bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of weather and microclimate on Dalbulus maidis (Homoptera: Cicadellidae) flight activity and the incidence of diseases within maize and bean monocultures and bicultures in tropical America
Authors: CASTRO VILMA , RIVERA CARMEN , ISARD SCOTT A. , GÁMEZ RODRIGO , FLETCHER JACQUELINE , IRWIN MICHAEL E. 
Published: February 2008

SummaryMixed cropping systems in tropical America have been shown to be less prone than monocultures to damage from pathogens carried by insects. This finding formed the basis for a series of experiments conducted in Costa Rica to evaluate the hypothesis that mixed cropping systems create a physical environment that influences vector movement and consequently the spread of leafhopper‐borne pathogens.The principle finding of the study is that both the mixture of plants and planting density have little influence on the spread of pathogens by Dalbulus maidis, an oligophagus leafhopper which prefers maize, within maize and bean single and mixed cropping systems. Leafhopper flight activity proved similar for high and low density monocultures and bicultures. The number of leafhoppers immigrating to and emigrating from a field appears dependent on the size of the field, not the density of maize plants. Single and mixed crops with the same density of maize plants were equally prone to damage by pathogens carried by leafhoppers. The lower percentage infection in high density than in low density maize treatments resulted from fewer vectors per plant in the former.
Validation of the European corn borer damage model on maize using X rays
Authors: LABATTE J. M. , GOT B. , CHARTIER M. , RUGET F. 
Published: February 2008

SummaryIn order to explain and predict yield losses caused by European corn borer larvae, Ostrinia nubilalis Hbn. (Lepidoptera: Pyralidae), a mechanistic model was proposed to describe cavity appearance, their lengthwise extension, and their within‐plant distribution. It integrates main dynamical processes of larvae: mortality, development and within‐plant distribution. After its estimation and test under field conditions in 1988 and 1989, its validation, based upon X‐ray photographs, is presented. This method allows cavity appearance and lengthwise extension to be followed without damaging the plants. This study confirms the relevance of the damage model and the rate of cavity lengthwise extension estimated with it.
Effect of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates of Phoma bakeriana
Authors: NEBANE C. L. N. , EKPO E. J. A. 
Published: February 2008

SummaryThe effects of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates (PB1, PB2, PB3) of Phoma bakeriana were investigated in vitro. There was no isolate effect on growth and pycnidium production but some evidence of a medium effect. Exceptionally high growth rate on two media corresponded with high pycnidium production; while low growth rates on other media were generally associated with high sporulation.There was a large temperature effect and an isolate effect on growth with a significant temperature by isolate interaction. Temperatures of 5°C, 10°C and 35°C inhibited pycnidium formation completely while the range 15–30°C had no effect on sporulation. Maximum growth and pycnidium production occurred at 25°C.Near‐ultraviolet radiation seemed to have caused higher pycnidium counts than the other light sources.
Interpretive value of symptoms of infection by Gaeumannomyces graminis in wheat seedlings grown in sand culture
Authors: PENROSE L. D. J. 
Published: February 2008

SummarySymptoms of infection by the fungal pathogen Gaeumannomyces graminis were studied in roots of wheat seedlings grown in sand culture in order to assess resistance. Three sets of wheat were studied, 10 cultivars previously thought to differ in infection, and 44 and 54 segregating families from two crosses between four of these wheats, Aus1080 × Condor and Termu89–72 × Bayonet respectively. The isolates of G. graminis employed had previously been selected for differences in virulence.The interpretive value of symptoms of infection were considered, by comparison with direct measurement of the spread of hyphae from a fixed point of inoculation, and by repeatability of measurements over experiments. Two symptoms of infection, cortical browning and stelar blackening, are thought to be host mechanisms to resist hyphal invasion and were suppressed by rapid colonisation of root tissues. A third symptom, general discolouring of tissue, appeared to be a necrotic symptom of aggressive colonisation.Since only root segments distal to the point of infection were studied, stelar blackening appeared the least flexible measure of severity of infection. Cortical browning appeared to be influenced by nutritive status of seedlings, and was negatively associated with the incidence of necrotic discolorations. Wheats differed consistently and mostly in cortical browning, and while also differing in extent of necrotic discoloration, difficulty in quantifying the latter character limited its value in assessing resistance to G. graminis in this study.
Interference between viroids inducing exocortis and cachexia diseases of citrus
Authors: SEMANCIK J. S. , GUMPF D. J. , BASH J. A. 
Published: February 2008

SummarySystemic interactions of long duration among the Group I] Citrus Viroids, CVd‐IIa and CVd‐IIb were investigated by grafting buds from established citron (Citrus medica L.) sources containing single viroids to a common healthy seedling. In healthy tissues, the two viroids became established in approximately equal titres as a mixed infection. By contrast, tissues that grew from the CVd‐IIa or CVd‐IIb source buds contained only trace amounts of the heterologous invading viroids.This interference between CVd‐IIa, a mild exocortis agent, and CVd‐IIb, the cachexia agent, was also demonstrated in the presence of CEVd, the severe exocortis agent but not a Group II viroid. When a CVd‐IIb bud was propagated on a citron containing CVd‐IIa, a dramatic reduction in the titre of CVd‐IIb was observed.The interference between CVd‐IIa and CVd‐IIb indicates that the mild and relatively innocuous isolate, CVd‐IIa, can interfere with the replication and/or accumulation of the severe cachexia agent, CVd‐IIb, in citrus. This offers a potential practical approach for the control of cachexia in commercial plantings by “viroid interference”.
The comparative effects of three formulations of diazinon on cropping of a hybrid and a non‐hybrid strain of the cultivated mushroom Agaricus bisporus
Authors: WHITE P. F. 
Published: February 2008

SummaryThree formulations of diazinon: flowable granules (FG); wettable powder (WP); and emulsifiable concentration (EC), which are used for the control of mushroom pests, were compared for toxicity towards a hybrid and non‐hybrid strain of the cultivated mushroom, Agaricus bisporus. With all formulations, yield and number of mushrooms were reduced according to dosage (linear trend). The EC was the most toxic and persistent formulation – equally so to both mushroom strains – and produced the most severe responses in all the parameters considered. The WP was the least toxic formulation. The hybrid strain was more susceptible to diazinon than the non‐hybrid, but not markedly so.
A screen of worldwide wheat cultivars for hydroxamic acid levels and aphid antixenosis
Authors: NICOL D. , COPAJA S. V. , WRATTEN S. D. , NIEMEYER H. M. 
Published: February 2008

SummaryIn a screen of seedlings of a worldwide range of 47 cultivars of Triticum (mainly T. aestivum) the concentration of the hydroxamic acid DIMBOA ranged between 1 and 8 mmol/kg fresh wt. In a bioassay in which alatae of the aphid Sitobion avenae were released among replicated test seedlings, there were highly significant correlations between aphid ‘preference’ and DIMBOA levels in the seedlings. The value of these results in work leading to the production of aphid‐resistant cultivars is discussed.
The impact of spiders and high temperatures on cereal aphid (Rhopalosiphum padi) numbers in an irrigated perennial grass pasture in South Australia
Authors: BARRO PAUL J. DE 
Published: February 2008

SummarySpiders were the most important group of aphid natural enemies in an irrigated perennial grass pasture. The Lycosidae and Linyphiidae were the only families encountered. An exclusion experiment found predation by spiders to be an important factor in controlling aphid numbers. Together with high temperatures, they maintained aphid numbers at a lower than expected level.
Effect of leaf age and nitrogen fertilisation on sporulation of crown rust (Puccinia coronata var. lolii) on perennial ryegrass (Lolium perenne L.)
Authors: PLUMMER ROSETTA M. , HALL R. L. , WATT TRUDY A. 
Published: February 2008

SummaryIndividual leaves of perennial ryegrass cv. Aberystwyth S23 of two leaf ages and at two levels of nitrogen fertilisation were point inoculated with Puccinia coronata f.sp. coronata in a growth chamber. In general, there was no significant difference in the lifespan of inoculated versus control leaves. However, the higher rate of nitrogen extended leaf lifespan more markedly in rusted than in control leaves.Uredospore production varied according to leaf age: colonies on juvenile leaves produced three times as many spores as those on mature leaves.
The influence of primary infection date and establishment of vector populations on the spread of yellowing viruses in sugar beet
Authors: WERF W. VAN DER , WESTERMAN P. R. , VERWEIJ R. , PETERS D. 
Published: February 2008

SummaryIn three field experiments in 1985 and 1986, we studied the effect of the date of primary infection on the spread of beet yellows closterovirus (BYV) and beet mild yellowing luteovirus (BMW) from artificially inoculated sugar beet plants. Laboratory‐reared vector aphids, Myzus persicae, were placed on these sources of virus. There was no substantial natural immigration of vectors or viruses. In two experiments, one with BMYV in 1985 and the other in BYV in 1986, populations of vector aphids remained low and there was little virus spread, i.e. c. 50 infected plants from one primarily infected source. The cause of this small amount of spread was the low number of vector aphids. In the third experiment, with BYV in 1986, large populations of M. persicae developed and there was substantial virus spread: c. 2000 infected plants in the plots which were inoculated before canopy closure. In later‐inoculated plots in the same experiment, there was much less spread: c. 100 infected plants per virus source plant. Differences between fields in predator impact are implicated as the most probable factor causing differences in vector establishment and virus spread between these three experiments. Virus spread decreased with later inoculation in all three experiments.A mathematical model of virus spread incorporating results from our work has been used to calculate how the initial proportion of infected plants in a crop affects the final virus incidence. This model takes into account the effect of predation on the development of the aphid populations. The processes underlying the spread and its timing are discussed.
Transmission of barley yellow dwarf virus by field collected aphids (Homoptera: Aphididae) and their relative importance in barley yellow dwarf epidemiology in southwestern Idaho
Authors: HALBERT SUSAN E. , CONNELLY B. JUNE , BISHOP G. W. , BLACKMER JACQUELYN L. 
Published: February 2008

SummaryPopulations of cereal aphids were sampled from 1985–1988 and assayed for transmission of barley yellow dwarf virus (BYDV), Rhopalosiphum padi, Rho‐palosiphum maidis, Sitobion avenae, Metopolophium dirhodum, Schizaphis graminum and Macrosiphum euphorbiae collected from host plants transmitted BYDV in bioassays. Of the 1028 Diuraphis noxia collected from plants, one may have transmitted BYDV. The isolate involved resembled SGV in serological and biological characteristics, but since it was not recoverable by any of more than 800 D. noxia subsequently tested, we suspect it may have been a contaminant.Among those aphids collected during the autumn from a suction trap adapted for live collection, R. padi transmitted BYDV most frequently. Other trapped species which transmitted BYDV included: R. maidis, Rhopalosiphum insertum, Macrosiphum euphorbiae, Metopolophium dirhodum and Ceruraphis eriophori. An adapted Infectivity Index indicated that R. padi is by far the most important vector of BYDV during the autumn sowing season in southwestern Idaho. Male R. padi consistently transmitted BYDV more frequently than did females collected during the same period.
Wild Narcissus species as a source of resistance to Fusarium oxysporum f.sp. narcissi
Authors: LINFIELD CHRISTINE A. 
Published: February 2008

SummaryThirty three species and varieties of Narcissus plus seventeen cultivars with recent species parentage were screened for resistance to Fusarium oxysporum f.sp. narcissi. Accessions were either wholly resistant (bulbs remaining uninfected), partially resistant (a variable portion of the bulbs infected) or susceptible (all of the bulbs infected). Although a pattern of resistance was found among the species tested the genetic basis of the resistance is not known.
Ploidy doubling by callus culture of potato dihaploid leaf explants and the variation in regenerated plants
Authors: FLEMING M. L. M. H. , DE M. J. , POWELL W. 
Published: February 2008

SummarySomatic chromosome doubling of potato dihaploids was achieved by culturing callus from leaf pieces derived from glasshouse and in vitro grown plants. The glasshouse‐grown leaves produced better callus on average but there was no significant difference between the average number of plantlets per callus regenerated from the two types of material.Mixtures of 2x and 4x plants were obtained from callus culture and the proportions of each ploidy type varied with the dihaploid genotype. Leaflet length/breadth ratios were chiefly determined but ploidy but there was variation within ploidy groups. There were also differences in blight and cyst nematode resistance between tetraploids derived from the same dihaploid.
Chilling tolerance in February seeded Chaite rices (Oryza sativa) of Nepal
Authors: STHAPIT B. R. , WILSON J. M. 
Published: February 2008

SummaryFive Chaite and three main season rices Oryza sativa genotypes were examined to assess the effect of low temperature on the germination and growth of roots and shoots, root regeneration capacity, the extent of chlorophyll synthesis of etiolated seedlings, total chlorophyll content and photo‐chemical efficiency (Fv/Fm) of chilled plants. Cultivated differences in the ability to germinate and grow at low temperatures have been found. The poor ability of Chaite rices to tolerate photo‐oxidative tissue damage during January and February seemed to be the major factor resulting in poor seedling growth.
The description of the growth stages of annual grass weeds
Authors: LAWSON H. M. , READ M. A. 
Published: February 2008

SummaryThe decimal code for the growth stages of cereal crops, devised by Zadoks, Chang & Konzak (1974) and expanded by Tottman & Makepeace (1979) and Tottman (1987) was found to be generally applicable to annual graminaceous species encountered as arable weeds in the United Kingdom. For the great majority of growth stages no difficulties were found in using the Zadoks code, but agronomists, crop protection advisers and farmers identified practical problems in assessing the transition from tillering to stem elongation to node development in certain species. It is recommended that these problems could be minimised if label and advisory statements avoided the use of GS30 ‐ pseudostem (leaf sheath) erection ‐ as a growth stage description for annual grass weeds. The benefits of being able to use one key for graminaceous crops and weeds in the United Kingdom considerably outweigh any inconvenience caused by the need to amend herbicide labels to achieve this objective.
Resistance in sorghum to the shoot fly, Atherigona soccata: epicuticular wax and wetness of the central whorl leaf of young seedlings
Authors: NWANZE K. F. , PRING R. J. , SREE P. S. , BUTLER D. R. , REDDY Y. V. R. , SOMAN P. 
Published: February 2008

SummarySorghum genotypes known to be resistant or susceptible to shoot fly, Atherigona soccata Rondani were examined by scanning electron microscopy for differences in epicuticular wax structure and wetness of the central leaf whorl. Two major types of wax structures were observed: shoot fly resistant and moderately resistant genotypes were characterised by a smooth amorphous wax layer and sparse wax crystals while susceptible genotypes possessed a dense meshwork of crystalline epicuticular wax. The density of wax crystals decreased from the third leaf to the seventh leaf stage and was related to both seedling age and leaf position. Water droplets on susceptible genotypes with dense wax crystals showed spreading at the edges indicating a tendency to wet easily. In resistant genotypes with less dense wax crystals the droplets remained intact and did not spread.
The effects of temperature on development of the large narcissus fly (Merodon equestris)
Authors: COLLIER ROSEMARY H. , FINCH S. 
Published: February 2008

SummaryEggs, larvae, pupae and adults of the large narcissus fly (Merodon equestris) were reared at a series of constant temperatures between 9–24°C. Egg development required from 37 days at 9°C to 7 days at 21.5°C. The low‐temperature threshold for development was 6.7°C. Larvae reared at 1424°C were fully‐grown after 18 weeks, but it took much longer for such insects to pupate, and adult flies emerged only after about 45 weeks of development. Large narcissus flies enter diapause during the larval stage and overwinter as fully‐fed larvae, forming pupae in the following spring. Post‐winter pupation and pupal development took from 169 days at 10°C to 36 days at 21.5°C. Of this, pupal development required from 91 days at 10°C to 19 days at 21.5°C. The low‐temperature threshold for post‐winter pupation and pupal development was 7.1°C, and for pupal development alone, 7.2°C.Females maintained at or below 19°C laid few eggs, whereas some females kept at or above 21.5°C laid more than 100 eggs (mean 69 ± 36). Approximately 50% of females maintained at or above 21.5°C laid less than 10 eggs during their lifetime. The mean egg‐laying time was 6 to 9 days. Although temperatures at or below 19°C inhibited mating, once a female had mated, such temperatures did not prevent oviposition.
Rottboellia yellow mottle virus, a new sobemovirus affecting Rottboellia cochinchinensis (Itch grass) in Nigeria1
Authors: THOTTAPPILLY G. , van LENT J. W. M. , ROSSEL H. W. , SEHGAL O. P. 
Published: February 2008

SummaryA hitherto undescribed virus, termed rottboellia yellow mottle virus (RoYMV), affecting Rottboellia cochinchinensis (syn. R. exaltata, itch grass) at Ibadan, Nigeria, was investigated.RoYMV virions are isometric, c. 29 nm in diameter, and sediment homogeneously at 114s. In isopycnic CsCl gradients, RoYMV virions band sharply at a buoyant density of 1.379 g cm‐3, but in Cs2SO4 gradients, virions band at two zones, at the densities of 1.300 g cm‐3 and 1.325 g cm‐3. Treatment with EDTA at pH 8.0 reduced the sedimentation value of RoYMV to c. 87s and rendered it susceptible to proteinase‐K, SDS and NaCl. The apparent molecular weight of RoYMV coat protein was c. 27 000. Virions encapsidate a single‐stranded RNA of mol. wt 1.4 × 106 Da. Besides R. cochinchinensis, RoYMV was mechanically transmissible only to maize (Zea mays). No reaction occurred when RoYMV was tested against antisera to 44 isometric plant viruses (belonging to 12 groups), including several that affect Gramineae.RoYMV exhibits striking similarities with other viruses belonging to the sobemovirus group, and it is tentatively designated as a new member of the sobemovirus group.
Survey of two beet viruses in South Kazakhstan and Central Asia
Authors: ROGOV V. V. , SOLOMYAKINA S. N. , KARASEV A. V. 
Published: February 2008

SummaryDuring two surveys of beet root crops in South Kazakhstan and Central Asia conducted in 1988 and 1989, 465 of 990 samples were found to contain beet mosaic virus (BMV) by double‐antibody sandwich (DAS) ELISA. BMV infection was widely scattered in the area surveyed, and its incidence varied considerably, reaching 100% in some fields adjacent to beet seed crops. BMV isolates from Kazakhstan, Kirgizia, Uzbekistan and Ukraine were found to be serologically closely related in DAS‐ELISA test. Beet yellows virus (BYV) was not detected in any location surveyed in South Kazakhstan and Central Asia. BYV spread into the area is probably prevented by its geographical isolation.
Assessment of yield losses as a result of co‐infection by maize streak virus and maize stripe virus in Mauritius
Authors: DOYLE M. M. ROCA DE , AUTREY L. J. C. 
Published: February 2008

SummaryThe effect of co‐infection by maize streak virus (MSV) and maize stripe virus (MStV) on plant growth and grain yield was investigated in a susceptible variety of maize (Zea mays), ZS 5206, in Mauritius. Under natural conditions MSV, transmitted by the leafhopper Cicadulina mbila, was normally established before MStV, which is vectored by the planthopper Peregrinus maidis; as a result, MStV symptoms were often partially or completely masked by those of MSV, making MStV detection by symptomatology very unreliable. MSV and MStV were diagnosed by ELISA and MStV by a novel method of detecting the MStV‐coded non‐capsid protein.The maize hybrid ZS 5206 was inoculated with either MSV, MStV or both, at two stages in the growth cycle (3–5 or 7–10 leaf stage). A greater reduction in plant growth was observed in plants inoculated singly with MStV (80% and 29% for first and second stage, respectively) than with MSV (50% and 23%, respectively). No cobs were produced by plants singly infected with MStV at the first stage, or co‐infected with MSV and MStV at both stages; however, marginal grain production was recorded in plants singly infected with MSV at the first stage (91% reduction), or infected either with MSV or MStV, at the second stage (65% and 80% reduction, respectively).In maize hybrid ZS 5206, MStV is more virulent than MSV; co‐infection by both viruses causes greater reductions in plant growth and grain yield than single infection by either virus at a given stage of plant development. In the event of co‐infection by MSV and MStV, yield losses can be erroneously attributed to MSV only if the symptoms of MStV are masked by those of the former and if adequate methods for MStV detection are not used.
Differential expression of root‐knot nematode resistance genes in tomato and pepper: evidence with Meloidogyne incognita virulent and avirulent near‐isogenic lineages
Authors: CASTAGNONE‐SERENO P. , BONGIOVANNI M. , DALMASSO A. 
Published: February 2008

SummaryReproduction of artificially selected near isogenic Meloidogyne incognita lineages virulent and avirulent against the Mi resistance gene of tomato was assessed on host and resistant lines and cultivars of pepper. Egg mass production following inoculation of individual potted seedlings with second‐stage juveniles was studied in experiments conducted in controlled environment. Artificially selected Mi‐virulent nematode populations were unable to develop on resistant pepper lines PM 217 and PM 687. This suggests that the genetic systems governing resistance to root‐knot nematodes are differently expressed in tomato and pepper, in spite of the very close phylogenetic relationships and structural genomic homologies occurring between these two vegetable crops. Moreover, these artificially selected nematode populations were also found unable to develop on the susceptible pepper cultivars California Wonder and Doux Long des Landes, while their pathogenicity was not significantly affected on susceptible tomatoes. Due to the existence of naturally virulent Meloidogyne populations, these results enhance the need for a better understanding of the mechanisms involved, in order to develop new forms of management of plant resistance to root‐knot nematodes.