摘要:

SUMMARYTen seed treatment formulations were assessed in the laboratory and glasshouse for their phytotoxicity to radish and effectiveness in preventing cabbage root fly damage. Bendiocarb, dimethoate, mecarphon and chlorfenvinphos were phytotoxic; carbophenothion, diazinon, iodofenphos and pirimiphos‐ethyl gave negligible protection. Chlorpyrifos and isofenphos performed adequately and so were compared at 14 and 20 g a.i./kg of seed in four field experiments with chlorfenvinphos soil treatments. With less than one‐third of the a.i. needed for soil treatments, the seed treatments gave similar or, in one experiment, better protection than 2·2 kg chlorfenvinphos/ha incorporated in the soil before sowing.Insecticide residues in mature radish from soil treated at 2·2 kg a.i./ha with a chlorfenvinphos e.c. were 0·04–0·06 μg/g, within the current Codex tolerance of 0·1 μg/g; the same dose of a granular formulation of chlorfenvinphos produced residues of 0·06‐0·21 μg/g. Chlorpyrifos residues in mature radish grown from seed treated at 20 g a.i./kg were 0·12‐0·65 μg/g, mostly less than the most relevant Codex tolerance, for carrots, of 0·5 μg/g. Seed treatment with the same dose of isofenphos, for which there are no Codex tolerances, produced residues of 0·17‐0·27μg/g.No insecticide treatments are currently approved in the U.K. to protect radish from damage by cabbage root fly larvae. Soil treatment with a chlorfenvinphos e.c. seems to be suitable for protecting single radish crops. If suitable formulations of chlorpyrifos or isofenphos were made available commercially, seed treatment with these insecticides would lessen the risk of residues accumulating in soil and contaminating successive radish crops grown in the same soil. Seed treatment would also provide an alternative to applying smaller doses to the soil f

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03890.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYPrior infection by barley yellow dwarf virus (BYDV) initially suppressed, then subsequently enhanced the amount of powdery mildew (Erysiphe graminisDC ex Mérat) on oat cv. Maldwyn and barley cv. Proctor. Carbendazim applied as a spray decreased mildew on virus‐free and BYDV‐infected plants, but had no effect on virus symptoms. In oats, both mildew and BYDV infection significantly increased the number of heads but decreased the number of grains per head. Mildew infection of BYDV‐infected plants had no further effect. BYDV significantly increased the 1000 grain weight of oats, but mildew caused no significant alteration in grain weights of either virus‐free or BYDV‐infected plants. Both mildew and BYDV reduced the yield of oats, but mildew infection of BYDV‐infected plants caused no further significant alteration. Percentage crude protein was increased in grain from both BYDV‐infected and mildew‐infected oats, but significantly only in BYDV‐infected plants.In barley, the number of spikelets on the main shoot, the number of heads and the number of grains per head were all significantly reduced by BYDV but not by mildew. Mildew infection of BYDV‐infected plants had no further effect. Both BYDV and mildew significantly reduced the 1000 grain weight of barley, but mildew infection of BYDV‐infected plants caused a significant increase in 1000 grain weight compared to mildew‐free, virus‐infected plants. The yield of barley was significantly reduced by mildew and by BYDV, but no additional yield loss was caused by mildew infection of BYDV‐infected plants. The percentage crude protein of barley was increased, but not signific

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03891.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYPot‐grown barley plants were exposed to infection by powdery mildew at different growth stages and for different periods of time. Mildew attacks up to G.S. 5·0 (Feekes scale, Large, 1954) greatly reduced the number of fertile tillers at harvest and also reduced the number of grains per head and grain size, even when the disease was controlled during later stages of growth. Mildew infection after G.S. 5·0 still reduced tiller numbers but to a lesser extent and yield loss at these later stages was due mainly to loss in grain size and grain number. In one experiment the size of the root system was recorded at harvest. Mildew, particularly when the infection occurred early (before G.S. 7·0), reduced the size of the root system. Root weight per plant was strongly correlated with grain yield per plant and tiller number per p

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03892.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYIncidence of eyespot was assessed in different‐length sequences of spring‐sown wheat and barley in field experiments. Disease levels in the fourth crop were greater with single cereal systems than when the alternative crop was grown in the fourth year. The existence of host specificity as a possible cause of this phenomenon was examined in comparative pathogenicity studies of isolate collections obtained from differentially‐cropped plots from the same field.In two experiments, isolates from the third, fourth or fifth consecutive barley crops produced more disease on barley than on wheat and isolates from wheat caused more disease on wheat than did isolates from barley. Isolates from 4‐yr wheat and barley sequences showed significant specificity of isolates for their original hosts but in another experiment such specificity was not detected in isolates from 3‐ and 7‐yr sequences of wheat and barley. However, there was a significant reduction in virulence of isolates in the seventh compared with the third crop, when comparisons were done on the alternative rather than on the original host species. This suggests that extreme selection pressure for pathogen virulence on a particular host species may lead to impairment of patho

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03893.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYIn field experiments in New South Wales, wheat inoculated withGaeumannomyces graminisvar.triticihad less take‐all and yielded significantly more grain (P≤ 0·05) when simultaneously inoculated withG. graminisvar.graminisand a lobed hypho‐podiatePhialophorasp. synonymous withPhialophora radicicolaCain var.radicicola sensuDeacon than when unprotected with these fungi. An isolate ofP. radicicolavar.graminicoladid not confer any protection. The yields of cross‐protected wheat approached those of healthy wheat where take‐all incidence was slight to moderate while control was less economically significant where disease was severe. If this form of control proved similarly effective against natural inoculum it might be best employed at the beginning of a wheat monoculture after a break crop and serve to delay the onset of severe take‐all.A preliminary survey of 28 wheat fields in New South Wales using a bait technique and examining for characteristic fungal structures showed thatG. g. graminiswas rarely present in the soil and the lobed hyphopodiatePhialophorasp. andP. r. graminicolawere absent. Significant populations ofG. g. graminisonly occurred in first wheat crops after a long period of native pasture. In New South Wales, at least, these avirulent fungi would have to be introduced to wheat fields for take

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03894.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYAn investigation concerning double strain occupancy of nodules and the competitive ability for nodulation ofRhizobium trifoliistrains 7Astrrand 32spcrwas carried out using red and white clover varieties grown in agar and soil.Only two nodules of the 498 typed from plants grown in soil contained both inoculated strains and none of those analysed by the replica plating technique were formed by both 32spcrand an indigenous strain. In contrast, plants grown on agar produced between 17% and 25% doubly infected nodules. Strain 32spcrwas more competitive for nodulation than 7Astrrboth in soil and agar. Indigenous rhizobia in soil were highly competitive for nodulation with the introduced strains; increasing the density of the inoculum resulted in an increase in the proportion of nodules occupied by the inoculated strains. The strains used as mixed inocula in soil were less successful in nodulation than the same strains used as pure inocula. The results also indicate that there was a host effect on the nodulation success of 7Astrr.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03895.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYPepino mosaic virus (PepMV), a previously undescribed virus, was found in fields of pepino (Solanum muricatum) in the Canete valley in coastal Peru. PepMV was transmitted by inoculation of sap to 32 species from three families out of 47 species from nine families tested. It caused a yellow mosaic in young leaves of pepino and either a mild mosaic or symptomless infection in 12 wild potato species, five potato cultivars and potato clone USDA 41956 butS. stoloniferumand potato cultivars Merpata and Revolucion reacted with severe systemic necrotic symptoms. The virus was transmitted by plant contact but not byMyzus persicae.It was best propagated and assayed inNicotiana glutinosa.Sap from infectedN. glutinosawas infective after dilution to 10‐1but not 10‐6, after 10 min at 65°C but not 70°C and after 3 months at 20°C.PepMV had filamentous particles with a normal length of 508 nm; the ends of some seemed damaged. Ultra‐thin sections of infected leaves ofN. glutinosarevealed many inclusions containing arrays of virus‐like particles some of which were banded or whorled; small aggregates of virus‐like particles were also common. The virus was purified by extracting sap from infected leaves in a solution containing 0·065 M disodium tetraborate, 0·435 M boric acid, 0·2% ascorbic acid and 0·2% sodium sulphite at pH 7·8, adding silver nitrate solution to the extract, and precipitating the virus with polyethylene glycol followed by two cycles of differential centrifugation. Particles of PepMV normally yielded two proteins with molecular weights of 26 600 and 23 200, but virus obtained from infective sap aged overnight yielded only the smaller protein suggesting that it was a product of degradation of the larger one. The virus is serologically related to two potexviruses, narcissus mosaic and cactus X and its properties are typical of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03896.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYFive spring barleys, grown either in pots out of doors or in the field, were inoculated with barley yellow dwarf virus (BYDV) using 5, 10, 20 or 50 infective aphids (Rhopalosiphum padi) per plant. Control plants of each variety received no aphids. Infection with all aphid numbers had highly significant adverse effects on all varieties except Cb 1029, an early maturing BYDV‐resistant barley of Ethiopian origin. 12583 Co, a locally bred, late maturing barley possessing the same resistance gene as Cb 1029 suffered more in a pot experiment, but less than three susceptible varieties all of which were severely damaged even when few infective aphids were used. Progressive effects with increasing aphid numbers, indicative of dosage response, occurred in some varieties. These effects included delay in heading and increased stunting, but not less yield. In Cb 1029, BYDV infection caused a reduction in the number of heads per plant, but this was partly compensated for by an increase in the number of grains per head. Conversely, BYDV infection in 12583 Co caused an increase in the number of heads, partly offset by a decrease in the number of Brains tier hea

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03897.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe cause of a previously undocumented leaf mottling ofSpartinaspecies was investigated. Negatively stained preparations of sap from mottled leaves revealed flexuous particles 725 × 12 nm. Pinwheels with associated laminar inclusion bodies were observed in thin sections of affected mesophyll cells. The virus was purified from infectedSpartina anglicaplants and had a sedimentation coefficient in 0·015mborate of 150S.The virus was transmitted by inoculation of sap to healthySpartina anglica, but not to a range of other graminaceous or dicotyledonous species tested. It was distantly serologically related to agropyron mosaic virus, but not to other viruses with similar morphology; the name spartina mottle virus is propose

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03898.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYApple chlorotic leafspot virus (CLSV) was detected in 27 of 109 hawthorn and three of 67 blackthorn plants sampled in various parts of Britain. The CLSV isolates possessed similar properties to those isolated from other rosaceous species but differed in the severity of symptoms they induced in woody indicators. No seed or aphid transmission of CLSV was detected.Prunus necrotic ringspot (PNRV) and prune dwarf (PDV) viruses were detected in four and three respectively of 67 blackthorn plants. The PNRV and PDV isolates were serologically closely related to isolates from cherry. Arabis mosaic virus was detected in one blackthorn plant, but plum pox virus was not found in any of the tested plants.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03899.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY