bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of a bracken (Pteridium aquilinum (L.) Kuhn) growth model in predicting the effects of control strategies across a range of climatic zones in Great Britain
Authors: PATERSON S. , PAKEMAN R J , MARRS R H 
Published: February 2008

SummaryA nationwide bracken control experiment provided data over a three‐year period for testing the accuracy of a bracken growth model (BRACON). Objective assessments of model validity identified the model as a reasonably accurate predictor of bracken stand dynamics given the range of environmental conditions currently prevailing in Great Britain, in relation to (1) cutting regimes and (2) spraying asulam. Ranking of treatment efficacy at individual sites was closely reflected in model predictions. Predicted response of the rhizome system to cutting treatments underestimated bracken resilience. Failure to consider the consequences of frond regrowth in the latter portion of the growing season as a means to offsetting energy loss was identified as a potential explanation for this discrepancy. The role of the model as a practical management tool is discussed with particular reference to relating model predictions, based upon generalised environmental data (40 km plusmn; 40 km grid cells), to bracken management at individual sites.
Classification of genetic diversity in Abelmoschus tuberculatus germplasm collection using morphometric data
Authors: BISHT I S , PATEL D P , MAHAJAN R K 
Published: February 2008

Summary Abelmoschus tuberculatus Pal & Singh is endemic to India and is the close relative of cultivated okra, A. esculentus. Data on 49 selected accessions of A. tuberculatus were used to study genetic diversity for a range of morphological characters through the use of multi‐variate statistics. Epicalyx segments, shape, size and persistence; petal colour and petal blotch; stem and fruit pubescence; pigmentation of various plant parts; days to flowering; plant height; and the fruit yield/plant were the important components of variation and contributed significantly to the total variation in germplasm accessions under study. The accessions could be grouped into four distinct clusters. The grouping pattern, however, did not reflect relationship between geographic origin and genetic diversity. The potential use of the variability in okra improvement programmes is discussed.
Developmental threshold, day‐degree requirements and voltinism of the aphid predator Episyrphus balteatus (Diptera: Syrphidae)
Authors: HART A J , BALE J S , FENLON J S 
Published: February 2008

Summary Episyrphus balteatus is the dominant syrphid predator of aphids in the UK, reestablishment of populations each season is mainly by migration from warmer climes, as overwintering in this country is minimal with an uncertain level of success. The effects of temperature on the developmental rate of E. balteatus were investigated to determine the potential voltinism of this species in the UK. Estimates of the developmental threshold temperature from oviposition to adult emergence varied between 6.0d̀C and 7.1d̀C with a day‐degree (DD) requirement of between 256 and 280 depending on the method of analysis used. Using the DD requirement derived from a weighted linear regression (261 DD above a threshold of 6.8d̀C) in combination with the required value from adult emergence to first oviposition, suggests a total requirement of approximately 374 DD above 6.8d̀C per generation. These data, together with climate records, indicate that one to three generations are possible each year, depending on the available DD and origin of the population. The advantages and limitations of different approaches and models used to estimate developmental thresholds and DD requirements are discussed.
Distribution of Burkholderia cepacia phenotypes by niche, method of isolaiton and pathogenicity of onion
Authors: YOHALEM DAVID S. , LORBEER JAMES W. 
Published: February 2008

SummarySeveral proposals have been made for the subdivision of the bacterial species Burkholderia cepacia. Data applying these schemes to a collection of 188 strains of B. cepacia, isolated using a variety of methods, from soils, decayed onions, and nosocomial sources are presented. None of the schemes could be shown to be associated with the method of isolation, niche from which a strain was isolated, pectolytic activity, or pathogenicity to onion. Strains isolated by serial dilution on onion slices were much more uniform than were strains isolated using semiselective media. The nutritionally stringent medium of Lumsden and Sasser (US Patent No. 4 588 584) was judged better for the collection of a phenotypically broad sample of B. cepacia than those of Hagedorn, Gould, Bardinelli & Gustavson (1987) and Wu & Thompson (1984), which are based on antibiotic insensitivity. Pectolytic activity and pathogenicity to onion were shown to be highly correlated characters. None of the strains of clinical origin was capable of macerating onion tissue.
Apparent absence of viruses in most symptomless field‐grown sweet potato in Uganda
Authors: GIBSON R W , MWANGA R O M , KASULE S. , MPEMBE I. , CAREY E E 
Published: February 2008

SummarySymptomless sweet potato (Ipomoea batatas) plants obtained from farmers' fields in each of the main sweet potato growing regions of Uganda were tested by nitro‐cellulose membrane enzyme‐linked immunosorbent assays (NCM‐ELISA) for sweet potato feathery mottle virus (SPFMV), sweet potato mild mottle virus (SPMMV), sweet potato chlorotic fleck virus (SPCFV), sweet potato latent virus (SPLV), C‐6 virus (C‐6) and sweet potato caulimo‐like virus (SPCa‐LV). Most of the plants tested gave negative reactions in all NCM‐ELISA, only c. 5% giving positive reactions to SPFMV and c 1% to SPMMV or SPCFV. Graft inoculations of cuttings from symptomless sweet potato plants, obtained either at Namulonge Agricultural and Animal Production Research Institute (NAARI) or from farmers' fields, onto seedlings of the near‐universal indicator plant for sweet potato viruses, Zpomoea setosa, caused symptoms in c. 15% of indicator plants; in all such cases, SPFMV alone was identified by NCM‐ELISA. Supplementary tests, involving further grafting of sweet potato to I. setosa seedlings or grafting sweet potato plants themselves with sweet potato sunken vein virus (SPSVV), which in the presence of SPFMV causes sweet potato virus disease (SPVD), confirmed the absence of infection in sweet potato cuttings which had not caused symptoms on I. setosa in the initial graft test. Possible mechanisms explaining the prevalence of virus‐free sweet potato plants in farmers' fields are discussed.
Occurrence of papaya ringspot potyvirus and cucurbit viruses in Nepal
Authors: DAHAL G. , LECOQ H. , ALBRECHTSEN S E 
Published: February 2008

SummaryA survey of papaya and 10 cucurbitaceous vegetables (ashgourd, zucchini, watermelon, cucumber, pumpkin, bottlegourd, snakegourd, spongegourd, bittergourd and choyote) during 1989 and from 1992 to 1994 in more than 68 locations (both experimental plots and farmers' fields) covering 18 terai and inner‐terai districts of Nepal, indicated that these crops were heavily affected with various virus‐like symptoms. The most commonly observed symptoms were severe mosaic, leaf distortion, oily streaks or spots on papaya; leaf distortion, blisters and shoe stringing on zucchini; and mosaic or yellow mosaic, blisters, and leaf distortion on other cucurbits. Average incidence of plants with symptoms ranged from 75% to 100% on papaya; 85% to 100% on zucchini; 4% to 100% on cucumber; 4% to 100% on pumpkin and 10–100% on bottlegourd, choyote and watermelon. The virus isolated from papaya and zucchini was confirmed as papaya ringspot potyvirus — watermelon strain (PRSV‐W). It was also detected in survey samples from ashgourd, bittergourd, snakegourd, spongegourd, zucchini, watermelon, bottlegourd and cucumber. Leaf extracts of some cucumber, choyote, pumpkin, zucchini and snakegourd samples reacted with cucumber mosaic cucumovirus (CMV) and zucchini yellow mosaic potyvirus (ZYMV) antisera. Leaf extracts of ashgourd, cucumber and pumpkin reacted with antibodies against cucurbit aphid‐borne yellow luteovirus (CABW). No samples reacted with antiserum to watermelon mosaic‐2 potyvirus (WMV‐2) or squash mosaic potyvirus (SqMV). Some papaya and most cucurbits leaf samples cross‐reacted with antibodies against Moroccan (Mor) and Algerian (Alg) isolates of WMV. The Nepalese PRSV isolate was related to but distinct from a PRSV‐W type strain from France. This is the first report on the identity of ZYMV and CABW in Nepal.
The effect of soil freezing on the survial of winter‐sown white lupins (Lupinus albus L.)
Authors: LEACH J E , STEVENSON H J , ScOTT T. , MILFORD G F J 
Published: February 2008

SummarySpecially constructed soil‐freezing growth boxes were used to study the effects of the intensity and duration of soil freezing on root injury and the survival of white lupin seedlings of different ages under controlled conditions. The extent of root damage depended on both the intensity of soil freezing and the stage of seedling development (measured as the extent of lignification of the central stele of the primary root). Seedlings whose secondary root development was well advanced, and in which the endodermis was completely lignified, survived intense soil freezing intact. Young seedlings with weakly lignified roots were damaged by moderate soil freezing (> 5 days at −1°C) and killed by more intense freezing (5 days at −2°C). The extent of root development and ligmfkation was correlated with the number of leaf primordia produced at the shoot apex so that the susceptibility to soil freezing damage could be accurately predicted by a simple physiological/leaf production model.
Virus‐like particules in the poison glant of the parasitic wasp Opius concolor
Authors: JACAS J A , BUDIA F. , RODRÍGUEZ‐CEREZO E. , VIÑUELA E. 
Published: February 2008

SummaryVirus‐like particles (VLP's) have been found in the poison glands of adult females of the parasitic wasp Opius concolor Szèpl. (Hymenoptera, Braconidae). These VLP's are found in the secretory cells either free in the cytoplasm or within cytoplasmic vesicles, sometimes associated to a secretory apparatus.Negative staining of these VLP's has revealed the occurrence of two different particles. The first type exhibits icosahedral symmetry (diameter around 70nm) and hollow surface spikes, this morphology being typical of the genus Cypovirus (Reoviridae). The other type is pleomorphic and presents an envelope with clubshaped projections (diameter ranging from 30 to 60nm), as classical textbook examples of Coronaviruses, but smaller. Function and full characterisation of these particles are not yet known.
Effects of azinphos‐methyl and pyrifenox on reproductive performance of Cydia pomonella L. (Lepidoptera: Tortricidae) at recommended rates and lower concentrations
Authors: ABIVARDI CYRUS , WEBER DONALD C. , DORN SILVIA 
Published: February 2008

SummaryThe effects of deposits of commercial formulations of azinphos‐methyl, an organophosphorous insecticide and acaricide, and pyrifenox, a systemic fungicide, on artificial surfaces on the survival and reproductive performance of codling moth adults, Cydia pomonella L., were examined in the laboratory. In contrast to pyrifenox, which did not influence the codling moth significantly, azinphos‐methyl affected the insect in a number of ways: (1) it exhibited a strong direct insecticidal activity on adults, eggs and larvae; (2) at low concentrations, it decreased copulation significantly, as reflected by a reduction in the number of spermatophores contained per female; and it inhibited oviposition strongly; (3) at low concentrations moths copulated more often initially and produced more eggs than the controls. However, if the moths were kept in contact with the azinphos‐methyl residues, they and their progeny died the following day so that the total number of eggs laid was reduced.Possible implications of the stimulatory effects, as well as repellency, of combined use of azinphos‐methyl in the phermone mating disruption technique are discussed.
Splash dispersal of Coniothyrium minitans in the glasshouse
Authors: WILLIAMS R H , WHIPPS J M , COOKE R C 
Published: February 2008

Summary Coniothyrium minitans, a mycoparasite with biocontrol activity against Sclerotinia sclerotiorum, was found to disperse during glasshouse trials where overhead irrigation was used. Consequently, the role of water splash in dispersal of C. minitans was investigated using soil‐incorporated inoculum and a range of irrigation regimes found to occur in the glasshouse. The resulting inoculum deposition over horizontal distances up to 2 m was measured. Using drops < 6 mm diameter at 680 mm h‐1, C. minitans was splash‐dispersed at least 2.0 m, whereas with drops > 6 mm diameter at 30 mm h‐1 it was dispersed to only 1.75 m. Irrigation with droplets < 1mm diameter at 49 mm h‐1 failed to disperse inoculum beyond 0.5 m. The dispersal gradient produced by drops < 6 mm diameter at 680 mm h‐1 was best described mathematically by the power function, whereas irrigation with drops > 6 mm diameter at 30 mm h‐ resulted in a gradient described well by power or exponential functions. The latter regime produced a significantly steeper gradient than irrigation with drops < 6 mm diameter at 680 mm h‐1. C. minitans was isolated using an Andersen air sampler at concentrations of 2839 cfu m‐3 or 22 cfu m‐3 during irrigation with drops < 6 mm diameter at 680 mm h‐1 or > 6 mm diameter at 30 mm h‐1, respectively. After irrigation, deposition of C. minitans‐canying aerosol particles declined exponentially and distance from source had no effect on the amount of inoculum isolated. Conidia of C. minitans, splash‐dispersed by irrigation with drops < 6 mm diameter at 680 mm h‐1 were able to infect sclerotia of S. sclerotiorum such that almost all sclerotia at 0.5 m from the inoculum source, and c. 50% of those at 2.0 m, became infected with the mycoparasite.
Durian flowering, pollination and incompatibility studies
Authors: LIM T K , LUDERS L. 
Published: February 2008

SummarySeasonal fluctuations in weather conditions were found to influence the flowering and fruiting phenology and reproductive biology of durian grown around Darwin. Manually assisted cross‐pollination resulted in higher fruit set of 31% in contrast to < 10% by selfing, producing higher yields and better quality fruit. Self‐pollination resulted in more fruit abortion and produced fruits that were mis‐shapen, curved with lower numbers of arils/locule, arils/fruit and lower numbers of seeds which were usually shrunken and disfunctional. Evidence from these studies also confirmed that the self‐incompatibility system in durian is gametophytically controlled and that cultivars could be totally self‐incompatible, partially self‐incompatible or totally compatible. The durian pollen was found to exert metaxenia effects that influenced the development of the fruit characteristics and also xenia effect on the seed.
Seedling and adult plant peaetions of Brassica napus‐B. juncea recombinant lines towards A‐ and B‐group isolates of Leptosphaeria maculans
Authors: SOMDA I. , RENARD M. , BRUN H. 
Published: February 2008

SummaryThe Brassica napus‐B. juncea recombinant lines MX and MXS carrying a B. juncea major gene (JLml) in the genetic background of a spring‐ or a winter type B. napus cultivar, respectively, were tested for their resistance level to Leptosphaeria maculans under controlled conditions. Inoculation with three A‐and four B‐group individual isolates and with different mixtures of isolates realised within or between these groups was performed on cotyledons, leaves and stems. Cotyledons and leaves of the two recombinant lines were more resistant to A‐group isolates than those of B. napus cultivars, except for one isolate recovered from the MX line. The recombinant lines were susceptible at cotyledon stage and resistant on leaves to B‐group isolates, as were B. napus cultivars. On stems, severe cortical damage was usually produced on B. napus cultivars by some A‐group isolates, whereas B‐group isolates induced pith blackening on all genotypes. Stems of the MX line and the resistant donor species (B. juncea cv. Picra) were more resistant than those of the susceptible B. napus (cv. Westar) to the individual A‐group isolates. Cultivar Picra was the most susceptible genotype to pith infection caused by the B‐group isolates. The consequence of the host pathogen differential interactions on the durability of the monogenic resistance to L. maculans introduced from B. juncea into B. napus is discussed.
A new group of endophytes in European grasses
Authors: NAFFAA W. , RAVEL C. , GUILLAUMIN J J 
Published: February 2008

SummaryPoaceae of subfamily Festucoideae frequently harbour endophytic, symbiotic fungi in their aerial parts. Isolations were made from 21 different species of Poaceae, belonging mainly to the genera Lolium and Festuca. Pure cultures of 45 fungal isolates were obtained. Morphology, isozyme and molecular analysis showed the presence of three groups of endophytes. Most of the isolates could be accommodated with the previously described species of Neotyphodium and Epichloë (the e endophytes). Two new endophytes isolated from Koeleria cristata and Melica ciliata were shown to belong to this group. Gliocladium like and Phialophora like isolates were obtained from Lolium perenne and Festuca gigantea respectively (the p endophytes). Nine isolates especially those from annual Lolium produced rod like conidia. These isolates belong to Acremonium sensu stricto and are morphologically similar to Acremonium chilense.
Disease development of Pythium root rot in bulbous Iris and Crocus
Authors: OS G J VAN , GULIK W J M VAN , BOER W J DE 
Published: February 2008

Summary Iris bulbs and Crocus corms were planted at two planting dates in sandy soil infested with Pythium spp. At monthly intervals during the growing season root rot infection was assessed over 3 consecutive years and disease development curves were predicted for both crops. The disease development was remarkably different for Iris and Crocus and the curve shape was determined by the crop rather than by the Pythium species. Planting date had a significant effect on disease development in both crops. No correlation was found between disease development and soil temperature.
Effect of nitrogen on interactions between ryegrass mosaic virus (RMV) and Lolium species in mixed swards
Authors: BAIN R A , RAYNOR E L , BAKER L J , BAGNALL A. 
Published: February 2008

SummaryThe effect of rate of nitrogen applied to three Lolium perenne‐based field swards on the development of RMV symptoms and on the impact of the virus on the growth and composition of the swards was examined over two growing seasons. Glasshouse experiments investigated the competition between Lolium spp. in relation to RMV infection and rate of nitrogen. In general, there was a higher incidence of RMV symptoms at the higher rates of nitrogen but the relationship was not consistent in all experiments. RMV infection only significantly reduced the cumulative total yield of the sward that contained the very susceptible Lolium multiflorum cv. Barverdi and was treated with the higher rate of nitrogen. However, yield losses were consistently greater at the higher rates of nitrogen. RMV altered the relative yields of sward components and the effect was greatest after an extended period of severe frost at the end of 1995. There is evidence that the frost severely restricted the yield of RMV‐infected L. multiflorum tillers in 1996. Where RMV reduced the yield of susceptible species, there was significant compensatory growth by less susceptible companion species, i.e. L. perenne and Phleum pratense, but the compensation was generally incomplete, resulting in reduced yields for virus‐infected swards. RMV had no significant effect on the overall quality of the three field swards but for cv. Barverdi grown in the glasshouse it significantly reduced the percentage organic matter and water soluble carbohydrate, and D value. The reductions were greater at the higher rates of nitrogen.
Aspects of resistance to sweet potato virus disease in sweet potato
Authors: ARITUA V. , ALICAI T. , ADIPALA E. , CAREY E E , GIBSON R W 
Published: February 2008

SummaryIn field trials during the first and the second rainy season of 1996 in Uganda, whiteflies were similarly abundant and aphids were absent on three clones of sweet potato (NIS‐93–63, cv. Tanzania and cv. New Kawogo) although the three clones differed considerably in their resistance to sweet potato virus disease (SPVD), a complex disease resulting from infection by both the aphid‐borne sweet potato feathery mottle virus (SPFMV) and the whitefly‐borne sweet potato chlorotic stunt virus (SPCSV). This suggests that vector resistance does not determine the relative SPVD resistance of these genotypes. SPFMV alone had only a low virus titre in sweet potato cvs Tanzania and New Kawogo, became increasingly difficult to detect in plants of these cultivars and was seldom acquired by aphids. However, this resistance to SPFMV was not apparent in plants which were also infected with SPCSV. Plants then had a high SPFMV titre, appeared unable to eliminate SPFMV and provided good sources for aphids to acquire it.
Detection of hatching inhibitors and hatching factor stimulants for golden potato cyst nematode, Globodera rostochiensis, in potato root leachate
Authors: BYRNE J. , TWOMEY U. , MAHER N. , DEVINE K J , JONES P W 
Published: February 2008

SummaryIn a comparison of four potato varieties, in‐soil hatch of the golden potato cyst nematode (Globodera rostochiensis) was positively correlated to in vitro hatch in response to potato root leachate (PRL). The in‐soil hatch of cysts of G. rostochiensis to two of the four varieties was significantly less than that of the control (cysts in gravel without potato plants) in the first 2 wk after plant emergence, suggesting the production of hatching inhibitors (HIs) by young potato plants. The hatching factor: hatching inhibitor ratio of PRL was positively associated with the net hatching activity of the PRL. Four zones of HI activity were resolved following gel permeation chromatography of PRL on Sephadex G‐10. Hatch‐inactive chemicals, which stimulated the activity of hatching factors (HFs) in PRL (hatching factor stimulants, HSs), were also isolated from PRL, hatch levels induced by individual HFs responding differently to the same HS preparation. The complex interactions between individual HFs and other hatching chemicals in PRL was illustrated when addition of the hatch‐active potato glycoalkaloid α‐solanine caused both inhibition and stimulation of PRL‐induced hatch, depending on the α‐solanine concentration.