bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phytophthora cryptogea root rot of tomato in rockwool nutrient culture. I. Analysis of root infection
Authors: PEGG G. F. , JORDAN M. M. 
Published: February 2008

SummaryThe spatial and temporal colonisation of tomato plants by Phytophthora cryptogea was studied in rockwool nutrient culture. Root growth and the distribution and progress of infection were measured on dissected root fragments obtained from a detailed destructive sampling of the substrate. Dissected fragments of root or roots and fibres were plated on BNPRA agar, a selective Phytophthora medium. Roots colonised all parts of the rockwool substrate 60 days after planting with the exception of surface marginal and central areas of the slab which had a lower solution content. Most root biomass occurred in and immediately beneath the original growing block. The distribution of P. cryptogea closely followed the pattern of root colonisation.An alternative, novel method for root analysis involved the dissolution of the mineral fibre and its formate bonding resin by digestion in 1 m H3PO4 for 45 min. Comparative recoveries of P. cryptogea from plated fragments of dissected root and fibre or comminuted samples of acid‐released or dissected root showed that the acid treatment initially reduced the number of Phytophthora colonies in block and slab roots by 67% and 61% respectively. After 28 days, colony recovery from acid‐released roots in the rockwool slab increased and was between 4% and 13% lower than from other plating methods. Since 1 m H3PO4 was lethal to zoospores and surface sporangia, the colonies recovered were interpreted as originating exclusively from root lesions. Root fresh weight of healthy and inoculated plants declined during the initial period of fruit formation. P. cryptogea infection led to a progressive reduction in root weight in the growing block and main slab and 28 days after inoculation, was approximately 50% of the controls.The acid digestion of rockwool fibre is proposed as a new approach to the problem of root and pathogen analysis in this substrate.
Role of temperature and light in the germination ecology of buried seeds of Potentilla recta
Authors: BASKIN J. M. , BASKIN C. C. 
Published: February 2008

SummaryFresh, mature seeds of the perennial weed, Potentilla recta L. (Rosaceae), were buried in early July of 1984 and 1985 and exposed to natural yearly temperature cycles. At monthly intervals for 28 (1984 seeds) and 25.5 (1985 seeds) months, seeds were exhumed and tested in light and darkness at 12/12 h alternating temperature regimes of 15/6, 20/10, 25/15, 30/15 and 35/20°C. At the time of burial, 2–38% of the seeds germinated in light at 15/6 and 20/10°C, but none germinated at any of the other test conditions. During summer, seeds after‐ripened, and by October they germinated to 41–87% in light at all thermoperiods. Seeds never gained the ability to germinate in darkness. Although buried seeds subsequently were exposed to low winter and high summer temperatures, they did not re‐enter dormancy or exhibit cyclic changes in germination responses. Thus, buried seeds can potentially germinate during any month of the growing season, if a disturbance brings the seeds to the soil surface and moisture is nonlimiting. However, only 23 to 50% of the exhumed seeds germinated at the July and August temperature (35/20°C) in July and August.
Partial characterisation of an induced virus inhibitory protein, associated with systemic resistance in Cyamopsis tetragonoloba (L.) Taub. plants
Authors: KHAN M. M. ABID ALI , VERMA H. N. 
Published: February 2008

SummaryAqueous leaf extract of Pseuderanthemum bicolor Radlk. when sprayed or rubbed onto Cyamopsis tetragonoloba provoked the synthesis of a virus inhibitory agent (VIA) associated with the induction of systemic resistance against virus infection. The VIA induced was highly potent and inhibited tobamo and potex virus infection. Synthesis of the VIA could be prevented by the simultaneous application of actinomycin‐D.Extracts from C. tetragonoloba were clarified with diethyl ether, the VIA precipitated with ammonium sulphate and further purified by ion‐exchange chromatography and gel chromatography. Purified VIA showed positive chemical tests only for proteins and was inactivated by incubation with proteolytic enzymes. Active protein had a molecular weight around 15 500 daltons and contained 18 different amino acids.
Use of isoelectricfocusing in barley varietal identification
Authors: THOMPSON D. M. , POWELL W. , FORSTER B. P. 
Published: February 2008

SummaryIsoelectricfocusing (IEF) was used to characterise 29 spring and winter barley varieties obtained from standard seed stocks of the National Institute of Agricultural Botany (NIAB), UK using eight isozyme and protein marker systems. The eight protein and isozyme marker phenotypes for each variety are described and 27 of the 29 barley varieties examined are uniquely distinguished. Isozyme and protein banding patterns as resolved by IEF provide character traits useful for varietal description and identification. Advantages of the technique include improved resolution of banding patterns, increased standardisation between gels and the ease of handling a large number of samples rapidly and effectively.
Differential cold hardiness in adults and nymphs of the peach‐potato aphid Myzus persicae
Authors: CLOUGH M. S. , BALE J. S. , HARRINGTON R. 
Published: February 2008

SummaryThe LT50 (lethal temperature) of first instar and adult stages of the peach‐potato aphid Myzus persicae was lowered following long term acclimation at low temperatures.First instars consistently showed greater cold hardiness than adult stages at each acclimation temperature, with the differential increasing as the temperature was lowered. When maintained at 5°C (the lowest acclimation regime) nymphs and adults had dLT508.3°C and 4.7°C respectively lower than those for non‐acclimated individuals.When 10°C acclimated adults were returned to 20°C, the acclimation effect was retained in full for 6 days but complete deacclimation occurred by day 10. In contrast the LT50 of their progeny increased gradually from the first day of adult deacclimation towards the level of the unacclimated control over a period of 10 days.A change in cold hardiness was observed in first instars according to their position in the birth sequence. The LT50 of first‐born nymphs (day 1 of reproduction) from 20°C parents was ‐ 15.9°C rising to ‐ 8.3°C by day 4 and remaining at this level until the end of the reproductive period.The differential mortality between nymphs and adults observed in the laboratory was supported by the results of a field experiment. Adult aphids kept in clip‐cages on a crop of oilseed rape showed greater mortality compared with those introduced as nymphs when the minimum temperature fell below ‐4°C for the first time in winter. At ‐ 10°C mortality of aphids introduced as adults approached 100% whereas more than 50% of those introduced as nymphs were still alive at this temperature.
Potential of the parasitoid Heterospilus prosopidis (Hymenoptera: Braconidae) as a vector of plant‐pathogenic Colletotrichum spp.
Authors: NEMEYE P. S. , MOORE D. , PRIOR C. 
Published: February 2008

SummaryA braconid parasitoid Heterospilus prosopidis was contaminated with either Colletotrichum coffeanum or C. gloeosporioides, causal agents of coffee berry disease and mango anthracnose respectively. Adult parasitoids could collect wetted and unwetted spores of both pathogens on their bodies. Viable spores were recovered in washings from these insects 10 days after infestation. Wetted spores of both species of pathogen had lower viability on the parasitoid's body than unwetted spores, probably because of the loss of the mucilage coating which protects against desiccation. The results suggest that the use of a related parasitoid, H. coffeicola, in biological control against the coffee berry borer, Hypothenemus hampei could pose a phytosanitary risk.
Seed‐borne cucumber mosaic virus infection of subterranean clover in Western Australia
Authors: JONES R. A. C. , McKIRDY S. J. 
Published: February 2008

SummaryIn Western Australia, infection with cucumber mosaic virus (CMV) was widespread in all three subspecies of subterranean clover (Trifolium subterraneum) growing in plots belonging to the Australian National Subterranean Clover Improvement Programme. Seed‐borne CMV was detected in seed harvested in 1984–1986 of 18/25 cultivars from two collections of registered cultivars; seed transmission rates ranged up to 8.8%. Seed samples from CMV‐inoculated plants of 11 cultivars transmitted the virus to 0.5–8.7% of seedlings. Seed transmission rates greater than 5% were obtained only with cvs Enfield, Green Range and Nangeela. CMV was not detected in seed harvested in 1975–1981 from one of the registered cultivar collections, in 17 commercial seed stocks from 1986 or in a survey of subterranean clover pastures.Symptoms in subterranean clover naturally infected with CMV included mottle, leaflet downcurling and dwarfing but severity varied with cultivar and selection. CMV isolates from different sources varied in virulence when inoculated to subterranean clover; two (both from subterranean clover) were severe, two moderate and three (including one from subterranean clover) mild. In pot tests, CMV decreased herbage production and root growth (dry wts) of cv. Green Range by 49% and 59% respectively. In spaced‐plants growing in plots, CMV decreased herbage production and root growth of cvs Green Range and Northam by 59–630 and seed production of cv. Green Range by 45%. In rows sown with infected seed, aphid spread increased infection levels to 75% in cv. Green Range and 44% in cv. Esperance and losses in herbage production of 42% and 29% respectively were recorded.CMV isolated from subterranean clover included isolates from both serogroups.
Stimulation of weed seed germination by 1–(3‐chlorophthalirnido) cyclohexanecarboxamide (AC 94377)
Authors: BOND W. , BURCH PHILIPPA J. 
Published: February 2008

SummaryThe N‐substituted phthalimide, AC 94377, promoted the germination of dry‐stored seeds of 17 out of 24 weed species in Petri‐dish tests maintained at 22°C. In a further test it was able to substitute for light and/or alternating temperatures in promoting the germination of some species. AC 94377 was more active than GA, in stimulating Solanum nigrum seed to germinate. When mixed with soil in the laboratory, AC 94377 again promoted germination of S. nigrum but the level and persistence of activity differed between soils. In the glasshouse, with soil containing a natural weed seed population, more seedlings emerged from treated than from untreated soil but this number represented fewer than half of the apparently viable seeds present. Field applications of AC 94377 promoted the germination of hand‐sown seeds of certain weed species but did not increase the number of seedlings emerging from the natural weed seed bank.
Ovipositional preferences amongst navel sweet orange types by the false codling moth, Cryptophlebia Ieucotreta
Authors: NEWTON By PHILIP J. 
Published: February 2008

SummaryFive different navel sweet orange cvs or cv. selections, planted in the Citrusdal area of the western Cape Province, South Africa, were evaluated for their susceptibility to false codling moth infestation. The proportion of yield lost by two of them, cv. Bahianinha and the ‘Buffelspoort’ cv. selection, was lower than losses from the others evaluated. Damage due to other factors causing fruit abscission was also lowest in the cv. Bahianinha. The greatest number of eggs laid throughout the season was on the ‘Addo’ cv. selection, and losses due to the false codling moth were also greatest on this orange type. Rate of oviposition was significantly (P > 0.05) lower on the cv. Bahianinha than on all the other types. Parasitism by a trichogrammatid egg parasitoid appeared to have no impact on overall egg mortality and did not account for any of the observed differences in fruit loss. The relationship between egg deposition and fruit loss was not clear and many factors require further investigation. Nevertheless, the distinct difference in rate of oviposition on the ‘Addo’ cv. selection, on the one hand, and on the cv. Bahianinha, on the other, indicates some consistent response to positive or negative stimuli.
Selection for high and low thiocyanate ion content in kale (Brassica oleracea var. acephala)
Authors: BRADSHAW J. E. , GRIFFITHS D. W. 
Published: February 2008

SummaryIn 1978 genetical variation for thiocyanate ion (SCN‐) was found in a kale population being selected for improved digestible organic‐matter yield. Four generations of half‐sib family selection for high and low SCN‐ content in young leaves resulted in subpopulations with almost a twofold difference in their means, no overlap in their distributions, no observable reduction in their genetical variation, and only small differences in other traits. The total observed divergence in SCN‐content was 82% of that expected for a random mating population in linkage equilibrium in the absence of genotype x environment interactions. Average heritability on a single plot basis was low, namely 30%, but was increased to 46% with two replicates. This maximised the predicted response to selection for a fixed number of families selected and a fixed total number of plots.Bulks of the high and low subpopulations were assessed in a trial in 1988. Averaged over September and December harvests of young and mature leaves, SCN‐ contents were 104.5 and 58.5 mg/100 g DM, respectively. Of eight controls, cv. Merlin had the lowest content, 63.5, and cv. Proteor had the highest content, 89.6. Cultivar x harvest date, cultivar x leaf age and cultivar x harvest date X leaf age interactions were removed by a logarithmic transformation of the data. Stem contents were very low and variable with an overall mean of 10.9 in September and > 5 in December, and no significant differences between cultivars or populations.The subpopulations will be valuable for research into possible effects of SCN content on the disease and pest resistance of kale and on the performance of animals fed kale.
The effect of Brevicoryne brassicae on leaf area, dry matter distribution and amino acids of the Brussels sprout plant
Authors: EMDEN H. F. VAN 
Published: February 2008

SummaryTwenty‐six direct or derived criteria were assessed, eight wk after infestation, of the effect of an initial inoculum of 0, 5, 25 or 50 Brevicoryne brassicae on the growth and dry matter distribution of Brussels sprout plants. Twenty‐four of these criteria showed significant (P > 0.05) effects of aphid infestation, though increasing aphid infestation above 5/plant had little further effect. Total fresh and dry weight (as well as of the components — leaves, stems and roots) was reduced by 25–730 with infestation, particularly so the root. The number of leaves as well as individual leaf area was reduced, and leaves on infested plants were less efficient assimilators. This could be explained by the drain on assimilates caused by the aphids, the leaf curling and the reduced density of stomata. The latter was also considered to account partly for the increased moisture content of infested plants. There was a general reduction in the concentration of leaf amino acids.
Characterisation of acetaldehyde effects on Rhizopus stolonifer and Botrytis cinerea
Authors: AVISSAR ILANA , DROBY S. , PESIS EDNA 
Published: February 2008

SummaryAcetaldehyde (AA) vapour reduced the in vitro growth of the fruit‐infecting fungi Botrytis cinerea and Rhizopus stolonifer, and decreased the respiration of R. stolonifer. Spore germination, germ tube elongation and sporulation were inhibited in both fungi. AA induced the leakage of electrolytes from B. cinerea and R. stolonifer membranes. The conductivity found in the fungal extracts was positively correlated with the AA concentration applied. The leakage of reducing sugars and amino acids suggest that cell membranes are irreversibly disrupted by AA as a first step in inhibition of the fungi in vitro.
Effect of neighbouring plants on the yield of potatoes from seed tubers affected with gangrene (Phoma foveata) or from plants affected with stem canker (Rhizoctonia solani)
Authors: HIDE G. A. , READ P. J. 
Published: February 2008

SummaryHealthy seed tubers and seed tubers with gangrene or inoculated with Rhizoctonia solani to induce stem canker were planted 38 or 76 cm apart or alternately at 38 cm spacing in 2‐row (1985) or 4‐row (1986) plots at Rothamsted.At 38 cm spacing, stem canker decreased yield by 5% and 8% respectively in 1985 and 1986 and gangrene by 5% and 14%, but usually by twice these amounts when seed was spaced at 76 cm. In all experiments, yields from plots with alternate healthy and inoculated seed (50% disease) were similar to yields from healthy seed, although within these mixed populations individual plant yields from healthy seed were larger and those from diseased seed were smaller than from plots of healthy or inoculated seed respectively. Samples in August showed a similar effect on fresh weight of foliage.Disease usually decreased the number of stemdplant but in 1985 gangrene increased stem numbers and probably accounted for small amounts of compensatory growth from neighbouring healthy plants.
Discrimination by gel‐diffusion serology of digitaria striate, maize sterile stunt and other rhabdoviruses of Poaceae
Authors: GREBER R. S. 
Published: February 2008

SummaryEight rhabdoviruses from grass and cereal hosts and their antisera were used to examine virus relationships by gel‐diffusion serology. Nucleocapsid (Nc) preparations from digitaria striate virus (DSV) and maize sterile stunt virus (MSSV) both contained a major protein of c. 52 OOO daltons, and antisera prepared to these readily discriminated related planthopper‐transmitted rhabdoviruses. MSSV showed a moderately close relationship to barley yellow striate mosaic virus (BYSMV) when an antiserum prepared to whole virus was used, but the Nc antiserum showed clearer discrimination. Worthern cereal mosaic virus and DSV showed a distant relationship to BYSMV and MSSV. There was no serological relationship between any of these viruses and cereal chlorotic mottle virus, cynodon chlorotic streak virus, festuca leaf streak virus or maize mosaic virus.
Studies on resistance of pea to pea seed borne mosaic virus and new pathotypes
Authors: KHETARPAL R. K. , MAURY Y. , COUSIN R. , BURGHOFER A. , VARMA A. 
Published: February 2008

SummaryStudies were carried out to search for virulent pathotypes of pea seed borne mosaic virus (PSbMV) on pea and to explore new sources of resistance in French and Indian pea collections. A virulent pathotype, PSbMV‐Pi, capable of partially overcoming the recessively resistant gene sbm 1, was identified for the first time in an Indian pea line. PSbMV‐Pi did not produce visible symptoms on sbm 1 lines, on which it had a reduced multiplication and could no longer be detected by ELISA seven wk after inoculation. However, it multiplied normally on the susceptible cultivars and could be differentiated from other strains on a set of strain differentials. Also, another strain, PSbMV‐Pv, of the virulent pathotype, that appeared to multiply slightly better than PSbMV‐Pi on sbm 1 lines, was recovered from the local strain of PSbMV.Five new sources of resistance to PSbMV were screened from the Indian pea collection by a rapid screening based on the assumption that, in germplasm collections, the virus is generalised to all susceptible lines by aphid vectors. The initial step of testing a few testas of each germplasm line in ELISA and the rejection of positive lines eliminated 85% of the germplasm before further testing in the field. The inheritance studies on four of the five resistant lines lead to reidentification of the sbm 1 gene. The sbm 1 lines behaved fairly well under heavy inoculum pressure in the pea fields in 1989.
Parasitism of cowpea by Striga gesnerioides: variation in virulence and discovery of a new source of host resistance
Authors: PARKER C. , POLNIASZEK T. I. 
Published: February 2008

SummaryIn glasshouse experiments in the United Kingdom, Striga gesnerioides‐resistant cowpea varieties, Suvita‐2 and 58–57, were assessed alongside a susceptible variety for their responses to seventeen samples of S. gesnerioides from four West African countries. The susceptible variety was attacked by all samples, while Suvita‐2 was resistant to samples from Burkina Faso and Mali, and 58–57 was resistant only to samples from Burkina Faso.At least three physiological groups of the parasite can be distinguished: samples from Burkina Faso attacking the smallest range of cowpea varieties; those from Mali being intermediate; those from Niger and Nigeria attacking all the cowpea varieties. A sample from Cameroon behaved slightly differently and may represent a fourth type.A cowpea line from Botswana, B.301, selected for its field resistance to Alectra vogelii proved resistant to all Striga populations to which it was exposed, including those from Niger and Cameroon.
Linkage of soybean cyst nematode alleles for incompatibility with soybean
Authors: LUEDDERS VIRGIL D. 
Published: February 2008

SummarySelection and inbreeding of soybean cyst nematodes increased populations' ability to produce cysts on some soybean lines with concurrent decreases in numbers of cysts on other soybean lines: evidence that some alleles for incompatibility were either linked or at the same loci. Some responses could be explained only by linkage of nematode genes for avirulence. Linkage of nematode alleles for incompatibility could be involved when selection increased numbers of cysts on several lines even though the usual interpretation has been that the lines had some of the same genes for resistance. Most of the lines used in this study may have fewer alleles for incompatibility than most “resistant” lines. Use of these lines with fewer genes for resistance should help in the identification of individual alleles for incompatibility necessary for resolving the allelism and/or linkage of these nematode genes.
A recessive soybean cyst nematode allele for incompatibility with soybean PI 88287
Authors: LUEDDERS VIRGIL D. 
Published: February 2008

SummaryThe objective of this research was to characterise the degree of dominance of a soybean cyst nematode (Heterodera glycines) allele for incompatibility which interacts with a recessive soybean (Glycine max) allele for incompatibility to prevent the formation of cysts. Crosses of inbred nematode populations were made and the F, and F, populations evaluated for the numbers of cysts they could produce on several soybean lines. The nematode gene for avirulence interacts with the one recessive gene for resistance in soybean line PI 88287 and also appears to be recessive. This is the first example of a recessive‐recessive gene‐for‐gene interaction; genes for avirulence and resistance are usually dominant. The difficulties of doing definitive genetic studies with cyst nematodes are discussed.