bluuebunny/crossref_metadata_2025 huggingface dataset:
Phytoalexin accumulation during infection of bean and soybean by ascospores and mycelium of Sclerotinia sclerotiorum
Authors: SUTTON D. C. , DEVERALL B. J.
Published: April 2007

Infection by ascospores of Sclerotinia selerotiorum caused hypersensitivity in epidermal cells in leaves and etiolated hypocotyls of bean and soybean. In bean, phaseollin and phaseollidin accumulated in leaves but kievitone alone in hypocotyls. In soybean, no phytoalexins were detected in leaves but glyceollin accumulated in hypocotyls.

Mycelial infection caused water‐soaked spreading lesions in leaves and etiolated hypocotyls of both hosts. In bean, no phytoalexins were detected in leaves but kievitone alone accumulated in hypocotyls. In soybean, glyceollin accumulated in leaves but was not sought in hypocotyls.

Transfer of bean hypocotyls infected with mycelium from 18 to 28°C caused lesion limitation and marked accumulation of phaseollin and kievitone.

Phaseollin, kievitone and glyceollin inhibited ascospore germination and growth of hyphae from preformed germ‐tubes and established mycelia, phaseollin being most active and glyceollin least active. Hyphal growth from mycelia was least affected by the phytoalexins.
The genetic control and expression of specificity in Bremia lactucae (lettuce downy mildew)
Authors: NORWOOD JUDITH M. , CRUTE I. R.
Published: April 2007

The inheritance of specific virulence in Bremia lactucae was studied in crosses involving 12 heterothallic isolates of the fungus. In one cross, virulence to eight of the II specific resistance factors examined segregated in the F1 generation. Although there were exceptions, most of the data were consistent with the hypothesis that pathogenicity was controlled by independent single loci with avirulence dominant to virulence. Linkage between loci determining virulence on R2 and R11 was confirmed. Loci controlling virulence on R5 and R8 also appeared to be linked but these may be identical R‐factors. Contrary to a previous suggestion, the locus determining virulence to R10 was independent of that for R5/R8. The expression of virulence to three R‐factors (Rl, R4 and R5/R8) was influenced by independent second loci. The presence of a dominant allele at the second locus inhibited avirulence. The expression of avirulence on R6 seemed to be influenced by modifier genes and environment in some isolates. Although the cultivars Mildura, Bourguignonne, Sucrine and Captain were originally thought to contain a single resistance factor, these data suggest that Sucrine carries R5/R8 in addition to R10 whilst Mildura may carry Rl in addition to R3. The stock of Bourguignonne appeared to be a mixture of resistance genotypes. The data add additional support to the suggestion that Capitan (Rll) may carry two resistance factors.
Reduction of cavity spot and root dieback in carrots by fungicide applications
Authors: LYSHOL A. J. , SEMB L. , TAKSDAL G.
Published: April 2007

Metalaxyl greatly reduced the incidences of root dieback and cavity spot in carrots in field and pot experiments, and in spray tests in growers' fields. Propamocarb and fosetyl‐Al also greatly reduced cavity spot in a pot experiment. No significant effects were attributable to aldicarb, benomyl, iprodione or a micronutrient compound containing Fe, Mn, Cu, Zn, Co, B and Mo.
Resistance to Sclerotium cepivorum in Allium and other genera
Authors: ESLER G. , COLEY‐SMITH J. R.
Published: April 2007

Stimulatory and non‐stimulatory species of Allium and four other members of the Liliaceae were susceptible to infection by germinating sclerotia of Sclerotium cepivorum in unsterile soil. Plants belonging to other families were not infected in soil even when germinating sclerotia were in contact with their roots. Under aseptic conditions S. cepivorum infected plant species not closely related to Allium, particularly when large amounts of inoculum were used. Infection was slight in the presence of germinating sclerotia. It is suggested that within the genus Allium and a few related genera resistance results from the lack of ability to stimulate germination of sclerotia. Non‐Allium plants also lack this ability but in addition possess tissue resistance to S. cepivorum.
Population structure of Cryptostroma corticate, the causal fungus of sooty bark disease of sycamore
Authors: BEVERCOMBE G. P. , RAYNER A. D. M.
Published: April 2007

Single conidium isolates of Cryptostroma corticate from 14 woodland sites in Wales and southern England belonged to 11 different somatic‐compatibility groups. Members of the same group intermingled on 3% malt agar, whereas those of different groups were mutually antagonistic, a zone of sparse mycelium developing between paired colonies. Isolates from the same stroma were all of the same compatibility group, and this was also sometimes true for isolates from different trees at the same woodland site. Some compatibility groups occurred in widely separated locations, but others seemed to be peculiar to a particular woodland. The implications of this population structure for the life cycle and epidemiology of the pathogen are discussed.
Inter‐and intracontinental sexual compatibility in Sclerospora graminicola
Authors: IDRIS M. O. , BALL S. L.
Published: April 2007

Oospore collections of Sclerospora graminicola, obtained from diverse locations in West Africa and India, were used to infect susceptible pearl millet plants. Asexual spores, collected from five infected plants from each collection were used as individual isolates to inoculate pearl millet seedlings, alone and in every possible combination to test for sexual compatibility type. Oospores were produced with some combinations of isolates but not others, indicating the presence of two compatibility types, designated g1 and G2 These were found in approximately equal proportions. There were also some isolates which produced a few oospores when inoculated alone. Tests for cross‐compatibility were made by combining isolates of opposite sexual compatibility types from different collections. Not only were collections from within continents cross compatible but there was also cross‐compatibility between isolates from different continents. The implications of such extensive outbreeding capacity in S. graminicola are considered.
The location of virus‐like particles in the male gametophyte of birch, walnut and cherry naturally infected with cherry leaf roll virus and its relevance to vertical transmission of the virus
Authors: MASSALSKI P. R. , COOPER J. I.
Published: April 2007

Virus‐like particles (VLPs) in close‐packed paracrystalline arrays were observed in cells forming the anther walls and in the sperm cell cytoplasm of immature pollen grains developing within cherry leaf roll virus (CLRV)‐infected birch (Betula pendula Roth.). VLPs within tubules, that were in some instances multiple and membrane bound, were also observed in anther cells and in pollen grains of CLRV‐infected walnut (Jugians regia L.). VLPs rarely coated the outer surfaces of developing grains. Washings from intact freshly collected pollen did not contain infective agents but pollen triturates were infectious after 12 months storage at‐70°C. Purified CLRV (concentration 6·4 ng/ml) was readily detected by enzyme‐linked immunosorbent assay (ELISA). CLRV‐specific antigens (detected by ELISA) and VLPs (detected on grids coated with an antiserum prepared against CLRV) were readily removed by washing intact pollen grains from infected birch, walnut and cherry (Prunus avium L. cv. F12/1). The antigen was less tenaciously held to the surfaces of anemophilous (birch and walnut) than entomophilous (cherry) pollen. Treatment of grains before ELISA testing with CLRV‐specific γ globulin virtually eliminated the antigenicity of pollen washings whereas γ globulin from a pre‐immune serum had no such effect. When anti‐CLRV γ globulin‐treated pollen grains were disrupted, CLRV‐specific antigens were liberated. VLPs trapped on CLRV‐antiserum coated grids to which pollen washings or extracts from disrupted grains had been applied were identified by decoration; a halo of antibody molecules enveloped VLPs treated with CLRV‐antiserum but not those treated with antiserum prepared against poplar mosaic virus.
Studies of Colletotrichum gloeosporioides disease on yam, Dioscorea alata, in Solomon Islands
Authors: WINCH J. E. , NEWHOOK F. J. , JACKSON G. V. H. , COLE J. S.
Published: April 2007

A detailed account of symptoms produced by Colletotrichum gloeosporioides on susceptible and resistant cultivars of yam (Dioscorea alata) in Solomon Islands is given. A superficial blackening of upper leaf surfaces of some cultivars is unusual and worthy of further study. In pathogenicity tests with isolates of C. gloeosporioides from various sources, those that were virulent on D. alata were all from D. alata except one from D. esculenta and one from Cucumis sativus but only nine of 30 isolates from D. alata were virulent on this host. Since all four isolates of the yam pathogen tested on D. nummularia and D. trifida were virulent, it is inappropriate to retain the epiphet f. sp. alatae proposed by earlier authors. Considerable variation in cultural morphology existed among virulent isolates, the only consistent character being production of dark pigment, although this was also produced by some saprophytic isolates. Most reisolations of C. gloeosporioides from lesions resulting from inoculation yielded isolates identical with the original inoculum but also some reisolates had a different morphology.
Adult plant resistance to powdery mildew (Erysiphe graminis)in three barley cultivars
Authors: WRIGHT ALISON J. , HEALE J. B.
Published: April 2007

The mechanism(s) of adult plant resistance (a.p.r.) to Erysiphe graminis f. sp. hordei were examined in two spring barley cultivars, Athos and Porthos, which possess similar identified mildew resistance genes and seedling resistance, but differential field resistance. These cultivars were compared with Golden Promise, a universally susceptible cultivar. Differential a.p.r. to a compatible race was detected as a reduction in the number and sporulation of colonies on later‐formed Athos leaves. Golden Promise exhibited some a.p.r., but much less than either Athos or Porthos. Differential a.p.r. was expressed at several infection stages, viz. appressorial formation, penetration and sporulation. Epidermal hypersensitivity occurred infrequently in all leaf position/cultivar interactions. Papillae were associated with >90% of all penetration failures. The incidence of papillae in successful penetrations at 96 h was 20% on later‐formed leaves of Athos compared to c. 60% on all other leaves.
Retention of iprodione on salad onion leaves in relation to the control of Botrytis spp.
Authors: PRESLY A. H.
Published: April 2007

Using bioassay and fluorescent tracer techniques it was demonstrated that more fungicide was retained on mature leaves of summer salad onion crops if 1 kg/ha iprodione wettable powder (w.p.) formulation plus wetting agent was sprayed at 280 1/ha than at 560 1/ha or 1120 1/ha.

The lowest spray volume (280 1/ha) with four sprays of iprodione w.p. (0.5 kg in October, November, December and January) gave effective control of Botrytis cinerea and significantly increased plant stand and yield. More fungicide was required to obtain equivalent results using a mixed programme of two thiram (4 kg/ha total) and two iprodione w.p. (2 kg a.i./ha total) sprays at the same application volume and intervals. Where the mixed programme was applied at 1 1 20 1/ha, 1 2 kg a.i. (total fungicide) was necessary to achieve equivalent disease control.

At 280 1/ha, retention and persistence of iprodione on onion foliage was greater with the oil‐based than with the wettable powder formulation. In summer especially this resulted in improved Botrytis control and greater numbers of marketable onions. In winter onions, oil and w.p. formulations were equally effective and gave equivalent improvements in plant stand and yield.
Isolation of a tobamovirus from rose
Authors: HICKS R. G. T. , FROST R. R.
Published: April 2007

The Rosaceae contain several natural hosts of tobacco mosaic virus (TMV), including apple (Kirkpatrick & Lindner, 1964), pear (Gilmer et al., 1966), cherry (Cilnier, 1967), plum (Albrech‐tova et al., 1974) and strawberry (Yankulova & Schmidt, 1974). In 1974 we isolated a virus, serologicalty related to TMV from rose (Hicks. 1979): the first record, we believe, of a tobamo virus in this host.

Petals (150 g) from an unidentified climbing cultivar (probably Danse de Feu) with symptoms (Fig. 1) similar to rose flower break (Farrar & Frost, 1972) were homogenized in cold 0.01 M borate buffer pH 7.8 containing 0.01 M sodium ethylene diamine tetra‐acetate and 0.01 M sodium sulphite, filtered through muslin, and given one cycle of low‐ and high‐speed centrifuga‐tion. The pellet was resuspended in 2 ml of 0.01 M borate buffer pH 7.8. centrifuged at low speed, and assayed on a range of test plants, which were grown in Levington compost (Fisons Ltd) at mean temperatures of either 22° or 26°C, given supplementary lighting in winter, shaded
Methods of reducing rhizoctonia patch of cereals in Western Australia
Authors: MACNISH G. C.
Published: April 2007

Cultivation reduced rhizoctonia patch of cereals. In a continuous cropping experiment where zero‐tillage and cultivation were compared over three seasons, cultivation reduced patch score in all seasons by an average of 83%. In the fourth season, when the treatments were reversed, the incidence of rhizoctonia patch was also reversed. Nitrogen (ammonium sulphate, sodium nitrate or urea) also reduced patch score under zero‐tillage, but sources of nitrogen did not differ significantly in their effects. In another experiment it was demonstrated that a contact herbicide used in the zero‐tillage system was unlikely to be responsible for the high incidence of patch in that system. One cultivation reduced total patch score by an average of 46% compared to zero‐tillage, but these scores were not reduced further by a second cultivation.
Further studies on resistance‐breaking strains of potato virus X
Authors: JONES R. A. C.
Published: April 2007

A stock culture of isolate CP of potato virus X (PVX) maintained by serial subculture in plants of Nicotiana glutinosa was found to contain PVX strain group four in addition to the original strain group two. The group four strain was separated from the mixture by sap‐inoculation to potato cultivars Maris Piper and Pentland Dell, both of which carry PVX hypersensitivity genes Nx and Nb, by graft‐inoculation to Maris Piper and by sap‐inoculation to cultivar Pentland Ivory which carries Nb but not Nx. Strain group four seemed to be a minor component of the strain mixture in N. glutinosa as few potato plants became infected with it when insusceptible plants were sap‐inoculated or when sap inoculum was diluted 500 times. The group four strain passed readily through tubers of infected potato plants and was stable on serial sub‐culture in N. glutinosa. When stock cultures of PVX group two isolates B and EX kept in N. glutinosa were tested on cultivar Pentland Dell, they also proved to be mixtures of group two and group four, indicating that spontaneous appearance of group four in cultures of group two strains may occur readily.

When group four strains derived from isolate CP and from PVX common strain isolate DX were graft‐inoculated to many plants of cultivar Cara, which carries PVX immunity gene Rx, there was no evidence of selection of a strain like HB which overcomes this gene. In mixed infection with isolate DX, HB was still present after passage through two generations of progeny tubers of cultivar Pentland Crown which lacks any resistance genes, indicating that HB is a fully competitive strain.
Barley yellow dwarf virus in ryegrass and its detection by ELISA
Authors: HOLMES S. J. I.
Published: April 2007

The enzyme‐linked immunosorbent assay (ELISA) effectively detected PAV‐ and MAV‐like strains of barley yellow dwarf virus (BYDV) in ryegrass. MAV‐like BYDV was found in a large proportion of ryegrass plants with foliar symptoms. There was a poor association between foliar symptoms and PAV‐like virus, which occurred with similar frequency in plants with and without symptoms. By August 1982, plots of perennial, Italian and hybrid ryegrass sown at Auchincruive in 1980 were extensively infected with PAV‐ and MAV‐like strains of BYDV. Tests on samples from 1981‐ and 1982‐sown plots in August 1983 also indicated early invasion by BYDV. Infection levels of 7–80% were found in 13 commercial crops of perennial ryegrass surveyed near Auchincruive in May 1983. PAV‐like BYDV occurred with greater frequency than did MAV‐like strains of the virus.
Cultivar dependence of polyacrylic acid effects on Pseudomonas syringae in Nicotiana tabacum
Authors: AHL PATRICIA , GIANINAZZI S. , SAMSON REGINE , BENJAMA A.
Published: April 2007

Polyacrylic acid (PAA) protected Xanthi‐nc tobaccos against necrosis provoked by Pseudomonas syringae (hypersensitive reaction). When highly concentrated bacterial suspensions (1 × 108 b/ml) were injected into PAA‐treated leaves, tissue collapse was delayed; with more dilute bacterial suspensions (3 × 107 or 1 × 107 b/ml), a significant reduction or a total suppression of necrosis was observed. This phenomenon occurred when the PAA treatment was applied 4 days prior to injection of the bacteria, but not when it was applied 3 h prior to injection. No such protection occurred in Samsum NN tobaccos. PAA had no toxic effect on P. syringae when added to the injected suspensions, or in vitro in culture media. The bacterial population remained constant in protected tissue, but declined sharply in necrosing tissues. These results suggest that host metabolism is involved in PAA‐induced suppression of necrosis.

Induced suppression of necrosis due to bacteria shows some analogies with induced resistance to viruses. The possibility of common steps in their biochemical mechanism is discussed.
Field occurrence of vinclozolin resistance in Monilinia fructicola
Authors: PENROSE L. J. , KOFFMANN W. , NICHOLLS M. R.
Published: April 2007

Strains of Monilinia fructicola resistant to vinclozolin were isolated from fruit affected by brown rot from an orchard where the fungicide had been used over four seasons. Resistant isolates were pathogenic to peach fruit, and resistance of one isolate was confirmed following dipping of inoculated fruit in fungicide suspensions. In culture, one of four resistant isolates was identical in colony morphology and sporulation to sensitive isolates from different geographic areas. The other resistant isolates produced dark mycelium on PDA and were slower growing. Vinclozolin‐resistant isolates were resistant in vitro to two other dicarboximide fungicides, iprodione and procymidone.
The effect of temperature and light intensity on growth and sporulation of Puccinia striiformis on wheat
Authors: McGREGOR A. J. , MANNERS J. G.
Published: April 2007

Urediniospore production by Puccinia striiformis on wheat per unit leaf area infected was much lower at low light intensities than at high light intensities. The number of pustules per unit area of infected leaf and the daily sporulation rate per pustule increased linearly with increasing light over the range 10–50 W/m2. Increasing temperature between 7 and 20°C shortened latent period and reduced the longevity of sporulating leaves. Colonization rate and the frequency of pustules per unit area of infected leaf increased between 7 and 15°C but declined markedly at 20°C. Spore production reached its peak earlier and declined more rapidly with increasing temperature between 7 and 15°C. this decline being less marked in the highly susceptible cultivar Maris Beacon than in the more resistant Maris Nimrod and Maris Huntsman.
Survey of benomyl resistance in Pseudocercosporella herpotrichoides on winter wheat and barley in England and Wales in 1983
Authors: KING J. E. , GRIFFIN M. J.
Published: April 2007

Surveys of 528 randomly selected commercial fields in England and Wales in 1983 showed that isolates of Pseudocercosporella herpotrichoides resistant to benomyl were common and widespread on winter wheat and winter barley. During June and July resistant strains were recovered from 16 to 66% of fields and the proportion of resistant isolates was 37–52%. The frequency of occurrence of resistant isolates was positively correlated with the number of applications of carbendazimgenerating (MBC) fungicides during the previous 8 years. Benomyl resistance was found in 21–48% of fields where it was claimed that MBC had never been used, and 7–28% of isolates from those fields, were resistant. Resistance was more frequent in R‐type than in W‐type isolates of the pathogen. The proportion of R‐type isolates decreased as the number of previous winter wheat crops rose and increased with the number of winter barley crops grown and with the number of MBC sprays applied to crops in previous years. The implications of these findings for the control of eyespot in England and Wales are discussed.
A simplified slice method for assessing tuber susceptibility of potato cultivars to Erwinia carotovora subsp atroseptica
Authors: LAPWOOD D. H. , READ P. J.
Published: April 2007

The susceptibility of 24 potato cultivars to soft rot caused by Erwinia carotovora subsp. atroseptica was assessed in a simplified form of a tuber slice test described previously. Freshly made wounds on tuber slices were inoculated with drops (0–02 ml) containing 108, 107 or 106 cells/ml and incubated aerobically for 3 days at 15° or 20°C. At 20°C differences between cultivars were clear at all concentrations but at 15°C less so at the lowest concentration unless incubation time was extended. The rank order of cultivar susceptibility was similar to that found in previous seasons.
Metalaxyl resistance in Phytophthora infestans on greenhouse tomatoes in Greece
Authors: PAPPAS A. C.
Published: April 2007

In winter/spring 1984 resistance to metalaxyl developed in Phytophthora infestans within tomato greenhouses in Preveza, Greece. The appearance of resistant isolates followed continuous applications of metalaxyl and prevalence of weather conditions favourable for late blight. The majority of resistant isolates grew on tomato leaf discs floated on solutions containing 100 μg/ml metalaxyl whereas sensitive isolates were inhibited at concentrations of 0.1 μg/ml.

In trials within polyethylene tunnels metalaxyl had no effect on the development of the late blight induced by resistant strains but both a mixture of this fungicide with mancozeb and mancozeb alone, gave satisfactory control of the disease when applied in a 7‐day schedule.
Thiabendazole as an iatrogenic agent in carrot black rot
Authors: REIFSCHNEIDER F. J. B. , VECCHIA P. T. DELLA
Published: April 2007

Negligible amounts of carrot (Daucus carota L.) seed were produced in Brazil prior to the release of cv. Brasilia in 1982. This cultivar is tolerant of high temperature and resistant to leaf blight caused by Alternaria dauci (Kühn) Groves & Skolko (Vieira et al., 1983). Since 1982 technology for production of Brasilia seed has developed rapidly and over 40 t of seed have been produced, representing more than 8000 ha planted. Fungicides are widely used on carrot root crops and growers have naturally extended their use to carrot seed crops. Mancozeb, thiabendazole, captafol and chlorothalonil, applied at weekly intervals, are the most common fungicides used although their efficacy in this new situation has not been evaluated.

A survey of pathogens associated with carrot seed production (Reifschneider & Della Vecchia. 1983) has shown that the most common fungal pathogen is Alternaria radicina Meier, Dreschler & Eddy, a species which is a common seed‐borne pathogen in the USA (Rader, 1952) and has been present in Brazil since 1970 or earlier (Luz, 1970).

Since information concerning the control of A. radicina in carrot seed crops is lacking we established a preliminary fungicide experiment in July 1982 within a 5‐ha commercial field planted with artificially vernalized roots of which 90% were infected, to varying degrees, with A. radicina. Plots were 25 m2 and each treatment (Table 1) was replicated five times, in a completely randomized design. Seeds were harvested manually at maturity and dried by forced air at c. 30°C. Infection by A. radicina was detected using the method of Soteros (1979) in which heat‐treated seeds (100°C for 1 h) are plated on malt agar. A total of 200 seeds per plot (20 seeds per plate) were used. Identification of A. radicina was based on conidium and conidiophore morphology (Ellis & Holliday, 1972).
Factors influencing the production of basidiocarps and the deposition and germination of basidiospores of Crinipellis perniciosa, the causal fungus of witches' broom on cocoa (Theobroma cacao)
Authors: ROCHA H. M. , WHEELER B. E. J.
Published: April 2007

The production of basidiocarps by Crinipellis perniciosa on detached, dead witches'brooms from cocoa was assessed in relation to temperature, light, cocoa clone, age of broom and type of tissue, in cabinets with a daily cycle of 8 h wet and 16 h dry. More basidiocarps formed and matured at 20–25°C than at 25–30°C. In the latter regime the pilei were smaller and white, instead of the usual crimson colour, and the stipes were longer. No basidiocarps formed at 30–35°C. At 20–25°C. more basidiocarps formed and matured with light at 100 μE m‐2 s‐1 during the wet period than at 10 μE m‐2 s ‐1. Only one basidiocarp and five primordia developed on 20 brooms kept in the dark. Brooms from 10 cocoa clones at Pichilingue. Ecuador, differed in basidiocarp productivity. most basidiocarps forming on brooms from Seavina and least on ICS clones. The numbers of basidiocarps produced on brooms aged 1.2.3 or 4 months when detached from cocoa trees were similar but time to initiation of the first primordium differed considerably. More basidiocarps formed at nodes than internodes.

The discharge of basidiospores was optimal at 20–25°C and 80% RH: germination was optimal in water agar films. Neither process was dependent on light.
The impermeability of powdery mildew conidia and their germination in arid environments
Authors: GAY JOHN L. , MARTIN MARION , BALL ELIZABETH
Published: April 2007

Conidia of Erysiphe graminis formed germ hyphae while floating on aqueous solutions of glutaraldehyde (0.25 M), formaldehyde (1 M), NaF (0.1 M), HgCl (0.05 M) and HgCl2. (0.1 M). Inhibition of germination ranged from 60.1% (NaF) to 88.8% (HgCl2). In an atmosphere of HCN gas (5 mM) inhibition was 72.8%. The detergents Triton X‐100. sodium dodecylsulphate and cetyl trimethylammonium bromide at 10 g 1‐1 caused approximately 90% inhibition but at lower concentrations Triton X‐100 was the most inhibitory, both to germination and germ hypha elongation. Results of simultaneous treatment with HCN and Triton X‐100 suggested that their actions were independent but comparisons of LD 50 for glutaraldehyde and Triton X‐100 used separately and together indicated antagonism.
Morphology, benomyl resistance and pathogenicity to wheat and rye of isolates of Pseudocercosporella herpotrichoides
Authors: HOLLINS T. W. , SCOTT P. R. , PAINE J. R.
Published: April 2007

Seventy‐one isolates of Pseudocercosporella herpotrichoides, a non‐random sample obtained from cereal crops in Britain between 1981 and 1983, were classified as either sensitive or resistant to 2 mg/l benomyl. In agar culture, isolates were of two distinct morphological types, described as ‘fast‐even’ and ‘slow‐feathery’. Pathogenicity to wheat and rye seedlings was determined for 21 fast‐even and 32 slow‐feathery isolates. Fast‐even isolates were much more pathogenic to wheat than to rye; nearly all slow‐feathery isolates were about equally pathogenic to wheat and rye. Thus, in morphology and pathogenicity, irrespective of sensitivity to benomyl, fast‐even isolates conformed to the published descriptions of W‐types, while slow‐feathery isolates conformed to the descriptions of R‐types.

Sensitivity to 2 mg/l benomyl was determined for 97 isolates, including W‐types and R‐types, collected between 1956 and 1983, mainly from England but including some from nine other countries. Only 16 isolates were resistant; three were fast‐even and 13 were slow‐feathery. All were collected in England since 1981, suggesting that resistance has been rare until recently. Resistance was not a feature of R‐type isolates collected before 1981. The increase in the proportion of resistant isolates since 1981 appears to have coincided with an increase in the proportion of R‐type isolates.
Transmission of the coconut cadang‐cadang viroid to six species of palm by inoculation with nucleic acid extracts
Authors: IMPERIAL JULITA S. , BAUTISTA ROSEMARIE M. , RANDLES JOHN W.
Published: April 2007

Seedlings of Areca catechu (betel nut palm), Corypha elata (buri palm), Adonidia merrillii (manila palm), Elaeis guineensis (oil palm), Chrysalidocarpus lutescens (palmera) and Oreodoxa regia (royal palm) were inoculated with nucleic acid extracts from coconut palms with cadang‐cadang disease. Within 2 years of inoculation, analysis using a 32P‐labelled DNA probe complementary to the coconut cadang‐cadang viroid (CCCV) showed that RNA sequences identical to CCCV were present in the inoculated seedlings. Electrophoresis in polyacrylamide gels showed that these palms also contained an RNA with mobility identical to CCCV. Four to five years after inoculation, the infected palms of four species were usually stunted compared with uninoculated palms, while betel nut and palmera were not stunted. Yellowing of leaflets was observed with defined spots or mottling of the older fronds in all except betel nut palms. All infected palms showed mild or severe yellow‐leaf spotting. These results widen the known host range and. hence, the potential number of viroid reservoir species in the field.
Antagonistic activity of fungi isolated from sclerotia of Sclerotinia sclerotiorum
Authors: ZAZZERINI A. , TOSI L.
Published: April 2007

Fungi isolated from soils in central Italy by a baiting technique with sclerotia of Sclerotinia sclerotiorum were evaluated for their antagonism in vitro to this fungus using dual cultures and tests with sclerotia. Trichoderma spp., Coniothyrium minitans and species of Fusarium and Penicillium all showed strong antagonistic activity. Morphological alterations were observed in the mycelium of S. sclerotiorum. Trichoderma spp. and Gliocladium catenulatum killed a very high percentage (96–100%) of the sclerotia.
Studies on Botrytis spp. occurring on onions (Allium cepa) and leeks (Allium porrum)
Authors: PRESLY A. H.
Published: April 2007

Botrytis byssoidea(mycelial neck rot) was more prevalent thanB. allii(sclerotial neck rot) on the leaves of field onions and the bulbs of stored onions grown in some of the areas where onions or onions and leeks had previously been grown sequentially.

B. byssoideaandB. porriwere also isolated from leeks. Spores ofB. allii, B. byssoidea(from onions and leeks),B. porri, andB. squamosacaused infection of seedlings of salad (green) and bulb onions.

Inoculation withB. squamosaspores caused severe infection of seedling leaves, but inoculation with mycelial discs caused little damage to onion bulb tissue. By comparison, mycelial discs of the remaining species were highly pathogenic to bulbs.

The practical implications of disease transfer of certain of these species between onions and leeks are discussed.
Yellow leaf curl and other virus diseases of tomato in Cyprus
Authors: IOANNOU N.
Published: April 2007

Outdoor and greenhouse tomato plantings in the main production centres of Cyprus were surveyed for virus diseases during 1978–1982. A disease characterized by prominent leaf yellowing and curling was the most prevalent and damaging. The causal agent was identified as tomato yellow leaf curl virus (TYLCV) because it infected Datura stramonium but not the tobacco cultivars Havana 423 or Virginia, was graft‐transmissible but not mechanically or seed‐transmissible, and was transmitted persistently by the tobacco whitefly, Bemisia tabaci. Minimum acquisition and inoculation feeding periods were 20–30 and 10–20 min. respectively; the latent period was 21–24 h. The vector was infective for about 12 days, but there was no transovarial transmission to progeny.

Four other, mechanically transmissible, viruses were also isolated from tomato and identified on the basis of symptomatology, indicator host reactions and serology; tobacco mosaic virus (TMV), potato virus Y (PVY). potato virus X (PVX), and cucumber mosaic virus (CMV). These viruses, especially TMV, were commonly associated with mosaic symptoms and occasionally with other leaf or fruit disorders; coinfection with TYLCV occurred frequently.
Effects of seed treatments and storage on the incidence of Phoma betae and the viability of infected red beet seeds
Authors: MAUDE R. B. , BAMBRIDGE JUDITH M.
Published: April 2007

Red beet seed clusters retained a high level of germination when stored for 13 years at 10°C and 50% RH in a seed store; seed infection by Phoma betae (black leg) declined from 27–5 to 4–5% over the same period. Seed treatment before storage by soaking in thiram or ethyl mercury phosphate significantly improved germination and reduced mean infection by P. betae from 17% to less than 1%.
Suppression of Sumatra disease symptoms in cloves treated with antibiotics
Authors: HUNT PETER , BENNETT CHRIS P. A. , ASMAN ARIFUL
Published: April 2007

Repeated infusions of a mixture of oxytetracycline and streptomycin into the wood of initially symptomless clove trees exposed to natural infection by Sumatra disease resulted in a delay in symptom onset and slower rates of symptom development compared with untreated trees. The numbers of bacterially occluded vessels in root samples of treated trees were significantly fewer than those from controls. These results strongly support the hypothesis that a xylem‐limited. Gram‐negative bacterium, known to be consistently associated with Sumatra disease symptoms, is the causal agent. The productive life of treated trees was usefully extended but some phytotoxicity was observed, resulting in leaf scorching and stunted flower buds. In view of the high value of the crop, antibiotic therapy merits further investigation as a short‐term control measure.
Life‐history of Phragmidium rubi‐idaei on red raspberry in the United Kingdom
Authors: ANTHONY VIVIENNE M. , SHATTOCK R. C. , WILLIAMSON B.
Published: April 2007

Phragmidium rubi‐idaei produced five spore stages on red raspberry and overwintered as teliospores adhering to canes. In the field spermagonia appeared in a single flush in early summer on leaves of the primocanes (first‐year canes) and on leaves of the lateral shoots of fruiting canes, and were followed by aecia, uredinia and telia. Aecia and uredinia occasionally appeared on petioles and sepals and uredinia on drupelets of mature fruit. Lesions caused by aecia and uredinia on the bases of primocanes did not become cankerous in the following fruiting year. Necroses associated with large aecia produced a shot‐hole effect and leaflets heavily affected by either aecia, uredinia or telia abscissed prematurely.

The sequence of spore stages on pot‐grown plants inoculated with mature overwintered teliospores took 60 days to the reappearance of telia. The rate of development of uredinia and associated necroses was faster on younger than on older leaves but the cumulative spore yield was not significantly different.

Optimum temperature for germination of urediniospores in vitro (18.4–20.9°C) was higher than for mature teliospores (14.6–18.4°C). Light inhibited germination of both types of spores. Teliospore germination was inhibited by wavelengths of 590–750 nm, but this was partially reversible under other light conditions. A reversible inhibition of basidiospore formation was also observed under shorter wavelengths.
Further studies on turnip yellow mosaic tymovirus isolates from an endemic Australian Cardamine
Authors: GUY P. L. , GIBBS A. J.
Published: April 2007

Native and introduced species of Cardamine and other brassicas were collected from various parts of south‐eastern Australia and tested for sap‐transmitted viruses. Isolates of turnip yellow mosaic virus (TYMV‐Cd) were obtained from a robust sward‐forming (SF) species, C. lilacina, that is an endemic species and restricted to the high glacial cirques of the Kosciusko alpine area. At two sites (Blue Lake and Club Lake) 22% of the plants were infected. An undescribed species of flightless pill beetle, Pedilophorus (Byrrhidae), was found on the C. lilacina SF plants. They preferred feeding on leaf discs infected with TYMV‐Cd rather than on virus‐free leaf discs and transmitted the virus for 48 h to seedlings of C. lilacina SF (2.5%) or Chinese cabbage (10%).

The pattern of distribution of TYMV‐Cd and its close association with Pedilophorus suggested that it is not a recent migrant to the area. The possible time of its arrival is discussed.

A carlavirus was isolated from up to 4% of three other native highland Cardamine species.
Studies on lettuce mosaic virus resistance in commercial lettuce cultivars
Authors: WALKEY D. G. A. , WARD C. M. , PHELPS KATHLEEN
Published: April 2007

The response to infection with lettuce mosaic virus (LMV) of 16 lettuce cultivars, known to possess the Momo gene for resistance to LMV, was studied in field trials over a 2‐year period. Some cultivars developed negligible mosaic symptoms following virus inoculation and had a low virus content as measured by ELISA, while others had more severe symptoms and a higher virus content. Resistant cultivars differed significantly in the effect of LMV upon yield and the correlation between cultivar rankings for yield depression and symptom severity was low.
Occurrence of the rare A2 mating type of Phytophthora infestans on imported Egyptian potatoes and the production of sexual progeny with A1 mating types from the UK
Authors: SHAW D. S. , FYFE A. M. , HIBBERD P. G. , ABDEL‐SATTAR M. A.
Published: April 2007

Phytophthora infestans from blighted potato tubers imported from Egypt and on sale to the public in North Wales were all of the A2 mating type which was thought, until recently, to be confined to Mexico, Zygotes from Welsh and Egyptian matings germinated readily; progeny were variable. The threat posed by a general spread of the A2 mating type is discussed.
A systemic pathway in the infection of oilseed rape plants by Leptosphaeria maculans
Authors: HAMMOND KIM E. , LEWIS B. G. , MUSA T. M.
Published: April 2007

In growth room regimes arranged to simulate field conditions which coincide with natural infection of oilseed rape by Leptosphaeria maculans, leaf inoculation resulted in systemic infection. After colonizing intercellular spaces in the spongy mesophyll of the lamina, the fungus reached a vascular strand and spread down the petiole mainly in xylem vessels or between cells of the xylem parenchyma and cortex, eventually invading and killing cells of the stem cortex and causing the stem canker symptom. The intercellular systemic phase of growth, which was biotrophic and virtually sytnptomless, occurred under a wide range of temperatures.
Some effects of canopy structure and microclimate on infection of tall and short wheats by Septoria nodorum
Authors: SCOTT P. R. , BENEDIKZ P. W. , ZONES H. G. , FORD M. A.
Published: April 2007

The results of three kinds of field experiment were consistent with the hypothesis that the canopies of taller wheat varieties generate a less favourable microclimate for development of S. nodorum from standard inoculum. (1) Measurements of photosynthetic area per unit volume of space occupied by canopies showed that taller varieties had lower canopy densities than shorter varieties. (2) Less disease developed in artificially thinned canopies of tall and short varieties. (3) Less disease developed in plots raised on mounds and more developed in plots sunk in trenches, relative to plots at ground level.

The results of three further kinds of field experiment were consistent with the hypothesis that reduced leaf surface wetness contributes to the tendency for taller varieties to be less infected by S. nodorum. (1) Continuous electrical measurement showed that leaf surface wetness (mainly dew) on two tall resistant varieties lasted for a shorter time than that on a short susceptible variety. (2) Instantaneous estimation of dew by weighing showed that less was deposited on taller and more resistant varieties than on shorter and more susceptible varieties. (3) For 10 sister lines from the same cross, selected only for their variation in height, there were correlations of duration of surface wetness with height (negative), amount of S. nodorum with height (negative), and amount of .V. nodorum with duration of surface wetness (positive). There was also genetic variation in surface wetness that was independent of height.

Nevertheless, a microclitnatic effect is thought to be only one of several mechanisms that contribute to the tendency for taller varieties to be more resistant. In addition, there is much genetic variation in resistance that is independent of height.
Cocoa quarantine: measures to prevent the spread of vascular‐streak dieback in planting material
Authors: PRIOR C.
Published: April 2007

Isolation of clonal cocoa material in screened shade houses for 6 months allows adequate opportunity for detecting vascular‐streak dieback caused by Oncobasidium theobromae and in Papua New Guinea a further period of 6 months in intermediate quarantine on an isolated island has been replaced by a similar period in screened houses at a quarantine station in the importing locality. Microscopic examination of transverse sections of budwood sticks and pod stalks provides a further very thorough precaution against disease transmission because hyphae of the pathogen are large and easily detected. Hyphae were found within the stalks and placentae of pods from diseased branches but seeds from these germinated normally and there was no evidence of seed transmission. Dipping rubbed seeds in 1 g/l propiconazole plus 5 g/l metalaxyl caused a small but statistically significant reduction in seedling stem height. However, root length and percentage germination were not affected and this prophylactic seed treatment may be useful in situations where quarantine authorities require additional precautions.
Relationships between establishment of Erysiphe cruciferarum and soluble amino‐acids in leaves of Brussels sprouts
Authors: RUDGARD S. A. , WHEELER B. E. J.
Published: April 2007

The ability of Erysiphe cruciferarum to establish infections on detached foliage and button leaves of two Fl cultivars of Brussels sprouts grown in the field was examined under standard conditions. Consistently more infections developed on Goldmine than on Ulysses. On foliage leaves of both cultivars the numbers of infections fluctuated from week to week but generally increased with time on samples taken from September to December. On Goldmine, more infections developed on the oldest foliage leaves than on those of intermediate position on the stem and only infections on the mature leaves sporulated well. The number of infections increased progressively on leaves further into the sprout buttons of both cultivars. Fungal establishment on foliage and button leaves of Goldmine was related to the amino‐acid content of comparable uninoculated leaves.
The development of Erysiphe cruciferarum on field‐grown Brussels sprouts and associated changes in soluble amino‐acids in foliage leaves
Authors: RUDGARD S. A. , WHEELER B. E. J.
Published: April 2007

Percentage leaf area diseased was assessed in two plantings of Brussels sprouts cv. Goldmine from June to October 1981. on marked leaves, enabling disease progress curves to be calculated for the crops and for individual leaves. Mean amounts of disease, corrected for loss of infections through leaf abscission, were compared with meteorological parameters by multiple regression analysis (MRA). Disease increase, especially on the upper leaf surface, was associated negatively with rainfall and positively with relative humidity. Temperature also contributed significantly to the regressions but its effects were not consistent. Disease, uncorrected for removals, was compared by MRA with changes in soluble amino‐N compounds in leaves, especially amino‐acids. The amounts of proline and alanine were positively associated with infection and those of glutamic acid, leucine and amides were negatively associated with infection.
Light and scanning electron microscope studies of leaf blotch of onion caused byCladosporium allii–cepae
Authors: HALL K. , KAVANAGH J. A.
Published: April 2007

The pre–penetration and post–penetration stages of infection byCladosporium allii–cepaeon onion foliage was examined on inoculated plants kept at 15° C and 80–90% r.h. The pathogen entered the leaf usually through stomata but occasionally by penetrating the cuticle. Invasion of the palisade and mesophyll tissues led to the formation of a leaf cavity after 7 days and after 30 days the pathogen sporulated on the leaf surface.
The use of potato tubers in pathogenicity studies of Armillaria isolates *
Authors: GREGORY S. C.
Published: April 2007

The pathogenicity to potato tubers of seven isolates, representing four species of Armillaria, was investigated to test the use of tubers for rapid pathogenicity screening. The pathogenicity of the isolates to young conifers was either known or was established in a preliminary trial. The tubers were presented to small woody inocula under conditions that allowed infection by rhizomorphs. In all experiments isolates classed as highly pathogenic to young conifers infected a higher proportion of tubers than did isolates of low pathogenicity. However, the magnitude of the differences between isolates varied between experiments and, in some instances, particularly with isolates of A. ostoyae, the failure to produce rhizomorphs led to unclear results. Although the technique described did not seem reliable enough for routine testing of field isolates, the experiments did reveal differences between isolates in the length of rhizomorph which became attached to the host surface. This was consistently greater in isolates of low pathogenicity than in those of high pathogenicity and may be of significance to field behaviour.
Effect of the polygalacturonase inhibitor from pea on the hydrolysis of pea cell walls by the endopolygalacturonase from Ascochyta pisi
Authors: TURNER J. G. , HOFFMAN R. M.
Published: April 2007

Exo–polygalacturonase (exo–PG) and endo–PG from Ascochyta pisi rapidly adsorbed to insoluble fragments of cell walls from pea leaflets as did the endo–PG inhibitor that was isolated from these organs. The wall fragments were hydrolysed by the exo– and endo–PG but the rates were, respectively, only 1–8 and 8% of the rate of hydrolysis of soluble polygalacturonic acid (PGA). Although the endo–PG inhibitor rapidly and completely inhibited the hydrolysis of soluble PGA by the endo–PG it had no effect on the rate of hydrolysis of pea cell wall fragments by this enzyme. Extracts of the intercellular fluid from pea leaflets contained only 4% of the inhibitor present in that organ and the remainder was presumably intracellular. These findings indicate that the endo–PG inhibitor may be less effective in vivo than was previously suspected.
A rapid bioassay for the determination of carbendazim residues in soil *
Authors: YARDEN O. , KATAN J. , AHARONSON N.
Published: April 2007

A simple and rapid bioassay for the direct determination of carbendazim residues in soil was developed. Pellets composed of mixtures of soil (200–500 mg) and agar were placed on an agar medium pre–inoculated with the test organism Penicillium digitatum. After cold pre–incubation followed by incubation at 27°C, the size of the inhibition zone was determined. The lowest detectable concentrations of carbendazim and thiabendazole in a sandy soil were 0.25 and 10 μg/g, respectively. The lowest detectable concentration was higher in heavy soils. In a study of carbendazim degradation in soil, chemical analysis and the pellet bioassay technique yielded similar results. This technique requires only small quantities of soil, without the need for soil extraction.