bluuebunny/crossref_metadata_2025 huggingface dataset:
Nematology: From curiosity to space science in fifty years!1
Authors: WEBSTER JOHN M
Published: February 2008

The young science of nematology has evolved and matured mostly in the last fifty years. This extraordinary growth reflects the agricultural needs of the foundation years, the 1950's and early 1960's, and the influence of scientific discovery and changing philosophies. The crucial role of chemical nematicides in increasing crop productivity was central to nematology's growth, and as other forms of nematode control have emerged so nematology has diversified in its usefulness to society. These changes are described with emphasis on the scientists and research laboratories in the United Kingdom.
Development of a system simulating commercial production conditions for assessing the potential spread of Phytophthora cryptogea root rot of hardy nursery stock in recirculating irrigation water
Authors: PETTITT T R , FINLAY A R , SCOTT M A , VIES E M DA
Published: February 2008

A system was developed for monitoring the potential spread of Phytophthora cryptogea root rot of the hardy nursery stock (HNS) species Chamaecyparis lawsoniana, Erica x darlyensis and Calluna vulgaris in recirculating irrigation water on semi‐commercial scale production beds. The spread of disease was monitored by measurements of symptoms and by baiting bioassays. A range of baits was tested and the most sensitive was found to be shoot segments of Lupinus angustifolius. The pathogen spread rapidly throughout the system from infected plants in the recirculating irrigation water. Although the percentage of plants infected was high (in Chamaecyparis 73% in 1994 and 93% in 1995), the percentage of infections actively sporulating at any one sample date was much less (47% in 1994 and 63% in 1995) and shoot symptoms were even less evident (in Chamaecyparis 22% in 1994 and 38% in 1995). In Chamaecyparis the incidence of shoot symptoms was less than expected from results of inoculations of similar plants not irrigated with recirculated water (80% infected, 60% with symptoms). The reason for this difference is not known but it poses a serious threat to the quality of HNS produced using recirculated irrigation water and underlines the need for reliable pathogen control methods.
Determining the effectiveness of grazing and trampling by livestock in transmitting white clover mosaic and subterranean clover mottle viruses
Authors: MCKIRDY S J , JONES R A C , SIVASITHAMPARAM K.
Published: February 2008

Glasshouse and mini‐sward experiments were done to determine the relative roles of grazing and trampling by livestock in transmitting white clover mosaic (WC1MV) and subterranean clover mottle (SCMoV) viruses between clover plants in pastures. Wounding due to grazing was simulated by repeatedly cutting plants with serrated scissors (glasshouse) or mowing (mini‐swards), while wounding due to trampling was simulated by repeatedly bashing plants with the flat end of a wooden hammer handle (glasshouse) or rolling (mini‐swards). In glasshouse experiments, cutting was more effective than bashing in transmitting WC1MV to white clover (Trifolium repens) plants but cutting and bashing transmitted it to subterranean clover (T. subterraneum) plants at similar rates. In an experiment with white clover mini‐swards, mowing was more effective than rolling in transmitting WC1MV, and when both were combined, initially spread exceeded that obtained when the spread from mowing and rolling alone was added together. In glasshouse experiments, bashing was more effective than cutting in transmitting SCMoV to subterranean clover plants. In one experiment, neither mowing nor rolling spread SCMoV in mini‐swards of subterranean clover. When transmission to subterranean clover cultivars which were ‘susceptible’ or ‘moderately susceptible’ to SCMoV was compared in glasshouse experiments, repeated bashing spread the virus more slowly to the ‘moderately susceptible’ cultivars. When mixed with ruminant saliva, infective sap containing WC1MV or SCMoV was still infective to clover plants after 4 wk storage at room temperature. When infective sap was allowed to dry naturally on a metal surface, SCMoV still infected clover plants when the dried sap was taken up in tap water after 4 but not 14 days, while WC1MV was infective after 24 h but not 4 days.

These results suggest that grazing and mowing are more effective than trampling at transmitting WC1MV to white clover plants in pastures, while trampling is more effective at spreading SCMoV to subterranean clover. However, both transmitted WC1MV to subterranean clover at similar rates. Possible reasons for these differences are discussed in relation to differences in clover plant morphology and virus‐specific factors.
The use of S1 nuclease treatment of hybrid PCR products for the differentiation between PVY isolates
Authors: ROSNER ARIE , SPIEGEL SARA , MASLENIN LUDMILA , LEVY DAVID
Published: February 2008

A new strategy based on treating PCR hybrids with S1 nuclease was used to differentiate between two PVY isolates. Mixed denatured and annealed hybrid PCR products of two PVY isolates including a tested strain and a reference N strain were treated with S1 nuclease. Single‐stranded mismatched regions were revealed by the S1 nuclease cleavage, yielding a characteristic pattern of bands in polyacrylamide gel by which virus isolates could be matched. Sequence analysis of the relevant PCR products revealed that only part of the mismatched regions were cleaved by the S1 nuclease. Still, the distinct pattern of degradation products enabled the differentiation between the PVY isolates. The general application of this procedure for strain differentiation is discussed.
Observations on patterns of granular fertiliser deposition beside hedges and its likely effects on the botanical composition of field margins
Authors: TSIOURIS S. , MARSHALL E J P
Published: February 2008

Patterns of granular fertiliser deposition differed markedly between a pneumatic boom applicator and a spinning disk machine, both of which were tractor‐mounted. The pneumatic applicator gave relatively even distribution across the boom width. A spinning disk gave more variable deposition and significant amounts were spread further than the expected 12 m overlapping pattern. When operating with a deflector plate on the spinning disk, significant amounts of fertiliser were also spread further than the expected 6 m. However, when operating next to a hedge, there was evidence of fertiliser concentration at the base of the hedge and prevention of granules passing through to adjacent habitat. A peak concentration of up to 150 kg ha‐1 of fertiliser was deposited at the hedge/field edge interface.

In a tray experiment on seedling competition and establishment, there was no evidence of nitrogen fertiliser effects, at rates found in the field, on early plant establishment or species diversity. However, in a competition experiment with established plants of four grass species grown in pots, the nitrophilous species Bromus sterilis was able to increase growth at increasing nitrogen level, at the expense of slow‐growing Brachypodium sylvaticum and Anthoxanthum odoratum. Whilst hedges may buffer fertiliser contamination of habitats adjacent to agricultural fields, deposition of concentrated nitrogen fertiliser beside the hedge is likely to encourage the growth of nitrophilous plant species. In the short term, this may not affect botanical composition or diversity, but to reduce the likely long‐term adverse effects of fertiliser misplacement, we recommend that farmers are encouraged to use pneumatic fertiliser applicators and to introduce vegetation buffer strips at field edges.
An ultrastructural study of bruising in stored potato (Solarium tuberosum L.) tubers
Authors: EDGELL T. , BRIERLEY E R , COBB A H
Published: February 2008

Potato tubers of the cultivar Pentland Dell were investigated for ultrastructural changes following impact. Studies were carried out on tubers after 12 and 24 wk of storage using a falling bolt delivering 0.7 J of energy. Ultra‐thin sections were examined by light and transmission electron microscopy. Tubers stored for 12 wk exhibited no visual bruise formation, whereas visible bruising resulted following impact of tubers stored for 24 wk. An ultrastructural sequence of events during bruising was established as (1) a collapse of intracellular compartmentation, (2) increased ribosomal and mitochondrial abundance within the cytoplasm, (3) increased density of cytoplasm adjacent to the cell wall and surrounding amyloplasts, and (4) the development of melanin in bruised cells. These observations are discussed in relation to tuber turgor and physiology during storage.
Daily activity rhythm and use of shelter in the slugsDeroceras reticulationandArion distinctusunder laboratory conditions
Authors: HOMMAY G. , LORVELEC O. , JACKY F.
Published: February 2008

Daily activity of slugs,Deroceras reticulatumandArion distinctus, was studied in the laboratory in relation to the presence of shelters so as to define optimal conditions for using traps to forecast crop damage. Under constant temperature and humidity, activity of slugs began with the lights off. Its arrest occurred after a period of activity with the lights on. Slugs rested most frequently under a shelter on bare earth and rarely used the same shelter for more than two consecutive days. When food was placed under the shelter, the number of slugs found under the shelter was more constant throughout the 24 h period, but lower during diurnal rest. The presence of 4% methiocarb pellets under the shelter led to an increased occupation by slugs, due to the poisoning of some of them. Acts of aggression were more numerous inA. distinctusthan inD. reticulatum.InD. reticulatumthe smallest slug was the least aggressive and suffered more attacks from the other slugs. InA. distinctusthe numbers of attacks suffered or provoked varied little with the size of the slug, but the smallest slug showed less interactions with other slugs.
Analysis of intraspecific and interspecific variation in the genusAlternariaby the use of RAPD‐PCR
Authors: COOKE DAVID E L , FORSTER JOHN W , JENKINS PETER D , JONES D GARETH , LEWIS D MARK
Published: February 2008

The RAPD‐PCR profiles of 13 phytopathogenicAlternariaspecies and two closely related outgroups were examined using six different primers. Each species produced a distinct pattern of DNA fragments which were used as a measure of the degree of relatedness between species.A. brassicaeisolates of diverse origin showed high levels of similarity but little similarity was noted between other species. The closest interspecific genetic distances were recorded betweenA. citri, A. alternataandA. longipes.The outgroup generaEmbellisiaandStemphylium, which are recognised as distinct, could not be clearly separated using RAPD banding criteria, suggesting a high level of genetic diversity amongst these groups of fungi.
Infectibility and sensitivity of UK raspberry, blackberry and hybrid berry cultivars to Rubus viruses
Authors: JONES A TEIFION , McGAVIN WENDY J
Published: February 2008

Six blackberry or hybrid berry cultivars and 19 raspberry cultivars were assessed for their infectibility with, and sensitivity to, graft inoculation with 10 distinct viruses found infecting Rubus in the UK. Cultivars were grafted with each of, two isolates of the pollen borne raspberry bushy dwarf virus (RBDV), five aphid borne viruses: black raspberry necrosis, raspberry leaf mottle (RLMV), raspberry leaf spot (RLSV), rubus yellow net and raspberry vein chlorosis (RVCV); and isolates of the nematode transmitted nepoviruses, arabis mosaic, raspberry ringspot, strawberry latent ringspot and tomato black ring. All tested cultivars were infectible with a resistance breaking isolate of RBDV but only about half of that number with the Scottish type isolate of the virus. The raspberry cvs Autumn Bliss, and occasionally Glen Garry and Glen Prosen, developed leaf yellowing symptoms following infection with RBDV, but none of the other infected cultivars showed obvious leaf symptoms when kept in a heated glasshouse during the growing season. All tested cultivars were infectible with each of the four viruses transmitted in nature by the aphid, Amphorophora idaei. Most were infected symptomlessly, but seven cultivars developed severe leaf spotting symptoms due to infection with RLMV or RLSV. All but one of the raspberry cultivars were infectible with RVCV, which is transmitted in nature by the aphid Aphis idaei, and almost all infected plants developed leaf symptoms; only one of the hybrid berry or blackberry cultivars tested was infected with RVCV. In tests with the four nepoviruses, all tested cultivars, except Tummelberry, were infectible with at least one or more of these viruses. However, cultivars responded differently to challenge inoculation with different isolates of individual nepoviruses. Several cultivars developed chlorotic leaf mottling following infection with some nepovirus isolates. The implications of these results for virus control are discussed in the light of the changing pattern of virus and virus vector incidence in the UK.
Emergence depth of triazine susceptible and resistant Solarium nigrum seeds
Authors: KREMER E. , LOTZ L A P
Published: February 2008

Effects of population with different origin, biotype, seed size, temperature and depth of burial on the emergence of germinated seeds were investigated to assess the possibilities for successful management of triazine resistant populations of Solanum nigrum. Emergence fraction increased with temperature and decreased with increasing depth of placement. Emergence fraction appeared to be highest at intermediate seed weights. Resistant seeds showed a higher emergence fraction than susceptible seeds while emergence rate of resistant seeds was slightly lower. Emergence rate increased with increasing temperatures and decreasing depths. The possibilities for management of resistant S. nigrum with a stale seedbed preparation are discussed.
Effect of Bradyrhizobium, VA mycorrhiza and fertilisers on seed composition of groundnut
Authors: ELSHEIKH E A E , MOHAMEDZEIN E M M
Published: February 2008

A field experiment was carried out to investigate the effect of Bradyrhizobium and mycorrhizal (Glomus sp.) inoculation compared to adding urea and super phosphate on proximate composition, in vitro protein digestibility (IVPD) and tannin content of groundnut. The results showed that mycorrhizal inoculation and/or superphosphate significantly (P≤ 0.05) increased both oil and protein content of groundnut seeds. Bradyrhizobium and/or nitrogen fertiliser significantly (P≤ 0.05) increased protein content and significantly decreased the oil content. Bradyrhizobium and/or mycorrhizal inoculation significantly (P≤ 0.05) increased the ash, crude fibre, IVPD and tannin content. Biological and chemical fertilisers significantly (P≤ 0.05) increased IVPD. Superphosphate fertilisers significantly (P≤ 0.05) increased the tannin content. The moisture content was not affected by any treatment.
Influence of pollination systems on fruit set and fruit quality in kiwifruit (Actinidia deliciosa)
Authors: GONZALEZ M V , COQUE M. , HERRERO M.
Published: February 2008

Kiwifruit (Actinidia deliciosa (Chev.) Liang and Ferguson) is a dioecious species highly pollination dependent, since fruit size is directly correlated with seed number. To evaluate the best pollination system for this species a study of two natural and two artificial pollination systems was carried out and their effect on fruit set and fruit quality was determined. While anemophilous pollination produced few and small fruits, that were not commercially acceptable, high fruit set percentages and good quality fruits were obtained when insects participated in the pollination process. Artificial pollination, performed as hand pollination, improved yield quantity and quality. When environmental conditions impair insect activity this method can be an useful agricultural practice in order to assure a good yield.
Pollen effects on fruit and seed characteristics in pistachio (Pistacia vera L.)
Authors: HORMAZA J I , HERRERO M.
Published: February 2008

The agronomic profitability of nut production in pistachio (Pistacia vera L.) is hampered by several factors such as the production of empty nuts, the small size and dry weight of the edible kernel and the low percentage of endocarp dehiscence. The causes underlining these problems are still unknown. The effect of pollinations with pollen from P. atlantica and six different P. vera genotypes on several fruit, nut and embryo characters was compared to study possible xenic and/or metaxenic effects. The use of P. atlantica pollen affected some traits, but there were no clear differences when the pollen of the different P. vera genotypes was used suggesting that, at the intraspecific level, the main limitation to pistachio fruit production problems might not be due to pollen factors.
The incidence of sweet potato virus disease and virus resistance of sweet potato grown in Uganda
Authors: ARITUA V. , ADIPALA E. , CAREY E E , GIBSON R W
Published: February 2008

Sweet potato virus disease (SPVD) was common (25–30% average incidences), and farmers recognised it as an important disease, in sweet potato crops in southern Mpigi, Masaka and Rakai Districts in Uganda, but SPVD was rare in Soroti and Tororo Districts. Whiteflies, which are the vector of sweet potato chlorotic stunt crinivirus (SPCSV) a component cause of SPVD, were correspondingly common on sweet potato crops in Mpigi and rare on crops in Tororo. However, aphids, which are the vectors of sweet potato feathery mottle potyvirus (SPFMV), the other component cause of SPVD, were not found colonising sweet potato crops, and itinerant alate aphids may be the means of transmission. Different sweet potato cultivars were predominant in the different districts surveyed and four local cultivars obtained from Kanoni in S. Mpigi, where whiteflies and SPVD were common, were more resistant to SPVD than four cultivars from Busia in Tororo District, where whiteflies and SPVD were rare. However, nationally released cultivars were even more resistant than the local cultivars from Kanoni. Yield results and interviews with farmers indicated that farmers in S. Mpigi were making compromises in their choice of cultivars to grow, some key factors being SPVD susceptibility, and the yield, taste, and marketability, duration of harvest and in‐ground storability of the storage roots. These compromises need to be included in an assessment of yield losses attributable to SPVD.
Molecular characterisation of papaya ringspot potyvirus isolates from India
Authors: JAIN R K , PAPPU H R , PAPPU S S , VARMA A. , RAM R D
Published: February 2008

Papaya ringspot potyvirus (PRSV) causes major diseases of papaya and cucurbits in the Indian subcontinent. Based on biological properties, PRSV isolates are classified as either papaya infecting (P), or non‐papaya infecting (W) types. To characterise the P and W isolates from India at the molecular level, c. 1.7 Kb of the 3′‐terminal regions comprising a part of the nuclear inclusion b (Nib) gene, the complete capsid protein (CP) gene and the untranslated region (UTR) of both the P and W isolates were cloned and sequenced.

Comparative sequence analyses showed that the 3′‐UTRs in isolates P and W were 209 nucleotides in length excluding the poly (A) tail, and shared 96% identity. The CP genes of the two isolates were also similar, with 87% nucleotide identity and 93% amino acid identity. The amino acid differences between the CP genes were mostly confined to the amino terminus. The DAG triplet associated with aphid transmissibility was present in the CP of isolate W, but it was replaced by DAD in the P isolate. The partially sequenced Nib genes were also 90% identical, but isolate W contained an additional amino acid (threonine) just upstream of the cleavage site (Q/S) between Nib and CP. This is the first reported comparison of the molecular characterisation of PRSV‐P and W isolates from the Indian subcontinent.
Serological detection and antigenic variation of two whitefly‐transmitted geminiviruses: tobacco leaf curl and croton yellow vein mosaic viruses
Authors: SWANSON M M , VALAND G B , MUNIYAPPA V. , HARRISON B D
Published: February 2008

A panel of 25 monoclonal antibodies (MAbs) raised against particles of two heterologous whitefly‐transmitted geminiviruses (begomoviruses) was used in triple antibody‐sandwich ELISA (TAS‐ELISA) to determine the detectability and epitope profiles of 26 Indian isolates of tobacco leaf curl virus (TLCV) and 13 of croton yellow vein mosaic virus (CYVMV). Stock cultures of the two viruses had indistinguishable epitope profiles although they differ in symptomatology and particle stability. Their epitope profiles also strongly resembled those of Indian isolates of bhendi (okra) yellow vein mosaic and Indian cassava mosaic (ICMV) viruses. TLCV isolates from Andhra Pradesh, Gujarat and Karnataka States differed slightly in epitope profile: they reacted with at least eight out of 10 MAbs raised to ICMV but only one to four out of 15 MAbs raised to African cassava mosaic virus (ACMV). Virus isolates serologically indistinguishable from TLCV were detected in symptom‐bearing weeds (Acanthospermum hispidum, Ageratum conyzoides, Euphorbia geniculata, Parthenium hysterophorus) found in leaf curl‐affected tobacco fields and shown previously to be experimental hosts of TLCV. Indian TLCV isolates had small, consistent differences in epitope profile from Pakistani isolates but large differences from isolates from Burkina Faso, Malawi or Uganda. Isolates from the three African countries reacted with four or five of the ACMV MAbs but only one or two of the ICMV MAbs, and there were small but consistent inter‐country differences. CYVMV isolates from three Indian States showed less epitope variation than did Indian isolates of TLCV. TAS‐ELISA with MAb SCR 18 was a more sensitive test for detecting Indian TLCV isolates than was double antibody‐sandwich ELISA with polyclonal antibodies.
The effect of Pymetrozine, a feeding inhibitor of Homoptera, in preventing transmission of cauliflower mosaic caulimovirus by the aphid species Myzus persicae (Sulzer)
Authors: BEDFORD I D , KELLY A. , BANKS G K , FUOG D. , MARKHAM P G
Published: February 2008

Mature turnip plants, mechanically infected as seedlings with the semi‐persistent, aphid transmitted caulimovirus, cauliflower mosaic (CaMV), were treated by spraying with either a solution of Pymetrozine plus adjuvant oil, adjuvant oil or water only. At the same time turnip seedlings were sprayed for each of the three treatments. Two h after spraying, Myzus persicae were caged onto an infected turnip plant for each of the three treatments. Twenty four h later, groups of 20 aphids were transferred from the infected plants, to seedlings from each of the three treatments. After 24 h, these were removed and seedlings were later recorded for infection. This acquisition/transmission assay was repeated at 3, 7, 14 and 21 days from treatment. Only aphids exposed to the Pymetrozine treated source plants were shown to move off the plant and failed to transmit CaMV effectively to treated or control seedlings during the 0 and 3 day assays. The majority soon died when transferred to test seedlings. Progressively, more aphids were found to survive and transmit CaMV during the 7 day and 14 day assays. By 21 days no significant effect could be recorded between treatments and controls. Aphids transferred from control treated source plants to Pymetrozine treated seedlings were able to transmit CaMV within all the assays, although higher mortality was recorded in the day 0 assessment when compared to those transferred to control treated seedlings. We conclude from this trial, that a single foliar treatment of 100 mg litre1 Pymetrozine to CaMV infected turnip plants, effectively reduces the vectoring capability of M. persicae, that feed on these plants, for up to 7 days. However, Pymetrozine failed to stop virus transmission to treated seedlings from the ingress of viruliferous aphids. Pymetrozine was not shown to cause any phytotoxic responses to plants used in this trial.
Interaction of endodormancy and paradormancy in raspberry (Rubus idaeus L.)
Authors: WHITE J M , WAINWRIGHT H. , IRELAND C R
Published: February 2008

Bud break in protected Northern European raspberry crops is often poor and uneven with many of the sub‐apical buds remaining in a dormant state. In order to improve bud break and therefore yields, the mechanism controlling bud dormancy must be determined. Canes of the biennial cultivar ‘Glen Moy’ were forced as isolated single nodes, trisections, or as intact canes after different lengths of cold storage chill unit (CU) accumulation in order to determine whether the buds were in an endodormant or paradormant state. The results showed that buds on the lower parts of the intact canes remained in a dormant state long after buds from higher up the intact cane and also the single nodes from all parts of the cane had emerged from the deepest phase of endodormancy. This would imply that these buds were being held in a paradormant state until large amounts of chilling units (>1000 CU) had been accumulated. The trisected cane portions revealed almost no significant differences in bud break levels throughout the experiment when compared with the single nodes. This suggests that removal of the apical part of the cane would be effective in improving bud break by reducing the paradormant condition. A period of secondary dormancy was also observed in the intact canes which may also exacerbate the poor bud break observed in protected crops. This was not seen in the single nodes or the trisected canes which indicates that treatments which reduce paradormancy may also minimise the risk of secondary dormancy. By identifying the phase of bud dormancy which causes poor bud break, attention can now be focused on methods which overcome paradormancy in protected crops. Such methods might include tipping (removal of the cane apex), horizontal training methods, more efficient chilling methods, and chemical treatments.
Effects of salt on rhizobia and bradyrhizobia: a review
Authors: ELSHEIKH ELSIDDIG A E
Published: February 2008

Rhizobia and bradyrhizobia strains vary in their tolerance to salt‐stress. Rhizobium strains (fast‐growers) are more salt‐tolerant than strains of Bradyrhizobium (slow‐growers). However, salt‐tolerance in both genera is dependent upon ionic species, pH value, temperature, carbon source and the presence of osmoprotectant solutes. The harmful effect of salts on growth of both genera can be attributed to the specific ion effect rather than the osmotic effect. The salt‐tolerance of different strains of rhizobia and bradyrhizobia is not related to their ecological origin. Data for salt tolerance of 684 strains of rhizobia and bradyrhizobia were collected from many reports. Most of the reports confound the effects of salt and express the concentrations of salts in percentage (%), electrical conductivity (dS m‐1), molar concentration (m) or osmotic pressure (MPa) regardless of their differences. All the published data were compiled and recalculated from the different expressions to their equivalent molar concentration (m) of NaCl. A suggested classification of salt‐tolerance of rhizobia and bradyrhizobia from the compiled data is presented.
Factors affecting the detection of potato mop‐top virus in potato tubers and improvement of test procedures for more reliable assays
Authors: SOKMEN M ARLI , BARKER H. , TORRANCE L.
Published: February 2008

Progeny tubers were harvested from plants of five potato cultivars that had been grown in potato mop‐top virus (PMTV) infested soil. The tubers were tested for virus infection by methods based on reverse transcriptase‐polymerase chain reaction (RT‐PCR) or enzyme‐linked immunosorbent assay (ELISA) incorporating monoclonal antibodies. Both RT‐PCR and ELISA detected PMTV in extracts from tuber flesh. However, when the assay results were compared for individual tubers, there was an incomplete correlation between the two methods, and more infected tubers were detected by ELISA than by RT‐PCR. PMTV was detected in some samples but not in others taken from different parts of the same tuber, and this uneven distribution may explain the discrepancy between the results of the ELISA and RT‐PCR tests. Storage of tubers of two cvs at an elevated temperature (20oC) for 4 wk prior to testing, nearly doubled the number of sample sites at which PMTV was detected by ELISA. Such pre‐treatment may improve the accuracy of tuber tests. Most tubers of cvs Saturna and Pentland Crown were symptomlessly infected indicating that PMTV may easily escape detection in tubers of these cvs if tests are based solely on presence of visual symptoms. The application of post‐harvest tuber testing, particularly to cvs that do not display obvious symptoms, and the subsequent elimination of contaminated tubers will help to provide effective control of spread, and the establishment of PMTV at new sites.
Influence of reduced agrochemical inputs on plant‐parasitic nematodes
Authors: BOAG B. , RODGER S J , WRIGHT G McN , NEILSON R. , HEBDEN P. , SQUIRE G R , LAWSON H M
Published: February 2008

Plant‐parasitic nematodes were monitored in the multidisciplinary TALISMAN (Towards a Lower Input System Minimising Agrochemicals and Nitrogen) experiment undertaken at ADAS experimental sites at Boxworth, Drayton and High Mowthorpe, England (1990–1994). The treatments compared standard and alternative rotations, reduced and full herbicide application and full and half rate nitrogen at all three sites. After 6 yr, results snowed no evidence of either a positive or negative impact of the reduced application of agrochemicals on the non‐target plant‐parasitic nematode populations. Greatest differences were the unexplained year to year variability in nematode numbers.
Yield components of potato microtubers: in vitro production and field performance
Authors: NAIK P S , SARKAR D. , GAUR P C
Published: February 2008

Genetic parameters, character association and path analysis for yield components of microtuber production in vitro and their field performance were studied in 37 potato (Solanum tuberosum L.) genotypes. Among the microtuber yield components, average microtuber weight had maximum genotypic (or phenotypic) coefficient of variation, heritability and predicted genetic advance; however, the estimated values of these genetic parameters were maximum for tuber yield among the field yield components. The heritability estimates of field yield components were higher than that of their corresponding in vitro yield components of microtuber production. The highest correlation coefficients between average microtuber weight and microtuber yield suggested that microtuber weight was more important than microtuber number in determining microtuber yield potential in vitro. However, tuber number was found to be more important than tuber weight in determining tuber yield potential under field conditions. Average microtuber weight had maximum direct effect on microtuber yield, whereas tuber number had maximum direct effect on tuber yield under field conditions. The study showed that the relative importance of the components of microtuber production in vitro differed from that of corresponding field yield components. The expression of a genotype for microtuber production in vitro is different from that of tuber production under field situation i.e. the performance of a genotype in vitro is not a measure of its field performance.
Canopy development and tillering of field‐grown crops of two contrasting cultivars of winter wheat (Triticum aestivum) in response to CO2 and temperature
Authors: BATTS G R , ELLIS R H , MORISON J I L , HADLEY P.
Published: February 2008

Elevated CO2 (691 cf. 371 /miol CO2 mol‐1 air) and warmer temperatures (over the range 1.0UC below to 1.6oC above ambient) increased light interception by crops of two contrasting cultivars (Hereward and Soissons) of winter wheat (Triticum aestivum L.) during winter growth in the field. The fractional interception of light by the canopy increased more rapidly initially in Soissons than in Hereward, but Hereward showed a much greater response to CO2 (35% increase in Hereward but only 7% in Soissons) at 500oCd after sowing. By terminal spikelet formation, in contrast, fractional interception was greater in Hereward than in Soissons, while the effect of CO2 was the same in both cultivars (9%). Thus, although differences in the relative response of canopy development to CO2 were detected between cultivars initially, differences were negligible during later development. The greater interception of light by the canopy in elevated CO2, at any one temperature, resulted from increased tillering. The number of tillers plant“‘ at terminal spikelet was a linear function of main stem dry mass at this developmental stage but with a greater response in elevated CO2, viz 2.3 and 3.8 tillers g‐1 main stem dry mass at 371 and 691 /μmol CO2 mol‐1 air, respectively; these relations were unaffected by cultivar.
Diagnosis of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape (Brassica napus) in the UK
Authors: FITT B D L , DOUGHTY K J , GLADDERS P. , STEED J M , SUTHERLAND K G
Published: February 2008

Light leaf spot lesions were generally first observed as light green areas on leaves of UK winter oilseed rape crops in January or February and later became brittle and bleached. Elongated lesions, which were brown with indistinct edges, developed on stems in the spring and summer, when lesions were also observed on flower buds, pedicels and pods. Development of diagnostic white pustules (spore masses of Pyrenopeziza brassicae, which erupt through surfaces of infected tissues) for confirmation of light leaf spot infection on symptomless plants or plants with indistinct or ambiguous symptoms in the autumn, winter or spring was enhanced by incubating plants in polyethylene bags. In experiments with artificially inoculated plants, glasshouse‐grown plants exposed in infected crops and plants sampled from crops, white pustules developed at all incubation temperatures from 2oC to 20oC on infected leaves of different cultivars. The period of incubation required before the appearance of pustules decreased as the time that had already elapsed since the initial infection increased. The longest periods of incubation were required at the lowest temperatures (2oC or 5oC) but leaves senesced and abscised from plants most quickly at the highest temperatures (15oC or 20oC), suggesting that the optimal incubation temperature was between 10oC and 15oC.
Improved purification and molecular properties of Omithogalum mosaic virus in Israel
Authors: ZEIDAN M. , COHEN J. , WATAD A. , GERA A.
Published: February 2008

Symptoms associated with infection by Omithogalum mosaic virus (OMV) were documented among horticulturally important Omithogalum spp. grown in commercial greenhouses and open fields in Israel. OMV was mechanically transmitted to Chenopodium quinoa and C. amaranticolor. The virus was purified from infected C. quinoa using CsCl step gradient centrifugation. Virus yield of 18–24 mg kg“1 were obtained. Antiserum produced to the purified virus was highly specific in immunoblots and immunosorbent electron microscopy. Reverse transcription ‐ polymerase chain reaction (RT‐PCR) utilising potyvirus‐specific primers and the viral RNA resulted in the amplification of a DNA product of 1275 nucleotides. This PCR product was cloned and sequenced; it encoded an open reading frame of 333 codons and a 3‘ non‐coding region of 275 nucleotides. Analysis of the amino acid sequences of the putative CP of the Israeli isolate of OMV showed 95% similarities to the South African isolate.
The contribution of tomato and alternative host plants to tomato leaf curl virus inoculum pressure in different areas of South India
Authors: RAMAPPA H K , MUNIYAPPA V. , COLVIN J.
Published: February 2008

Indian tomato leaf curl virus (ToLCV) (Geminiviridae: Sub‐group III) was detected both in field‐collected and laboratory‐reared B. tabaci using a triple‐antibody sandwich enzyme‐linked immunosorbent assay (TAS‐ELISA). ToLCV was detected in six of the 10 group samples of field collected B. tabaci. ToLCV was also identified in 13 weed species commonly found in Karnataka, both by symptom expression and TAS‐ELISA. ToLCV from c. 61% of infected plants was transmitted successfully to tomato by B. tabaci.

Tomato plots were planted at three locations on the University of Agricultural Sciences Campus, Bangalore. Indian tomato leaf curl virus disease (ToLCVD) incidence increased most rapidly when the tomato plot was situated adjacent to an older ToLCVD‐infected tomato field. When the plots were positioned in a dryland or a wetland area, at least 500 m away from any infected tomato fields, the ToLCVD incidence increased less rapidly, although in all sites it was 100% by 11 wk after transplanting. The numbers of B. tabaci caught on yellow traps in all sites increased during weeks 1–3 after transplanting and thereafter remained at between 10–15 adults trap‐1 24 h_1. Adult numbers recorded on tomato plants by direct counts remained approximately constant at 2–4 adults plant“”1.

Tomato fields were planted in three taluks (administrative areas) of Karnataka, that had different current and previous histories of tomato production. ToLCVD incidence increased most and least rapidly, respectively, in Kolar taluk where tomato is grown continuously and Doddaballapur tuluk where tomato was grown in the area for the first time. In Malur tuluk, where tomato was grown discontinuously (once a year), the incidence of ToLCVD increased at an intermediate rate.

Weed host‐plant species growing near the experimental sites had averages of between 1.5–10.0 B. tabaci nymphs per plant, whereas the tomato plants had only 0.3 nymphs per plant. The percentage parasitism of B. tabaci nymphs on tomato and weed species, respectively, was 0.7% and 2–6%. Nymphs and pupae were parasitised by an Encarsia sp. and Eretmocerus mundus Mercet.

The relevance and implications of these findings for the epidemiology and management of ToLCVD in Karnataka State, South India is discussed.
Effect of inter‐cropping bell‐pepper with ginger on plant parasitic nematode populations and crop yields
Authors: SHARMA G C , BAJAJ B K
Published: February 2008

During 1994 studies were undertaken to improve ginger (Zingiber officinale Roscoe) yield against the nematodes Pratylenchus penetrans, Meloidogyne incognita, Helicotylenchus dihystera and Tylenchorhynchus mashhoodi in Himachal Pradesh (HP) (India) by inter‐cropping bell‐pepper (Capsicum annum L) in eight different sequences (treatments). Inter‐cropping of “one rhizome of ginger x one plant of bell‐pepper” gave the highest ginger yield (600 g per rhizome). This treatment was completely free from P. penetrans and M. incognita. All treatments with bell‐pepper plants equal to or higher in number to that of ginger rhizomes had higher ginger yields than treatments with ginger alone or with fewer bell‐pepper plants. In the former, populations of P. penetrans and M. incognita were lower than in the latter treatments. The yield of ginger varied irrespective of population densities of H. dihystera and T. mashhoodi, indicating that P. penetrans and M. incognita are the major nematode problems of ginger in HP. Bell‐pepper was a non‐host to P. penetrans and non‐preferred host to M. incognita. This helped to improve ginger yields by making the rhizosphere unfavourable for the development and multiplication of the major ginger nematode pests.
Herbicide resistance and gene flow in wild‐oats (Avena fatua and Avena sterilis ssp. ludoviciana)
Authors: CAVAN G. , BISS P. , MOSS S R
Published: February 2008

The process of resistance evolution to fenoxaprop‐P‐ethyl was investigated in the cereal weeds wild‐oats (Avena fatua L. and Avena sterilis ssp. ludoviciana Malzew) at a number of locations in England, including one farm where distinct patches occur within fields. Genetic fingerprints produced using PCR‐based techniques provided evidence for hybridisation between the species and that resistance had spread from one patch to others. The proportion of total variation due to differences between populations (Gst) was estimated at 33^2%, and herbicide‐resistant patches contained on average less genetic diversity than herbicide‐sensitive counterparts: both findings were consistent with a high degree of self‐pollination. It was however concluded that cross‐pollination occurs both within and possibly between species, and that this can result in the spread of herbicide resistance.
Heat tolerance in cowpea: effect of timing and duration of heat stress
Authors: CRAUFURD P Q , BOJANG M. , WHEELER T R , SUMMERFIELD R J
Published: February 2008

Reproductive processes and pod yield in cowpea (Vigna unguiculata (L.) Walp), an important crop grown in semi‐arid sub‐Saharan Africa, are adversely affected by high temperature. Genotypic differences in heat tolerance have been identified under hot, long‐days, but it was not known if this tolerance is also exhibited in hot, short‐day environments typical of sub‐Saharan Africa. The objectives of the work reported here were to determine whether heat tolerance identified under hot, long‐days was expressed at the same stages of development under hot, short‐days, and whether responsiveness to temperature was additive and quantitative. A heat‐tolerant (Prima) and heat‐susceptible (IT84S‐2246) cultivar of cowpea were grown in controlled environments under short‐days (12 h day‐1), initially at 30°C/24°C (Mod‐T), and then transferred at 0, 10, 20, 30 and 40 days after emergence (DAE) to 36°C/27°C (High‐T), where they remained for 5, 10 or 20 days duration before returning to Mod‐T. Control plants remained at Mod‐T or High‐T for 50 days, when the first pods were mature and the experiment was terminated. There were significant effects of duration (D) and timing (T) (P < 0.001), and interactions between D × T (P < 0.001), T × genotype (G) (P < 0.01) and D × T × G (P < 0.05) on pod weight plant‐1. Prima was significantly (P < 0.001) more tolerant to high temperature during flowering than IT84S‐2246, confirming that heat tolerance was expressed under hot, short days. The greater heat tolerance of Prima was associated with an ability to maintain peduncle and flower production at High‐T, and with greater podset. The sensitive period in IT84S‐2246 started at floral bud initiation (15–20 DAE), and effects of High‐T thereafter were additive and quantitative.
Alterations in growth of tissue‐cultured tansy (Tanacetum vulgare L.) treated with antibiotics
Authors: KESKITALO MARJO , POHTO ARJA , SAVELA MERVI‐LEENA , VALKONEN JARI P T , SIMON JAMES , PEHU EIJA
Published: February 2008

Effects of three antibiotics (cefotaxime, rifampicin and gentamicin) were tested on in vitro shoots cultures of tansy (Tanacetum vulgare L.)‐ These antibiotics were selected because endophytic bacteria isolated from the in vitro shoot cultures of tansy showed that all bacteria were Gram‐negative and their growth was reduced by these three antibiotics. Five isolates were Enterobacteriaceae, three were fluorescent Pseudomonas, and two were aerobic bacteria. Increased concentrations of antibiotics caused usually linear or quadratic changes on the initiation of shoot growth, shoot number, growth rate, and shoot height. These changes and changes in pH of the culture media were tansy genotype‐dependent following treatments with gentamicin. Also, the treatment with rifampicin or cefotaxime showed a genotype‐dependent effect, because they resulted in significantly higher percentage of rooted plants in one of the three tansy genotypes tested. The growth rate and length of shoots were reduced in the media containing both gentamicin and rifampicin, but less so than in media containing both gentamicin and cefotaxime.
Feeding preferences of woodpigeons and flea‐beetles for oilseed rape and turnip rape
Authors: LAMBDON P W , HASSALL M. , MITHEN R.
Published: February 2008

Winter turnip rape Brassica rapa ssp. oleifera was shown to have reduced palatability to woodpigeons, enhanced susceptibility to adult flea beetle feeding and reduced susceptibility to larval flea‐beetle infection when compared with winter oilseed rape (B. napus) cultivars in field trials. Levels of leaf waxes were negatively correlated with feeding preferences of adult flea beetles. Analysis of volatiles from damaged leaves showed that while all cultivars produce a similar range of nitriles, cyanoepithioalkanes and isothiocyanates, derived from 3‐butenyl, 4‐pentenyl and phenylethyl glucosinolates, B. rapa leaves produced relatively high levels of 1‐methylpropyl isothiocyanate, although there was significant plant‐to‐plant variation. The possible involvement of this mustard oil glycoside and variation in epicuticular waxes in plant‐herbivore interactions are discussed.
Selection of resistance breaking strains of tomato spotted wilt tospovirus
Authors: LATHAM L J , JONES R A C
Published: February 2008

In glasshouse tests, sap from plants infected with 15 different isolates of tomato spotted wilt tospovirus (TSWV) from three Australian states was inoculated to nine genotypes of tomato carrying TSWV resistance gene Sw‐5 or one of its alleles. A further two resistant tomato genotypes were inoculated with four isolates each. The normal response in resistant genotypes was development of necrotic local lesions in inoculated leaves without systemic invasion, but 22/752 plants also developed systemic reactions in addition to local hypersensitive ones. Using cultures from two of these systemically infected plants and following four cycles of subculture in TSWV resistant tomato plants, two isolates were obtained that gave susceptible type systemic reactions but no necrotic spots in inoculated leaves of resistant tomatoes. When these two isolates, DaWA‐1d and ToTAS‐1d, were maintained by repeated subculture for 10 successive cycles in Nicotiana glutinosa or a susceptible tomato genotype, they still induced susceptible type systemic reactions when inoculated to resistant tomato plants. They were therefore stable resistance breaking isolates as regards overcoming gene Sw‐5. When resistance‐breaking isolate DaWA‐1ld multiplied together with original isolate DaWA‐l in susceptible tomato, it was fully competitive with the original isolate. However, when DaWA‐ld and ToTAS‐ld were inoculated to TSWV resistant Lycopersicon peruvianum lines PI 128660R and PI 128660S and to TSWV resistant Capsicum chinense lines PI 152225, PI 159236 and AVRDC CO0943, they failed to overcome the resistance, producing only necrotic local lesions without systemic infection. Thus, although the ease of selection, stability and competitive ability of resistance breaking isolates of TSWV is cause for concern, L. peruvianum and C. chinense lines are available which are effective against them.

The effectiveness of the resistance to TSWV in nine tomato genotypes was examined in a field experiment. Spread was substantial in the susceptible control genotype infecting 42% of plants. Resistance was ineffective in cv. Bronze Rebel, 26% of plants developing infection. In contrast, it held up well in the other eight resistant genotypes with only 1–3 or no plants of each becoming infected. Accumulated numbers of Thrips tabaci, Frankliniella occidentalis and F. schultzei were closely correlated with TSWV spread.