as negative regulators of mRNA targets by similar mechanisms . Three ta-siRNA gene families (TAS1, TAS2, and TAS3) are known in Arabidopsis thaliana. Biogenesis of TAS3 ta-siRNAs, which target mRNAs encoding several AUXIN RESPONSE FACTORs (including ARF3/ETTIN and ARF4 ) involves miR390-guided processing of primary transcripts, conversion of a precursor to dsRNA through RNA-DEPENDENT RNA POLYMERASE6 (RDR6) activity, and sequential DICER-LIKE4 (DCL4)-mediated cleavage events. We show that the juvenile-to-adult phase transition is normally suppressed by TAS3 ta-siRNAs, in an ARGONAUTE7-dependent manner, through negative regulation of ARF3 mRNA. Expression of a nontargeted ARF3 mutant (ARF3mut) in a wild-type background reproduced the phase-change phenotypes detected in rdr6-15 and dcl4-2 mutants, which lose all ta-siRNAs. Expression of either ARF3 or ARF3mut in rdr6-15 plants, in which both endogenous and transgenic copies of ARF3 were derepressed, resulted in further acceleration of phase change and severe morphological and patterning defects of leaves and floral organs. In light of the functions of ARF3 and ARF4 in organ asymmetry, these data reveal multiple roles for TAS3 ta-siRNA-mediated regulation of ARF genes in developmental timing and patterning.

Reducing Curl in Multilayer Blown Film: Experimental Results, Model Development, and Application to A Cereal Liner Film

Multilayer blown films often curl, particularly if the layers are not distributed symmetrically. Experimental results from simple two- and three-layer structures are described in an effort to understand the underlying mechanisms behind curl. A model from the literature based on “beam theory” was adapted to film applications. In this model, force and momentum balances are used to solve for curl as a function of each layer’s thickness, stiffness, and shrinkage during fabrication. The difficulty in using such an approach is estimating differential shrinkage. Pressure-Volume-Temperature (PVT) data give good qualitative information on differential shrinkage, but they are generated under experimental conditions that differ greatly from commercial blown film processes. To correct the PVT data, a semi-empirical approach was utilized. The model was run “backwards” to compute the differential shrinkage in two-layer structures where the curl has been measured. From this, PVT correction factors are obtained to predict the curl of multilayer structures. The model was applied to a (HDPE-tie-EVOH-tie-sealant) cereal liner structure. A sensitivity analysis showed that curl can be reduced by: increasing the thickness of the high density polyethylene (HDPE) layer, reducing the shrinkage of the HDPE, and reducing the thickness and stiffness of the ethylene vinyl alcohol (EVOH) layer. Experiments on a five-layer blown film line confirmed the model predictions: a standard cereal liner structure had severe curl, yet by using the model as a guide, we were able to make essentially flat film.

Control of Hawthorn (Two Circuli) Mealybug and A Woolly Aphid, Fort Collins, Colorado, 1995

Abstract Plots were established at the W.D. Holley Plant Environmental Research Center located on the campus of Colorado State University. Two trees, approximately 8-20 ft (4 inch dbh) and established at the site for approximately 10 years were utilized in the experiment. Individual branches were sprayed with different compounds to run-off. Each branch was treated as a single experimental unit, with a complete replication being a group of branches with similar orientation on the tree. Plot design was a RCB with 5 replications. Treatments were applied on 5 May by spraying 2 ft terminal branch segments with a pump-mister sprayer to the point of run-off. Although weather was clear at the time of application, soil moisture was high at the site due to prior rainfall and V5 inch of rain fell at the site in the 24 h following application. Treatments were sampled on 7 Jun by counting the number of mealybugs present on 19 inches of terminal branch segment. Aphid ratings were taken on the same date by assessing the damage and curling caused by an infestation of a woolly aphid. An eleven point rating system was used to rate leaf curling damage by the aphids per 19 inches of terminal branch segment. The rating scale was as follows: 0 = No leaves curled, 1 = 1-5 leaves with light curling, 2 = 6-10 leaves with light curling, 3 = 10+ leaves with light curling, 4 = 1-5 leaves with moderate curling, 5 = 1-5 leaves with moderate curling, 6 = 6-10 leaves with moderate curling, 7 = 10+ leaves with moderate curling, 8 = 1-5 leaves with severe curling, 9 = 6-10 leaves with severe curling, 10 = 10+ leaves with severe curling.

Hawthorn Insect Control, Trial One, Ft. Collins, Colorado, 1995

Abstract Plots were established at the WD. Holley Plant Environmental Research Center located on the campus of Colorado State University. Two trees, approximately 8-20 ft (4 inch dbh) and established at the site for approximately 10 years were utilized in the experiment. Individual branches were sprayed with different compounds to run-off. Each branch was treated as a single experimental unit, with a complete replication being a group of branches with similar orientation on the tree. Plot design was a RCB with 5 replications. Treatments were applied on 5 May by spraying terminal branch segments with a pump-mister sprayer to the point of run-off. Although weather was clear at the time of application, soil moisture was high at the site due to prior rainfall and VS inch of rain fell at the site within 24 h of application. Treatments were evaluated on 7 Jun by counting the number of mealybugs present on 19.5 inches of terminal branch segment. Aphid ratings were taken on the same date by assessing the damage and curling caused by an infestation of a woolly aphid. An eleven point rating system was used to rate leaf curling damage by the aphids per 19.5 inches of terminal branch segment. The rating scale was as follows: 0 = No leaves curled, 1 = 1-5 leaves with light curling, 2 = 6-10 leaves with light curling, 3 = 10+ leaves with light curling, 4 = 1-5 leaves with moderate curling, 5 = 1-5 leaves with moderate curling, 6 = 6-10 leaves with moderate curling, 7 = 10+ leaves with moderate curling, 8 = 1-5 leaves with severe curling, 9 = 6-10 leaves with severe curling, 10 = 10+ leaves with severe curling.

Epidemiology of tobacco leaf curl virus in India

SummaryThe incidence of disease caused by tobacco leaf curl geminivirus (TbLCV) in ten tobacco growing areas of India ranged from 1.2% to 77%. The highest incidence of disease was observed in Andhra Pradesh (77%) followed by Gujarat (59%), Karnataka (17%), Bihar (11.6%) and West Bengal (5.4%). Under field conditions, an average of 32 adult whiteflies (Bemisia tabaci) per plant were recorded in Andhra Pradesh followed by Gujarat (20), Karnataka (12), Bihar (8) and West Bengal (5). In sequential sowings at Bangalore, all the plants were infected within 90 days in plots planted from February to June. Infection in plots planted later was progressively less. There was a positive correlation between whitefly catches and the final incidence of leaf curl disease in plantings. TbLCV was transmitted by Bemisia tabaci to 35 plant species, including Beta vulgaris, Capsicum annuum, Carica papaya, Cymopsis tetragonoloba, Lycopersicon esculentum, Sesamum indicum, Phaseolus vulgaris and Petunia hybrida. Forty five TbLCV isolates from different parts of India induced four distinct types of symptoms on tobacco cultivars Samsun and Anand 119. Group 1 isolates caused severe curling and cup‐shaped enations; group II isolates induced pale green leaves, pit‐like depressions and thorny enations: group III isolates caused leathery leaves, narrow and tiny protruding enations between the veins, and group IV isolates induced irregular thickening and swelling of veins and green flap‐like enations on veins. Nylon net covers protected tobacco seedlings in nursery beds for 45 days. Ricinus communis and Helianthus annuus sown around the tobacco nursery bed as barrier crops attracted adult whiteflies and decreased the number found on tobacco.

Potato Leafhopper and Seedcorn Maggot Efficacy Trials, 1979

Abstract Twenty-four soybean plots (var. Elf) were established near Ames, Iowa. Each measured 40 ft by 4 rows (30-in centers) and was bordered by 2 rows. Five treatments (Table 1) and a check were arranged in a randomized completeblock design, with 4 blocks. Granular insecticides were applied in-furrow at planting on May 23 with a 2-row John Deere 71 flex planter. Plants emerged on May 31. Stand counts were taken on June 14. Each plot was examined for phytotoxic symptoms and assigned a value from 0 (no symptoms) to 5 (severe curling and discoloration of leaves and growing tip). Seedcorn maggot damage was evaluated by counting the number of plants with snakeheads (maggot-eaten growing tip) and/or cotyledonary scarring in 4 1-m row sections/plot. Plots were sampled (10-sq ft/plot) for potato leafhopper nymphs and adults with a D-Vac vacuum insect net (1-sq ft sampling cone). Post-emergence samples (20, 30, 45, and 60 days post-emergence) were taken on July 19 (3-trifoliate stage), June 29 (5-trifoliate stage), July 13 (mid-bloom stage) and July 27 (beginning pod-fill stage), respectively. D-Vac sampling was supplemented with shake sampling, 2 samples of 2 adjacent 1 row-ft/plot, for nymphs at 45 and 60 days post-emergence. Total rainfall for June and July was 2.9 and 4.5 in, respectively. Plots were harvested Oct 25 and bean weight/10 row-ft determined.

Physiology of Sugarcane Under Water Stress: Invertase, ATP-ase and Amylase Behavior in Plants Experiencing Water Deficiency, Night Flooding and Continuous Flooding

Effects of water stress on growth, sugar production and enzymology of sugarcane were evaluated in two greenhouse experiments in which sugarcane of the variety P.R. 980 was grown in sand culture with controlled nutrient supply. At 14 weeks of age, four water regimes were created for each of the two experiments: No water, normal water (2 liters daily), normal water plus night flooding, and continuous flooding. One experiment was pretreated with a 0.01-percent solution of active gibberellic acid (GA) 10 days before water variables were initiated. Samples of leaf, leaf sheath, immature storage tissue and stalk tissue were harvested at 0, 2, 5, and 9 days. Enzyme assays were conducted with leaf and immature storage tissue preparations for acid invertase, adenosine triphosphatase (ATP-ase), and ß-amylase. The following results were obtained: 1. Foliar symptoms appeared between the fifth and ninth day among the low-water and continuous flooding regimes. Wilting of leaves and leaf sheaths, yellowing of leaf tips, extensive yellowing of older leaves and leaf sheaths, and severe curling of spindle tissues was general among both treatments. Symptoms were delayed but not prevented by GA pretreatment. Normal water and night flooding produced no visible effects. Whorls of adventitious roots grew from submerged nodes of continuously flooded plants. 2. Sheath moisture values ultimately declined in water-deficient and water-toxic plants regardless of GA treatment. Continuously flooded plants increased total fresh weight, regardless of leaf and sheath desiccation, when pretreated with GA. A GA role in promoting water uptake is suggested. 3. Leaf sucrose declined in water-deficient and continuously flooded sugarcane but increased in immature storage tissues. This was taken as evidence of continued sucrose transport under moisture conditions restrictive against sugar synthesis. Polarization values for milled juice indicated that GA pretreatment caused a decline of storage sucrose under a normal water regime, but GA prevented storage sucrose losses under a regime of continuous flooding. The former GA effect is interpreted in terms of growth stimulation, the latter in terms of GA involvement in sugar accumulation processes effective in transport of sucrose to storage areas. 4. Invertase was suppressed both by deficient and excessive water regimes and by GA pretreatment. Night flooding produced little effect. 5. ATP-ase was strongly suppressed by night flooding but no consistent effects were produced by the other water regimes. The ATP-ase suppression by excessive night water was interpreted as a perturbation of normal diurnal-nocturnal rhythms rather than a sensitivity of synthesis mechanisms to flooding per se. GA pretreatment suppressed ATP-ase among all water regimes. Assuming that foliar ATP-ase is a functional entity of photosynthetic phosphorylation, the GA effect was taken as further evidence of a GA influence upon sugarcane photosynthesis. 6. Foliar amylase remained at a constant level in water-deficient cane, while other water regimes tended to increase the enzyme. Amylase was less sensitive to water regime than invertase and appeared to be synthesized under flood conditions highly repressive for invertase. It is concluded that low- and high-water regimes tend to produce common effects upon the overall synthesis and utilization of sugar in the cane plant. Hormone level may affect the rate of sugar utilization within high and low water regimes without altering the outward manifestations of these regimes. Hydrolytic enzyme level is apparently affected indirectly by prolonged water stress or by perturbation of endogenous day-night rhythms. However, the enzymes measured were not sufficiently sensitive to changing water supply to serve as indicators of water status.