摘要:

SUMMARYSeveral factors influencing the efficiency of water‐traps in capturing cabbage root flies were studied at Wellesbourne in 1971 and 1972. In both the laboratory and field, approximately twice as many flies were caught in fluorescent as in non‐fluorescent yellow traps. Depending upon trap density, addition of a source of the attractant allylisothiocyanate (ANCS) increased the numbers of females captured by approximately twofold in fluorescent traps and from two‐ to sevenfold in non‐fluorescent traps. Traps were equally efficient irrespective of whether the ANCS was renewed every 2, 3, 4 or 5 days. On the first day of trapping, the number of flies caught per unit area was linearly related to the square root of the number of traps in that area. On the following days the rate was probably in equilibrium with the combined effect of immigration and the rate of development of responsive flies in the trapping zone. Most males were caught 30 cm above the soil surface and most females at soil level. Traps 120 cm above the soil surface caught few flies.Populations of marked flies were released into large field cages containing both a section of hedgerow and a plot of cauliflowers. Even after a week, only 81 % of the males and 55 % of the females had been recaptured from the most responsive of these captive populations. Furthermore, only 30 % of females were recaptured when they were more than 8 days old, the age at which most probably enter the new ho

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01398.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYWyerone acid was produced by leaves ofVicia fabain response to infection by bothBotrytis cinereaandB.fabae.Host cell death caused by either fungus appeared to be the trigger for rapid wyerone acid synthesis, although the phytoalexin was not confined to brown cells. AtB. cinereainoculation sites wyerone acid concentration increased rapidly, at the time of fungal invasion of the epidermis, to levels greater than that completely inhibitory to mycelial growth. Wyerone acid is therefore probably the primary cause of the inhibition ofB. cinereawithin infected tissue. The partial blackening ofB.fabaeinoculation sites and surrounding peripheral tissues was accompanied by an increase in wyerone acid. There followed a striking decrease as tissues became completely blackened and invaded byB.fabae. B.fabaeappeared to metabolize wyerone acid and prevent its accumulation in invaded tissues. Mycelial growth ofB. fabaewas less sensitive to wyerone acid than wasB. cinerea.The differing abilities ofB.fabaeandB. cinereato spread from lesions after both have induced wyerone acid production probably depend on both their differing sensitivities to the phytoalexin and their abilities to metabolize it to less toxic products.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01399.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYSeed tubers of the varieties King Edward, Majestic and Pentland Crown selected as ‘clean’ (lesion‐free), moderately, or severely affected by gangrene lesions were planted in field experiments. Infection delayed plant emergence, increased the number of stems/plant, sometimes caused gaps in crops and was associated with increased blackleg. On average severely affected seed yielded 20% less than ‘clean’ seed. Seed infection also increased the proportion of tubers in smaller size grades so that crops from severely infected King Edward seed averaged 1·4 ton/acre (3·5 t/ha) less small ware and 2·5 ton/acre (6·3 t/ha) less large ware than ‘clean’ seed. With Majestic, small ware was increased (0·7 ton/acre (1·8 t/ha)) and large ware decreased (4·4 ton/acre(11·0 t/ha)); Pentland Crown was similarly affected (small ware increased 0·8 ton/acre (2·0 t/ha); large ware decreased 3·9 ton/acre (9·8 t/ha)). In eight of twelve experiments unselected diseased stocks yielded significantly less than ‘clean’ tubers.Other experiments compared seed stocks with different proportions of gangrene‐infected seed tubers. Yields decreased as the proportion of diseased seed tubers increased, but differences were significant only when more than 60% were affected. Surprisingly, yields from ‘clean’ tubers also decreased as the proportion of diseased tubers increased in the stocks from which they were selected.Gangrene on progeny tubers after storage was not always related to the amount of gangrene visible on the seed. It was increased by riddling or wounding and decreased by dipping tubers in organo‐mercury fu

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01400.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYUredospore production ofPuccinia striiformisin single wheat seedlings was assessed by weighing spores on an electrical microbalance, by counting on a haemocytometer or by measuring turbidity of spore suspensions with a spectrophotometer and compared with production from groups of seedlings determined by weighing spores on an analytical balance. The data were used to assess differential interaction of wheat cultivars Hybrid 46 and Joss Cambier with two isolates of race 104 E137 ofP. striiformisand cvs Maris Templar and Joss Cambier with two isolates of race 41 E136. A significant differential interaction was shown in both experiments by each method but most rapidly and with the minimum of materials by the single‐plant microbalance technique. Measurements of spore production demonstrated differences between isolates within races more clearly than the conventional visual assessment of yellow rust symptom

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01401.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYStrains ofPhytophthora infestansof the same race (P4) isolated from a range ofR0potato varieties differed markedly in their rate of growth on agar but differences in growth rate were not related to variety of origin. Two isolates from each of the varieties Duke of York, Majestic and Arran Consul were grown for six successive subcultures on tubers of these three varieties. The six isolates differed in aggressiveness as shown by their growth on individual varieties. There was a marked difference in growth rate between alternate subcultures which is attributed to the use of too long an incubation period. Analysis of the data for subcultures 1, 3 and 5 revealed a significant interaction between isolates and varieties which reflected the enhanced growth of five of the isolates on the variety from which they had been obtained. Serial subculture on potato tubers of the same variety had no general or specific effect on the aggressiveness of the isolates. It is concluded that strains ofP. infestansof the same race may be differentially adapted to the variety on which they are growing in the field. Differential interactions between pathogen biotypes and non‐immune hosts are considered to be widespread in host‐pathogen syst

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01402.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYRaspberry bushy dwarf virus (RBDV) was transmitted to raspberry seed both through the pollen and through the ovule and it infected plants pollinated with infected pollen. It did not infect plants prevented from flowering, and transmission through pollen seems to be the only method of spread in the field; in the proximity of infectors, most plants became infected during the first two or three flowering seasons. Plants containing RBDV showed no obvious symptoms, but healthy or infected flowers pollinated with infected pollen produced ‘crumbly’ fruit, containing a high proportion of aborted drupelets. RBDV was difficult to eliminate from infected raspberry by heat therapy. Raspberry cultivars that fail to become infected naturally were also immune to infection by grafting. Use of immune cultivars offers the only method of control and, because infected plants may produce crumbly fruit, future cultivars should if possible possess immunity to R

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01403.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThin sections of diseased raspberry (Rubus idaeus) were examined by electron microscopy. Plants of the cv. Baumforth's B and of an aphid (Amphorophora rubi)‐resistant breeding selection (6820/54), both infected with raspberry vein chlorosis virus (RVCV) but not with other detectable viruses, contained large bacilliform particlesc.430 × 65 nm. Particles occurred in the cytoplasm and perinuclear space of a small proportion of xylem parenchyma cells. They had an inner corec.25–30 nm in diameter with cross‐banding of periodicity 4·5 nm, and were bounded by an outer membrane. They are probably the particles of RVCV.Plants of cv. Mailing Jewel and of a selection (M14) both showing symptoms of raspberry mosaic (veinbanding) disease contained smaller bacilliform particlesc.125 × 30 nm, which occurred singly or in clusters in the cytoplasm of a small proportion of vascular parenchyma cells. It is not known which, if any, of the viruses associated with raspberry mosaic are represented by the p

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01404.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYMaize streak virus (MSV) was purified by homogenising infected leaf tissue in 0·01mpH 3·9 phosphate buffer and clarifying the extract withn‐butanol (7 ml/100 ml extract). Purified preparations contained particles 20 nm in diameter, some occurring singly, but most occurring in pairs, forming structures of 30 × 20 nm. The sedimentation coefficients of single and paired particles were 54 and 76 S respectively.When centrifuged in sucrose density gradients preparations made by extracting leaves at pH 3·9 gave a single intense light‐scattering zone containing paired particles. Preparations made at pH 5·9 or 7·9 gave one or two additional upper zones containing single particles and fragmented material. Preparations treated with 0·05 or 0·1methylene diamine tetra‐acetic acid, disodium salt, (EDTA) contained no paired particles, few single particles and much fragmented material. In immunoelectrophoresis, the major component in preparations without EDTA migrated to the cathode whereas that in EDTA‐treated preparations migrated to the anode.Virus isolates from streak‐diseased sugarcane and guinea grass (Panicum maximum) were serologically related to MSV and had similar particles with identical sedimentation coefficients. No such particles were seen in purified preparations of healthy maize, sugarcane, or guinea grass. The viruses from sugarcane and guinea grass are probably host‐adapted and are referred to correctly as the sugarcane and guinea grass strains of MSV.MSV probably contains single‐stranded RNA, and the cryptogram

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01405.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYAbout half the nurseries and glasshouses in the Lea Valley of Hertfordshire were found to be infested with either or bothPratylenchus vulnusandXiphinema diversicaudatum.The latter nematode probably occurred naturally in the soil on which the glasshouses were built butP. vulnusis thought to have been imported with rose rootstocks and is not known to occur outdoors in Britain. Both nematode species can cause decline of roses and even small numbers seem harmful. Numbers ofP. vulnuscan increase greatly, especially on rootstocks ofRosa canina, although numbers were often smaller when roses were severely damaged than on healthier crops. Numbers ofX. diversicaudatumincreased more slowly andR. caninawas a better host for it thanR. chinensis. X. diversicaudatumseemed to respond less quickly thanP. vulnusto reduced host‐plant vigour. The two rootstocks exhibited different host‐status for the two species of nematode and cuttings of various rose cultivars showed different host‐status toP. thornei, another species of lesion nematode which is not known to be pathogenic to roses. Two applications of dibromochloropropane liquid at the rate of 70 l/ha in a large volume of water maintained nematode densities at an acceptably low level, and growers who adopted this treatment as a supplement to pre‐planting steam sterilisation and/or DD (dichloro‐propane: dichloropropene) prolonged the productive life of their crops for seve

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01406.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01407.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY