bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some properties of a previously undescribed virus from cassava: Cassava American Latent Virus
Authors: WALTER B. , LADEVEZE ISABELLE , ETIENNE L. , FUCHS M. 
Published: February 2008

SummaryA virus with spherical particles c. 28 nm in diameter was sap‐transmitted from different cassava (Manihot esculenta) cultivars to a limited range of species in the families Chenopodiaceae and Solanaceae. Cassava seedlings infected by inoculation with sap or with purified virus preparations did not show any symptom, although the virus was readily detected by ELISA or by further inoculations. Leaf extracts from infected Nicotiana benthamiana were infective after dilution of 10‐‐3but not 10‐‐4, and after heating for 10 min at 70°C, but not at 72°C. The virus was purified from N. benthamiana, N. clevelandii or from cassava. On sucrose gradients, the virus particles sediment as three components all containing a protein of mol. wt c. 57000. The genome of the virus is composed of two RNAs of mol. wt c. 2.54 times 106(RNA‐1) and 1.44 times 106(RNA‐2). RNA‐2 was detected in the middle and the bottom nucleoprotein components, and RNA‐1 only in the bottom component. An antiserum prepared to purified virus particles was used to readily detect the virus in cassava and other host plants by ELISA and by ISEM. No serological relationship was shown between this virus and eight nepoviruses, including the recently described cassava green mottle nepovirus infecting cassava in the Solomon Islands (Lennon, Aiton & Harrison, 1987). The virus described here is the first nepovirus isolated from cassava in South America, and is named cassava American latent virus.
Temperature effects on the life history of the eulophid wasp Diglyphus isaea, an ectoparasitoid of leafminers (Liriomyza spp.), on tomatoes
Authors: MINKENBERG OSCAR P. J. M. 
Published: February 2008

SummaryThe effect of constant and alternating temperatures on the life‐history of Diglyphus isaea, as an ectoparasitoid of Liriomyza leafminers on tomato plants, was examined in the laboratory.Parasitoid development and size were significantly affected by temperature and sex. Males showed a shorter development time and pupal size than female parasitoids. Both development time and pupil size in D. isaea differed according to the host species. Pupal size showed no consistent relationship with temperature. The lower thermal threshold for development and oviposition was determined. Fecundity with L. byroniae as host did not differ significantly between temperature regimes. Furthermore, larger females did not produce larger numbers of offspring. Development and reproduction under the alternating temperature regime did not differ from those at the comparable constant temperature, suggesting a rapid response to changes in temperature.The intrinsic rate of increase (rm) and net reproduction (Ro) of D. isaea nearly doubled from 15°C to 25°C and 20°C, respectively, and generation time at 25°C was less than half that at 15°C. Because the parasitoid's population growth is higher than that of these pest insects at all temperatures, D. isaea is a promising candidate for seasonal inoculative biological control of Liriomyza on tomato crops in Scandinavian and western European glasshouses. Possible constraints to its effectiveness are discussed.
Estimation and validation of a function describing the rate at which Mycosphaerella graminicola causes yield loss in winter wheat
Authors: SHAW M. W. , ROYLE D. J. 
Published: February 2008

SummaryAn experiment designed to generate a wide variety of epidemics of Mycosphaerella graminicola without deliberate replication was done in two years. Disease severity was estimated at frequent intervals during the life of the crop and yields measured at harvest. Absolute estimates of disease severity were derived by regression of visual estimates on subsamples of leaves on which severity was estimated objectively using an image analysis system. Yield was predicted best by the integral of the square root of M. graminicola severity over the normal lifetime of each leaf, measured in thermal time. Only the top two leaves contributed to yield loss; no influence of the third leaf on yield was detected. Thousand grain weight was best predicted by the integral of the square root of M. graminicola severity on the flag leaf alone. Parameter estimates were similar in the two years. The prediction equations were consistent with yields observed in an experiment done in a third year using two sowing dates and two rates of nitrogen fertilisation, despite a much greater range of disease severity. Although critical point models could describe each year's results adequately, neither parameter estimates nor the growth stage at which the best relation occurred were consistent across years. The equations to predict loss may be useful for farmers in decision‐support systems which are based on prediction.
A hydathode inoculation technique for the simulation of natural black rot infection of cabbage by Xanthomonas campestris pv. campestris
Authors: ROBESON D. J. , BRETSCHNEIDER KARIN E. , GONELLA M. P. 
Published: February 2008

SummaryA technique was developed for the reliable inoculation of Xanthomonas campestris pv. campestris into the cabbage host, in a manner which simulates a natural process of penetration. By introducing the inoculum into guttation droplets on the leaf margin, the bacteria are taken into the plant via the hydathodes, thereby avoiding mechanical injury to the plant and the possibility of producing artefacts. This technique, while being highly efficient, possesses several advantages over commonly used methods of inoculation.
Host plant preference and the influence of different cabbage cultivars on the toxicity of abamectin and cypermethrin against Plutella xylostella Lepidoptera: Plutellidae
Authors: ABRO G. H. , WRIGHT D. J. 
Published: February 2008

SummaryThe toxicity of avermectin B, (abamectin) and cypermethrin was determined against fourth instar larvae of Plutella xylostella L. reared on three cabbage cultivars which differed in their suitability as host plants. Cabbage cultivars were assessed as hosts for P. xylostella on the basis of larval and pupal weight and adult fecundity. Larvae reared on the best host, the cabbage cv. Offenham Flower of Spring were significantly (P > 0.01) less sensitive to topically‐applied abamectin (4.7‐fold at LD50) or cypermethrin (2.3‐fold) when compared with larvae reared on the intermediate host, the Savoy cabbage cv. Aquarius F1. Larvae reared on Offenham Flower of Spring were also significantly (P > 0.01) less sensitive (4.5‐fold) to topically‐applied abamectin compared with larvae reared on the poorest host tested, the cabbage cv. Minicole Fl. In contrast, the residual/ingestion toxicity of abamectin against fourth instars was significantly (P > 0.01) greater (2.5‐fold at LC50) on Offenham Flower of Spring than on Minicole F1. The results are discussed in terms of larval weight and larval feeding rates on the different cabbage cultivars.
Resistance in lettuce to the leaf aphids Macrosiphum euphorbiae and Uroleucon sonchi
Authors: REININK K. , DIELEMAN F. L. 
Published: February 2008

SummaryScreening of 90 lettuce genotypes revealed great variation in resistance to the leaf aphids Macrosiphum euphorbiae and Uroleucon sonchi. Butterhead genotypes were usually, but not always, moderately to highly resistant to both aphid species. On the other hand mcjst crisphead genotypes had little or no resistance to both species. The results for the modern crisphead cultivar Marbello showed that it is possible to transfer resistance to M. euphorbiae from the butterhead to the crisphead type. Breeding programmes should benefit from the fact that in many cases resistance to M. euphorbiae and to U. sonchi, and in some cases also to other aphid species, was found in the same genotype. However, correlations between resistance scores for M. euphorbiae and U. sonchi were rather low, indicating that some components of resistance are specific to only one of the aphid species. Also within three groups of genotypes with resistance to Nasonovia ribisnigri, Myzus persicae and Pemphigus bursarius, respectively, large differences in resistance to M, euphorbiae and U. sonchi were found. The accumulation in one genotype of various resistance components to create cultivars with broad aphid resistance is a challenging and difficult task for practical plant breeding.
Further studies on breeding for resistance to Botrytis cinerea in red raspberry canes
Authors: JENNINGS D. L. , BRYDON E. 
Published: February 2008

SummaryA high level of resistance to cane botrytis caused by Botrytis cinerea was transferred from Rubus pileatus to the red raspberry through three generations of backcrossing. The strength of the resistance showed little diminution through these generations and it was therefore thought that a major gene for resistance had been transferred. But discontinuity in the resistance levels observed was detected in plants of only one group of the progenies and so evidence for a major gene is lacking. The results showed the considerable influence of gene H, which confers pubescence, and emphasised that resistance must be separately assessed for pubescent and non‐pubescent segregates.
Segregation of a viroid complex from a graft‐transmissible dwarfing agent source for grapefruit trees
Authors: HADAS RIVKA , BAR‐JOSEPH M. , SEMANCIK J. S. 
Published: February 2008

SummaryA marked variation in tree size occurred in grapefruit trees budded in trifoliate orange rootstock and inoculated with a graft‐transmissible dwarfing agent (GTD) from grapefruit. Etrog citron (Citrus medico) inoculated with budwood collected from two GTD sub‐types displaying very mild (VM) and mild (M) dwarfing effects showed only mild leaf epinasty, whereas the severe (S) subtype induced severe epinasty and stunting typical of infection by the original GTD source 225‐T. The characteristic symptoms of the three sub‐types were persistent following three serial transfers to ‘Etrog’ indicators.Extracts from ‘Etrog’ citron containing either the 225‐T or its derivative S displayed a profile of five viroid bands when analysed by the sequential PAGE system for detection of circular RNAs. The profile obtained included the well characterised 371 nucleotide citrus exocortis viroid (CEV) and four additional viroids of approximately 330, 300, 295 and 275 nucleotides. Sub‐types M and VM lacked the CEV band and each contained a complement of only three viroids of 330, 295, 275 and 300, 295, 275 nucleotides, respectively. These results indicate that a segregation of the viroid complex in grapefruit budwood was a major factor in the variation seen among trees inoculated from the GTD source 225‐T.
Distribution of 14C‐sucrose applied to leaves at different nodes of okra (Abelmoschus esculentum) during flowering and early pod growth
Authors: RAO N. K. SRINIVASA , BHATT R. M. 
Published: February 2008

SummaryThe distribution pattern of 14C‐sucrose from 14C‐sucrose applied to vegetative okra plants and leaves 1–9 on separate plants during the green pod development stage were investigated in relation to duration and leaf position. Results indicated bi‐directional transport of assimilates to both apical and basal portions of the stem. Within 48 h 14C moved to all plant parts; stem and leaves appeared to be strong sinks. In plants fed at the vegetative stage, 48 h after feeding, 66% of the fed activity was exported from the fed leaf. At the pod development stage, about 35% of the activity exported from the fed leaf was present in green pods and 65% in vegetative parts. In plants where leaf 1–9 was fed, irrespective of the position of the fed leaf, the subtending fruit was the strongest sink among the reproductive parts. Leaves and stems were the principal sinks.
Competition between maize and Echinochloa crus‐galli analysed by a hyperbolic regression model
Authors: SPITTERS C. J. T. , KROPFF M. J. , de GROOT W. 
Published: February 2008

SummaryYield reduction of maize in relation to naturally established populations of Echinochloa crus‐galli and Chenopodium album was studied in field experiments over 2 years in which the maize was grown at a wide range of weed densities. Both the crop and the weeds were harvested at intervals during the season. The competitive relations were described accurately by a model based on a hyperbolic relation between yield and plant density. The model can be linearised by considering the reciprocals of the average weight per plant. However, estimating the regression coefficients by linear regression introduced a severe bias due to heterogeneity of variances. Estimation was improved by applying non‐linear regression, using a logarithmic transform of the yield equation. Fitted regressions were used to interpolate the yield data to standard weed densities. At a density of 100 Echinochloa plants m‐2, maize yields were reduced by 8% and 82% in 1982 and 1983, respectively, illustrating the problems in generalising the results of one competition experiment to the other. Three possible fields of application of the competition model are discussed, i.e. adjustment of experimental plot yield for variation in weed population, prediction of expected crop yield losses, and prediction of long‐term changes in weed seed populations.
The effect of pod growth stages in cowpea on aphid reproduction and damage by the cowpea aphid, Aphis craccivora (Homoptera: Aphididae)
Authors: OFUYA T. I. 
Published: February 2008

SummaryCowpea, Vigna unguiculata was infested at the young, mid‐fill and mature pod growth stages with, respectively, one, two and three pre‐reproductive adult apterae of Aphis craccivora per pod in a screen house. A. craccivora caused pod shrivelling at the young and mid‐fill pod stages, on which the aphid was more fecund. All levels of infestation caused significant reduction in seed yield irrespective of age of pod.
Cross‐protection between arabis mosaic virus and grapevine fan leaf virus isolates in Chenopodium quinoa
Authors: HUSS B. , WALTER B. , FUCHS M. 
Published: February 2008

SummaryCross‐protection experiments were performed in Chenopodium quinoa using arabis mosaic virus (ArMV) and grapevine fanleaf virus (GFLV) isolates.Two factors were specially studied, namely the time interval and the distance between the two inoculations, respectively, with the hypovirulent isolate and with the hyper virulent challenge isolale.ArMV‐S clearly protected C. quinoa from a super infection with GFLV‐F13 as shown by a diminution, or even suppression, of the synthesis of the coat protein and the nucleic acids of the GFLV‐F13 isolate. In the homologous interaction between GFLV isolates (GH and F13), protection was also observed. In the interaction between GFLV‐GH and ArMV‐862, by contrast, symptoms were typical of the hyper virulent ArMV‐862 and the amount of coat protein of ArMV‐862 was normal.
Aspects of herbicide activity and persistence under low level polyethylene covers
Authors: BOND W. , WALKER A. 
Published: February 2008

SummaryIn an experiment prepared in autumn, weed numbers were not affected by covering the soil with clear perforated polyethylene. Weed growth was enhanced, however, and the fresh weight at the time of polyethylene removal in spring was more than three times greater on the covered compared with the uncovered areas. In a similar experiment prepared in spring, covering with perforated polyethylene increased weed numbers by a factor of two and weed fresh weight by a factor of seven. The performance of a number of herbicides used in carrots, in terms of percentage reduction in weed number and weed fresh weight, was similar under covers and in the open. The most effective weed control was achieved with broad‐spectrum herbicide treatments, particularly under the polyethylene, since surviving weed seedlings grew rapidly in the protected environment. When weed control was good, covering enhanced carrot yield. Measurement of the distribution of herbicide residues in the soil demonstrated that persistence was increased and movement in the soil decreased by covering with polyethylene.
Photosynthetic assimilation of 14CO2 and fate of 14C‐labelled photosynthate in winter wheat (Triticum aestivum) near‐isoclines differing in alleles at the Rht1 and Rht2 reduced‐height loci*
Authors: KIYOMOTO R. K. , GENT M. P. N. 
Published: February 2008

SummaryThe mechanism by which reduced‐height genes, Rht1 and Rht2 influence yield and harvest index (HI) were investigated in dwarf (D, Rht1Rht2), semidwarf (SD‐1 and SD‐2, Rht1rht2 and rht1Rht2, respectively), and tall (T, rht1rht2) near‐isogenic lines (isolines) derived from winter wheat cv. Burt. Dry matter accumulation, yield, and assimilation, distribution, and retention of 14C label from photosynthetic assimilation of 14CO2, was followed in field‐grown plants in Connecticut, USA. The relationships among the isolines were similar over the two years of study. The tall isoline ranked highest in grain yield and biomass, but had a small HI; SD‐1 was similar to T in yield and biomass, but had the largest HI; SD‐2 was similar to SD‐1 in HI, but its yield and biomass were less than SD‐1 and T; and D yielded the least grain and biomass and had a small HI similar to T.Following photosynthetic assimilation of 14CO2 during grain filling, the distribution of 14C in ears at maturity was similar for SD‐1, SD‐2, and T. When labelled shortly after anthesis or late in grain filling, the distribution of 14C to the mature ear of D was less than that for other isolines. At maturity D also retained the smallest amount of the radioactivity initially assimilated. The low yield and HI of D may be related to its inability to retain photosynthate and distribute it to the grain. The SD‐1, SD‐2, and T isolines did not differ in retention at maturity of 14C in the whole plant. When labelled shortly after anthesis, stems of T retained more 14C, which may represent a tendency to sequester more photosynthate in its stems that would reduce its HI at maturity. In contrast, the yield of SD‐2 was limited by photosynthetic capacity.
The response of apples cv. Cox's Orange Pippin to different concentrations of oxygen in the storage atmosphere
Authors: STOW J. 
Published: February 2008

SummaryThe response of apples cv. Cox's Orange Pippin to storage in flowing streams of air and nitrogen mixed to generate atmospheres ranging from 0.5% to 2% oxygen was examined in two seasons. The benefits of reducing store oxygen concentrations below 1.25% were small but storage in 0.75% may be advantageous for Cox's Orange Pippin apples in seasons when flesh firmness is low at harvest. Ethanol‐induced flesh breakdown was recorded in samples stored in 0.5% O2 in one season and the risk of low temperature breakdown was increased in oxygen levels below 1.25%. Ethylene production was reduced by lowering the oxygen concentration.
The effects of temperature and host quality on the rate of increase of the grain aphid (Sitobion avenae) on wheat
Authors: ACREMAN S. J. , DIXON A. F. G. 
Published: February 2008

SummaryFrom 10°C to 25°C Sitobion avenae reared on wheat developed faster, had a higher mean relative growth rate and a higher intrinsic rate of increase on ears than on the flag leaves. At temperatures above 25°C there is a marked decline in the performance of the aphid. The intrinsic rate of increase is strongly correlated with the mean relative growth rate during development for both aphids reared on ears and flag leaves from 10°C to 25°C.
Genetic control of immunity to turnip mosaic virus in winter oilseed rape (Brassica napus ssp. oleifera) and the effect of foreign isolates of the virus
Authors: WALSH J. A. 
Published: February 2008

SummaryImmunity to a UK isolate (UK 1) of turnip mosaic virus (TuMV) was studied in eight lines of oilseed rape selected from cv Rafal. Six of these lines were uniformly immune and two segregated. Segregation ratios in the F2 generation of reciprocal crosses between two uniformly immune lines and two uniformly susceptible cultivars (Mikado and Yeoman) showed that immunity was controlled by a dominant nuclear allele. The immunity was confirmed by the inability to detect virus particles in mechanically inoculated plants by back inoculations, ELISA and ISEM tests. Plants were immune to repeated inoculations and aphid transmissions.The immunity was effective against one other UK isolate and two German isolates of TuMV. Another UK isolate (UK 3) and a Greek isolate partially overcame the immunity causing local infection and a Canadian and a Danish isolate overcame it completely causing systemic mosaic‐type symptoms. When these immunity‐breaking strains were tested against swede line 165 which is also immune to UK 1 TuMV, the Canadian isolate overcame the immunity whereas the Danish isolate did not. Using this swede line, one susceptible and one immune line of oilseed rape as differentials, four distinct groups of TuMV isolates could be identified. Selections of oilseed rape immune to UK TuMV isolates were more severely affected by the Canadian TuMV than UK TuMV susceptible selections. The gene determining immunity to TuMV had no pleiotropic effect on susceptibility to cauliflower mosaic virus.The implications on these findings in relation to breeding for virus resistance are discussed.
The pattern of frost‐hardening of leaves of winter cauliflower (Brassica oleracea var. botrytis cv. Clause 30)
Authors: FULLER M. P. , GROUT B. W. W. , TAPSELL C. R. 
Published: February 2008

SummaryThe suitability of an electrical conductivity assay of leaf material for determining frost hardiness in winter cauliflower was established. The assay was used to monitor the changes in hardiness of field‐grown plants during two seasons at two sites.Levels of frost hardiness were related to mean air temperature over the 7‐day period prior to sampling (r = 0.6008, P< 0.001). There was no clear disjunction of any temperature to indicate a threshold temperature of hardening. Dehardening occurred in spring and during mild spells in winter. In the mild regions where this crop is grown commercially it is likely that plants are not fully hardened for much of the winter. This may facilitate curd growth but may put the crop at risk from frost damage.
Establishing the large scale osmotic priming of onion seeds by using enriched air
Authors: BUJALSKI W. , NIENOW A. W. , GRAY D. 
Published: February 2008

SummaryOnion seeds were primed in polyethylene glycol solutions (PEG) (‐1.5 MPa) for 14 days at 15°C on filter paper and in bubble columns containing 50 g seed litre‐1 PEG using air or enriched air (75% O2/25% N2) to aerate and suspend the seeds. Compared with untreated seeds, priming seeds in bubble columns using enriched air increased the percentage seed germination but it did not when air was used, or when seeds were primed on filter paper. Mean germination times (tm) were significantly reduced in all cases but the reduction was greatest using enriched air and least using air. The spread of germination times was significantly reduced only for seeds primed in enriched air.Drying seeds following priming reduced the percentage germination compared with untreated seeds, but only significantly for those primed in bubble columns using air. Drying also increased the mean germination times by 1.5 to 1.8 days (relative to primed seed which had not been dried). Seeds primed in enriched air were least affected. This increased time is that typically required for water re‐imbibition after drying.Priming with enriched air followed by drying gave the same number of normal seedlings as untreated seeds.
A ribosomal DNA probe to distinguish populations of Rhopalosiphum maidis (Homoptera: Aphididae)
Authors: LUPOLI R. , IRWIN M. E. , VOSSBRINCK C. R. 
Published: February 2008

SUMMARYTotal DNA from clones of Rhopalosiphum maidis was digested with restriction endonucleases and hybridised with a heterospecific ribosomal DNA probe. DNA banding patterns exhibited sufficient differences to distinguish five different clones, and provided greater resolving power than gel electrophoresis of allozymes. The mechanisms and applications of this marking technique are discussed.