Quality versus quantity: spring wheat seed size and seeding rate effects on Avena fatua interference, economic returns and economic thresholds     

R N STOUGAARD  & Q XUE 《Weed Research》2005,45(5):351-360

A 3-year field experiment was conducted at Kalispell, Montana, USA, to investigate the effects of spring wheat seed size and seeding rate on wheat yield loss (YL), economic returns and economic thresholds (ETs), as a function of Avena fatua density. Crop competitive ability increased as wheat seeding rate and seed size increased, with the greatest differences among treatment factors being observed at low weed densities. Both treatment factors decreased spring wheat YL, increasing economic returns during all 3 years of the study despite the higher associated seed costs. Averaged over all other factors, adjusted gross returns (AGR) were 477 and 537$ ha⁻¹ for the low and high seeding rates, while values of 453, 521 and 547$ ha⁻¹ were obtained for the small, bulk and large seed size classes respectively. Weed-free yield potential varied yearly. As yield potential increased, A. fatua competitive effects were more evident and ETs decreased. Nonetheless, both treatment factors increased ETs in 2 of 3 years. These results demonstrate that the use of higher seeding rates and larger seed size classes both improve wheat competitive ability towards A. fatua while simultaneously increasing economic returns.  相似文献   

Effectiveness of Coniothyrium minitans and Trichoderma atroviride in suppression of sclerotinia blossom blight of alfalfa   总被引：3，自引：0，他引：3  

G. Q. Li  H. C. Huang †  S. N. Acharya  R. S. Erickson 《Plant pathology》2005,54(2):204-211

The effects of the mycoparasites Coniothyrium minitans and Trichoderma atroviride on the suppression of alfalfa blossom blight caused by Sclerotinia sclerotiorum were evaluated under indoor and field conditions. When T. atroviride (9·0 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) or C. minitans (9·0 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) were applied to detached young alfalfa florets, T. atroviride effectively inhibited saprophytic growth of S. sclerotiorum, whereas C. minitans showed no inhibition under the same conditions. When T. atroviride (6·9 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) or C. minitans (6·9 × 10⁴ conidia/floret) + S. sclerotiorum (6·0 × 10³ ascospores/floret) was applied to young alfalfa petals in vivo just after pollination, the percentage of pod formation was higher for T. atroviride+S. sclerotiorum than that for C. minitans+S. sclerotiorum, and the percentage of pod rot was lower for T. atroviride+S. sclerotiorum than that for C. minitans+S. sclerotiorum. However, when they were applied to senescent petals attached to developing pods of alfalfa at 9·2 × 10⁴ conidia/floret together with S. sclerotiorum at 4·5 × 10³ ascospores/floret at 14 days after pollination, C. minitans was more effective than T. atroviride in suppressing sclerotinia pod rot and seed rot of alfalfa. Field experiments showed that three applications of C. minitans (5·4 × 10⁶ conidia mL⁻¹) or T. atroviride (5·4 × 10⁶ conidia mL⁻¹) at a 7-day interval to blossoms of alfalfa effectively suppressed sclerotinia pod rot in two out of three annual trials. Coniothyrium minitans effectively suppressed sclerotinia seed rot in all three years, whereas T. atroviride was not effective against seed rot in any of the trial years. The efficacy of C. minitans was not significantly different (P > 0·05) from benomyl (250 µg ai mL⁻¹). This study suggests that C. minitans has potential as a biocontrol agent to control blossom blight of alfalfa caused by S. sclerotiorum.  相似文献   

Distribution and properties of geographically distinct isolates of sugar beet yellowing viruses   总被引：1，自引：0，他引：1  

M. Stevens  N. J. Patron ‡  C. A. Dolby  R. Weekes §  P. B. Hallsworth  O. Lemaire  H. G. Smith 《Plant pathology》2005,54(2):100-107

From a total of 261 yellow sugarbeet leaves collected from 10 countries representing three continents, the incidence and distribution of strains of Beet mild yellowing virus (BMYV), Beet chlorosis virus (BChV) and Beet yellows virus (BYV) were analysed using serological and molecular methods. BMYV was found in all countries except Greece, and more frequently in the northern and western areas of Europe, whereas BYV predominated in Turkey, Spain, Greece, the USA and Chile. BChV, originally found in the USA and the UK in 1989, was identified in France, Spain, the Netherlands and Chile. Nine sugar beet poleroviruses, plus a reference isolate of Turnip yellows virus (TuYV, syn. Beet western yellows virus ), were further characterized and compared. Isolates obtained from sugar beet infected this species, but not oilseed rape or lettuce; all isolates except one infected Capsella bursa-pastoris . The coat-protein sequences of these isolates were highly similar, with the consensus sequence representing 89% of nucleotide residues. Within the coat-protein gene, two regions were identified that could represent specific epitopes to which monoclonal antibody BYDV-PAV-IL-1 could bind; this antibody is used to distinguish beet poleroviruses in ELISA. Comparison of the sequences at the 5' end showed that sequence homology existed only between isolates with the same host range. The first sequence data of polerovirus isolates from Chile are presented, showing that the coat protein and the 5' end of their genomes are highly similar to those of BMYV isolates found in Europe. Chilean polerovirus isolates may have been imported from the northern hemisphere in sugar beet breeding material.  相似文献   

Binucleate Rhizoctonia sp. AG G causing root rot in yacon (Smallanthus sonchifolius) in Brazil     

R. C. Fenille  M. B. Ciampi  N. L. Souza  A. K. Nakatani  E. E. Kuramae † 《Plant pathology》2005,54(3):325-330

A new rot caused by a binucleate Rhizoctonia sp. affecting the tuberous root cortex of the domesticated yacon ( Smallanthus sonchifolius ) has been observed in Brazil. Isolates of a binucleate Rhizoctonia sp. were collected from roots with rot symptoms and characterized by the number of nuclei per cell, hyphal anastomosis, RAPD molecular markers, ITS-5·8S rDNA sequence and pathogenicity tests. All isolates had a mean of 1·9–2·2 nuclei per cell and anastomosed with the binucleate Rhizoctonia sp. AG G-tester strain. RAPD analysis was carried out between 11 isolates recovered from yacon and 11 AG (A, Ba, Bb, Bo, C, D, F, G, O, P, Q) standard testers of binucleate Rhizoctonia sp. Genetic similarities of 94·8–100% were observed among isolates of the binucleate Rhizoctonia sp. from yacon and all isolates were genetically more closely related to the AG G tester than other strains according to upgma analysis using RAPD markers. Homologies of complete ITS nucleotide sequences were 100% between binucleate isolates of Rhizoctonia sp. from yacon and the AG G tester. According to pathogenicity tests, the isolates caused typical rot symptoms of yacon tubers 90 days after inoculation  相似文献   

Pathogenicity of the root-knot nematode Meloidogyne javanica on potato     

N. Vovlas  D. Mifsud  B. B. Landa  P. Castillo † 《Plant pathology》2005,54(5):657-664

Host–parasite relationships and pathogenicity of Meloidogyne javanica on potatoes (newly recorded from Malta) were studied under glasshouse and natural conditions. Potato cvs Cara and Spunta showed a typical susceptible reaction to M. javanica under natural and artificial infections, respectively. In potato tubers, M. javanica induced feeding sites that consisted of three to four hypertrophied giant cells per adult female. Infection of feeder roots by the nematode resulted in mature large galls which usually contained at least one mature female and egg mass. In both tubers and roots, feeding sites were characterized by giant cells containing granular cytoplasm and many hypertrophied nuclei. Cytoplasm in giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P ) [0–64 eggs + second-stage juveniles (J2s) per cm³ soil] and growth of cv. Spunta potato seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m  + (1 −  m ) z ^{( P − T )}] was fitted to fresh shoot weight and shoot height data of nematode-inoculated and control plants. Tolerance limits ( T ) for fresh shoot weight and shoot height of cv. Spunta plants infected with M. javanica were 0·50 and 0·64 eggs + J2s per cm³ soil, respectively. The m parameter in that model (i.e. the minimum possible y -values) for fresh shoot weight and shoot height were 0·60 and 0·20, respectively, at P  = 64 eggs + J2s per cm³ soil. Root galling was proportional to the initial nematode population density. Maximum nematode reproduction rate was 51·2 at a moderate initial population density ( P  = 4 eggs + J2s per cm³ soil).  相似文献   

Direct examination of soil for sporangia of Synchytrium endobioticum using chloroform, calcium chloride and zinc sulphate as extraction reagents     

G. C. M. van Leeuwen  J. G. N. Wander  J. Lamers  J. P. Meffert  P. H. J. F. van den Boogert  R. P. Baayen 《EPPO Bulletin》2005,35(1):25-31

Fields infested with Synchytrium endobioticum can be descheduled when the soil is found free from sporangia of S. endobioticum . For direct examination, EPPO Standard PM 3/59 describes a soil extraction technique based on the use of a sieve shaker with six sieves. We compared recovery of sporangia between this (modified) method and an extraction method employed by the Dutch Plant Protection Service (PPS method). Recovery was determined using an inoculum dilution series: 125, 25, 5, 1, 0.2 or 0.04 sporangia per g soil. Extraction reagents used were chloroform and calcium chloride in the method described by EPPO, calcium chloride and zinc sulphate in the PPS method. At 125 sporangia per g soil, the mean density determined for the modified EPPO method was 228 sporangia per g soil when chloroform was used. Using calcium chloride, recovery percentage was higher for the modified EPPO method than for the PPS method (286, 136%, n.s. P  < 0.05). The advantage of the modified EPPO method was the larger soil volume to be processed; its disadvantages were use of complex equipment and noxious reagents (chloroform). Both extraction methods showed high variation in recovery between samples, making accurate estimation of sporangial densities in soil awkward.  相似文献   

CABI/EPPO distribution maps of plant pests and plant diseases and their important role in plant quarantine     

N. M. Pasiecznik  I. M. Smith  G. W. Watson  A. A. Brunt  B. Ritchie  L. M. F. Charles 《EPPO Bulletin》2005,35(1):1-7

Never before has the need for accurate distribution data for plant pests been so important. CAB International (CABI) and EPPO are international organizations with a long history and strong involvement in collating and disseminating information on the global distribution of plant pests. Distribution Maps of Plant Pests and Distribution Maps of Plant Diseases, first published in 1951 and 1942, respectively, are respected, referenced sources of such data, expertly compiled and validated and used by plant health organizations around the world. They have been joint CABI/EPPO publications since 1997, and provide an essential complement to expanding knowledge on plant pest distribution. The Distribution Maps continue to be the most authoritative sources of information on the presence and extent of specific plant pests, sourced from the 4.5 million records in CAB Abstracts as a basis and numerous other sources. They also feed directly into CABI's Crop Protection Compendium (CPC) and EPPO's Plant Quarantine Data Retrieval System (PQR) databases. Their history, compilation and value are discussed.  相似文献   

Detection and characterization of two strains of Grapevine fanleaf nepovirus in Tunisia     

S. Fattouch  H. Acheche  S. M'hirsi  M. Marrakchi  N. Marzouki 《EPPO Bulletin》2005,35(2):265-270

The nematode-borne Grapevine fanleaf nepovirus (GFLV) causes severe degeneration of grapevines in vineyards worldwide. In a recent survey of the sanitary status of grapevine plants in north Tunisian vineyards, we were interested to study the polymorphism of GFLV. Purified virus, from mechanically inoculated Chenopodium quinoa , was used to produce anti-GFLV antiserum, which specifically recognized GFLV in different Tunisian grapevine samples using the DAS-ELISA technique. Positive samples were subjected to oligoprobe-RT-PCR to amplify a 606 bp region of the viral coat protein sequence. PCR products used for RFLP analysis after digestion with endonuclease Alu I produced 3 restriction profiles. RFLP data allowed clear distinction of two GFLV strains in Tunisia. The nucleotide sequence of the PCR-generated amplicons from each strain was determined showing 93.4% identity at the nucleic acid level and 97.5% similarity at the aminoacid sequence level compared to the previously characterized GFLV-F13 French isolate. This paper is the first report on molecular variability of GFLV in Tunisia.  相似文献   

Perineal Nets of Proteoglycans and Glycoproteins in Albino Rat Hippocampus     

W. Mubarak    M. N. Saleh    R. Sayed    A. Ohtsuka    T. Taguchi    T. Murakami 《Anatomia, histologia, embryologia》2005,34(S1):34-35

Perineuronal nets (PNs) of condensed extracellular matrix (ECM) have been shown to characterize the microenvironment of individual neurons and the chemoarchitecture of some brain regions. In the present study, PNs in the hippocampus were visualized with a cationic iron colloid method for sulphated proteoglycan content and a plant lectin from Vicia villosa agglutinin (VVA) for N-acetylgalactosamine containing glycoconjugates. The ECM molecules were organized in reticular coats (PNs) around non-pyramidal cells in the Ammons horn (Corneu Ammons, CA) and subicular region, in addition to pyramidal neurons located in CA2 and CA3 regions. CA2 stratum pyramidale exhibited the most intense staining of its PNs and a diffuse intervening neutrophil labelling, while CA3 region showed a graded fashion of staining intensity. The subiculum displayed intensely stained perineuronal coats. Notably, the hippocampal perineuronal nets revealed overlapped staining characteristics with both staining methods. However, cell coats of the subicular neurons showed various degrees of labelling characteristics with both markers. It is suggested that the PNs in the hippocampus are correlated with the fast spiking inhibitory GABAergic neurons and their target pyramidal cells, and this is important to keep the excitatory elements under control and therefore control the information processes within the hippocampus.  相似文献   

New ovine PrP gene haplotypes as a result of single nucleotide polymorphisms in the PrP gene promoter     

G.T. O'Neill  D. Cairns  L. Toovey  W. Goldmann  & N. Hunter 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2005,122(2):86-94

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