bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specificity, interaction and additivity in host‐pathogen systems
Authors: VANDERPLANK J. E. 
Published: April 2007

In the literature of plant pathology, unspecific interaction, as statisticians use the word, is commonly called ‘specificity’ or ‘race specificity’. Specificity, in the sense used by Flor, is confused with interaction, defined statistically. Admittedly, specificity in Flor's sense implies statistical interaction. But the converse is not true. Statistical interaction does not necessarily imply Flor's specificity.This confusion prompted me to inquire into the concepts of what seem to me to be the three major systems of host‐pathogen relations: additivity, interaction, and specificity. I suggest definitions, the definitions of additivity and interaction following standard statistical usage and the definition of specificity following Flor's sense. Further, I examine briefly tests to distinguish (unspecific) interaction from specificity, and additivity from interaction.Interaction, as the word is used by statisticians, arises from the variation in row differences from column to column or in column differences from row to row (Adams, 1955). Put differently, interaction is measured by the failure of effects to be additive (Snedecor, 1956).Additivity is the antithesis of interaction. There is no significant variation in row differences from column to column or in column differences from row to row.Specificity in a gene‐for‐gene system refers to complementary one‐for‐oneness. Flor's hypothesis reads: “for each gene conditioning resistance in the host there is a specific complementary gene conditioning pathogenicity in the parasite”. Flor's use of the word specific goes back to 1942 when his hypothesis was still embryonic; “The data in the present paper indicate that the range of pathogenicity of a physiologic race of Melampsora lini is determined by pathogenic factors specific for each resistance factor possessed by the host” (Flor, 1942).Specificity is a form of interaction. There is specific interaction, i.e. interaction with complementary one‐for‐oneness, and unspecific interaction, i.e. interaction without one‐for‐oneness.
Evaluation of antisera raised against Phytophthora fragariae for detecting the red core disease of strawberries by enzyme‐linked immunosorbent assay (ELISA)
Authors: MOHAN SUDESH B. 
Published: April 2007

Antiserum was raised against pooled mycelial suspensions from five isolates (designated Pf 1, Pf 2, Pf 3, Pf 10 and Pf 11) representing five physiologic races of Phytophthora fragariae. In enzyme‐linked immunosorbent assay (ELISA), this antiserum detected homologous soluble antigens at protein concentrations as low as 2 ng/ml.Fungal antigens could also be detected in extracts of strawberry plants infected with P. fragariae. Root extracts prepared from the alpine strawberry Fragaria vesca and F. ananassa cv. Cambridge Favourite infected with any of the five isolates studied produced strong reactions in ELISA. In F. vesca, ELISA‐positive material was detectable 6‐8 days after inoculation before macroscopic symptoms appeared. The cultivar Red Gauntlet, which is resistant to Pf 1, 2 and 3 but susceptible to Pf 10 and 11, reflected this differential response in ELISA; the absorbance produced by extracts of plants infected with virulent isolates was significantly higher than that obtained with the corresponding extracts of plants inoculated with a virulent isolates. The recently introduced cultivars Hapil, Ostara and Providence were found to be susceptible to all isolates in this study: the corresponding root extracts were also positive in ELISA.The antiserum also detected P cactorum infections. Nevertheless, the ELISA test described should prove valuable in screening certified strawberry stocks.
Studies on the inheritance of resistance to metalaxyl in Bremia lactucae and on the stability and fitness of field isolates
Authors: CRUTE I. R. , HARRISON JUDITH M. 
Published: April 2007

One hundred and eighty‐one sexual progeny isolates from three F1, one F2, five BC1 and one BC2 generations of crosses involving two metalaxyl‐resistant and two metalaxyl‐sensitive isolates of Bremia lactucae were assessed for response to metalaxyl. In most cases, isolates were also tested for virulence phenotype and sexual compatibility type. Isolates could be classified into three phenotypes (sensitive, resistant and intermediate) on the basis of their response to fungicide. Sensitive progeny isolates were similar to the sensitive parents and did not sporulate on lettuce seedlings grown in the presence of > 1.0 μg/ml metalaxyl. Resistant progeny isolates, in common with the resistant parents, sporulated as readily on lettuce seedlings grown in the presence of 100 μg/ml metalaxyl as on untreated seedlings. Progeny isolates which expressed an intermediate phenotype not observed in field samples were also recovered. This phenotype was more variable but isolates so classified were able to sporulate on seedlings grown in the presence of 100 μg/ml metalaxyl but exhibited a latent period (time from inoculation to appearance of sporulation) which was on average twice as long as that observed on seedlings grown in the absence of fungicide.Segregation patterns suggested that response to metalaxyl is controlled at a single locus exhibiting incomplete dominance but that the expression of response in the heterozygous condition may be affected by modifier genes. There was evidence that the metalaxyl‐resistant parental field isolates were heterokaryotic (possibly carrying nuclei homozygous and heterozygous at the locus controlling metalaxyl response). After 10‐30 asexual generations in the absence of fungicide, the response to metalaxyl of resistant field isolates began to approach that of an intermediate type. This phenomenon did not occur with a resistant sexual progeny isolate (presumed homokaryotic) and is additional evidence for the heterokaryosis of field isolates. The relative fitness of a range of isolates was examined by observing changes in the proportions of spores over three asexual generations after they were initially mixed in a 1:1 ratio with mutant isolates carrying a microscopically visible genetic marker (large lipid droplets). Most field isolates were more fit than the mutant isolates used, regardless of whether they were resistant or sensitive to metalaxyl, and there was no evidence that resistant isolates carried any fitness deficit in comparison with the sensitive isolates examined. In contrast, sexual progeny isolates (particularly from BC1 generations) were often less fit than the mutant isolates used, but there was no evidence that this was associated with response to fungicide. These findings are discussed in relation to the mode of action of metalaxyl and disease control strategy.
Field performance of Rendezvous, a wheat cultivar with resistance to eyespot (Pseudocercosporella herpotrichoides) derived from Aegilops ventricosa
Authors: HOLLINS T. W. , LOCKLEY K. D. , BLACKMAN J. A. , SCOTT P. R. , BINGHAM J. 
Published: April 2007

Rendezvous is a new cultivar of winter wheat with potent eyespot resistance derived from Aegilops ventricosa. In 11 field experiments conducted over 6 years with both natural and artificial inoculum, Rendezvous was significantly more resistant than other commercial wheat cultivars, many of which have resistance derived from Cappelle‐Desprez. It was also more resistant than its parent VPM 1, the donor of the potent eyespot resistance, suggesting that it possesses resistance genes from both Ae. ventricosa and Cappelle‐Desprez.In severe eyespot epidemics, Rendezvous lodged less and had a greater mean yield than the moderately resistant cultivar Norman. Treatment with fungicide reduced disease and increased yield in both cultivars, so that they were equal in yield. Rendezvous should not need routine fungicidal treatment for eyespot control, but under exceptional disease pressure may benefit from treatment.
Importance of the proportion of grassy weeds within legume crops in the perpetuation of Gaeumannomyces graminis var. tritici
Authors: COTTERILL P. J. , SIVASITHAMPARAM K. 
Published: April 2007

Various grass species susceptible to infection by Gaeumannomyces graminis var. tritici were mixed‐sown into a legume crop in order to assess their influence on density of inoculum and take‐all disease in a subsequent crop of wheat.In a pot experiment take‐all inoculum increased (P< 0.001) in all treatments containing a proportion (from 20 to 100%, in increments of 20%) of grass in subterranean clover. In a plot trial, most severe take‐all occurred in the 20% legume/80% grass stands and least in the 100% legume and 80% legume/20% grass stands. Total grain weight was highest (P<0.1) after the 100% legume stands. There was no difference in severity of take‐all after pure stands of medic, subterranean clover and lupin, but there was more severe take‐all after the grass‐infested medic stands than after those of subterranean clover (P< 0.1) or lupin (P < 0.05). No significant differences (P > 0.1) in yield occurred in wheat following any of the legumes or mixed stands.
Differences in the extent of fungal development, host cell necrosis and symptom expression during race‐cultivar interactions between Phaseolus vulgaris and Colletotrichum lindemuthianum
Authors: O'CONNELL R. J. , BAILEY J. A. 
Published: April 2007

The cellular reactions of excised hypocotyl segments of 31 cultivars of Phaseolus vulgaris to infection by two races of Colletotrichum lindemuthianum were surveyed. Consistent differences in the extent of fungal development and host cell necrosis were used to establish six infection categories.Extreme susceptibility (category 5) involved initial formation of infection vesicles in living epidermal cells and a prolonged period of intracellular biotrophic development prior to necrotrophic growth and production of spreading lesions. Extreme resistance (category 0) involved rapid death and browning of penetrated epidermal cells, without formation of infection vesicles or a detectable biotrophic phase. Fungal growth and host necrosis were limited to single epidermal cells. Intermediate reactions (categories 1 to 4) initially resembled category 5, but after a biotrophic phase of varying duration, infected cells and some adjacent uninfected cells died and became brown, and fungal growth ceased. Symptoms ranged from flecks (small groups of dead cells) to large areas of necrosis (limited lesions). Similar intermediate reactions also occurred in normally susceptible hypocotyls which were transferred from 17 to 25°C, or which retained cotyledons.The finding that resistance is expressed at different stages of infection is discussed in relation to the regulation of cultivar specificity.
Genetic variation in tolerance of host monoterpenes in a population of the ascomycete canker pathogen Crumenulopsis sororia
Authors: ENNOS R. A. , SWALES K. W. 
Published: April 2007

Twenty families of single‐ascospore isolates of the canker pathogen Crumenulopsis sororia were collected from eight trees of Pinus sylvestris in a native pinewood. Measurements were made of growth rate of each isolate in the presence and absence of a saturating atmosphere of the five principal monoterpenes of P. sylvestris cortical oleoresin (α‐pinene, β‐pinene, 3‐carene, β‐myrcene and limonene).All monoterpenes significantly reduced the mean linear growth rate of the C. sororia population. However, there was highly significant genetic variation among isolates in their tolerance of all five monoterpenes. The extent of genetic variation was greatest for β‐myrcene and limonene tolerance, and least for α‐pinene and 3‐carene tolerance. Significant positive correlations between tolerance of different monoterpenes were found, implying the presence of tolerance mechanisms common to a range of compounds.
Pathogenic variability amongst isolates of Crinipellis perniciosa from cocoa (Theobroma cacao)
Authors: WHEELER B. E. J. , MEPSTED R. 
Published: April 2007

Dry witches' brooms from cocoa were imported from various areas within Bolivia, Brazil, Colombia, Ecuador, Trinidad and Venezuela. Basidiocarps of Crinipellis perniciosa were induced to form on these brooms and seedlings of different types of cocoa were inoculated with basidiospores either on the hypocotyl or cotyledon bud. Host reactions were assessed mainly by recording stem base swelling and broom development at the cotyledon node (hypocotyl inoculations) or the extent of swelling and branching of shoots (cotyledon bud inoculations).Results from 30 experiments indicated considerable diversity amongst isolates in inducing disease symptoms, but suggested that two groups or populations of C. perniciosa exist on cultivated cocoa. One group (A), comprising isolates from Bolivia and Pichilingue (Ecuador) and most isolates tested from Colombia, induced severe symptoms on cocoa with Scavina 6 as one parent; the other group (B), comprising isolates from Brazil, Trinidad and Venezuela, did not. Within these groupings variants could be further distinguished by particular host reactions. Isolates from Ecuador, especially from the Oriente, a centre of diversity for Theobroma cacao, showed a range of pathogenicity comparable to that found amongst isolates from cultivated cocoa over a much wider area.
Growth rates of, and mycelial interactions between, isolates of Crinipellis perniciosa from cocoa
Authors: McGEARY F. M. , WHEELER B. E. J. 
Published: April 2007

Growth of 87 single‐basidiospore isolates of Crinipellis perniciosa, derived from witches' brooms on cocoa in 10 localities throughout South America and the Caribbean, was examined at 25°C on five agar media (Czapek‐Dox, prune extract, potato‐dextrose, V8 and carboxymethylcellulose). Interactions (designated intermingling or mutually antagonistic) between paired mycelia of 64 isolates were determined on V8 plates.Six somatic‐compatibility groups were identified comprising isolates from; (1) Pichilingue and Rio Palenque in Ecuador, Chigorodo and Manizales in Colombia; (2) Sucua (Ecuador); (3) Manaus (Brazil); (4) Ouro Preto (Brazil); (5) Castanhal (Brazil); (6) Trinidad and Tobago. This geographical separation of isolates was supported by results of the growth tests; growth of isolates within each compatibility group differed from other groups on at least one of the five media.Separation of isolates by these methods did not conflict with previous results from tests of pathogenicity and could be useful in selecting isolates for screening cocoa lines for resistance to C. perniciosa.
Quantitative histological studies of compatible and incompatible interactions between accessions of Macroptilium atropurpureum and Uromyces appendiculatus
Authors: OGLE H. J. , IRWIN J. A. G. , BRAY R. A. 
Published: April 2007

Quantitative histological studies of pre‐penetration, penetration and post‐penetration events were made for one compatible interaction and five interactions showing varying degrees of incompatibility between Uromyces appendiculatus and Macroptilium atropurpureum. Four histologically different resistant responses to infection were observed, CPI 91348 exhibited a response, characterized by significantly fewer pustules per unit area and a longer generation time than the susceptible cultivar Siratro. Significantly fewer urediniospores produced appressoria on 91348 than on Siratro. Resistance in CPI 84997 was associated with the development of large areas of necrotic tissue; 99.8% of colonies showed an indeterminant hypersensitive response. Colony areas for the above three host genotypes were not significantly different at 144 h after inoculation.The remaining lines developed varying degrees of chlorosis only. Colonies in CQ 1382 and (CPI 92643 grew only slowly, but were still growing 144 h after inoculation and, as with CPI 84997, this growth continued after necrotic tissue appeared (indeterminant hypersensitivity), In CQ 1398, colony growth ceased by 96 144 h after inoculation, coinciding with the appearance of necrotic tissue (determinant hypersensitivity).
Effects of treatments to perennial ryegrass on the development of Septoria spp. in a subsequent crop of winter wheat
Authors: JENKYN J F. , KING J. E. 
Published: April 2007

An experiment started in spring 1979 tested the effects of different treatments to perennial ryegrass, established as pure stands or undersown in spring wheat, on the severity of septoria diseases on the grass and in a following crop of winter wheat, sown in autumn 1980. Other plots were fallowed in 1979 and 1980 before sowing to winter wheat, also in autumn 1980. Septoria tritici was most severe in winter wheat after fallow and least severe in wheat that had been direct‐drilled after ryegrass. These effects were attributed to differences in amounts of available nitrogen, and consequent differences in crop growth, rather than to any differences in primary inoculum.Symptoms attributed to S. nodorum on the ryegrass were more common where the grass had been established under spring wheat than where it had been sown as a pure stand. They also tended to be more common where ryegrass had been inoculated with spores of S. nodorum than where it had been sprayed with captafol. Similar effects on symptoms attributed to Septoria spp. (mostly S. tritici) on the wheat were apparent in July. The results support the conclusion that the greater severity of septoria diseases that often occurs on wheat after grass than after non‐graminaceous breaks, is probably due in part to survival of the pathogens on grass and, in some circumstances, on debris remaining from a previous wheat crop. However, other factors are also likely to be involved.
Fungicide and nitrogen applications in relation to the improvement of disease control and yield in winter barley
Authors: JORDAN V. W. L. , STINCHCOMBE G. R. , HUTCHEON J. A. 
Published: April 2007

In crops of winter barley, cvs Igri and Halcyon, crop structure and intensity of foliar diseases were altered by delaying the main top dressing of nitrogen until mid‐April. A single application of fungicide then was sufficient to decrease substantially the severity of fungal disease and improve grain yield at harvest.Disease control and yield responses were greatest when fungicides were applied during a 3‐week period after the main nitrogen application in April. No additional yield benefits were obtained by making two fungicide applications at growth stage (GS) 31 and GS 39.
Control of Glomerella cingulata f.sp. camelliae with fungicides
Authors: COOK R. T. A. 
Published: April 2007

A critical test of fungicidal activity against the wound pathogen Glomerella cingulata f.sp. camelliae on camellias involved the application of a conidial suspension to scratches on detached leaves, treated with fungicide 24 h previously. In this test, prochloraz at 250–500 μg/ml a.i. in both EC and manganese WP formulations was highly effective, inhibiting leaf rotting by 90–100% compared with 55% or less in some tests with benomyl, chlorothalonil and captafol at 500–1000 μg/ml and captan at 1200 μg/ml. Prochloraz gave similar protection to leaves when applied to whole plants. Protection was less, especially on older leaves, when wounding and inoculating were delayed by 7 or more days after treatment. Prochloraz did not prevent all infection through comparatively large wounds, e.g. leaf scars, made on stems 24 h after treatment.Poor control of the disease in a nursery was not due to resistance of the pathogen to benomyl; in vitro tests failed to detect full resistance at this time. Under nursery conditions a statutory policy of destroying infected plants and spraying the remainder with prochloraz or prochloraz manganese (both at 500 μg/ml), alternating with benomyl (500 μg/ml) on a weekly basis apparently prevented spread of the disease to healthy plants.
Isolation and characterization of a potyvirus associated with bushy dwarf symptom in chickpea, Cicer arietinum, in India
Authors: ANJAIAH V. , REDDY D. V. R. , MANOHAR S. K. , NAIDU R. A. , NENE Y. L. , RATNA A. S. 
Published: April 2007

A potyvirus that induced stunting and a characteristic bushy appearance at the apical region, due to proliferation of terminal branches with narrowed, reduced and deformed leaflets, was isolated from chickpea in India. The virus was sap‐transmissible to 14 species of Chenopodiaceae, Leguminosae, Solanaceae and Malvaceae; Chenopodium amaranticolor was a good local lesion host. Virus particles, trapped by immunosorbent electron microscopy and stained with uranyl acetate, were 710 ×10 nm long. Purified virus preparations contained a single polypeptide species of 32,500 Da and one nucleic acid species of 3.1 · 106 Da. The virus was serologically related to soybean mosaic, azuki bean mosaic and peanut mottle viruses but not to clover yellow vein, pea seed‐borne mosaic and bean yellow mosaic viruses.On the basis of these properties, the virus was identified as a previously undescribed potyvirus in chickpea, for which the name chickpea bushy dwarf virus is proposed.
Histopathology of compatibility and incompatibility between oilseed rape and Albugo Candida
Authors: LIU Q. , RIMMER S. R. , SCARTH R. 
Published: April 2007

Cotyledons of one resistant and three susceptible rape lines/cultivars were inoculated with zoospores of Albugo Candida race 7. Samples of whole cotyledons were examined by differential interference contrast microscopy. The time course of the infection process was followed histologically. Germination of zoospore cysts occurred 2‐3 h after inoculation. Infection was initiated with germ‐tubes penetrating through stomata. Haustorium formation was first observed in the palisade mesophyll cells adjacent to the substomatal chambers 8 h after inoculation.Only after the establishment of the first haustorium did compatible and incompatible interactions begin to differentiate. In the resistant cultivar, most primary hyphae produced single haustoria. Necrosis of the invaded host cell was first observed 12 h after inoculation followed by cessation of fungal growth. The death of host cells was largely restricted to the penetration site; the adjacent non‐penetrated cells remained apparently unaffected. In the susceptible hosts, necrosis of infected cells occurred only infrequently, and hyphal growth continued unabated, resulting in mycelial ramification into the mesophyll. Numerous haustoria were produced.Histological studies showed that the earliest event distinguishing a compatible from an incompatible interaction occurred after formation of the first haustorium and that resistance was not manifested until the host mesophyll cell had come into contact with the first haustorium. The distinction between compatibility and incompatibility was substantiated by quantitative analysis of white rust development on both resistant and susceptible lines/cultivars.