bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transmission characteristics of Spiroplasma citri and its effect on leafhopper vectors from the Circulifer tenellus complex
Authors: ALMEIDA LYNETTE DE , RACCAH B. , KLEIN M. 
Published: February 2008

Summary.Several leafhopper variants of the Circulifer tenellus complex were collected in “citrus stubborn” affected areas in Israel. Two of these variants transmitted the Spiroplasma citri to Matthiola incana after being injected with the disease agent. The variant from Atriplex halimus was designated Circulifer tenellus‐A (CTA) and the variant from Portulaca oleracea was designated Circulifer tenellus‐? (CTP). Transmission characteristics were determined for both leafhoppers. A high rate of transmission (43.3%) was obtained by single CTA leafhoppers that were injected with the Amiad S. citri isolate from the Upper Galilee, compared with 7% transmission obtained with the CTP leafhoppers. The Gilgal S. citri isolate from the Jordan Valley, was not transmitted by either. Injection was more effective than acquisition access feeding to render the leafhopper infective for both CTA and CTP. The minimum acquisition access period needed for the CTA variant to transmit the Amiad isolate was 1 h. Longer AAPs did not necessarily result in a higher rate of transmission. The minimum incubation period was 6 days and the maximum was 32 days. The LP50 calculated from the logarithmic curve y = 45.74Ln(x)–53.68 was 9.64 days. The minimum inoculation access period (IAP) was lh. The same transmission parameters for the CTP variant could not be determined, as no transmission was obtained even when groups of five‐six insects were placed on a single plant.
Rhabdovirus‐like and closterovirus‐like particles in ultrathin sections of Ribes species with symptoms of blackcurrant reversion and gooseberry veinbanding diseases
Authors: ROBERTS I M , JONES A T 
Published: February 2008

Summary.In attempts to determine the causal agents of blackcurrant reversion (BCRD) and gooseberry veinbanding (GVBD) diseases of Ribes species, details of the ultrastructure of different kinds of tissue from plants affected with these different diseases were studied. In three of 12 blackcurrant plants affected with BCRD, leaves and flowers of plants showing symptoms typical of the severe (R) form of the disease, contained rhabdovirus‐like particles c. 65–80 nm × 215–485 nm. They were seen most often in the nucleus of cells as single particles but were also found in clusters or rafts. In leaves, these virus‐like particles (VLPs) were present only in cells associated with the xylem parenchyma where they occurred as membrane‐bound clusters within the nucleus. In flowers, they were also found in phloem parenchyma cells in the peripheral cytoplasm and very occasionally in the cytoplasm of epidermal cells. All non‐nuclear VLPs were membrane‐bound, either singly or in groups and the membrane seemed to be part of the endoplasmic reticulum. The proportion of vascular cells containing these VLPs was very low (< 1%). In a few cells, smaller bacilliform particles, c. 40–50 nm × 200–250 nm, were found in the nucleus together with the larger particles. Double‐membrane bodies, detected in fig leaves affected with fig mosaic (the agent of which is also mite‐transmitted), were not detected in any BCRD‐affected plants. In leaf tissue of one of three gooseberry and one of two blackcurrant plants affected with GVBD, two kinds of VLPs were found. Rhabdovirus‐like particles, similar to those in BCRD‐affected material, were present in the nuclei, perinuclear space and cytoplasm of xylem parenchyma cells. They were c. 60–72 nm × 155–230 nm but there was no evidence of the smaller rhabdovirus‐like particles detected in a few cells of BCRD‐affected tissues. The second kind of VLP was found in noncrystalline masses, with a mean centre‐centre spacing of c. 10 nm, in the cytoplasm of phloem cells. These particles, together with other ultrastructural changes, were typical of those reported for aphid‐transmitted closteroviruses. No badnavirus‐like particles, reported previously from GVBD‐affected plants, were observed in any of the plants studied. The significance of these findings in relation to these two important diseases of commercial Ribes species is discussed.
The effect of temperature on viability of imbibed weed seeds
Authors: THOMPSON A J , JONES N E , BLAIR A M 
Published: February 2008

Summary.Imbibed seed of 10 common arable weeds were placed in trays in initially moist soil and, after imbibing for 2h, heated in ovens/incubators set to 31oC, 42oC, 56oC, 75oC or 100oC for 0.5, 1, 2, 4, 8 or 16 days or at 102oC, 155oC, 204oC or 262oC for 0.5, 1, 2, 5, 7.5 or 10 min. After heating, seeds were incubated for 28 days at 10/20oC or 20/30oC on a 12 h dark/light regime, depending on species, and germination recorded. At the lower temperatures, germination of all species was prevented by temperatures of 75oC or higher for periods of 0.5 days or more. Germination was lower after treatment at 56oC than at 31oC or 42oC for all species except Rumex obtusifolius. The maximum temperature required to prevent germination varied among species and was of greater importance than the duration of heating. Germination was variable with duration of heating. At the higher temperatures, there was very little germination of any species after heating at 204oC for 7.5 min or 262oC for 5 min or more. Seeds were greatly buffered from the air temperature by 3 mm of soil, throughout the shorter duration of heating. The average temperature of the soil, over the 10 min heating required to prevent over 90% germination, varied among species and ranged from 48oC for Avena fatua to 65oC for R. obtusifolius. This work implies that composting systems maintained at 65oC are unlikely to provide an efficient method of weed control. Recommendations for improvement of the laboratory technique are suggested.
Natural resistance to cucumber mosaic virus in lupin species
Authors: JONES R A C , LATHAM L J 
Published: February 2008

Summary.Ten species of lupins (Lupinus spp.) were tested for resistance to cucumber mosaic cucumovirus (CMV) in field experiments where inoculation was by naturally‐occurring aphid vectors, and in the glasshouse by sap or graft‐inoculation. L. albus and six species of ‘rough‐seeded’ lupins did not become infected with CMV either under intense inoculum pressure in the field or when graft‐inoculated. Two L. hispanicus, 17 L. luteus and four L. mutabilis genotypes became infected with CMV in the field, but no infection was detected in L. hispanicus P26858 or seven L. luteus genotypes. CMV was detected at seed transmission rates of 0.2–16% in seedlings of infected L. luteus, differences in levels of seed transmission between genotypes being significant and relatively stable from year to year. Graft‐inoculation of CMV to plants of six genotypes of L. luteus in which no infection was found in the field induced a systemic necrotic reaction suggesting that the resistance they carry is due to hypersensitivity.In L. hispanicus accessions P26849, P26853 and P26858, CMV sub‐group II isolate SN caused necrotic spots in inoculated leaves without systemic movement, while sub‐group I isolate SL infected them systemically without necrosis. Another sub‐group I and two other sub‐group II isolates behaved like SL in P26849 and P26853 but infected only inoculated leaves of P26858. This suggests that two strain specific hypersensitive resistance specificities are operating against CMV in L. hispanicus. When plants of L. luteus genotypes that gave hypersensitive reactions on graft‐inoculation were inoculated with infective sap containing two sub‐group I and seven sub‐group II isolates, they all responded like L. hispanicus P26858. A strain group concept is proposed for CMV in lupins based on the two hypersensitive specificities found: strain group 1 represented by isolate SN which induces hypersensitivity with both specificities, strain group 2 represented by the three isolates which induced hypersensitivity only with the specificity present in L. luteus and L. hispanicus P26858, strain group 3 by as yet hypothetical isolates that induce hypersensitivity only in presence of the specificity in L. hispanicus P26849 and P26853 that responded just to isolate SN, and strain group 4 by isolate SL which overcomes both specificities. When F2 progeny plants from crosses between hypersensitive and susceptible L. luteus parents were inoculated with isolate SN, the resistance segregated with a 3:1 ratio (hypersensitive:susceptible), suggesting that a single dominant hypersensitivity gene, Ncm‐1, is responsible. As gene Ncm‐1 had broad specificity and was not overcome by any of the five CMV isolates from lupins tested, it is valuable for use in breeding CMV resistant L. luteus cultivars.
Occurrence of Acremonium endophytes in wild populations of Lolium spp. in European countries and a relationship between level of infection and climate in France
Authors: LEWIS G C , RAVEL C. , NAFFAA W. , ASTIER C. , CHARMET G. 
Published: February 2008

SummaryInfection with endophytic fungi (Acremonium spp.) was detected in wild populations of Lolium spp. from 15 of 20 European countries. Of 523 populations examined, 38% contained no infection, 48% contained 1–50% infection and 14% contained 51–100% infection. Level of infection was slightly but significantly associated with abundance of Lolium in the sward.For data from France, significant correlations were obtained between level of infection and five climate variables; the highest correlations were with evapotranspiration (0.66, P < 0.001) and water supply deficit (‐0.66, P < 0.001). A model established using multiple regression analysis and incorporating five climatic variables, accounted for 56% of total variation; water supply deficit alone accounted for 43%. These climatic variables were shown by geostatistical analysis to account for a spatial structure in infection level. Groups of Lolium populations with a high level of infection were located mostly in Mediterranean regions, where stress from summer drought is common.
Positive and negative sense coat protein gene‐mediated protection against poplar mosaic carlavirus in Nicotiana benthamiana
Authors: EDWARDS M L , LIU Y Y , HAWES W S , HENDERSON J. , COOPER J I 
Published: February 2008

SummaryPlants of Nicotiana benthamiana were transformed with four constructs based on the coat protein gene of a poplar mosaic carlavirus (PMV) isolate from the UK. The four constructs were: the capsid protein coding sequence plus a portion of the adjacent sequence encoding a protein with a molecular mass of 14 kDa (CP14k); the capsid protein coding sequence in the positive sense (CPP); a mutated capsid protein coding sequence (CPM) and the capsid protein coding sequence in the negative sense (CPN). Forty‐one regenerated plants, after selection for their kanamycin resistance, were confirmed by PCR to contain the appropriate sequences. Virus coat protein was detected in small amounts in 50% of the plants transformed with the CP14k or CPP constructs. Primary transformants showed a range of reactions to challenge with two isolates of PMV. These varied from apparently no infection in inoculated or in later‐formed young leaves, as assessed by ELISA, to typical systemic symptoms associated with large amounts of serologically detected virus. There was no correlation between the level of protection against virus infection and the observed accumulation of transgene protein product. Plants were protected whether transformed with the coat protein coding sequence in the positive or negative sense.
Effects of simulated insect damage and weed interference on cotton growth and reproduction
Authors: SADRAS V O 
Published: February 2008

SummaryEarly‐season insect pests of cotton (Gossypium hirsutum L.) crops, including Lepidoptera larvae and mirids, feed on vegetative buds. The loss of vegetative buds transiently delays the plant's development and growth and has the potential to reduce its competitive ability. Yield reductions due to weed interference and insect damage, therefore, could be greater than expected from the additive effects of weeds and damage acting separately. Three varieties, two levels of weed infestation, and two levels of simulated damage were combined in a factorial experiment designed to assess the responses of cotton plants to the combined effects of damage and weeds. Weed treatments were: with (+W) and without weeds (‐W), and damage treatments included: undamaged control (‐D) and damaged plants (+D) which had their active vegetative buds removed at 30 and 49 days after sowing.Variety and interactions between variety and other factors were normally nonsignificant for all the response variables measured in this experiment. Cotton height, width, production of flowerbuds and production of fruit were all affected by both damage and weeds. While the effects of damage on these growth variables were transient, the effects of weeds normally increased with time throughout the season. Non‐additive effects of weeds and damage were minor for plant height and width, and large for flowerbud and fruit production.At maturity, weed dry matter ranged from about 20 g m‐2 (‐W treatments) to 300 gm‐2 (+W), cotton dry matter from 144 gm (+W+D) to 945 gm‐2 (‐W‐D), and seed cotton production from 54gm‐2 (+W+D) to 417 gnT‐2 (‐W+D). Damage did not affect vegetative dry matter and marginally increased seed production in ‐W plots. Non‐additive effects of weeds and damage were negligible for vegetative dry matter but highly significant for seed production (P < 0.0001). These contrasting responses of vegetative and reproductive growth are in agreement with neighbouring models of plant competitive interactions that emphasise the effects of neighbour interference on the fecundity of target plants that are not mediated by changes in target‐plant size.
Efficacy of bracken (Pteridium aquilinum (L.) Kuhn) control treatments across a range of climatic zones in Great Britain
Authors: PATERSON S. , MARRS R H , PAKEMAN R J 
Published: February 2008

SummaryBracken control field experiments were conducted at six locations across Great Britain. The effects of various cutting and herbicide management regimes upon the seasonal dynamics of bracken fronds and rhizomes were examined over a three year period. This enabled a national overview towards bracken control to be constructed. Initially, spraying with asulam was the most effective treatment in reducing frond biomass and density but was least effective in reducing rhizome biomass. Differential reductions in rhizome biomass were observed in relation to cutting frequency, with cutting twice yearly giving superior control. The national trends confirmed a number of previous observations from independent single‐site studies; however, others were contradicted. Comparable management options were ranked consistently between the current and former investigation, however, the initial importance of differences in cutting frequencies did not agree between studies. This multiple‐site study improves understanding of the consequences of a national bracken control programme by reducing the influence of confounding site‐specific factors, and recommendations for the most appropriate bracken control techniques are made. The extent to which individual sites reflect a national trend in response to bracken control is considered and sites are compared. The hierarchy of treatments identified at the national scale was found to apply generally within individual sites. However, several responses which proved significant at the countrywide level were not so clearly defined at the site scale. Cutting once yearly was the only management regime which appeared to give different bracken control between sites. All other treatments gave similar responses between sites. This result was found in the Scottish Borders, during the second year of control, when frond biomass and density (relative to untreated plots) were greater than that recorded at other sites. This contrast was not found in subsequent monitoring. In terms of rhizome biomass depletion, poorer control was achieved following cutting once yearly at the northern sites (Mull, Scottish Borders, Lake District) compared with the southern sites (Clwyd, Breckland, Devon). The implications of experimental results are discussed in relation to increased cost effectiveness of national bracken control programmes.
Linkage between Frl (Fusarium oxysporum f.sp. radicis‐lycopersici resistance) and Tm‐2 (tobacco mosaic virus resistance‐2) loci in tomato (Lycopersicon esculentum)
Authors: VAKALOUNAKIS D J , LATERROT H. , MORETTI A. , LIGOXIGAKIS E K , SMARDAS K. 
Published: February 2008

SummaryA study was carried out on the linkage relationship between the Frl locus carrying resistance to Fusarium oxysporum f.sp. radicis‐lycopersici and the Tm‐2 locus carrying resistance to several races of tobacco mosaic virus in the tomato inbred line IRB‐301‐31. The inbred line Motelle (Frl+/Frl+, Tm‐2+/Tm‐2+) was crossed with the inbred line IRB‐301‐31 (Frl/Frl, Tm‐2/Tm‐l). The resulting 222 F2 plants were selfed, and from each F3 family groups of 15–60 seedlings were tested for resistance to either F. oxysporum f.sp. radicis‐lycopersici or tobacco mosaic virus race 0. Segregation data indicated a very tight linkage between Frl and Tm‐2, equal to 5.1 ± 1.07 map units.
Factors affecting winter survival of the florally determinate white lupin cv. Lucyane
Authors: BATEMAN G L , FERGUSON A W , SHIELD I. 
Published: February 2008

SummaryIn a series of three field experiments with factorial design, on sites that had not grown lupins previously, sowing date was the main factor affecting over‐winter survival of autumn‐sown white lupin. In 1993, the sowing dates (23 September and 20 October) were too late to prevent much plant death in autumn and early winter, with the onset of frosts. In 1994, the sowing dates (30 August and 22 September) were early enough to prevent severe frost damage, but infestations of bean seed fly (Delia platura) occurred, more in the later than in the earlier sown crops, causing wilting and plant death. Losses were decreased where furothiocarb seed treatment was applied. In 1995, losses were greater in early‐sown (12 September) than in later sown (28 September) crops; plant death was gradual, occurring into the spring, and was apparently associated with over‐development of young shoots before an unusually long, cold winter. A chlorpyrifos spray (13 or 29 September for early or late sown plots, respectively) slightly increased survival, possibly by controlling Thrips angusticeps. Fungicides applied to seed or as sprays in late autumn had little or no effect in these experiments. In another series of experiments to test fungicides, in 1992‐93 and 1993‐94, survival was poor following late sowing (in October), but was increased by application of prochloraz in December or January, or, in 1994, by seed treatment with thiram.
Preferences and apparent digestibilities of sugars by fruit damaging birds in Japan
Authors: LANE SIMON J 
Published: February 2008

SummaryGray starlings Sturnus cineraceus, azure‐winged magpies Cyanopica cyana and brown‐eared bulbuls Hypsipetes amaurotis are among the main bird pests in commercial fruit orchards in central Japan. Recently Brugger & Nelms (1991) suggested that developing high‐sucrose fruit cultivars could reduce crop damage, because some pest birds lack the enzyme sucrase and can develop an aversion to sucrose. Preferences for, and digestibilities of, the monosaccharides glucose and fructose and the disaccharide sucrose by these pests species were therefore studied to assess whether this idea would be applicable in central Japan. Gray starlings and brown‐eared bulbuls were able to detect glucose, fructose, a mixture of glucose and fructose, and sucrose at a concentration of 12% w/v. Azure‐winged magpies also detected glucose and fructose, but failed to detect sucrose at the same concentration. In pairwise preference trials gray starlings and azure‐winged magpies selected the monosaccharides over sucrose, but brown‐eared bulbuls did not. To estimate the digestibility of the sugars the apparent assimilated mass coefficient, AMC*, was calculated for each species eating each sugar by measuring intake and faecal output. Monosaccharides had mean AMC*s of 0.77, 0.96 and 0.92 when consumed by gray starlings, azure‐winged magpies and brown‐earned bulbuls respectively. AMC* values for sucrose were 0.82 and 0.49 for brown‐eared bulbuls and azure‐winged magpies respectively, but gray starlings were shown to be unable to digest sucrose. As AMC* values varied from 0.75 to 0.97, consumption rates of sugars increased as digestibility decreased. Although increasing sucrose contents of commercial fruits may deter sucrase‐deficient birds such as gray starlings from depredating fruits, it may also lead to increased crop damage by species such as the azure‐winged magpie and brown‐eared bulbul which may have to consume more of the less digestible fruit in order to meet their energy requirements.
Assessment of the efficiency of a hand‐held suction device for sampling spiders: improved density estimation or oversampling?
Authors: SAMU FERENC , NÉMETH JÓZSEF , KISS BALÁZS 
Published: February 2008

SummaryIn the study a comparison is made between the results of two sampling procedures, both based on the application of the same hand‐held suction apparatus. Sampling was aimed at spiders, and was carried out on two alfalfa fields. In the first method suction sampling was applied to an enclosure of 0.48 m2. The enclosed area was sampled intensively, which was facilitated by the removal of the vegetation. The second method was a transect sampling procedure during which the suction apparatus with a 0.01 m2 nozzle was applied to single unenclosed sampling points 1 m apart. A linear series of 48 such subsamples comprised a transect, thus the total area covered in a transect equalled the area of the enclosure. In the transect samples three times more spiders were caught than in the enclosures. This result was consistent on different occasions and at both fields. This basic trend was found in all spider families that were present in significant numbers in the samples. Species composition in the samples collected by the two methods was similar, and species abundance ranks were highly correlated across dates. We propose that an “edge effect” can explain higher catches in transect samples. This edge effect is caused by lateral suction at the edges, which inflated the number of animals caught in the transect application.
The effect of hydoroxamic acid concentration at late growth stages of wheat on the performance of the aphid Sitobion avenae
Authors: NICOL D. , WRATTEN S D 
Published: February 2008

SummaryFrom a previous worldwide screen of wheat cultivars as seedings, five were selected to encompass a wide concentraiton range of the hydroxaminc acid DIMBOA (0.99‐8.07 mmol Kg ‐1 fr. wt). Compared with those in seedings, the concentrations of DIMBOA in flag leaves of the same cultivars were relatively low (0.06‐0.87 mmol kg‐1 fr. wt). Concentraions of hydroxamic acids in whole ears at anthesis and the early milk stage were even lower, ranging from undetectable to 0.05 mmol kg‐1 fr. wt. The three‐day mean relaive growth rate (MRGR) was determined for nymphs of Sitobion avenace on the flag leaf (GS 39) and on the ear (GS 60‐60) of the five cultivars. No significant differences in MRGR were found between cultivatrs at the same growth stage, although MRGR was higher on ears on than on flag leaces. The results are discussed in realtion to the potential of hydroxamic acids in programmses aimed at breeding mature‐plant aphid resistance into wheat cultivars.