bluuebunny/crossref_metadata_2025 huggingface dataset:
Selection of brown spot‐resistant rice plants from Helminthosporium oryzae toxin‐resistant calluses
Authors: VIDHYASEKARAN P. , LING D. H. , BORROMEO E. S. , ZAPATA F. J. , MEW T. W.
Published: February 2008

Helminthosporium oryzae toxin induced electrolyte leakage from rice callus tissues and caused their browning and death. A virulent isolate of the pathogen invaded and colonised callus tissues rapidly, while a less virulent and a nonpathogenic isolate colonised calluses only weakly if at all. Addition of the toxin to calluses permitted colonisation of calluses by the nonpathogenic isolate. Four toxin‐resistant calluses were selected and plants regenerated from two of these resistant calluses showed resistance to the pathogen. This resistance was heritable and stability of resistance was observed in the R1, R2 and R3 generations.
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

The 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

Fresh, 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

Aqueous 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

Isoelectricfocusing (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

The 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

A 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

In 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

The 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

Five 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

In 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

Twenty‐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

Acetaldehyde (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

Healthy 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

Eight 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

Studies 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

In 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

Selection 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

The 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.
A comparison of the effects of sward improvement on invertebrates, sward establishment and herbage yield
Authors: ELLIS S. A. , CLEMENTS R. O. , BALE J. S.
Published: February 2008

Field experiments were done at two widely separated sites in England (Tadcaster, North Yorkshire and North Wyke, Devon). In each case an old permanent sward was re‐seeded after ploughing or by direct drilling, or was left intact and fertilised. The carbamate pesticide aldicarb was applied to half of each experimental plot. The effects of sward improvement and pesticide on various soil invertebrate groups were assessed. Soil‐dwelling macrofauna arthropods were scarce at both sites. Stem‐boring dipterous larvae, however, were numerous at both sites. At Tadcaster, Oscinella vastator was the only species present in the original sward, but 0. frit was by far the most prevalent species in re‐seeded areas. These can only have arisen from direct oviposition of eggs by adults on or near the emerging seedlings and not by migration of larvae from buried turf or the desiccated old pasture.

Mites and Collembola were abundant. Their numbers were reduced initially by cultivation and pesticide usage, but the effects of these practices were transient and their numbers recovered to previous levels usually within 10 wk.

Earthworms were present at both sites. Deep burrowing species, e.g. Lumbricus terrestris and Allolobophora longa were less affected by the treatments imposed than species such as A. chlorotica and L. rubelius which usually live close to the soil surface. Effects on their numbers were in any case, short‐lived.

No improvement method consistently provided the greatest herbage dry matter yield. Pesticide application, however, greatly increased seedling stand and/or herbage yield at both sites and showed the benefits of using crop protectants, especially on direct‐drilled re‐seeds.
A key for stages of development of the faba bean (Vicia faba)
Authors: KNOTT C. M.
Published: February 2008

A key is presented to describe stages of development of the faba bean (Vicia faba), and is based on similar principles to the key for peas (Pisum sativum) (Knott, 1987). The coded description is divided into five principal stages; germination and emergence, vegetative, reproductive, pod senescence and stem senescence. These are sub‐divided into secondary stages. The practical use of the key is discussed with reference to timing of crop husbandry operations.
The effects of yellowing viruses on yield of sugar beet in field trials, 1985 and 1987
Authors: SMITH HELEN G. , HALLSWORTH PHILIPPA B.
Published: February 2008

The separate effects of beet yellows virus (BYV) and beet mild yellowing virus (BMYV) on yield of sugar‐beet cultivars inoculated at different growth stages were assessed in field trials in 1985 and 1987. Early or mid‐season inoculation decreased sugar yield by up to 47% for BYV, and up to 29% for BMYV. Infections after the end of July had no significant effect on yield. Both viruses caused significant increases in the juice impurities sodium, potassium and amino‐nitrogen after infecting plants early in the season. Yield losses associated with infection were determined by the causative virus, the time of infection, and susceptibility of the sugar‐beet cultivars.
Interactions of Meloidogyne javanica, Fusarium udum and Rhizobium on pigeon pea in the presence of nickel and cobalt as pollutants
Authors: KHAN M. WAJID , SALAM M. ABDUL
Published: February 2008

The interactions between Meloidogyne javanica, Fusarium udum and Rhizobium on pigeon pea, in the presence of nickel (Ni) and cobalt (Co) as soil pollutants, were studied. In single inoculations, M. javanica caused a reduction in plant growth, particularly at higher inoculum levels (1000 and 10 000 JJ2). Fusarium udum induced wilting symptoms and the higher concentrations of Ni and Co suppressed plant growth. Meloidogyne javanica and F. udum interacted to show more severe wilting symptoms than F. udum alone. Wilting was completely inhibited by Ni but reductions in plant growth and nodulation occurred. In the presence of Ni, M. javanica did not cause galling but nodulation was suppressed. Cobalt also suppressed wilting and nodulation but interacted with M. javanica to increase root galling and to reduce plant growth by a greater amount than the total of reductions caused by the individual treatments.
Organophosphorus resistance in Aphis gossypii (Hemiptera: Aphididae) on chrysanthemum in the UK
Authors: FURK C. , VEDJHI S.
Published: February 2008

The FAO standard dip‐test was used to test resistance of glasshouse populations of Aphis gossypii from chrysanthemums to the organophosphorus insecticides heptenophos and diazinon. Compared with a susceptible population collected in 1981, resistance factors to diazinon of up to 538 were found in populations collected after 1984. Resistance to heptenophos was less than that to diazinon but some populations collected after 1984 were 34 times as resistant as the susceptible strain. Possible reasons for the sudden increase in resistance in A. gossypii and current prospects for control of resistant populations are discussed.
Weed management in direct‐seeded lowland rice under iron toxic sites in Nigeria
Authors: IMEOKPARIA P. O.
Published: February 2008

Field trials carried out during the wet season of 1987 at Edozhigi in the Southern Guinea Savanna and in 1988 at Bende in the Forest Zones of Nigeria indicate that the performance of rice varieties under iron toxic soils could be improved by delayed flooding due to the application of selective soil persistent herbicides. Yield increments of 33.3% and 76.9% were recorded at Edozhigi when the mixture of oxadiazon plus propanil at 0.5 + 2.4 kg a.i./ha was applied compared with bentazon alone at 3.0 kg a.i./ha under IR26 and Farox 306–3–6 (susceptible). Similarly at Bende, yield increments of 76.1% and 84.6% were obtained when the mixture of piperophos plus dimethametryn at 1.6 + 0.4 kg a.i./ha was applied compared with pre‐emergence butachlor alone at 4.0 kg a.i./ha also under IR26 and Farox 306–3–6. Breeding resistance to iron toxicity will be desirable because of poor peristence of herbicides in warm flooded soils.
Resistance to the aphids Sitobion avenae and Rhopalosiphum padi in Gramineae in relation to hydroxamic acid levels
Authors: THACKRAY D. J. , WRATTENT S. D. , EDWARDS P. J. , NIEMEYER H. M.
Published: February 2008

Aribiotic resistance to the aphid Sitobion avenae was assessed in relation to levels of hydroxamic acids (Hx) in a wide genetic range of cultivars and species of Triticum. Within hexaploid and tetraploid Triticum material, total plant concentrations of Hx explained a significant proportion of the variation in intrinsic rate of increase (rm) of S. avenae. Significant correlations were also found between resistance to Rhopalosiphum padi and Hx levels. Although the concentrations of Hx in whole plants declined during seedling growth, concentrations of Hx in newly‐emerging leaves remained high in plants of all ages, including in the emerging flag leaves of mature plants. When the mean relative growth rate of S. avenae over three days was used instead of rm and the control of environmental conditions was improved, a higher proportion of the variation in aphid performance was explained by Hx concentrations in six cultivars.
An analysis of genetic variation in sugar beet (Beta vulgaris L. using an augmented biparental (ABIP) mating design
Authors: SMITH M. C. , CORNISH M. A. , MACKAY I. J.
Published: February 2008

An augmented biparental (ABIP) mating design was used to investigate the quantitative variation, particularly the dominance variation, for morphological and chemical characters in sugar beet. Diploid O‐type plants were both crossed and selfed and the progeny were grown in a single‐plant randomised field trial. A comparison of the two kinds of family provided tests for both dominance variation and directional dominance effects. Estimates of the narrow heritability were also obtained for each character. Germination problems reduced the size of the final analysis but evidence was obtained of dominance variation and positive directional dominance effects for leaf length, root weight and potassium concentration and, to a lesser extent, sugar concentration. Genetic control of sodium and alpha‐amino nitrogen concentrations appeared to be mostly additive. Hybrid varieties of sugar beet should exploit these directional dominance effects and the more closely varieties approach true F, hybrids the more they will capitalise on these advantages. It is possible that other factors such as epistasis, contamination, competition and seed effects may cause us to under‐ or overestimate the importance of dominance.
Effects of defoliation at different growth stages and in different grain‐filling environments on the growth and yield of spring barley
Authors: JENKYN J. F. , ANILKUMAR T. B.
Published: February 2008

The yield of spring barley grown outside was little affected by the removal of all fully expanded leaves during late tillering or early stem extension but was decreased by defoliation either earlier or later. Removal of all except the top two leaves when 50% of the ears were fully emerged also had relatively little effect on yield but damage was increased if only the flag leaf was retained, especially if the leaves apart from the flag leaf were removed 10 days earlier when the first awns were visible. Defoliation treatments, including those which had little effect on barley grown outside, generally had proportionately greater effects if the plants were moved to a warm glasshouse at the start of grain filling.
A comparison of two large‐scale seed priming techniques
Authors: GRAY D. , ROWSE H. R. , DREW R. L. K.
Published: February 2008

Leek seed lots of high (91%) and low (82%) viability were primed in aerated polyethylene glycol (PEG) solutions in Bubble‐columns and by a non‐osmotic priming technique in both 1987 and 1988 and the seeds were then sown in the field. Both methods of priming established a similar seed moisture content during treatment and, in the laboratory, produced seeds with more rapid and uniform germination than untreated seeds, with a greater advantage for Drum compared with Bubble‐column priming in PEG. In the field, both priming techniques gave seedling emergence responses similar to those from priming in PEG by the laboratory‐scale technique on filter paper. Both large‐scale priming methods gave earlier and more uniform emergence than untreated seeds and gave similar or slightly higher levels of seedling emergence, except on one sowing occasion when seeds were stored before sowing followed by sowing into a drying seedbed.
Studies on the frequency distribution of Pythium‐induced cavity spot of carrots
Authors: PHELPS K. , WHITE J. G. , HENN A. J.
Published: February 2008

Data on Pythium‐induced cavity spot from experimental plots and commercial fields were collated to study the frequency distribution of cavities on carrots. It was shown that cavities tended to occur in clusters with strong evidence that they followed a Polya‐Aeppli distribution rather than the Negative Binomial distribution often associated with clustering. Possible biological interpretations of the Polya‐Aeppli distribution are discussed, also their implications for estimation of inoculum potential and analysis of cavity spot field trials.
Narcissus latent, a virus with filamentous particles and a novel combination of properties
Authors: MOWAT W. P. , DAWSON S. , DUNCAN G. H. , ROBINSON D. J.
Published: February 2008

As previously reported, narcissus latent virus (NLV) has flexuous filamentous particles measuring c. 650 nm × 13 nm, is manually transmissible to Nicotiana clevelandii and Tetragonia expansa, and is transmitted by the aphid Myzus persicae following brief acquisition access periods. In contrast to previous reports the virus particle protein has an apparent mol. wt of c. 45 kD. Moreover, infected cells in N. clevelandii leaves contain cytoplasmic inclusion bodies resembling those of potyviruses. In vitro translation of NLV RNA produced only one major product (mol. wt c. 25 kD) which was not precipitated by antisera to virus particle protein or to cytoplasmic inclusion protein. Antisera to 12 potyviruses and nine carlaviruses failed to react with sap containing NLV particles. Similarly antiserum to NLV particles did not react with particles of seven potyviruses or four carlaviruses.

A weak reaction was detected between NLV particles and antiserum to particles of maclura mosaic virus (MMV), a virus which resembles NLV in particle morphology and particle‐protein size, and in inducing pinwheel inclusions. The cytoplasmic inclusion proteins (CIPs) of NLV, MMV and from narcissus plants with yellow stripe symptoms were serologically inter‐related. These proteins were also serologically related to, and had mol. wt similar to, the CIP of members of the potyvirus group. Particles with the size and antigenic specificity of those of NLV were found consistently in narcissus plants with yellow stripe disease.

Narcissus latent and narcissus yellow stripe viruses therefore seem to be synonymous and, together with MMV, have properties distinct from those of any previously described virus group.
Analytical pyrolysis‐pattern recognition for the characterisation of leafy spurge (Euphorbia esula L.) biotypes
Authors: EVANS J. O. , TORELL J. M. , VALCARCE R. V. , SMITH G. G.
Published: February 2008

Curie‐point pyrolysis‐gas chromatography‐pattern recognition was used to elucidate chemical variations within leafy spurge (Euphorbia spp.). Hierarchical cluster analysis (HCA) readily identified two major clusters corresponding to E. esula and E. cyparissias. The E. esula cluster further separated into three distinct subclusters. Results from principal components analysis (PCA) and fuzzy c‐varieties (FCVPC) pattern recognition were similar, verifying the presence of three biotypes among the E. esula samples studied. It is suggested that analytical pyrolysis in combination with pattern recognition may predict the behaviour of biocontrol agents introduced into fields to control leafy spurge.
A mathematical model describing the combined effect of exposure time and temperature of hot‐water treatments on survival of gladiolus cormels
Authors: ROEBROECK E. J. A. , JANSEN M. J. W. , MES J. J.
Published: February 2008

Gladiolus cormels of five cultivars were given hot‐water treatments at 50.0°C, 52.5°C, 55.0°C or 57.5°C for different exposure times. Survival of cormels was determined. A mathematical model to describe the combined effect of exposure time and temperature on cormel death is presented. Consequences of these relationships for the practical application of hot‐water treatments to control cormel‐borne Fusarium oxysporum f.sp. gladioli are discussed.
Longevity of pearl millet (Pennisetum glaucum) seeds harvested at different stages of maturity
Authors: RAO N. KAMESWARA , RAO S. APPA , MENGESHA M. H. , ELLIS R. H.
Published: February 2008

The storage potential of seeds harvested at weekly intervals after controlled pollination was studied in three diverse cytoplasmic male sterile pearl millet (Pennisetum glaucum) lines. In the first experiment in 1989, a comparison of p50 (time for viability to decline to 50% during storage) among seeds of the line DSA 105A harvested 14, 21, 28, 35 and 42 days after pollination (DAP), and then stored at 35°C with 15% moisture content or 40°C with 13% moisture content, showed that those harvested 35 DAP had the greatest longevity. In the second experiment in 1990, a comparison of p50 within the lines 5141A and L 67A harvested 28, 35 and 42 DAP, and then stored at 40°C with 13% moisture content, showed that seeds of both lines harvested 42 DAP had the greatest longevity. In both the seasons, and in all three lines, maximum seed longevity (p50) was attained one week after physiological maturity (defined as the end of the grain filling period), which is therefore the optimum time of harvest to obtain good quality seeds for conservation.
Behavioural response of the entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis bacteriophora to oxamyl
Authors: GAUGLER RANDY , CAMPBELL JAMES F.
Published: February 2008

Infective juveniles of the entomopathogenic nematode Steinernema carpocapsae show a low level of locomotory activity that is presumed to limit their usefulness as biological insecticides. A 30 μg ml‐1 solution of the carbamate pesticide oxamyl reduced the proportion of nonmobile nematodes by nearly two thirds to 35%, while stimulating a 7.5‐fold increase in sinusoidal movement. This increase in activity did not result in a corresponding increase in host‐finding. Oxamyl treatment did not enhance infective juvenile pathogenicity to Galleria mellonella larvae. At higher concentrations, oxamyl caused aberrant nematode movement and partial paralysis. Heterorhabditis bacteriophora infective juveniles maintain a high level of locomotory activity. Treatment with 30 μg ml‐1 oxamyl increased the proportion of sinusoidal over nonsinusoidal movements, but infective juvenile host‐finding and pathogenicity were significantly reduced. Higher rates impaired movement and induced complete paralysis. We conclude that oxamyl is incompatible with S. carpocapsae and H. bacteriophora. The concept of chemically activating infective juveniles to increased locomotory activity and thereby achieving enhanced efficacy is inconsistent with our results.
Evaluation of entomopathogenic nematodes for control of Cosmopolites sordidus Germar (Coleoptera: Curcilionidae), a pest of bananas in Australia
Authors: TREVERROW N. , BEDDING R. A. , DETTMANN E. B. , MADDOX C.
Published: February 2008

Applications of Steinemema carpocapsae All strain in water thickener into cuts or holes made in residual rhizomes of bananas gave significant mortality of Cosmopolites sordidus larvae in the rhizomes. The methods proved suitable for field application and two large scale field trials using S. carpocapsae All and S. carpocapsae NC513 gave acceptable levels of control as measured by Vilardebo's (1973) Co‐efficient of Infestation. Mortality of adult C. sordidus attracted to the application sites on treated rhizomes was observed during these field trials.
Interactions between Chromolaena odorata (Asteraceae) and Pareuchaetes pseudoinsulata (Lepidoptera: Arctiidae)
Authors: MARUTANI M. , MUNIAPPAN R.
Published: February 2008

Feeding of Pareuchaetes pseudoinsulata caterpillars caused the leaves of Chromolaena odorata to turn yellow. Leaf yellowing could not be induced either by artificial removal of leaves or by drenching the plant with a solution of excreta from P. pseudoinsulata caterpillars. Yellow leaves appeared tougher but had the same energy level as that of green leaves. The amount of nitrate‐nitrogen was significantly higher in yellow leaves than green leaves. P. pseudoinsulata caterpillars prefer to feed on green leaves. When forced to feed on yellow leaves, they exhibit slow growth and high mortality. Defensive factors in plants attacked by insects seemed to prevent further infestation of plants. In the field, caterpillars on the yellow plants were found during both day and night whereas on green plants they appeared to feed at night and hide in the ground at daytime.
Changes in the hydroxamic acid content of maize leaves with time and after artificial damage; implications for insect attack
Authors: MORSE S. , WRATTEN S. D. , EDWARDS P. J. , NIEMEYER H. M.
Published: February 2008

The dynamics of hydroxamic acids (Hx) in maize plants were examined, along with the effects on this process of artificial leaf damage. The concentration of Hx in maize (cv. LGH) leaves declined rapidly with age, although young emerging tissue did have relatively high levels. The decline was not entirely due to a growth dilution effect, as the total Hx content in leaves also decreased with age. This effect was less pronounced in isolated leaves. The plant hormone abscisic acid (ABA) accelerated the decline in Hx in isolated maize leaves, while indole acetic acid (IAA) had no apparent effect. Artificial leaf damage on growing plants produced a significant increase in the concentration of Hx relative to undamaged controls. The difference was greatest (about 18%) two days after damage, but seemed to be largely due to a slower rate of decline relative to controls. Isolated maize leaves generally showed a much higher level of increase (20 ‐ 40%). The results are generally consistent with the theory that Hx functions as a defence against insect attack.
The effect of maize leaf damage on the survival and growth rate of Rhopalosiphum padi
Authors: MORSE S. , WRATTEN S. D. , EDWARDS P. J. , NIEMEYER H. M.
Published: February 2008

Two different types of artificial leaf damage, crushing and cutting, were assessed for their effects on the growth and survival of Rhopalosiphum padi caged on maize (cv. LG11) leaves. Crushing significantly reduced aphid growth rate by up to 23% and their survival by five to six times, while cutting had no significant effects. Although the area of tissue involved was lower for crushing relative to cutting (c. 5% and 10% respectively), the greater level of cellular damage inflicted by crushing may have resulted in more phytochemical changes. These effects suggest that the feeding of one herbivore guild such as leaf chewers may adversely affect the performance of another, such as phloem feeders.
Responses of micropropagated peach cultivars to thermotherapy for the elimination of prunus necrotic ringspot virus
Authors: STEIN A. , SPIEGEL S. , FAINGERSH G. , LEVY S.
Published: February 2008

Peach (Prunus persica (L.) Batsch) shoot‐cultures infected with prunus necrotic ringspot virus (PNRSV) were selected for evaluating the responses of in vitro grown shoots of cvs Hermosa and Summerset to thermotherapy. The survival of shoot‐cultures during thermotherapy was improved by selection of the optimum concentration of 6‐benzylamino purine in the medium and optimum age of shoots for treatment. Alternating high and low temperature thermotherapy regimes were more effective in decreasing virus titre than constant high temperatures. Of the regimes tested, the most effective inhibition of PNRSV combined with a high survival of shoots was obtained by applying 38°C for 16 h in light alternating with 28 CC for 8 h in darkness for 18 days for Hermosa and 22 days for Summerset. Following this treatment 90% of Hermosa and 40% of Summerset shoot‐cultures were virus‐free as determined by enzyme‐linked immunosorbent assay. Relatively large (about 10 mm) apices excised from these shots regenerated into virus‐free plants. The advantage of the in vitro system for thermotherapy is discussed.
Particle purification and properties of cassava Ivorian bacilliform virus
Authors: FARGETTE D. , ROBERTS I. M. , HARRISON B. D.
Published: February 2008

A virus found in cassava from the north‐west of the Ivory Coast was transmitted by inoculation with sap extracts to herbaceous species in six plant families. Chenopodium quinoa was used as a propagation host and C. murale was used for local lesion assays. The virus particles are bacilliform, c. 18 nm in diameter, with predominant lengths of 42,49 and 76 nm and a structure apparently similar to that found in alfalfa mosaic virus. Purified preparations of virus particles had A260/A280 of 1.7 ±0.05, contained one protein of Mrc. 22 000, and yielded three species of RNA with Mr (× 10‐6) of c. 0.7, 0.8 and 1.2. Although the virus particles were poorly immunogenic, an antiserum was produced and the virus was detected by enzyme‐linked immunosorbent assay (DAS‐ELISA) in leaf extracts at concentrations down to c. 6 ng/ml. Four other field isolates were also detected, including a strain which caused only mild systemic symptoms in C. quinoa instead of necrosis. The naturally infected cassava source plants were also infected with African cassava mosaic virus (ACMV) but when the new virus was cultured in Nicotiana benthamiana, either separately or together with ACMV, its concentration was the same. The new virus did not react with antisera to several plant viruses with small bacilliform or quasi‐bacilliform particles, and alfalfa mosaic virus reacted only weakly and inconsistently with antiserum to the cassava virus. The new virus, for which the name cassava Ivorian bacilliform virus is proposed, is tentatively classified as the second member of the alfalfa mosaic virus group.