bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic diversity in South Asian okra (Abelmoschus esculentus) germplasm collection
Authors: BISHT I S. , MAHAJAN R K. , RANA R S. 
Published: February 2008

SUMMARYGenetic 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

SummaryTo 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

SummaryThe 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.
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

SummaryThree 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

SummaryThe 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

SummaryExperiments 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

SummaryThe 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

SummaryObservations 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

SummaryVariation, 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

SummaryExperiments 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

SummaryA 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

SummaryEven 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

SummaryThe 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

SummaryArtichoke 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

SummaryField 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

SummaryThis 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.