bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity to prochloraz in populations of the eyespot fungus,Pseudocercosporella herpotrichoides, in relation to fungicide treatments and their efficacy in continuous winter wheat
Authors: BATEMAN G L. , LANDAU S. , WELHAM S J.
Published: February 2008

Eyespot was assessed and grain yields determined in the eighth and ninth years (1992 and 1993) of a field experiment in which the fungicides carbendazim and prochloraz were applied, separately or in mixtures, to plots of successive crops of winter wheat. Populations of the eyespot fungus,Pseudocercosporella herpotrichoides, were characterised by the proportions of cultures grown on agar from infected stems that were W‐type or R‐type, or were carbendazim‐resistant or carbendazim‐sensitive. Sensitivity to prochloraz in agar was determined for isolates from populations sampled in 1992 using restricted maximum likelihood analysis of EC50s (concentrations needed to decrease colony growth by 50%), to deal with the unbalanced data, and comparisons were made by Wald statistics.

Control by prochloraz was maintained but in 1992, as in some previous years, its application with carbendazim was more effective than its application alone. Selection by prochloraz for strains sensitive to carbendazim continued to occur and may have contributed to its sometimes relatively poorer performance in the absence of carbendazim. R‐type isolates taken from prochloraz‐treated plots, with or without carbendazim, in 1992 were less sensitive to prochloraz than were isolates from plots untreated with prochloraz. There was evidence of a greater range of sensitivities to prochloraz in R‐type than in W‐type isolates (although some uncertainty results from the small numbers of W‐type isolates obtained from some treatments), which would explain the selection of the R‐type by prochloraz. The significance of these findings to modern wheat growing practices is considered.
Transmission of tomato leaf curl geminiviruses by Bemisia tabaci: effects of virus isolate and vector biotype
Authors: McGRATH P F. , HARRISON B D.
Published: February 2008

Cultures of Bemisia tabaci from Ivory Coast (IC), Pakistan (PK) and USA (US B‐type) were compared for the frequency with which they transmitted three tomato geminivirus isolates: Indian tomato leaf curl virus from Bangalore (ITmLCV), and tomato yellow leaf curl viruses from Nigeria (TYLCV‐Nig) and Senegal (TYLCV‐Sen). Frequency of transmission from tomato to tomato depended both on the whitefly culture and the virus isolate. US B‐type and IC whiteflies transmitted TYLCV‐Sen more frequently than ITmLCV whereas PK whiteflies transmitted ITmLCV more frequently than TYLCV‐Sen. US B‐type whiteflies transmitted both viruses four to nine times more frequently than IC whiteflies. TYLCV‐Nig was transmitted rarely by US B‐type and not at all by IC whiteflies.

Previous work indicates that the geminivirus coat protein controls vector transmissibility. The differential adaptation of TYLCV‐Sen to transmission by US B‐type whiteflies and of ITmLCV to PK whiteflies was associated with a large difference in epitope profile of the coat proteins of the two viruses. Also, the readily transmissible TYLCV‐Sen differed appreciably in epitope profile from the poorly transmissible TYLCV‐Nig, which reached a consistently greater concentration in source tissues but lacked epitope 18. However, the lack of epitope 18 in ITmLCV did not prevent its transmission by US B‐type whiteflies. Differences in frequency and specificity of geminivirus transmission by whitefly cultures from different countries therefore were associated with differences among epitope profiles of the coat proteins of the viruses, but the structural features of the proteins that control transmission remain to be determined.
A two parameter model for prediction of crop loss by weed competition from early observations of relative leaf area of the weeds
Authors: KROPFF M J. , LOTZ L A P. , WEAVER S E. , BOS H J. , WALLINGA J. , MIGO T.
Published: February 2008

The recently introduced empirical model for early prediction of crop loss by weed competition based on the relative leaf area of the weeds shortly after crop emergence (Kropff & Spitters, 1991), assumes a maximum yield loss of 100% at high weed infestations. This is biologically not realistic. If weeds have a shorter life cycle than the crop, when they emerge much later than the crop or when they are unable to overtop the crop, maximum yield loss at high weed infestations is expected to be less than 100%. A two parameter model is introduced in this paper that accounts for a variable maximum crop yield loss by weed competition. The parameters are the “relative damage coefficient”q, and a parameter that describes the maximum yield loss caused by the weeds (m). The one and two parameter models were evaluated with data on the effects of weeds on rice, sugarbeet and tomato.

Both models were able to describe the data on the effect of different weed densities and periods between crop and weed emergence fairly well. The introduction of the second parameter resulted in a significantly better description of observed data in five out of nine datasets. The value of the parameter q depends on the time of observation of the relative leaf area. The change in the value of q in time could be estimated from the difference in relative growth rate of the species. The accuracy of this estimation is strongly determined by the variability in the relative growth rate of the leaf area of single plants. Possibilities for scientific and practical application of the model are discussed.
The effect of modifying the glucosinolate content of leaves of oilseed rape (Brassica napus ssp. oleifera) on its interaction with specialist and generalist pests
Authors: GIAMOUSTARIS A. , MITHEN R.
Published: February 2008

Twenty eight Brassica napus lines were developed which had contrasting leaf glucosinolate profiles to those found in commercial oilseed rape cultivars. The lines varied both in the total amount of aliphatic glucosinolates and in the ratio of different side chain structures. The lines were used in field experiments to assess the manner by which glucosinolates mediate the interactions between Brasssica and specialist pests (Psylliodes chrysocephala and Pieris rapae) and generalist pests (pigeons and slugs). Increases in the level of glucosinolates resulted in greater damage by adult flea beetles (P. chrysocephala) and a greater incidence of Pieris rapae larvae, but reduced the extent of grazing by pigeons and slugs. Decreasing the side chain length of aliphatic glucosinolates and reducing the extent of hydroxylation of butenyl glucosinolates increased the extent of adult flea beetle feeding. The implications of modifying the glucosinolate content of the leaves of oilseed rape and the role of these secondary metabolites in plant/herbivore interactions are discussed.
Movement of apterous Sitobion avenae (Homoptera: Aphididae) in response to leaf disturbances caused by wind and rain
Authors: MANN J A. , TATCHELL G M. , DUPUCH M J. , HARRINGTON R. , CLARK S J. , McCARTNEY H A.
Published: February 2008

The effect of wind and rain on initiation of dispersal and subsequent distances moved by apterous Sitobion avenae was quantified in five laboratory experiments. Wind duration and type (steady and gusting), rain duration and intensity, and a combination of wind and rain were investigated. With increased duration of wind there was an increase in the average distance aphids moved. There was less movement when aphids were exposed to gentle gusting, than to steady wind or strong gusting. With increased duration of rain there was an increase in the proportion of aphids lost from plants. Under heavy rain, the proportion of aphids off the release plant, the distance moved by them and the proportion of aphids lost, was greater than for drizzle or light rain. When wind and rain were compared, rain had the greater impact on aphid dispersal. It was concluded that leaf disturbances caused by strong gusts of wind or large rain droplets are of considerable importance in the initiation of aphid dispersal, but that wetness alone is not.
The movement and distribution of citrus tristeza virus and citrus exocortis viroid in citrus seedlings1
Authors: GAFNY R. , MOGILNER N. , NITZAN Y. , BEN‐SHALOM J. , BAR‐JOSEPH M.
Published: February 2008

The systemic movement of citrus tristeza virus (CTV) in sour orange (Citrus aurantium) seedlings and of citrus exocortis viroid (CEVd) in Etrog citron (C. medica) seedlings was studied. The movement of the two pathogens was analysed by detection in sections of roots and stems at different time intervals. Both pathogens were detected initially in the basal parts and the roots and subsequently spread to the shoot. CTV and CEVd moved in young citrus seedlings at similar rates. The findings are consistent with long distance phloem transport of the virus and the viroid. The practical implications of the pattern of systemic movement for diagnosis of infected trees are discussed.
Characterisation and serological relationships of strains of Kashmir bee virus
Authors: ALLEN M F. , BALL B V.
Published: February 2008

Isolates of novel strains of Kashmir bee virus (KBV) were obtained from field‐collected dead adults of Apis mellifera from honey bee colonies in Canada and Spain. They differed from other strains of KBV in their tendency to aggregate in dilute buffer solution and in containing only three proteins when analysed by SDS‐polyacrylamide gel electrophoresis compared with five proteins resolved in the type strain of KBV from Apis cerana in India and six proteins in KBV strains from South Australia and New Zealand. Immunodiffusion tests and Western blotting studies indicated that the five virus isolates were serologically related and all were related to acute paralysis virus (APV). The world distribution of KBV strains and their apparent relationship with APV are discussed.
Biology of the hop cyst nematode Heterodera humuli
Authors: MENDE N VON , McNAMARA D G.
Published: February 2008

Heterodera humuli inhibited plant growth in pot experiments when the nematode population exceeded 500 eggs g‐1 of soil; below this density there was evidence of stimulated growth. The development of H. humuli was tested on seven hop cultivars. No differences were found in the numbers of newly produced cysts on different cultivars but the sizes of the cysts differed significantly. The biggest cysts were found on a wild hop and the smallest on the cultivar ‘OR/55’. The nematode and the fungus, alone or in combination, did not affect the bine length of cvs Northdown or Target. The growth of nematode infested plants of a wilt susceptible hop cultivar was significantly reduced when the plant pathogenic fungus Verticillium albo‐atrum was also present. Verticillium did not significantly influence the reproduction of H. humuli under either laboratory or field conditions although hatching of juveniles in the field was delayed by two weeks and more juveniles were found in the soil during late summer around the roots of fungus infected plants in the field.
The effect of temperature on leaf appearance and canopy establishment in fibre hemp (Cannabis sativa L.)
Authors: WERF H M G VAN DER , BROUWER K. , WIJLHUIZEN M. , WITHAGEN J C M.
Published: February 2008

The effects of temperature on the development and growth of hemp (Cannabis sativa L.) have never been quantified. Therefore, to establish the effect of temperature on leaf appearance and canopy establishment of fibre hemp under controlled and field conditions, plants were grown in growth chambers at 11 regimes with average temperatures between 10°C and 28°C, and three cultivars were sown in the field in March, April and May in 1990, 1991 and 1992. In the field, thermal time (base 0°C) between sowing and emergence ranged from 68°Cd to 109.5°Cd (average 88.3°Cd). Rates of leaf appearance and stem elongation increased linearly with temperature between 10°C and 28°C. The base temperature for leaf appearance was 5.7°C from the growth chamber experiments and 1°C from the field experiments. In the field, the base temperature for the relationship between light interception by the canopy and thermal time was 2.5°C, and thermal time, calculated at the appropriate base temperature, accounted for about 98% of the variance in the number of leaves and for 98.6% of the variance in the proportion of light intercepted by the canopy. Days from emergence accounted for less of the variance in both parameters than thermal time. Interception of 90% of light was attained on average at 465°Cd (base 0°C) after emergence. It is concluded that thermal time is a simple and accurate tool to describe leaf appearance and light interception in fibre hemp.
Surface movement rates of the New Zealand flatwormArtioposthia triangulata: potential for spread by active migration
Authors: MATHER JANICE G. , CHRISTENSEN OLE M.
Published: February 2008

Movement rates for the surface activity of the New Zealand flatwormArtioposthia triangulata(Dendy) (Tricladida: Terricola) were estimated under semi‐field conditions in the Faroe Islands. The distance travelled during 10 consecutive 1‐minute periods per individual was measured from mucus trails left behind as the flatworms moved over black plastic sheeting sprayed with fine droplets of water. Adult specimens were found to crawl at rates of up to 28 cm min‐1(almost 17m h‐1), whereas juveniles crawled at rates of between 3 and 4cm min‐1(approximately 2m h‐1). This study provides the first data concerning the potential for species spread by active migration.
Development of black dot disease (Colletotrichum coccodes (Wallr.) Hughes) and its effects on the growth and yield of potato plants
Authors: READ P. J. , HIDE G. A.
Published: February 2008

Seed tubers of cvs Désirée and Pentland Crown with different severities of black dot were planted in 1988 and 1989 at Rothamsted in fields in 4– or 7‐course rotations, respectively. Tubers treated with prochloraz (1988) or imazalil (1989) were planted in some plots, and in others Colletotrichum coccodes inoculum was added to the soil at planting. In further experiments at Mepal, Cambridgeshire in 1989 and 1990 and at Rothamsted in 1990 on sites where potatoes had not been grown for more than 15 years, large amounts of inoculum were added to the soil around disease‐free seed tubers of two (1989) or three (1990) cultivars at planting. In all experiments plants were sampled during the season and the effects of treatments on disease development, growth and yield were recorded.

Disease on roots, stem bases and tubers was found early in the season and was more severe on Désirée than on Pentland Crown plants from fields in 4– or 7‐course rotations. Severity increased throughout the season and with increasing amounts of disease on the seed tubers, especially with Desiree. Disease was also found on plants from disease‐free tubers and was more severe in 1988 than 1989. At harvest, black dot on tubers was significantly more severe from severely affected than from disease‐free seed, and was most severe where inoculum, especially large amounts, had been added at planting. Fungicide treatment decreased disease early in the season but had no effect on tuber infection at harvest. In 1989 the weight loss of seed tubers during sprouting increased with increasing amounts of black dot, but the disease had little effect on plant size through the season. At harvest the yield of ware tubers (>50 mm) decreased with severe disease but total tuber yields were not significantly affected. However, at harvest in 1988 severely affected seed yielded significantly less than healthy seed.

Plants grown from mini‐tubers were free from disease on sites where potatoes had not been grown for at least 15 years. Inoculum applied at planting caused severe disease on all cultivars in both years, whereas disease was slight on uninoculated plants. Inoculated plants senesced early at Mepal in 1990, but there were no significant differences in total tuber yield in any experiment. However, yields of ware tubers (>50 mm) were sometimes decreased and the total tuber number per plant increased.
Isolation and characterisation of a new Venezuelan strain of cassava common mosaic virus
Authors: MARYS EDGLORIS , IZAGUIRRE‐MAYORAL MARÍA LUISA
Published: February 2008

A new strain of cassava common mosaic virus, designated CsCMV‐ve, was isolated from cassava (Manihot esculenta Crantz) plants growing in Venezuela. The 520 nm long semi‐flexuous virus particles sedimented in sucrose gradients as one component and contained a single coat protein molecule of c. 28 kDa, and a ssRNA of c. 2.1 times 106. A single dsRNA species of c. 4.2 times 106kDA was isolated from virus‐infected cassava leaves. In double antibody sandwich enzyme‐linked immunosorbent assay, CsCMV‐ve reacted strongly with antisera to CsCMV and potato virus X, but not with those to other typical members of the potexvirus group. Ultrastructural studies of CsCMV‐ve infected cells showed the presence of large bundles of inclusion bodies in the cytoplasm, a proliferation of the rough endoplasmic reticulum, and large crystals in the peroxisomes. CsCMV‐ve in crude buffered sap or in purified preparations was not mechanically transmitted to known hosts of the Chaya and Brazilian strains of CsCMV. Isolated virus RNA also failed to infect a range of test‐plant species. This is the first report of the presence of CsCMV in Venezuela.
Towards genetic based insect resistance in strawberry using the Cowpea trypsin inhibitor gene
Authors: GRAHAM J. , McNICOL R. J. , GREIG K.
Published: February 2008

An efficient shoot regeneration system has been developed involving organo‐genesis from stem tissue of the strawberry cultivars Melody, Rhapsody and Symphony. Regeneration also occurred in the presence of antibiotics. The system was shown to be suitable for transformation using the GUS:Intron marker gene construct. Histological analysis using the substrate 5‐bromo‐4‐chloro‐3‐indolyl B‐D‐glucuronide (X‐Gluc) and the polymerase chain reaction (PCR) using specific primers permitted the identification of transformants.

Inoculations were then carried out using the Cowpea protease trypsin inhibitor (CpTi) gene construct. A simple visual assay technique was developed to identify those plants expressing CpTi, allowing them to be selected for further analysis. Trypsin acts on the substrate α‐N‐benzoyl‐DL‐arginine‐p‐nitroanilide (BAPNA) to produce p‐nitroaniline (p‐na). Trypsin inhibition CpTi was easily detected as a reduction in or elimination of yellow colour development which occurred as the hydrolysis of BAPNA to pna proceeded (Preiser, Schmitz, Maestracci & Crane, 1975). The polymerase chain reaction (PCR) was used to confirm the presence of the gene sequence.
Prolonged aerated hydration for improvement of seed quality in Brassica oleracea L.
Authors: THORNTON J. M. , POWELL A. A.
Published: February 2008

Seeds of cauliflower cv. Hipop and Brussels sprouts cv. Asmer Aries were aged at 20% moisture content for 24 h; all seeds retained a germination of over 70% after ageing although the mean germination time increased. Prolonged aerated hydration for up to 32 h at 20°C followed drying resulted in improved performance of both unaged and aged cauliflower seeds and aged Brussels sprouts. Thus, all seed showed reductions in the mean germination time to the extent that after 32 h hydration the aged cauliflower seeds performed as well as high quality unaged seed. The improvement of aged seeds was also revealed an increase in germination after the controlled deterioration test following up to 24 h (cauliflower) or 32 h (Brussels sprouts) aerated hydration. This increase was indicative of a decrease in the extent of deterioration present after aerated hydration. Deleterious effects of prolonged hydration were observed in Brussels sprouts after 32 h although these may be explained desiccation injury after treatment since radicle emergence had occurred during hydration. The improvements in seed performance may be explained the activation of metabolic repair occurring during the early part of the hydration period therereducing the extent of deterioration that has been sustained during ageing, with further improvements due to the advancement of the germination process.
Interactions between diurnal temperature fluctuations and salinity on expansion growth and water status of young tomato plants
Authors: McCALL D. , ATHERTON J. G.
Published: February 2008

Expansion growth is limited if the difference between day and night temperature (DIF) is negative. Growth is also limited high salinity. Expansion growth of tomato seedlings was studied under day/night temperatures of 16/24°C and 24/16°C, and nutrient solution salinities of 3 and 15 mS cm‐1 to ascertain whether interactions exist between the two stress forms. Water status was also studied in order to assess possible mechanisms of growth retardation. A significant interaction between DIF and salinity was found for all recorded growth variables. Hypocotyl length, plant height, leaf area and fresh and dry weight were lower at negative DIF than at positive, the reduction being greater at low salinity than at high. Increased salinity also reduced growth, more so at positive DIF than at negative. Growth reduction at negative DIF was accompanied increased shoot water and osmotic potentials. Pressure potential was unaffected DIF. Growth reduction at high salinity was accompanied reduced water and osmotic potentials. Pre‐dawn pressure potential was increased at high salinity, whereas no effect of salinity on pressure potential at midday was found. The differences in effects on water status between the two stress forms may suggest differing mechanisms of growth retardation.
Detection of groundnut rosette umbravirus infections with radioactive and non‐radioactive probes to its satellite RNA
Authors: BLOK V. C. , ZIEGLER A. , SCOTT K. , DANGORA D. B. , ROBINSON D. J. , MURANT A. F.
Published: February 2008

A cloned cDNA copy of the satellite RNA of groundnut rosette virus (GRV), labelled with either 32P or digoxigenin, was used as a probe to detect the satellite RNA in infected leaves. The test was successfully applied to N. benthamiana and to groundnuts, infected with isolates of GRV from East and West Africa and with isolates which cause different types of symptom in groundnuts, including one which is almost symptomless. Although the probe did not react with extracts from plants infected with GRV isolates from which the satellite RNA had been artificially eliminated, all naturally occurring GRV isolates contain the satellite RNA. The test therefore provides a reliable indicator of infection by GRV.
Control of Western flower thrips (Frankliniella occidentalis Pergande) pupae in compost
Authors: Helyer Neil L. , Brobyn Patricia J. , Richardson Paul N. , Edmondson Rodney N.
Published: February 2008

Western flower thrips (Frankliniella occidentalis) develops from an active larval stage through to a non‐feeding, almost immobile, pre‐pupal and pupal stage. This generally occurs in the compost or soil below the plant on which the larvae fed. Control of thrips at this stage in their development offers a chance of utilising pathogens or pesticides not suitable for use in an integrated control programme aimed at adult and larval stages. Trials were done with F. occidentalis pupae and pre‐pupae in a soil/peat based compost using 11 pesticides, three fungal pathogens and four species of insect parasitic nematodes. The pesticides malathion and chlorpyrifos‐methyl gave the most promising result with 97.5% and 96.5% control, respectively. The fungal pathogen Metarhizium anisopliae proved better when applied as a pre‐pupation rather than as a post‐pupation treatment (74.5% : 26.6% control). The insect parasitic nematode Steinernema carpocapsae gave 76.6% control when applied at 25 times 104 nematodes litre‐1 of compost. The results are discussed in relation to control of thrips in glasshouses.
A greenhouse assay to screen sunflower for resistance to Alternaria helianthi
Authors: Kong G A. , Kochman J K. , Brown J F.
Published: February 2008

A greenhouse assay to screen sunflower for resistance to Alternaria helianthi is described. A comparison of conditions led to the following standard conditions being recommended. The first or second pair of leaves of seedling plants at the V8 growth stage are inoculated using inoculum grown on sunflower leaf extract agar for 5–10 days at an inoculum density of 1–2 spores cm2 of leaf tissue. A 48 h dew period should be applied to plants covered by a plastic tent. A dew period temperature of 26/26°C night/day and a post‐dew period temperature relative to that experienced under local growing conditions should be applied. Lesions are measured 7 days after inoculation, and mean lesion size per plant is calculated. Mean lesion size of lines being tested is expressed as a proportion of the mean lesion size of a susceptible standard included in each screening experiment.
Allelopathic potential in rice (Oryza sativa L.) germplasm
Authors: Olofsdotter Maria , Navarez Domingo , Moody Keith
Published: February 2008

Allelopathy is the direct influence of a chemical released from one living plant on the development and growth of another plant. The use of allelopathy to control weeds of food crops could contribute towards increasing yields in sustainable agricultural systems. Various research teams have identified several hundred rice accessions which show indications of allelopathic potential, 60 of them showing promising allelopathic activity against one or more weeds. These accessions have different origin and stage of improvement. This, combined with the involvement of several allelochemicals and the ability to release these chemicals, indicates that allelopathic potential is a polygenic characteristic weakly correlated with yield or other important agronomic features. Successful allelopathy research, however, must be focused both on the discovery and subsequent validation of allelopathic potential. Experimental factors such as choice of test plants, collection of allelochemicals, concentration, osmotic pressure and bioassay methodology need considerable attention together with validation through assays with known chemicals of known concentrations. Without validation using known chemicals, the contribution of allelopathic research remains obscure. Several putative allelochemicals are found in extracts of rice leaf and straw, decomposing straw, and in rice soil. Evidence that these chemicals are being released from living plants is still lacking, but as it is a prerequisite for allelopathic activity in nature, it must be proved. Methods of collecting test solutions from living plants need further description. Allelopathic activity is believed to be a joint action of several secondary metabolites, and this must be confirmed for rice. Dilution assays with mixtures of putative rice allelochemicals need to be conducted to evaluate possible synergistic effects. In validation, these mixture‐dose response curves must be compared with assays using collected test solutions. A joint, coordinated and focused research effort on rice allelopathy is necessary before the full potential of allelopathic cultivars can be realised.
Comparison of resistance to potyviruses within Solanaceae: infection of potatoes with tobacco etch potyvirus and peppers with potato A and Y potyviruses
Authors: VALKONEN J P T , KYLE M M , SLACK S A
Published: February 2008

The reaction of several cultivated potato varieties (Solarium tuberosum L.) to three strains of tobacco etch potyvirus (TEV‐F, TEV‐Mex21 and TEV‐ATCC) and the reaction of several pepper lines (Capsicum annuum L. and C. chinense L.) to two strains of potato Y potyvirus (PVYO and PVYN) and one strain of potato A potyvirus (PVA‐M) was tested. The potato varieties included in this study carried resistance genes against PVY, PVA and potato V potyvirus, but all were susceptible to TEV and developed mottle and mosaic symptoms. TEV was readily transmitted by mechanical inoculation from tobacco and potato to potato, whereas transmission from pepper to potato occurred infrequently. TEV was transmitted through potato tubers, and from pepper to potato plants by aphids. Lack of detectable systemic infection following graft‐inoculation indicated extreme resistance to PVYO and PVA in several pepper lines. No pepper line was systemically infected with PVYN following mechanical inoculation (graft‐inoculation was not carried out with PVYN). The development of necrotic lesions following mechanical and graft‐inoculation indicated hypersensitive response to PVYO in several pepper lines which resembled the resistance responses to these potyvirus strains in potato. Results of this study together with previous work indicate that C. annuum cv. Avelar is resistant to four potyviruses [PVY, PVA, pepper mottle potyvirus (PepMoV) and some isolates of TEV]; C. annuum cv. Criollo de Morelos and C. chinense PI 152225 and PI 159236 are resistant to three potyviruses (PVY, PepMoV and PVA; and PVY, PepMoV and TEV, respectively); C. annuum 9093–1 and 92016–1 are resistant to PVY and PepMoV; and C. annuum cv. Jupiter and C. annuum cv. RNaky are resistant to PVYN and PVA.
Significance of secondary infections with lily symptomless carlavirus to cut‐flower production of Lilium
Authors: BLAKE M R , WILSON C R
Published: February 2008

The commercial significance of secondary infections of lily symptomless carlavirus (LSV) to commercial Lilium cut‐flower producers was assessed by comparing growth of plants and quality of blooms produced from bulbs of eight Asiatic and two Oriental hybrid cultivars both infected and free from infection with LSV. In comparison to LSV‐free plants, LSV‐infected plants grown under Tasmanian commercial cut‐flower production conditions had decreased stem length (mean of 8.5% and 10.4% decrease across cultivars in each of two experiments; P= 0.007 and < 0.001) and fresh weight (18.8% and 23.4%; P= 0.008 and 0.004). Bud size was significantly decreased in one experiment (12.3%; P= 0.001), while bud number and vase life were not affected (P= 0.05). LSV‐infected plants grown in a temperature controlled glasshouse had decreased stem length (15.8%; P < 0.001) and petal length (8.7%; P= 0.001) but petal width and bud number were no different to LSV‐free plants (P= 0.05). The characters considered to be of greatest economic importance to cut flower producers (viz the number of inflorescences per stem, flower quality and vase life) were not or were only mildly affected by LSV‐infection in any cultivar and unlikely to be of major commercial concern.
A damaging outbreak of arabis mosaic nepovirus in blackcurrant, the occurrence of other nepoviruses in Ribes species, and the demonstration that alfalfa mosaic virus is the cause of interveinal white mosaic in blackcurrant
Authors: JONES A T , McGAVIN W J
Published: February 2008

In a crop of blackcurrant (Ribes nigrum), cv. Baldwin in Eire, chlorotic mottling and ringspot symptoms in leaves on plants and severe crop loss was associated with infection with arabis mosaic nepovirus (ArMV) and the presence in the soil of its nematode vector, Xiphinema diversicaudatum. This is only the second report of ArMV damaging a crop of blackcurrant. Tomato black ring (TBRV) and raspberry ringspot nepoviruses were detected in single plants of redcurrant (R. rubrum) in England and flowering currant (R. sanguineum) in Scotland respectively; each of these infected plants showed foliar chlorotic line‐pattern symptoms. This is the first record of TBRV in redcurrant. A single blackcurrant plant in New Zealand showing symptoms typical of those described for interveinal white mosaic disease, contained alfalfa mosaic virus (AMV). When AMV particles were purified and concentrated from herbaceous test plants and mechanically inoculated to young blackcurrant plants, several became infected with AMV and most infected plants developed systemic symptoms typical of the original disease. This provides the strongest evidence to date that AMV is the causal agent of interveinal white mosaic disease.
Effect of the seed coat on water uptake and electrolyt leakage of sorghum (Sorghum bicolor (L.) Moench) seeds
Authors: SHEPHARD HELEN L , NAYLOR ROBERT E L
Published: February 2008

Four seed lots of sorghum cultivar IS 34213 were obtained which had been harvested early or at full maturity and then dried either swiftly in the sun or slowly in the shade. The earlier harvested seeds were lighter, smaller and of lower density. Earlier harvested seeds had pericarps which permitted faster water uptake and greater leakage of electrolytes. Water uptake and electrolyte leakage were positively correlated. The method of seed drying had no effect on water uptake or leakage. Greater leakage was associated with lower final germination. The results are interpreted in relation to germination testing.
Water deficit, root demography, and the causes of internal blackening in field‐grown tomatoes:(Lycopersicon esculentum Mill.)
Authors: REID J B , WINFIELD DIANA , SORENSEN ISABELLE , KALE A J
Published: February 2008

An internal blackening disorder may cause substantial losses in the value of tomatoes grown for processing. The disorder resembles an internal form of blossom‐end rot and appears to be more common in dry seasons. In an experiment to test whether the internal blackening is caused by water deficit and whether it is indeed blossom‐end rot, plots of cv. Cannery Row were irrigated to keep the soil moisture deficit <50 mm and others were sheltered from rain and not irrigated from early flowering onwards. Shoot growth (total and fruit dry mass) was measured destructively at intervals, and root growth and death nondestructively using minirhizotrons. There was a greater incidence of internal blackening and blossom‐end rot, and lower Ca concentrations, in the fruit of non‐irrigated plants. Root growth and root death were accelerated in these plants around the time that internally‐blackened fruit were set. Although the internal blackening syndrome shared some features with blossom‐end rot some differences were apparent in this experiment. It is suggested that internal blackening could have resulted from increased root competition for photosynthate, leading to abnormal seed development. Root turnover was appreciable (30–40% of the roots survived 28 days). This suggests there may be substantial errors in contemporary models of dry matter partitioning in tomato crops.
The land planarianAustraloplana sanguineavar.albaat a horticultural site in New Zealand
Authors: MATHER JANICE G , CHRISTENSEN OLE M
Published: February 2008

Morphometric data and general observations of habitat conditions, feeding behaviour and reproductive biology are presented for the land planarianAustraloplana sanguineavar.alba, based upon a population established at a garden centre in Alexandra, South Island, New Zealand.

The flatworm species considered in this study appears to be identical to an alien flatworm initially referred to asGeoplana sanguinea(Moseley) var.alba(Dendy) which has successfully colonised areas of the British Isles over the past few decades.

The study also highlights the importance of garden centres and nurseries as modified habitats that provide favourable conditions for terrestrial planarians, implying that exotic flatworm species have the potential to spread and exist in pockets world‐wide.
Effect of increased CO2 concentration and temperature on the phyllosphere mycoflora of winter wheat flag leaves during ripening
Authors: MAGAN NARESH , BAXTER ESTHER S
Published: February 2008

The impact of elevated carbon dioxide (CO2, 600/700 μmol mol‐1) and temperature (+ 4°C) on phyllosphere fungi colonising flag leaves of mini crops of winter wheat cv. Mercia between anthesis and harvest was determined in a computer‐controlled environment facility in 1993 and 1994. In both years the total fungal populations (cm2 leaf) were found to have increased due to exposure to either elevated CO2 and elevated CO2+ temperature treatments. This was mainly due to significant increases in populations of Cladosporium spp. (C. cladosporioides and C. herbarum) on the flag leaves during ripening. Other phyllosphere component species such as white and pink yeasts were not markedly affected by treatments. The range of fungal species found in such controlled environment chambers was narrower than that commonly found on flag leaves of field grown crops. Common and important colonisers of leaves and ripening ears such as Aureobasidium pullulans, Epicoccum nigrum and Fusarium spp. were seldom isolated.
Resistance of Hibiscus esculentus L. and Vigna sinensis (L.) Endl. to Pseudocercospora and plant peroxidase activity in relation to infection
Authors: LEINA M J , TAN T K , WONG S M
Published: February 2008

Five cultivars of Hibiscus esculentus L. and six cultivars of Vigna sinensis (L.) Endl. were tested for their relative resistance to Pseudocercospora spp. Differences in susceptibility to the leaf spot pathogen were observed in both host and non‐host interactions. The H. esculentus cv. South Sea and V. sinensis cv. Purple Mart were most susceptible to Pseudocercospora abelmoschi and P. cruenta, respectively. The H. esculentus cv. Pure Luck was most tolerant to P. abelmoschi while the V. sinensis cv. KY Bush was highly resistant to P. cruenta. A distinct host‐specific interaction was observed among the different species of Pseudocercospora. Cultivar specific interactions were most pronounced between V. sinensis and P. cruenta. A direct correlation was observed between the variation in peroxidase activity in the soluble fraction of inoculated leaves and resistance to infection in H. esculentus and V. sinensis cultivars. The soluble fraction of inoculated leaves had higher peroxidase activity than either mitochondrial or chloroplast extracts.
Effect of ascochyta blight (Mycosphaerella pinodes) on yield components of single pea (Pisum sativum) plants under field conditions
Authors: TIVOLI B. , BEASSE C. , LEMARCHAND E. , MASSON E.
Published: February 2008

Field studies were made in 1992 and 1993 to examine the yield components of pea inoculated with Mycosphaerella pinodes and those of healthy pea (sprayed with a mixture of flutriafol + chlorothalonil), in a split‐plot design with the cv. Solara sown at different plant densities. Ascochyta blight was severe on leaves and on internodes of the basal part of the plants; pods had few lesions. The number and length of stems per plant were the same for diseased and healthy plants. The number of reproductive nodes and pods per stem were affected by disease only in 1993. In 1992 and 1993 respectively, disease caused reductions in the number of seeds per stem of 18% and 25%, and in seed size of 13.5% and 16.7%, compared with healthy plants. The harvest index and total biomass were lower in diseased than in healthy plants and seed yield was reduced by 40% in diseased plots. These results show a high relationship between the disease parameters (disease mean on stipules/nodes 8–18/ and on internodes/nodes 5–15/, percentages of stipules or internodes with a disease score 4, and percentage of stems encircled by lesions), plant density and yield reduction.
The effect of reduced phytoalexin production on the resistance of upland cotton (Gossypium hirsutum) to verticillium and fusarium wilts
Authors: ELDON S. , HILLOCKS R J
Published: February 2008

The effect on disease development of inhibiting the production of the sesquiterpenoid phytoalexin hemigossypol (HG) in cotton resistant to both verticillium and fusarium wilts was investigated. Inhibition was achieved by treating the plants with the sodium salt of compactin, a competitive inhibitor of hydroxy‐methylglutaryl (HMG) CoA reductase. Compactin treatment (150 μg litre‐1) reduced HG production by a mean of 48%. The enzyme inhibitor did not mimic symptoms in uninfected plants or significantly reduce the ability of the conidia of either Fusarium oxysporum f.sp. vasinfectum or Verticillium dahliae to germinate. Treatment of infected plants with compactin resulted in a breakdown of resistance to verticillium wilt but not to fusarium wilt. These results support the view that HG production is the primary mechanism of resistance to verticillium wilt, but not to fusarium wilt.
Peanut yellow spot virus: A distinct tospovirus species based on serology and nucleic acid hybridisation
Authors: SATYANARAYANA T. , REDDY K LAKSHMINARAYANA , RATNA A S , DEOM C M , GOWDA S. , REDDY D V R
Published: February 2008

Nucleocapsids of peanut yellow spot virus (PYSV), purified from peanut (= groundnut) plant tissue, contained a protein with a molecular mass of 29 kDa. In ELISA and immuno‐blot analysis the virus did not react with tomato spotted wilt virus (TSWV), Impatiens necrotic spot virus (INSV) and peanut bud necrosis virus (PBNV) antisera. PYSV contained three RNA species, a large (L) RNA (c.8900 nucleotides), a medium (M) RNA (c.4800 nucleotides) and a small (S) RNA (c.3000 nucleotides), similar to other tospoviruses. In addition, a fourth RNA species of approximately 1800 nucleotides was also present in purified preparations. Hybridisation analysis under high stringency conditions revealed no hybridisation between PYSV RNAs and cDNA probes representing the nucleocapsid (N) gene, the glycoprotein (GP) gene and the 3' half of the RNA polymerase gene of PBNV. PYSV genomic RNAs also failed to hybridise with cDNA probes from the GP genes of TSWV and INSV. In reciprocal tests, the cDNA clones of PYSV S and M RNAs did not hybridise with any of the PBNV RNAs. Based on the absence of serological relationships between PYSV and PBNV, TSWV and INSV and lack of nucleotide homology based on hybridisation studies between the PYSV RNAs and cDNA clones from PBNV, TSWV and INSV, PYSV should be considered as a distinct species of the genus Tospovirus under a new serogroup, putatively designated ‘V’.
Enhanced cold tolerance of the entomopathogenic nematode Steinernema feltiae through genetic selection
Authors: GREWAL PARWINDER S , GAUGLER RANDY , WANG YI
Published: February 2008

Cold sensitivity of entomopathogenic nematodes severely restricts their biological control potential in some environments. We selected the SN strain of Steinernema feltiae together with its bacterial symbiont, Xenorhabdus bovenii, for improved cold tolerance by repeated passage through the wax moth Galleria mellonella larvae at 15°C. Nematode virulence (total insect mortality and speed of kill) and establishment (initiation of nematode development following penetration) were evaluated after six (= 12–24 generations) and 12 passages (= 24–36 generations). Cold selection enhanced nematode virulence at the cooler temperatures. Virulence measured as total insect‐mortality at 8°C improved by 5.3‐ and 6.6‐fold after six and 12 passages, respectively. Only small improvements (1.2–1.5‐fold) were observed in speed of kill. Nematode establishment improved at all temperatures after 12 passages; the highest increase of 9‐fold was observed at 8°C. Our results lend support to the hypotheses that functional traits along a continuously distributed environmental variable are genetically correlated and that the area under the fitness function is not always constant. Trade‐offs in percentage mortality and speed of kill by the selected nematodes were observed at the warmer extreme after six passages of selection only. The implications of rapid changes in thermal sensitivity for economic mass‐production of nematodes are discussed.
Identification of Heterodera cysts by SOD isozyme electrophoresis profiles
Authors: MOLINARI S. , EVANS K. , ROWE J. , RUSSELL M.
Published: February 2008

Superoxide dismutase (SOD), the enzyme which converts superoxide anions into hydrogen peroxide, has been found to be highly expressed in the cyst stage of a number of Heterodera species likely to occur together in the field. By examining isoforms of this enzyme in polyacrylamide gel electrophoresis, we have been able to show different SOD profiles in six common species of Heterodera (H. avenae, H. cruciferae, H. glycines, H. goettingiana, H. schachtii and H. trifolii). The method is quick and therefore lends itself to routine use in a diagnostic laboratory.
The effect of plant age and infection with virus yellows on the survival ofMyzus persicaeon sugar beet
Authors: KIFT N B , DEWAR A M , WERKER A R , DIXON A F G
Published: February 2008

Survival ofMyzus persicaeconfined in clip‐cages on mature leaves of sugar beet declined as the plants aged. Death of aphids was often preceded by the appearance of a black deposit in the aphids' stomachs, which may have been the cause of death. Both the rate of death and the proportion of aphids dying with black deposits was significantly less when plants were infected with beet yellows virus or beet mild yellowing virus, by comparison with healthy plants. The implication of these phenomena on the onset of mature plant resistance is discussed.
Development of two spotted spider mite (Acari: Tetranychidae) populations on strawberry and raspberry cultivars
Authors: SONNEVELD T. , WAINWRIGHT H. , LABUSCHAGNE L.
Published: February 2008

Five strawberry (Fragaria sp.) and five raspberry (Rubus ideaus L.) cultivars were evaluated for resistance to two spotted spider mite (Tetranychus urticae Koch.). Two methods of assessing the development of two spotted mite populations using detached leaves were compared. The number of eggs laid and mites which developed were compared. The strawberry cvs Hapil and Pegasus had significantly greater development of two spotted mite populations than the cvs Rhapsody, Symphony and Elsanta. The raspberry cv. Joan Squires had higher populations of two spotted mite whilst the raspberry cv. Leo the least, when compared with cvs Glen Clova, Glen Moy and Glen Prosen. Differences were observed in oviposition sites and mite distribution when comparing raspberries with strawberries. The method of assessing the populations development of two spotted mite which involved maintaining the cut leaf stem in water may be of potential use for studying population dynamics of both two spotted mite and possible predators over extended periods of time.
Incidence of fungal species associated with leaf rot disease of coconut palms in relation to weather and the stage of lesion development
Authors: SRINIVASAN N. , GUNASEKARAN M.
Published: February 2008

Leaf rot disease (LRD) of coconut occurs in Kerala State, India, and is generally severe during the monsoon, a time of high rainfall and r.h. and low maximum temperature. The pathogenic fungi Colletotrichum gloeosporioides, Exserohilum rostratum, Gliocladium vermoeseni, Fusarium solani, F. moniliforme var. intermedium, Thielaviopsis paradoxa and Rhizoctonia solani were among 14 species isolated from spindles of palms with LRD in multiple samplings of two experiments, each lasting 1 year. Co‐occurrence of fungi was observed in 70–76% of spindles although leaf pieces yielded mostly individual fungi irrespective of the stage of lesion development. C. gloeosporioides occurred most frequently on early lesions. The incidence of C. gloeosporioides was most strongly correlated with rainfall and r.h. and, negatively, with maximum temperature and hours of sunshine. It was the fungus isolated most commonly during the monsoon and occurred on early lesions more frequently than on advanced lesions (determined in one experiment). C. gloeosporioides is thus implicated as the principal pathogen involved in initiation of the disease during monsoons. Its relatively low incidence in the dry season suggests a quiescent phase between periods of parasitic activity. E. rostratum was isolated less frequently and its incidence was less strongly or consistently correlated with weather or with the stage of lesion development. Fusarium spp. and R. solani were associated with dryer weather and higher temperatures. The Fusarium spp. were the fungi isolated most commonly during part of the dry season (January‐March) and occurred more on early than on advanced lesions at one sample (January) when they may have been primary disease agents. R. solani was also more frequent on advanced lesions and may be principally a secondary coloniser of established lesions. The incidence of other fungi, which occurred less frequently and more sporadically, was not associated with weather or consistently with different stages of lesion development.