bluuebunny/crossref_metadata_2025 huggingface dataset:
A serological test for detecting Botrytis allii, the cause of neck rot of onion bulbs
Authors: LINFIELD CHRISTINE A. , KENNY SIÂN R. , LYONS N F.
Published: February 2008

Polyclonal antisera for the immunological detection of Botrytis allii, the cause of onion neck rot, were raised from cell wall and cytoplasmic fractions of the fungus, and from surface plate washings of two isolates of the pathogen. These antisera were used to develop an indirect ELISA for the detection of latent B. allii infection in stored onion bulbs. The antisera did not react with healthy onion tissue and showed only minimal recognition of fungi from other genera. Some cross‐reactivity was observed with B. cinerea but not with other Botrytis spp. tested. In many instances following infection, fungal antigen could be detected earlier by ELISA than by direct culture. In tests on bulbs from a commercial store, the level of B. allii infection was found to be 3.3% by both ELISA and direct plating, but this result was achieved 7 days sooner by ELISA. In field tests, the indirect ELISA gave a good indication at harvest of the probable incidence during storage of neck rot in untreated and artificially inoculated plants, whilst culturing gave results consistently lower than the ELISA until bulbs had been in store for several months, when results for ELISA and culturing were the same. Spores applied to growing plants during the growing season led to greater levels of neck rot than did infested seed, indicating that field debris and waste from cold stores may be more important sources of inoculum in some years than seed contamination.
Shoot growth, radiation interception and dry matter production and partitioning during the establishment phase of Miscanthus sinensis‘Giganteus’ grown at two densities in the UK
Authors: BULLARD M J. , HEATH M C. , NIXON P M I.
Published: February 2008

Photosynthetic area index (PAI), radiation interception (I) and dry matter partitioning between shoots and roots were measured for Miscanthus sinensis‘Giganteus' grown from micro‐propagated transplants on a fertile peaty loam soil in eastern England. In the establishment year, Miscanthus plants produced 35 and 70 shoots plant‐1 at densities of 4.0 and 1.8 plants m‐2 respectively. At the higher density, there were 140 shoots m‐2 with the largest reaching a height of 1.8 m; these canopies attained a maximum PAI of 5.45, intercepting 94% of incident radiation. Leaf lamina contributed c. 90% of total photosynthetic area with stems contributing the remainder. At the lower density, maximum PAI and I values were 2.88 and 86% respectively. PAI was related to I by calculating attenuation coefficients (k); these indicated that Miscanthus canopies were more effective at intercepting radiation per unit PAI at the lower density (k= ‐0.31) compared with the higher density (k= ‐0.20). Radiation interception was related to dry matter accumulated by calculating conversion efficiencies (e). At 4 plants m‐2, × for shoot dry matter production was 1.17g MJ‐1. Miscanthus partitioned a relatively large amount of total dry matter into below‐ground biomass. By plant senescence, c. 30% of total dry matter had been partitioned into root and rhizome; rhizome biomass contributed 80% of below‐ground dry matter, × increased to 1.62 g MJ‐1 when calculated on a total dry matter basis (shoot + root + rhizome). Total dry matter production was increased 68% by a 2.2‐fold increase in plant density.
Studies on the effect of protoplast density and genotype mixing on cell regeneration
Authors: GILBERT JULIE E. , SHOHET S. , CALIGARI P D S.
Published: February 2008

Genotypes of Solanum tuberosum, assessed for their differential response to a protoplast regeneration protocol, were identified. This enabled comparisons to be made in relation to their abilities to regenerate into dividing cells and colonies. Protoplasts from genotypes with contrasting regeneration responses were plated as single or mixed genotype cultures at various plating densities in replicated, randomised experiments, and the effect on the regeneration of particular cell types observed. Protoplasts from single genotype cultures showed intergenotypic variation in the extent of cell regeneration and there were significant effects of genotype mixing and density × genotype mixing interactions. Overall, the effect of mixing was beneficial to a regenerating culture but significant density genotype mixing interactions showed only a positive benefit at the lowest plating density. The protoplast mixing phenomenon was not correlated with the behaviour of the same genotypes at the plantlet level in experiments with in vitro meristem cultures.
The development of Steinernema feltiae (Nematoda Steinernematidae) in the sciarid fly Bradysia paupera (Diptera: Sciaridae)
Authors: GOUGE DAWN H. , HAGUE N G M.
Published: February 2008

There was only one generation of Steinernema feltiae in Bradysia paupera. Infection occurred after 3 h, adults developed 27 h after invasion and new infective juveniles (IJ) were produced after 48 h. Stunted females were produced in B. paupera larvae and in other small hosts and these stunted females produced small IJs. The small IJs were capable of infecting hosts and normal sized Us were produced in succeeding generations in Galleria mellonella.
Effect of temperature and diet on hind wing colouration development and elytral hardness of adult Colorado potato beetle (Coleoptera: Chrysomelidae)
Authors: FOLLETT PETER , HILBECK ANGELIKA
Published: February 2008

The effects of food and temperature on the development of colour pigment in the hind wings of adult Colorado potato beetle,Leptinotarsa decemlineata(Say), were investigated. In a replicated study, adults were held at 18°C, 28°C and 18/28°C on potato foliage (Solanum tuberosumL.), potato tubers, or without food in controlled‐environment chambers. Representative subsamples of wings were collected at two‐day intervals, mounted on microscope slides, and photographed to document the progression of colour change. Observations were also made on elytral hardening over time.

Hind wing colour developed more quickly at 28°C than at 18°C, and after three weeks had attained a deeper red colour at the higher temperature. Colour development was also more rapid when adult beetles were fed on foliage compared with tubers. In foliage‐fed beetles, elytra hardened more quickly at 28°C than 18°C, and many tuber‐fed beetles never developed hardened elytra, regardless of temperature treatment. Unfed beetles developed no hind wing colour pigment and their elytra remained soft for the duration of the experiment. Colour plates documenting wing colour development over time are presented; variation in colour development under the conditions tested, suggests that the use of hind wing colouration to estimate beetle age in the field may be problematic.
Analysis of Microdochium nivale isolates from wheat in the UK during 1993
Authors: PARRY D W. , REZANOOR H N. , PETTITT T R. , HARE M C. , NICHOLSON P.
Published: February 2008

A total of 144 isolates of Microdochium nivale from stem bases of winter wheat were taken from 30 sites and 91 isolates from grain were taken from seven sites throughout the UK. Identification by polymerase chain reaction (PCR) amplification of the internal transcribed spacer (ITS) region followed by restriction enzyme digestion of the PCR product revealed that 70% of stem base isolates were M. nivale var. majus and 30% var. nivale while 93% grain isolates were var. majus and 7% var. nivale. Almost all isolates were resistant to the benzimidazole fungicide benomyl. Perithecial production in vitro was more common in var. majus isolates and occurred in almost all grain isolates, but was less common in stem base isolates. The implications of the findings in terms of epidemiology and chemical control of this important cereal pathogen are discussed.
Setting confidence limits for the detection of prune dwarf virus in Prunus avium with a monoclonal antibody‐based triple antibody‐sandwich ELISA†
Authors: RAMPITSCH C. , EASTWELL K C. , HALL J.
Published: February 2008

A triple antibody sandwich enzyme‐linked immunosorbent assay (TAS‐ELISA) with a monoclonal antibody was developed and evaluated for the detection of prune dwarf virus (PDV) in sweet cherry trees (Prunus avium). An independent reverse transcribed polymerase chain reaction test was also developed to establish, in conjunction with a bioassay, the incidence of PDV in 40 sweet cherry trees and to confirm the absence of virus in 15 control trees. Trees with two‐thirds of their leaves positive for PDV would be identified with 99% probability by testing four leaves per tree with TAS‐ELISA. The monoclonal antibody did not cross‐react with Prunus necrotic ringspot virus in the TAS‐ELISA.
Acquisition and transmission of potato mop‐to furovirus by a culture of Spongospora subterranea f.sp. subterranea derived from a single cystosorus
Authors: ARIF M. , TORRANCE L. , REAVY B.
Published: February 2008

Potato mop‐top virus (PMTV) was detected by ELISA in primary zoospores from four out of six isolates of Spongospora subterranea f.sp. subterranea. One virus‐free isolate (N) of S. subterranea was used to acquire PMTV from potato roots and to transmit the virus to healthy plants. A mono‐fungal culture of S. subterranea (isolate N) was derived by infecting tomato plant roots with a single cystosorus. The culture was used successfully to acquire PMTV from the roots of infected Nicotiana debneyi plants that had been manually inoculated with virus isolates, and subsequently to transmit the virus to healthy bait plants. These experiments confirm that S. subterranea is a vector of PMTV. Two PMTV isolates that had been maintained by manual inoculation for 19 and 21 passages were also acquired and transmitted by the fungus culture.
Observations on the population dynamics of Globodera pallida under single and double cropping conditions
Authors: HALFORD P D. , RUSSELL M D. , EVANS K.
Published: February 2008

The population dynamics of Globodera pallida were studied on susceptible potato plants. Oxamyl treated and untreated plots were planted with a G. pallida susceptible crop, from the first early maturity class, under polythene at the end of February and immediately followed, after harvest in June, by a susceptible second crop. Other nematicide treated and untreated plots were sown in April with a G. pallida susceptible cultivar. The results were variable but showed that reproduction of G. pallida under double cropping conditions was greater than on a single main crop.
Genetic diversity in South Asian okra (Abelmoschus esculentus) germplasm collection
Authors: BISHT I S. , MAHAJAN R K. , RANA R S.
Published: February 2008

Genetic diversity for a range of morphological characters within 260 accessions of okra collected from India, Bangladesh, Nepal and Sri Lanka was investigated through the use of uni‐, bi‐ and multivariate statistics. The pubescence and pigmentation of various plant parts, among qualitative descriptors, seemed to be most significant in the analysis of variability. The multivariate analysis, mainly on quantitative descriptors, using principal component and non‐hierarchical cluster analysis suggested that days to flowering, plant height, and various fruit characteristics were important components of variability and contributed significantly to the total variation observed. Only two of the 10 principal components had eigen values more than 1 and together accounted for 54.52% of the total variation. The accessions were grouped into eight distinct clusters which further emphasised the relative contribution of various quantitative characters to the total variability. The pattern of genetic variation is of great importance both to germplasm collectors and plant breeders. Specific accessions were also identified that could be passed on to breeders for utilisation in crop improvement programmes.
Factors determining the pest status of the rose‐grain aphid, Metopolophium dirhodum (Walker), on winter barley in the United Kingdom
Authors: HOWARD M. T. , DIXON A. F. G.
Published: February 2008

To test the hypothesis that early maturation of barley affords it some resistance to cereal aphids, the colonisation, survival, growth, reproduction and emigration of M. dirhodum on barley was measured and compared with previously published results for this aphid on wheat.

Barley plants were colonised as readily as wheat plants. Survival to maturity was similar on both hosts. Relative growth rate was higher on wheat than on barley for most of the season while reproduction was similar on both. Emigration, measured alate production, was significantly higher on mature wheat than on mature barley.

It is proposed that the increase of M. dirhodum populations on barley is normally terminated early in the year directly plant maturation and consequent drying out of the leaves, resulting in the death of aphids. This is different to the situation on wheat, which matures later, and where emigration following plant induced alate induction has been shown to be the major factor affecting the decline in population growth.

These results support the hypothesis that early maturation of barley provides some resistance to M. dirhodum.
Effects of seed size, planting density and planting pattern on the severity of silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) diseases of potatoes
Authors: FIRMAN D. M. , ALLEN E. J.
Published: February 2008

The effects of different seed sizes, planting densities and planting patterns on the transmission of silver scurf (Helminthosporium solani) and black scurf (Rhizoctonia solani) diseases of potatoes were examined in five field experiments with cv. Estima in 1991–93.

In all experiments, silver scurf was more severe with increase in seed size and planting density. At high planting density, silver scurf was less severe from a square planting pattern than from planting in wide rows. The incidence of black scurf also tended to increase with increase in seed size and was increased markedly high planting density.
Character interrelationships and path coefficient analysis for oil yield in the oil palm
Authors: ATAGA C. D.
Published: February 2008

Path coefficient analysis of eight yield components correlated with yield in 22 oil palm progenies showed that number of bunches per palm had the largest direct effect on oil yield followed single bunch weight and percent oil‐to‐mesocarp ratio.
Effects of plastic film covers on dry‐matter production and early tuber yield in potato crops
Authors: JENKINS P. D. , GILLISON T. C.
Published: February 2008

Three experiments, conducted in 1988, 1989 and 1990, examined the effects of date of removal of a clear, perforated (200 X 10 mm holes m‐2), plastic film cover on the growth and early yield of potato crops. Results confirmed that the highest early yields were achieved when the cover was removed 2 wk after 50% crop emergence and the resulting yield increase over a non‐covered control varied from 6–14 t ha‐1. Later removal reduced the benefit from covering and in some cases eliminated any advantage. Covering increased mean soil and air temperatures 2.9°C and 3.2°C respectively (mean of three experiments), thereadvancing crop emergence between 3 and 5 days. The number of day‐degrem accumulated between planting and emergence was very similar in covered and non‐covered treatments within a season but varied between seasons from 190°C to 293°C day (> 0°C). Delaying removal resulted in an increased physical restriction to canopy expansion and reduced the capacity of the crop to intercept solar radiation. Total dry‐matter yield was determined largely the amount of radiation intercepted crops (R2= 0.98). Plastic covering had relatively little effect on partitioning of dry matter to tubers but reduced tuber dry‐matter percentage at early harvests when removal occurred later than 3 wk after crop emergence.
Varietal resistance, population dynamics and timing insecticidal application with peak oviposition by Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae) on rice
Authors: KUMAR HARISH
Published: February 2008

The flight activity of yellow stem borer Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae) peaked in the months of April‐May, May‐June, August‐September and October. The number of egg masses and the number of adults attracted to light sources were the indicators of S. incertulas flight activity. The rice varieties TKM6, IR22, IR60, IR66 and IR74 were infested at 7, 10, 12 and 16 wk after planting with 5, 10, 20 and 40 neonates of S. incertulas. All varieties except IR66 were susceptible to dead heart damage by S. incertulas. When the rice varieties TKM6, BPIRi2, BPIRi4, IR22, IR36, IR60, IR66 and IR74 were treated with carbofuran insecticide at the time of peak oviposition by S. incertulas in the field, the dead heart damage on all the varieties was significantly reduced in comparison with the untreated plots. Indiscriminate routine insecticidal treatments (fixed schedule) can be replaced by a treat‐when‐necessary schedule based on the population dynamics of S. incertulas.
Effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brassicae) on oilseed rape (Brassica napus)
Authors: HONG C. X. , FITT B. D. L.
Published: February 2008

Experiments were done under controlled environment and glasshouse conditions to study the effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brussicae) on oilseed rape (Brassica napus). On leaves of potted oilseed rape plants (cv. Bienvenu) inoculated with A. brassicae conidial suspensions, the severity (number of lesions cm‐2) of dark leaf spot increased as inoculum concentration increased from 80 to 660 spores ml‐1and as leaf age increased from 4 to 14 days. On pods on detached racemes of spring oilseed rape (cv. Starlight), the incidence of dark pod spot (% of pods diseased) increased as inoculum concentration increased from 80 to 104spores ml‐1. Increasing inoculum concentration above 104spores ml‐1did not increase the incidence but did increase the severity of dark pod spot. A minimum wetness period of 4 h was needed for infection of oilseed rape leaves (cv. Envol) by A. brussicue at 18°C and disease severity increased with increasing wetness period up to 12 h. The length of dry interruptions after 3–8 h of initial wetness affected the severity of dark leaf spot. A second wetness period increased the severity of dark leaf spot if the dry interruption was ≤ 6 h and if the first wetness period was ≤ 8 h. The incubation period of A. brassicae decreased from 3.5 to 2.5 days as inoculum concentration increased from 80 to 660 spores ml‐on leaves (cv. Bienvenu) at 17–25°C and from 3.8 to 1.0 day as inoculum concentration increased from 80 to ≥2 ≥ 103spores ml‐1on pods (cv. Starlight) at 18°C.
Detection of the luteoviruses, beet mild yellowing virus and beet western yellows virus, in aphids caught in sugar‐beet and oilseed rape crops, 1990–1993
Authors: STEVENS M. , SMITH H. G. , HALLSWORTH P. B.
Published: February 2008

The incidence of beet mild yellowing luteovirus (BMYV) and non‐beet‐infecting strains of beet western yellows luteovirus (BWYV) in individual winged aphids, caught in yellow water‐traps, in sugar beet during the spring and early summer, and in oilseed rape plots in the autumn, was monitored using monoclonal antibodies in ELISA tests from 1990 to 1993. Between 0% and 8% of the Myzus persicae trapped in sugar beet each year carried BMYV, whereas 0% to 4% caught in oilseed rape in the autumn contained this virus. In 1990, 6.5% of Macrosiphum euphorbiae trapped in sugar beet contained BMYV, but in subsequent years less than 1% were carrying virus. Much higher proportions (26–67%) of the M. persicae tested from sugar beet contained BWYV, and similar proportions tested from oilseed rape (24–45%) also carried this virus in the autumn. In contrast only 3–19% of the M. euphorbiae caught in sugar beet contained BWYV, and none in oilseed rape. In 1991 and 1992 large numbers of Breuicoryne brassicae were caught in the plot of oilseed rape, of which over 50% contained BWYV; none were carrying BMYV.

In transmission studies between 1990 and 1992, 1% and 27% of M. persicae transmitted BMYV and BWYV respectively to indicator plants; subsequent ELISA tests on the same aphids showed that 3% and 33% respectively contained the two viruses. One percent of M. euphorbiae transmitted BMYV, but none were found to contain BMYV using ELISA; 15% transmitted BWYV whilst only 5% were found to carry the virus.

In 1992 and 1993 the incidence of BMYV‐infection in the sugar‐beet fields in which aphids had been trapped ranged from 1.2%, in a field which had received granular pesticide (aldicarb) at drilling plus three foliar aphicidal sprays, to 39.5% in a field which had received only one foliar spray. In 1992 in a sugar‐beet crop which had received no aphicidal treatments, and where 2.8% of immigrant M. persicae and 2.5% of M. euphorbiae contained BMYV, 11.6% of plants developed BMYV infection. Lowest levels of infection were associated with the use of granular pesticides at drilling.

In 1990, 80% of oilseed rape plants in a field plot were infested with a mean of seven wingless M. persicae per plant by mid‐December; 37% of these plants were infected with BWYV. The studies show that M. persicae is the principal vector of BWYV, and large proportions of winged M. persicae carry the virus, in contrast to BMYV, which is consistent with the common occurrence of BWYV in brassica crops such as oilseed rape.
Maternal effects in progeny of field pansy (Viola arvensis) subjected to different herbicide and nitrogen rates
Authors: GRUNDY A. C. , FROUD‐WILLIAMS R. J. , BOATMAN N. D.
Published: February 2008

Observations were made on the effects of reduced rates of herbicide and nitrogen on naturally occurring populations of Viola aruensis. Progeny arising from these plants were grown in a uniform environment and monitored through to maturity. The size and number of reproductive structures produced by the maternal plants were positively correlated with the maternal plant weight. Herbicide dose affected the plant height of offspring and the effects were more pronounced in those from plants which had received 160 kg N ha‐1than 40 kg N ha‐1. Although the maternal effects on offspring size diminished with time, the number of reproductive structures in the offspring was significantly correlated with plant height during early development. Increased nitrogen availability to the maternal plant in the absence of herbicide may therefore increase the overall productivity of the subsequent generation.
Path‐coefficient analyses and genetic parameters of the components of field resistance of potatoes to late blight
Authors: BIRHMAN R. K. , SINGH B. P.
Published: February 2008

Variation, genetic parameters, interrelationships and phenotypic and genetic path analyses for components of field resistance of potatoes to Phytophthora infestuns were studied using detached leaves from 16 potato cultivars. Inter‐genotypic variability was significant for the components and the Area Under Disease Progress Curve (AUDPC). The resistant cultivars generally had a longer latent period and lower lesion size and spore production than the susceptible cultivars. The correlations between AUDPC and infection efficiency, and between AUDPC and spore density were not significant, but latent period, lesion size and sporulation did correlate significantly with AUDPC. Genetic and phenotypic path‐coefficient analyses indicated lesion size to be the most important component of field resistance. The genetic correlation coefficients between the AUDPC and infection efficiency, latent period and spore density arose mainly because of their indirect effects on AUDPC via lesion size. Lesion size and AUDPC had a high genetic coefficient of variation, heritability and genetic advance (genetic gain).
A study of the tensile force required to pull wheat roots from soil
Authors: EASSON D. L. , PICKLES S. J. , WHITE E. M.
Published: February 2008

Experiments were carried out to determine the tensile properties of mature wheat roots and the force necessary to pull roots from undisturbed soils at a range of moisture contents using an Instron materials testing rig. Roots decreased in cross sectional area from 1.5 to 0.1 mm2and in tensile strength from 7.0 to 2.3 Newtons (N) along the first 12 cm of their length. Breaking strain was constant along the root but the breaking stress increased. Increased seeding rate decreased root diameter and tensile strength but plant growth regulators and fertiliser nitrogen level did not affect the tensile properties. Roots were pulled from mesh tubes of soil (25 mm ± 75 mm) into which they had grown. The peak loads for sandy clay loam and sandy loam soils were 4.8 and 3.9 N respectively and increasing the soil moisture from 17% to 26% reduced the peak load from 5.2 N to 3.5 N. With the drier soil the inner stele pulled free leaving the outer periderm in the soil in a higher proportion of the roots indicating a stronger root/soil bond than in the wetter soil. The load us displacement relationship when pulling roots from soil resembled that for a fibre reinforced composite material. The presence of branch roots resulted in an uneven trace in which there were a number of sub‐peaks as branch roots gave way. It is suggested that soil wetting could contribute to lodging of wheat by reducing the resistance of roots to slippage and breaking.
The potential spread of terrestrial planarians Artioposthia triangulata and Australoplana sanguinea var. alba to continental Europe
Authors: BOAG B. , EVANS K. A. , NEILSON R. , YEATES G. W. , JOHNS P. M. , MATHER J. G. , CHRISTENSEN O. M. , JONES H. D.
Published: February 2008

A survey in Great Britain of the introduced terrestrial planarians Artioposthia triangulata and Australoplana sanguinea var. alba, which are obligate predators of earthworms, indicates that after 30 years Artioposthia triangulata is established throughout Scotland. However, apart from an initial record in 1965, Artioposthia triangulata was unrecorded from England until it was found again in 1992; currently there are 25 records.

There are fewer records of Australoplana sanguinea var. alba and these are mainly from the south and west of England. Ecoclimatic data from Edinburgh, where Artioposthia triangulata is common, and Plymouth, close to where Australopiana sanguinea var. alba has been recorded, were used by the computer programme CLIMEX to predict the potential spread of these planarians within Europe. Results suggest that Artioposthia triangulata could become established in north west Europe, including areas of Scandinavia, Germany and Poland, whereas Australoplana sanguinea var. alba would be confined to western Europe, including northern Spain. To slow their spread within Britain and prevent their establishment on continental Europe it is suggested that all nurseries and garden centres which sell containerised plants should initiate and maintain stringent hygiene regimes.
Use of additive models to represent trends in a barley field trial
Authors: HACKETT CHRISTINE A. , REGLINSKI T. , NEWTON A. C.
Published: February 2008

Even when a field experiment has been designed with care, subsequent examination of the plot values may reveal additional unforeseen trends. In this paper we examine data from a barley pathology field trial and show that additive models provide a flexible representation of environmental trends, in one or two dimensions. Such models smooth out noise in the observed data, rather than fit an equation specified in advance. This approach tends to increase the precision of treatment comparisons relative to a classical analysis of variance. We recommend the use of residual plots to explore experimental data for underlying trends, and additive models to display these trends and estimate treatment effects.
Inheritance of partial resistance to the leaf aphids Macrosiphum euphorbiae and Uroleucon sonchi in lettuce
Authors: Reinink K. , Dieleman F L. , Groenwold R.
Published: February 2008

The genetics of partial resistance (PR) of lettuce to the leaf aphid species Macrosiphum euphorbiae and Uroleucon sonchi was studied in F1 and F2 generations of six crosses between four cultivars. Partial resistance inherited mainly additively. With M. euphorbiae the estimates of broad‐sense F2 heritability were low and non‐significant in crosses between parents of the same resistance level (S x S and PR x PR), and high (0.69‐0.76) in crosses between parents of different resistance level (PR x S). The level of resistance in lettuce cultivars ‘Charan’ and ‘Marbello’ led to a marked reduction in percentage of plants with colonies of M. euphorbiae in a field experiment. With U. sonchi the highest estimates of F2 heritability were found in ‘Charan x ‘Avoncrisp’ (0.51) and ‘Charan’ x ‘Chou de Naples' (0.48). In the cross ‘Charan’ x ‘Marbello’ (PR x PR) no significant segregation for resistance to M. euphorbiae was found, indicating that these cultivars may have the same genetic constitution for resistance to M. euphorbiae.‘Charan’ has additional genes for resistance to U. sonchi, that are not, or only weakly linked to the gene(s) for resistance to M. euphorbiae. The heritability estimates for the partial resistance to M. euphorbiae and U. sonchi indicate that it is possible to effectively select for these traits in plant breeding programmes.
Artichoke Italian latent virus causes artichoke patchy chlorotic stunting disease
Authors: Kyriakopoulou P E.
Published: February 2008

Artichoke patchy chlorotic stunting (APCS) is the most serious disease affecting artichoke in Greece. It is widespread in Argolis, the main artichoke centre in Greece, where the local thornless artichoke, cv. “Argos”, is cultivated. The disease was first noticed in 1982, but to growers it was known since earlier times. Data collected during 1980–1990 revealed its wide distribution in the area, its patchy dispersal in fields, and its annual radial increase of the patches during the years, as well as a centripetal symptomatological severity gradient within each patch. These observations indicated a soil‐borne nature for the disease. Field surveys for several viruses indicated a correlation of APCS with artichoke Italian latent nepovirus (AILV), a soil‐borne virus known to occur in such patches and transmitted by the vector nematode Longidorus fasciatus Roca et Lamberti. In experiments fulfilling Koch's postulates, it was possible to reproduce the symptoms of APCS, demonstrating that AILV is a cause of the disease, if not the only one. Field surveys also revealed the ubiquitous occurrence of artichoke mottled crinkle virus (AMCV), independently of any particular symptoms. In the same survey, broad bean wilt virus (BBWV), also, was recovered from artichoke in Greece for the first time.
Analyses of the effects of potato cyst nematodes (Globodera pallida) on growth, physiology and yield of potato cultivars in field plots at three levels of soil compaction
Authors: Van Oijen M. , De Ruijter F J. , Van Haren R J F.
Published: February 2008

Field experiments were carried out in 1991 and 1992 on sandy soil highly infested with the potato cyst nematode Globodera pallida. Half the trial area was fumigated with nematicide to establish two levels of nematode density. Three levels of soil compaction were made by different combinations of artificial compaction and rotary cultivation. Two potato cultivars were used in 1991 and four in 1992.

Both high nematode density and soil compaction caused severe yield losses, of all cultivars except cv. Elles which was tolerant of nematode attack. The effects of the two stress factors were generally additive. Analysis of the yield loss showed that nematodes mainly reduced cumulative interception of light while compaction mainly reduced the efficiency with which intercepted light was used to produce biomass. This indicates that nematodes and compaction affect growth via different damage mechanisms.

Nematodes reduced light interception by accelerating leaf senescence, by decreasing the specific leaf area and indirectly by reducing overall crop growth rate. Partitioning of biomass between leaves, stems and tubers was not affected by nematode infestation but compaction decreased partitioning to leaves early in the growing season while increasing it during later growth stages.

The effects of nematodes and compaction on root length dynamics and nutrient uptake were also additive. This suggests that the commonly observed variation in yield loss caused by nematodes on different soil types is not related to differences in root system expansion between soils of various strength.

Cv. Elles, which showed tolerance of nematodes by relatively low yield losses in both experiments, was characterised by high root length density and thick roots. These characteristics did not confer tolerance of soil compaction, since compaction affected root lengths and tuber yields equally in all cultivars.

In the first experiment only, high nematode density led to decreased root lengths and lower plant nutrient concentrations. The yield loss which occurred in the second experiment was attributed to the effects of nematodes on other aspects of plant physiology.
Effect of light environment during soil disturbance on germination and emergence pattern of weeds
Authors: Jensen Peter Kryger
Published: February 2008

This paper describes results from experiments which investigated the effects of light intensity during soil disturbance on germination and emergence pattern of weeds. Different emergence patterns were demonstrated for seeds which are instantly flash induced compared to seeds which are induced to germinate by integrating a weak light signal over a period of time. A reduced and delayed emergence is achieved after a disturbance in darkness compared to a soil disturbance in daylight. The increased emergence after soil disturbance in daylight is due to additional plants originating from seeds placed at a soil depth in the pots where daylight cannot penetrate and induce seeds to germinate, but which are induced during the short exposure period. A close relationship between soil disturbance intensity and number of weed plants emerging was found in field experiments with shallow harrowings. It was also shown that a portion of the increased number of seedlings arising when soil disturbance is carried out in daylight, compared to soil cultivation in darkness, originates from seeds germinating from deeper soil layers, resulting in a deeper average germination depth.
Comparison of ELISA and immunoblotting techniques for the detection of cherry mottle leaf virus
Authors: JAMES D. , MUKERJI S.
Published: February 2008

Formaldehyde treated cherry mottle leaf virus (ChMLV) and the isolated coat protein were used successfully for the production of polyclonal and monoclonal antibodies. The monoclonal antibodies had a titre of 1:51 200 and consisted of IgG1 and IgG2. The antibodies reacted with all 11 isolates of ChMLV, from five locations in Canada and the USA, included in this study.

Several serological procedures were assessed to compare their sensitivity for detecting ChMLV. Plate‐trapped antigen ELISA (PTA‐ELISA) and dot‐blot immunobinding assay (DBIA), using virus specific MAbs, were the most sensitive tests in this study. Triple antibody sandwich ELISA (TAS‐ELISA) and Western blot were found to be less sensitive. Dilution of the samples appeared to increase the sensitivity of both PTA‐ELISA and Western blot detection. Young leaves and flowers of Prunus avium were the best tissue for detecting the virus which could also be detected in the fruit and leaves of P. tomentosa. April and May were optimal for detection of the virus in the field, whereas both April to May and August to September were optimal for screenhouse‐grown plants.
Using RAPD markers to identify genets of an arable grass weed, Arrhenatherum elatius ssp. bulbosum
Authors: MILLER A C E , BROOKES C P , LOXDALE H D , CUSSANS G W
Published: February 2008

RAPD (Random Amplified Polymorphic DNA) markers were used to identify genets within a weed infestation of Arrhenatherum elatius ssp bulbosum (“onion couch”). Three selected primers could discriminate between 18 sexually‐derived plants of A. elatius ssp. elatius. Using these primers, RAPD phenotypes were obtained for ramets of ssp. bulbosum from a population of unknown sexual derivation, i.e. predominantly sexual or vegetative. Thirty three RAPD phenotypes were observed amongst 65 plants. Ramets with identical RAPD phenotypes were termed “genets”. Some genets of ssp. bulbosum were found in localised patches, whereas others had much wider ranges, indicating long‐distance dispersal by farm machinery. RAPD markers provide a useful tool for discriminating between genets within an established plant population.
Arachidonic acid‐induced hypersensitive cell death as an assay of downy mildew resistance in pearl millet
Authors: GEETHA S. , SHETTY SUDHEER A , SHETTY H SHEKAR , PRAKASH H S
Published: February 2008

Arachidonic acid (AA) induces hypersensitive response (HR) on coleoptile/root regions of two‐day‐old pearl millet seedlings. The response is comparable to the HR induced by the downy mildew pathogen, Sclerospora graminicola. A time gap in the appearance of cell necrosis among genotypes of pearl millet was related to the degree of resistance to downy mildew. Based on the time required for the development of necrotic spots induced by AA, the pearl millet genotypes were categorised as highly resistant/resistant (HR in 3–6 h), susceptible (HR in 7–12 h) and highly susceptible (HR in 13 h and above). The percentage disease incidence in each genotype was compared with the time required for the development of AA‐induced HR. The appearance of hypersensitive cell necrosis was rapid in genotypes having high resistance to downy mildew and was slow in genotypes with high susceptibility. This simple method of screening various pearl millet genotypes in the absence of the pathogen aids in identifying the downy mildew resistant/susceptible host cultivars without the risk of introducing the virulent race of the pathogen.
Long term lily scale bulblet storage: effects of temperature and storage in polyethylene bags
Authors: BONNIER FRANS J M , JANSEN RITSERT C , TUYL JAAP M VAN
Published: February 2008

Collections of lily genotypes are usually maintained by yearly planting, harvesting and storage of the bulbs. To facilitate this maintenance, a storage method has been developed for a collection of lily genotypes, including Asiatic hybrids, Oriental hybrids,Lilium longiflorumandL. henryi.Scale bulblets were stored either dry, sealed air‐tight in polyethylene bags, or in moist vermiculite in open polyethylene bags for a period of 2 yr. The decrease in mass, sprouting proportion and ion leakage or sprouting proportion alone were determined for treatments carried out at ‐2°C, °C and 17°C. Sealing scale bulblets in polyethylene bags at ‐2°C resulted in the smallest decrease in mass, the least ion leakage and the highest sprouting proportion after 2 yr of storage.
Rapid detection of cowpea aphid‐borne mosaic virus in cowpea seeds
Authors: KONATE G. , NEYA B J
Published: February 2008

Four cultivars of cowpea (Vigna unguiculata [L]. Walp.) were infected with cowpea aphid‐borne mosaic virus (CABMV) by natural infection in field plots. Seeds taken from these plants were tested for the presence of the virus by ELISA and symptom observation on the plantlets grown from the seeds. A biotin/ streptavidin ELISA technique was used and found to be more sensitive than a standard ELISA protocol for detecting CABMV infection in seed. There was a good correlation between the ELISA detection of CABMV in tissue taken from single cowpea seeds and subsequent development of infected plants grown from the same seeds. The ELISA technique is reliable for selecting CABMV‐free stocks of cowpea seeds.
Some biological and genomic properties of rice tungro bacilliform badnavirus and rice tungro spherical waikavirus from Nepal
Authors: DAHAL G. , DRUKA A. , BURNS T M , VILLEGAS L C , FAN Z. , SHRESTHA R B , HULL R.
Published: February 2008

A survey of rice fields during the main growing seasons in 81 locations from 21 districts of the Southern Terai region of Nepal indicated that rice tungro was primarily restricted to the Hardinath (Janakpur) and Parwanipur (Bara) regions. The tungro incidence in Hardinath ranged from 17% to 51% and in Parwanipur from 6% to 61% causing about 89% grain yield loss in Hardinath.

Both rice tungro bacilliform badnavirus (RTBV) and rice tungro spherical picornavirus (RTSV) were found in tungro isolates collected from Hardinath and Parwanipur. These isolates were transmitted by Nephotettix virescens and leaf extracts reacted to antisera against RTBV and RTSV. In a dot blot hybridisation assay, leaf extracts of 12 weed species collected from the tungro‐affected area in Hardinath and Parwanipur also reacted with RTBV DNA probes. On mass inoculation of 15 popular rice cultivars most became more than 50% infected and only cv. Radha 9 had low (22.2%) infection.

RTBV DNA and the coat protein region of RTSV from the Hardinath isolate were cloned and partially characterised. A comparative analyses by restriction endonuclease digestion, cross hybridisation, the polymerase chain reaction and partial sequencing indicated that the Nepalese RTBV DNA clone and the cDNA clones of the RTSV RNA were more similar to the various tungro isolates from the Indian subcontinent than to those from the Philippines.
Population decline of potato cyst nematodes (Globodera rostochiensis, G. pallida) in field soils in Northern Ireland
Authors: TURNER SUSAN J
Published: February 2008

The decline rates of potato cyst nematodes (Globodera rostochiensis, G. pallida) in agricultural soils in Northern Ireland were monitored over 13 years. Initial decline rates appeared erratic due to variable cyst ages and high Standard Errors at low population levels, but were, generally, slower than those previously reported with less than 10% annual decline within each category of assessment (cysts sample‐1, eggs g‐1 and eggs cyst‐1). Rate of decline was not affected by the range of soil types studied, but regular cultivation of infested land appeared to accelerate it. Juveniles present within cysts over 30 years old were either dead or inactive and such field populations were considered non‐viable.
Susceptibility of willow clones (Salix spp.) to herbivory by Phyllodecta vulgatissima (L.) and Galerucella lineola (Fab.) (Coleoptera, Chrysomelidae)
Authors: KENDALL D A , HUNTER T. , ARNOLD G M , LIGGITT J. , MORRIS T. , WILTSHIRE C W
Published: February 2008

Levels of damage by mixed natural infestations of the leaf‐feeding chrysomelid beetles, Phyllodecta vulgatissima (L.) (the blue willow beetle) and Galerucella lineola (Fab.) (the brown willow beetle), were determined in replicated field plots of 24 Salix clones at Long Ashton (Bristol, UK) during 1993–94.

Over the same period, the host plant preferences of both chrysomelids were investigated in a standard multiple‐choice laboratory procedure, where beetles were enclosed in Petri dishes with leaf discs cut from young pot‐grown trees propagated from shoot cuttings taken from 20 of the 24 willow clones represented in the field study. The laboratory experiments indicated that P. vulgatissima and G. lineola had similar host plant preferences in the range of willows examined (r >0.85). In both field and laboratory, the least preferred Salix clones and hybrids were those of 5. eriocephala, followed by S. purpurea, S. burjatica, S. dasyclados and S. triandra. Clones of S. eriocephala and S. purpurea were frequently rejected altogether in laboratory tests. Most preferred were clones of S. viminalis and several hybrids of S. viminalis, S. aurita, S. caprea and S. cinerea. These results substantiate the reports that P. vulgatissima and G. lineola are deterred from feeding on willows which have relatively high concentrations of phenolic (salicylate) glucosides in the leaves. The least preferred willows, particularly S. eriocephala, S. purpurea and S. burjatica, could be of great potential value in plant breeding for resistance to these willow beetle pests.
Reduction of shoot fly damage in irrigated post‐rainy season sorghum by manipulating irrigation
Authors: NWANZE K F , REDDY Y V R , NWILENE F E , SOMAN P. , LARYEA K B , JAYACHANDRAN R.
Published: February 2008

Soil moisture was manipulated in an attempt to control shoot fly (Atherigona soccata Rondani) incidence in irrigated post‐rainy season sorghum grown under a rainout shelter (ROS) and in field conditions. After uniform irrigation at sowing, the plants were subjected to water stress at young seedling stage (7–28 days after emergence, DAE) for different lengths of time. Soil water had profound effects on the production of water droplets on the surface of the central whorl leaf of seedlings (leaf surface wetness, LSW) of sorghum genotypes. LSW, which facilitates movement of the larvae, was more drastically affected in susceptible (CSH 5) than in moderately resistant (IS 1054) sorghum genotypes.

Shoot fly oviposition (infestation) and deadhearts (crop damage) were much higher in treatments with full irrigation (control) than in treatments to which less water was applied during the first 3 wk after seedling emergence. This resulted in higher plant biomass and overall grain yield in the latter treatments than in the control. Using insecticides to control shoot fly infestation, it was shown that a simple cultural practice of inducing plant stress by reduced soil moisture content during early plant growth gave the same or better control of shoot fly damage and the same or higher grain yield than insecticide‐protected plots with full irrigation. Thus the costs associated with irrigation requirement and insecticide can be greatly reduced in the former management option compared with the latter. It is suggested that manipulation of soil water content during the vulnerable early stages of crop growth can reduce shoot fly damage in irrigated post‐rainy season sorghum.
The role of volunteer potatoes in the spread of potato virus YN in ware crops of cv. Record
Authors: JONES D A C , WOODFORD J A T , MAIN S C , PALLETT D. , BARKER H.
Published: February 2008

Surveys were made for the presence of potato virus Y (PVY) in the planted seed and harvested tubers in ware potato crops of cv. Record grown at three sites in England in 1994 (survey 1) and seven sites in 1995 (survey 2). PVY was not found in samples of planted seed, but high levels of infection were found in many, but not all, harvested crops. However, plants of volunteer potatoes (VP) (i.e. plants arising from tubers or true seed derived from previous crops and surviving in the soil) were frequently found to be infected.

Infection in tubers harvested from crops in the first survey ranged from 2–52%. In 1995, VP were collected from two of the three English sites where potato crops had been grown the previous season and also from a site in Scotland where PVY infection in an experimental crop of cv. Record had been monitored in 1994. The percentages of infected VP ranged from 2–54%. PVYN was the predominant strain found in sampled VP, with only two plants (out of 300 infected) containing PVYO.

In the second survey, VP were assessed within the 1995 ware crops and were found at four sites, at which they comprised between 4–8% of emerged potato plants. Between 31–93% of VP were infected. Again, PVYN was the predominant strain with one plant containing PVYO and another PVYC (out of 189 infected). A sample of harvested tubers from each site was also tested for PVY. At those sites which had many infected VP, the harvested crop contained a large percentage of infected tubers, ranging from 60–97%. Two sites which had not previously been used for cropping potatoes had no VP and a very low incidence of PVY infection in the harvested tubers (1% and 2%). However, although no VP were found at one site, 31% of harvested tubers were infected, suggesting that alternative inoculum sources may be important.