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Artificial Inoculation (artificial + inoculation)

Distribution by Scientific Domains

Life Sciences	94%

Distribution within Life Sciences

Plant Pathology	50%
Plant Science	38%

Selected Abstracts

Age-dependent Grey Mould Susceptibility and Tissue-specific Defence Gene Activation of Grapevine Berry Skins after Infection by Botrytis cinerea

JOURNAL OF PHYTOPATHOLOGY, Issue 5 2007
M. Kretschmer
Abstract The correlation between the degree of maturity of grapevine berries and their susceptibility to infection by the grey mould fungus Botrytis cinerea was studied. Artificial inoculation with B. cinerea conidia of detached berries from cultivars Riesling and Pinot noir revealed an increasing susceptibility during the last weeks of berry ripening. Wound inoculation resulted in increased lesion formation when compared with inoculation of non-wounded berry skins. Lesion development after non-wounding inoculation was stimulated by the addition of nutrients. Riesling berries were more readily infected than Pinot noir berries, indicating that the Riesling berry skin is more easily colonized by the grey mould fungus. Analysis of defence gene activation in the berry skin tissue revealed increased transcript levels of phenylalanine ammonium lyase and stilbene synthase after inoculation with B. cinerea conidia, while mRNA abundance of osmotin was similar in inoculated and non-inoculated tissue. Our data indicate that properties of the grape berry skin, including its ability for infection-induced defence gene activation, are important for the outcome of grey mould infections. [source]

QTL analysis of resistance to Fusarium head blight in wheat using a ,Wangshuibai'-derived population

PLANT BREEDING, Issue 4 2005
M. Mardi
Abstract Fusarium head blight (FHB) is a devastating disease that reduces the yield, quality and economic value of wheat. For quantitative trait loci (QTL) analysis of resistance to FHB, F3 plants and F3:5 lines, derived from a ,Wangshuibai' (resistant)/,Seri82'(susceptible) cross, were spray inoculated during 2001 and 2002, respectively. Artificial inoculation was carried out under field conditions. Of 420 markers, 258 amplified fragment length polymorphism and 39 simple sequence repeat (SSR) markers were mapped and yielded 44 linkage groups covering a total genetic distance of 2554 cM. QTL analysis was based on the constructed linkage map and area under the disease progress curve. The analyses revealed a QTL in the map interval Xgwm533-Xs18/m12 on chromosome 3BS accounting for up to 17% of the phenotypic variation. In addition, a QTL was detected in the map interval Xgwm539-Xs15/m24 on chromosome 2DL explaining up to 11% of the phenotypic variation. The QTL alleles originated from ,Wangshuibai' and were tagged with SSR markers. Using these SSR markers would facilitate marker-assisted selection to improve FHB resistance in wheat. [source]

Biscogniauxia nummularia: pathogenic agent of a beech decline

FOREST PATHOLOGY, Issue 6 2004
G. Granata
Summary Decline of European beech (Fagus sylvatica) in Sicily and Calabria (Italy) was observed to be associated with the ascomycete Biscogniauxia nummularia. This fungus is naturally present in beech stands and to date has not been considered a primary pathogenic agent. Artificial inoculations were performed to assess its pathogenicity on beech and to determine if Sicilian and Calabrian isolates differ in virulence. Biscogniauxia nummularia played an evident primary pathogenic role under the environmental conditions studied. Virulence of the isolates was variable and did not depend neither on the geographic origin nor the environmental conditions at the sites where pathogenicity testing was performed. Résumé Le champignon ascomycète Biscogniauxia nummularia a été observé en association avec un dépérissement du hêtre européen (Fagus sylvatica) en Sicile et en Calabre (Italie). Ce champignon est naturellement présent dans les hêtraies et n'était pas considéré jusqu'à présent comme un agent pathogène primaire. Des inoculations artificielles ont été réalisées pour évaluer son pouvoir pathogène sur hêtre et déterminer si les isolats de Sicile et de Calabre présentent des différences de virulence. Dans les conditions de l'étude, B. nummularia prèsente clairement un rôle pathogène primaire. Les isolats ont une virulence variable, qui ne peut pas être reliée à l'origine géographique ou aux conditions environnementales des sites d'étude du pouvoir pathogène. Zusammenfassung Der Ascomycet Biscogniauxia nummularia wurde im Zusammenhang mit dem Absterben von Buchen (Fagus sylvatica) in Sizilien und Kalabrien (Italien) beobachtet. Der Pilz stellt eine natürliche Komponente von Buchenwäldern dar und wurde bis anhin nicht als ein primäres Pathogen eingestuft. Die Pathogenität von B. nummularia wurde mittels Infektionsversuchen an Buchen neu beurteilt, und die Virulenz von sizilianischen und kalabrischen Isolaten verglichen. Unter den getesteten Umweltbedingungen wirkte B. nummularia als primäres Pathogen. Die Virulenz der Isolate war unterschiedlich, hing aber weder von der Herkunft der Isolate noch den Umweltbedingungen an den Versuchsstandorten ab. [source]

Breeding for resistance: conventional breeding for Plum pox virus resistant apricots (Prunus armeniaca L.) in Greece

EPPO BULLETIN, Issue 2 2006
I. Karayiannis
A large apricot breeding programme has been conducted at NAGREF-Pomology Institute, Naoussa-Greece, for the control of sharka disease, since 1989. Ten apricot cultivars of North American origin: ,Stark Early Orange', ,Stella', ,NJA2', ,Sunglo', ,Veecot', ,Harlayne', ,Henderson', ,Goldrich', ,Orangered' and ,Early Blush', selected for their resistance to the highly virulent local strain of Plum pox virus (PPV)-M (Marcus), have been used as parents in crosses with quality cultivars, mainly with the local cv. Bebecou, from 1989 to 2003. Approximately 7000 hybrids have been created. Resistance to PPV was the main criterion of selection. Most hybrids have been subjected to artificial inoculation by PPV-M and examined for symptom expression for more than five years. Indexing to GF-305, as well as laboratory diagnostic tests, have been applied. The genetic analysis showed that: (1) 50% of the hybrids inherited resistance to PPV in the families where cvs. Stark Early Orange, NJA2, Sunglo, Veecot and Harlayne were used as a parent, and (2) 100% of the hybrids inherited resistance to PPV in the families where cv. Stella was one of the parents. Resistance to PPV appears to be under simple genetic control involving one gene locus. Promising apricot selections resistant to PPV-M have been released. [source]

Relationship between stump treatment coverage using the biological control product PG Suspension, and control of Heterobasidion annosum on Corsican pine, Pinus nigra ssp. laricio

FOREST PATHOLOGY, Issue 1 2008
K. V. Tubby
Summary The relationship between the proportion of the stump surface covered by the biological stump treatment agent PG Suspension, containing Phlebiopsis gigantea and its efficacy against the pathogen Heterobasidion annosum sensu stricto was studied during a first thinning of Corsican pine (Pinus nigra ssp. laricio) in Thetford Forest, UK. PG Suspension was manually applied to 100%, 75%, 50% or 0% of the surface of 150 stumps. Spores of H. annosum were inoculated onto 75 of the stumps, and the remaining stumps exposed to natural airborne spore deposition. The relationship between coverage and efficacy was found to be quantitative. Covering all the stump surface with PG Suspension completely excluded the pathogen, whereas stumps not treated with PG Suspension (the 0% treatment) became infected with H. annosum. Partial (75%) PG Suspension coverage resulted in the pathogen colonizing 40% of stumps following artificial inoculation with H. annosum, and just 7% of stumps exposed to ambient H. annosum spore infection. Decreasing levels of coverage allowed increasing areas of the stump surface to be colonized by H. annosum. Some small gaps in coverage were closed by lateral growth of P. gigantea, but it is recommended that operators aim for full stump coverage to give complete protection against H. annosum. [source]

A medium to enhance identification of Septoria musiva from poplar cankers

FOREST PATHOLOGY, Issue 3 2002
J. C. STANOSZ
A series of experiments was conducted to determine the relative tolerance in vitro of an isolate of Septoria musiva (a fungus that causes a severely damaging stem canker disease of poplars) for selected chemicals. Inhibition of diameter growth of this fungus on a V-8 vegetable juice-based medium with captan, chlorothalonil, iprodione, mancozeb and streptomycin sulphate at concentrations, respectively, of 50, 1, 10, 10, and 100 mg l,1 was relatively low compared to inhibition of eight other fungi cultured from cankers on poplars. In addition, the presence of captan stimulated profuse sporulation of the fungus. These properties assisted in the identification of S. musiva from cankers resulting from artificial inoculation of poplar branches in the field. Un milieu de culture pour aider à l'identification de Septoria musiva isolé de chancres sur peuplier Un isolat de Septoria musiva, champignon responsable de chancres de tronc sur peupliers, àété testéin vitro pour sa tolérance à un certain nombre de substances. L'inhibition de la croissance en diamètre a été déterminée sur milieu V8 additionné de captan, chlorothalonil, iprodione, mancozèbe et sulfate de streptomycine aux concentrations respectives de 50, 1, 10, 10, et 100 mg par litre; l'inhibition était relativement faible comparée à celle de huit autres champignons isolés de chancres de peuplier. La présence de captan stimulait la sporulation du champignon. Ces propriétés ont aidéà l'identification du S. musiva réisoléà partir de chancres obtenus au champ par inoculation artificielle de branches de peuplier. Ein Medium zur Verbesserung der Identifikation von Septoria musiva aus Pappelkrebsen Es wurde eine Serie von Experimenten zur Bestimmung der relativen Toleranz eines Septoria musiva Isolats (ein Erreger ausserordentlich schädlicher Stammkrebse an Pappeln) gegenüber ausgewählten Chemikalien durchgeführt. Das Wachstums des Pilzes auf einem auf V-8 Gemüsesaft basierenden Medium mit 50 mg l,1 Captan, 1 mg l,1 Chlorothalonil, 10 mg l,1 Iprodion, 10 mg l,1 Mancozeb und 100 mg l,1 Streptomycinsulfat wurde im Vergleich zum Wachstum von acht anderen Pilzarten, die ebenfalls aus Pappelkrebsen isoliert wurden, nur schwach gehemmt. Zudem regte Captan den Pilz zu intensiver Sporulation an. Als hilfreich erwiesen sich diese Eigenschaften in Feldversuchen bei der Identifikation von S. musiva aus Krebsen, die sich nach künstlicher Inokulation von Pappelzweigen entwickelten. [source]

Lesion development in stems of rough- and smooth-barked Eucalyptus nitens following artificial inoculations with canker fungi

FOREST PATHOLOGY, Issue 3 2001
Z. Q. Yuan
A study of lesion development in stems of Eucalyptus nitens following artificial inoculations with canker fungi was carried out on 16-year-old plantation trees. In a first trial cambium bark wounds on smooth- and rough-barked trees were inoculated with the mycelium of nine species of canker fungi, including Endothia gyrosa. In a second trial spores or mycelium of E. gyrosa were applied directly onto undamaged or superficially wounded bark surfaces. Infection subsequent to artificial inoculation via wounding (whatever the wounding technique or type of inoculum) resulted in significantly larger external lesions (mean lesion area up to 35.6 cm2 20 months after inoculation) on smooth bark compared with those on rough bark (up to 19.0 cm2). Microscopic studies of infected rough and smooth bark suggest that, once smooth bark is compromised by wounding and artificial inoculation, the particular anatomical structure of smooth bark may offer less mechanical resistance to post-penetration hyphal spread in comparison with rough bark. It is suggested that at a pre-penetration stage under natural conditions spores of E. gyrosa more easily infect rough bark via cracks associated with this type of bark but not present in smooth bark. Développement des lésions sur les troncs d'Eucalyptus nitens àécorce lisse ou rugueuse, après inoculation par des champignons agents de chancre L'étude a été conduite en plantation sur des arbres de 16 ans. Dans un premier essai, des blessures de l'écorce jusqu'au cambium sur des arbres àécorce lisse ou rugueuse, ont été inoculées avec le mycélium de 9 espèces de champignons agents de chancre, dont Endothia gyrosa. Dans un deuxième essai, des spores ou du mycélium de E. gyrosa ont été appliqués directement sur l'écorce intacte ou blessée seulement superficiellement. Quel que soit la technique d'inoculation ou le type d'inoculum, l'infection a été plus importante extérieurement (surface moyenne jusqu'à 35,6 cm2 après 20 mois) chez les écorces lisses que chez les rugueuses (jusqu'à 19,0 cm2). L'étude microscopique des écorces infectées suggérait qu'à condition que l'écorce lisse soit impliquée dans la blessure, sa structure anatomique particulière offre moins de résistance mécanique à la post-pénétration mycélienne que l'écorce rugueuse. Il est suggéré qu'au stade de la pré-pénétration en conditions naturelles, les spores de E. gyrosa infectent plus facilement l'écorce rugueuse à la faveur des fissures qui sont présentes chez ce type d'écorce mais absentes chez les écorces lisses. Entwicklung von Läsionen am Stamm von rauh- und glattrindigen Individuen von Eucalyptus nitens nach künstlicher Inokulation mit krebserregenden Pilzen Es wurde die Entwicklung von Läsionen an Stämmen 16jähriger Eucalyptus nitens -Pflanzungen nach künstlicher Inokulation mit Krebserregern untersucht. In einem ersten Versuch wurden an rauh- und glattrindigen Bäumen Rindenwunden, die bis zum Kambium reichten, mit Myzel von neun Arten krebserregender Pilze, einschliesslich Endothia gyrosa, beimpft. In einem zweiten Versuch wurden Sporen oder Myzel von E. gyrosa direkt auf unverletzte oder nur oberflächlich verletzte Rinde aufgebracht. Künstliche Inokulation von Wunden (unabhängig von der Methode der künstlichen Verwundung oder der Art des Inokulums) führte zu signifikant grösseren, äusseren Wunden auf glatter (durchschnittliche Läsionsfläche 35.6 cm2 20 Monate nach Inokulation) als auf rauher Rinde (bis 19.0 cm2). Mikroskopische Untersuchungen zeigten, dass glatte Rinde gegen die Ausbreitung von Pilzhyphen mechanisch weniger resistent ist als rauhe Rinde. Unter natürlichen Bedingungen dürften dagegen Sporen von E. gyrosa Bäume mit rauher Rinde leichter durch vorhandene Rindenrisse infizieren, die bei glatter Rinde fehlen. [source]

Yield Responses of Barley to Leaf Stripe (Pyrenophora graminea) under Experimental Conditions in Southern Syria

JOURNAL OF PHYTOPATHOLOGY, Issue 8-9 2004
M. I. E. Arabi
Abstract The seed-borne pathogen, Pyrenophora graminea is the causal agent of barley leaf stripe disease. Field trials were undertaken to investigate the impact of leaf stripe on barley yield in two growing seasons in Southern Syria, by comparing plots with and without artificial inoculation. Ten barley cultivars originating from widely dispersed areas were used. The overall response to leaf stripe differed with the differences in susceptibility levels of the cultivars. Grain yield, the number of tillers, kernel weight and plant biomass decreased as disease severity increased. Diseased plants had fewer tillers, and as a consequence a reduced grain yield per plant. High yield losses resulted from leaf stripe in susceptible cultivars in Arrivate, Furat 1, WI2291 and Arabi Abiad with 44%, 50%, 73% and 92%, respectively. The cultivar Banteng had the best level of resistance to the disease, and is a candidate donor for resistance in future breeding programmes. As leaf stripe can dramatically reduce barley yields under favourable conditions, the disease should be considered by crop improvement programmes in Mediterranean and similar environments. [source]

Scanning electron microscopy applied to seed-borne fungi examination

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 7 2009
Marcelo De Carvalho Alves
Abstract The aim of this study was to test the standard scanning electron microscopy (SEM) as a potential alternative to study seed-borne fungi in seeds, by two different conditions of blotter test and water restriction treatment. In the blotter test, seeds were subjected to conditions that enabled pathogen growth and expression, whereas the water restriction method consisted in preventing seed germination during the incubation period, resulting in the artificial inoculation of fungi. In the first condition, seeds of common bean (Phaseolus vulgaris L.), maize (Zea mays L.), and cotton (Gossypium hirsutum L.) were submitted to the standard blotter test and then prepared and observed with SEM. In the second condition, seeds of cotton (G. hirsutum), soybean (Glycine max L.), and common bean (P. vulgaris L.) were, respectively, inoculated with Colletotrichum gossypii var. cephalosporioides, Colletotrichum truncatum, and Colletotrichum lindemuthianum by the water restriction technique, followed by preparation and observation with SEM. The standard SEM methodology was adopted to prepare the specimens. Considering the seeds submitted to the blotter test, it was possible to identify Fusarium sp. on maize, C. gossypii var. cephalosporioides, and Fusarium oxysporum on cotton, Aspergillus flavus, Penicillium sp., Rhizopus sp., and Mucor sp. on common bean. Structures of C. gossypii var. cephalosporioides, C. truncatum, and C. lindemuthianum were observed in the surface of inoculated seeds. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source]

Quantitative-genetic analysis of leaf-rust resistance in seedling and adult-plant stages of inbred lines and their testcrosses in winter rye

PLANT BREEDING, Issue 6 2002
T. Miedaner
Abstract Leaf rust is the most frequent leaf disease of winter rye in Germany. All widely grown population and hybrid varieties are susceptible. This study was undertaken to estimate quantitative-genetic parameters of leaf-rust resistance in self-fertile breeding materials with introgressed foreign leaf-rust resistances and to analyze the relative importance of seedling and adult-plant resistance. Forty-four inbred lines and their corresponding testcrosses with a highly susceptible tester line were grown in a field in four different environments (location-year combinations) with artificial inoculation. Plots were separated by a nonhost to promote autoinfections and minimize interplot interference. Leaf-rust severity was rated on three leaf insertions at three dates. The testcrosses showed a considerably higher disease severity than the lines. High correlations (r , 0.9, P = 0.01) existed among the leaf insertions and the rating dates. Large genotypic variation for resistance was found in both the inbred and testcross populations. Genotype-environment interaction and error variances were of minor importance, thus high entry-mean heritabilities were achieved. A tight correlation between the inbreds and their corresponding testcrosses was found (r = 0.88, P = 0.01). Heterosis for resistance was significant (P = 0.05), but not very important. In a seedling test with 20,30 single-pustule isolates, 34 out of 44 inbreds reacted race-specifically. From the remaining inbred lines, three were medium and seven highly susceptible. In a further greenhouse test with 16 inbreds, seven were susceptible and five were resistant in both seedling and adult-plant stages. The remaining four lines had adult-plant resistance. In conclusion, race-specific leaf-rust resistance can be selected among inbred lines per se. Lines should also be tested in the adult-plant stage. [source]

Components of genetic variation for resistance of strawberry to Phytophthora cactorum estimated using segregating seedling populations and their parent genotypes

PLANT PATHOLOGY, Issue 2 2008
D. V. Shaw
Strawberry (Fragaria × ananassa) seedlings from 50 bi-parental crosses among 20 elite genotypes were evaluated for resistance to Phytophthora cactorum after artificial inoculation. Plots of seedlings or runner plants were rated using a disease severity score and the percentage of stunted plants per plot. The distribution of cross means for percentages of plants with stunting was highly skewed; 79% of the inoculated seedlings showed some level of stunting compared to non-inoculated control seedlings, and all but one of the crosses had 50% or more stunted plants. Disease severity scores for the bi-parental crosses were normally distributed and expressed a range of variation not reflected by the percentage of visibly stunted plants. Factorial analysis based on seedling plot means demonstrated significant additive genetic variance for the disease severity score, and the additive genetic variance was 1·9 times greater than the estimated dominance variance. The cross-mean heritability was for the severity score. Estimates of the additive genetic variance component using the covariance of severity scores obtained from the seedling analysis and with severity scores for their parents evaluated in a commercial environment were similar, and 0·30, respectively. Most of the selection response obtained through genotypic selection would thus be transferred to segregating offspring. [source]

Eradication of Plasmodiophora brassicae during composting of wastes

PLANT PATHOLOGY, Issue 4 2006
L. Fayolle
Survival of infectious inoculum of the clubroot pathogen Plasmodiophora brassicae was assessed following bench-scale flask composting experiments and large-scale composting procedures. Clubroot-affected material was provided by artificial inoculation of Chinese cabbage or naturally infected Brussels sprout and cabbage roots. Both sets of diseased material were used in flask experiments, and the latter in large-scale windrow and aerated tunnel experiments. Municipal green wastes, onion waste and spent mushroom compost were evaluated in flask experiments with varying temperature, aeration and moisture conditions. Green wastes were used in larger-scale composts. Within the limits of a Chinese cabbage seedling bioassay, both temperature and moisture content were critical for eradication of P. brassicae spores extracted from composted clubroot-affected residues. Incubation in compost at 50°C for 7 days or 1 day at 60°C with high moisture levels (= ,5 kPa matric potential or 60% w/w moisture content) eradicated inoculum from artificially inoculated Chinese cabbage roots. In large-scale windrows and aerated tunnels, the pathogen was eradicated from naturally infected brassica wastes after 6,7 days at 54,73°C. [source]

Bacterial leaf blight of strawberry (Fragaria (x) ananassa) caused by a pathovar of Xanthomonas arboricola, not similar to Xanthomonas fragariae Kennedy & King.

PLANT PATHOLOGY, Issue 6 2001
Description of the causal organism as Xanthomonas arboricola pv. fragariae (pv. nov., comb. nov.)
A new bacterial disease of strawberry is described. This disease, called bacterial leaf blight of strawberry, is characterized by dry, brown necrotic leaf spots and large brown V-shaped lesions along the leaf margin, midrib and major veins. Symptoms are different from angular leaf spot of strawberry caused by the bacterium Xanthomonas fragariae. Strains of the bacterial leaf blight pathogen were characterized in a polyphasic approach by biochemical tests, fatty acid analysis, protein electrophoresis, serology, PCR, pigment analysis, ice-nucleation activity, AFLP analysis, DNA:DNA hybridization, pathogenicity and host range tests, and compared with a number of reference strains of X. fragariae and other Xanthomonas species. Bacterial leaf blight strains formed a homogeneous group in all tests, completely different from X. fragariae. They were the only strains causing leaf blight of strawberry upon artificial inoculation into strawberry. Fatty acid and protein electrophoretic analysis showed that the strains belong to the phenon X. campestris (sensu latu, including pathovars now classified as belonging to X. arboricola). AFLP analysis and DNA:DNA hybridization further clarified their taxonomic position as belonging to X. arboricola. The name X. arboricola pv. fragariae is proposed for the bacterium causing leaf blight of strawberry with strain PD2780 (LMG 19145) as pathovar type strain. Criteria for routine identification are given and the taxonomic status is discussed. [source]

Hand position on the bunch and source,sink ratio influence the banana fruit susceptibility to crown rot disease

ANNALS OF APPLIED BIOLOGY, Issue 2 2010
L. Lassois
The postharvest development of crown rot of bananas depends notably on the fruit susceptibility to this disease at harvest. It has been shown that fruit susceptibility to crown rot is variable and it was suggested that this depends on environmental preharvest factors. However, little is known about the preharvest factors influencing this susceptibility. The aim of this work was to evaluate the extent to which fruit filling characteristics during growth and the fruit development stage influence the banana susceptibility to crown rot. This involved evaluating the influence of (a) the fruit position at different levels of the banana bunch (hands) and (b) changing the source,sink ratio (So,Si ratio), on the fruit susceptibility to crown rot. The fruit susceptibility was determined by measuring the internal necrotic surface (INS) after artificial inoculation of Colletotrichum musae. A linear correlation (r = ,0.95) was found between the hand position on the bunch and the INS. The So,Si ratio was found to influence the pomological characteristics of the fruits and their susceptibility to crown rot. Fruits of bunches from which six hands were removed (two hands remaining on the bunch) proved to be significantly less susceptible to crown rot (INS = 138.3 mm 2) than those from bunches with eight hands (INS = 237.9 mm 2). The banana susceptibility to crown rot is thus likely to be influenced by the fruit development stage and filling characteristics. The present results highlight the importance of standardising hand sampling on a bunch when testing fruit susceptibility to crown rot. They also show that hand removal in the field has advantages in the context of integrated pest management, making it possible to reduce fruit susceptibility to crown rot while increasing fruit size. [source]

Finnish Cronartium ribicola does not infect alternate hosts of Cronartium flaccidum

FOREST PATHOLOGY, Issue 4 2006
J. Kaitera
Summary Susceptibility of the main alternate hosts of Cronartium flaccidum, Vincetoxicum spp. and Melampyrum spp., to C. ribicola was investigated by artificial inoculations on detached leaves in the laboratory and on whole plants in the greenhouse. Neither uredinia nor telia developed on the leaves of either Vincetoxicum hirundinaria, Vincetoxicum nigrum, Melampyrum sylvaticum, Melampyrum pratense, Melampyrum nemorosum, Melampyrum arvense, Melampyrum cristatum or Melampyrum polonicum following inoculation by the 26 aeciospore sources collected from Pinus strobus, Pinus monticola, Pinus flexilis and Pinus peuce in 2000,2003. The results suggest that Finnish C. ribicola does not infect the main alternate hosts of C. flaccidum. Cronartium ribicola and C. flaccidum can thus be identified reliably by inoculations on their main alternate hosts. Résumé La sensibilitéàCronartium ribicola des principaux hôtes alternants de C. flaccidum, au sein des genres Vincetoxicum et Melampyrum, a étéétudiée par inoculations artificielles sur feuilles détachées au laboratoire et sur plantes entières en serre. Aucune formation d'urédinie ou de télie n'a été observée sur feuilles de Vincetoxicum hirundinaria, V. nigrum, Melampyrum sylvaticum, M. pratense, M. nemorosum, M. arvense, M. cristatum ou M. polonicum après inoculation par 26 sources d'éciospores récoltées sur Pinus strobus, P. monticola, P. flexilis et P. peuce en 2000,2003. Les résultats suggèrent que C. ribicola ne peut infecter les principaux hôtes alternants de C. flaccidum en Finlande. Cronartium ribicola et C. flaccidum peuvent donc être identifiés de façon fiable par inoculations de leurs principaux hôtes alternants. Zusammenfassung Die Anfälligkeit der wichtigsten Dikaryontenwirte von Cronartium flaccidum, Vincetoxicum spp. und Melampyrum spp. auf C. ribicola wurden mit künstlichen Inokulationen auf abgetrennten Blättern im Labor und auf ganzen Pflanzen im Gewächshaus untersucht. Es entwickelten sich weder Uredo- noch Teleutosporenlager auf den Blättern von Vincetoxicum hirundinaria, V. nigrum, Melampyrum sylvaticum, M. pratense, M. nemorosum, M. arvense, M. cristatum oder M. polonicum nach einer Inokulation mit 26 Aecidiosporen-Herkünften, die 2000,2003 von Pinus strobus, P. monticola, P. flexilis und P. peuce gesammelt wurden. Aus diesen Ergebnissen lässt sich schliessen, dass finnische C. ribicola die hauptsächlichen Dikaryontenwirte von C. flaccidum nicht infizieren. Somit können C. ribicola und C. flaccidum durch Inokulation auf ihre Dikaryontenwirte bestimmt werden. [source]

Lesion development in stems of rough- and smooth-barked Eucalyptus nitens following artificial inoculations with canker fungi

Erysiphe trifolii, a newly recognized powdery mildew pathogen of pea

PLANT PATHOLOGY, Issue 4 2010
R. N. Attanayake
Diversity of powdery mildew pathogens infecting pea (Pisum sativum) in the US Pacific Northwest was investigated using both molecular and morphological techniques. Phylogenetic analyses based on rDNA ITS sequences, in combination with assessment of morphological characters, defined two groups of powdery mildews infecting pea. Group I (five field samples and three glasshouse samples) had ITS sequences 99% similar to those of Erysiphe pisi in GenBank and exhibited simple, mycelioid type of chasmothecial appendages typical of E. pisi. Erysiphe pisi is normally considered as the powdery mildew pathogen of pea. Group II (four glasshouse samples and two field samples) had ITS sequences 99% similar to those of E. trifolii and produced chasmothecia with dichotomously branched appendages similar to those of E. trifolii. There are fourteen nucleotide differences in the ITS region between the two groups. The correlation of rDNA ITS sequences with teleomorphic features for each of the two groups confirms their identity. Repeated samplings and artificial inoculations indicate that both E. pisi and E. trifolii infect pea in the US Pacific Northwest. Erysiphe trifolii is not previously known as a pathogen of pea. The existence of two distinct powdery mildew species infecting pea in both glasshouse and field environments may interfere with the powdery mildew-resistance breeding programmes, and possibly explains putative instances of breakdown of resistance in previously resistant pea breeding lines. [source]

Modelling the effect of cuticular crack surface area and inoculum density on the probability of nectarine fruit infection by Monilinia laxa

PLANT PATHOLOGY, Issue 6 2009
C. Gibert
The effects of cuticular crack surface area and inoculum density on the infection of nectarine fruits by conidia of Monilinia laxa were studied using artificial inoculations with conidial suspensions and dry airborne conidia during the 2004 and 2005 seasons, respectively. Additionally, the effect of ambient humidity on fruit infection was evaluated in the 2005 experiment. An exploratory analysis indicated that (i) ambient humidity did not significantly explain the observed variability of data, but that (ii) the incidence of fruit infection increased both with increasing inoculum density and increasing surface area of cuticular cracks. The product of these two variables represented the inoculum dose in the cracks, and was used as a predictor of fruit infection in the model. Natural infection in the orchard was observed to increase throughout the season in both 2004 and 2005. The relationship between the probability of fruit infection by M. laxa and the artificially inoculated dose in the cuticular cracks was well described by a logistic regression model once natural inoculum density was taken into account (pseudo R2 = 65%). This function could be helpful for estimating the risk of fruit infection at harvest based on fruit size and natural inoculum density. [source]