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Partial Resistance (partial + resistance)

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Life Sciences	87%
Medical Sciences	12%

Distribution within Life Sciences

Plant Science	57%
Plant Pathology	18%
Entomology	9%
3 Other Subdomains	16%

Selected Abstracts

Development of Greenhouse Inoculation Procedures for Evaluation of Partial Resistance to Cercospora zeae-maydis in Maize Inbreds

JOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2005
G. Asea
Abstract Greenhouse experiments were conducted to determine the effects of inoculation methods on incubation period, lesion length, percentage leaf area affected and sporulation of Cercospora zeae-maydis on young maize (Zea mays L.) plants inoculated at V3 growth stage. Seedling plants were inoculated by four methods: (i) application of conidial suspension while puncturing the leaves within the whorl several times, (ii) spraying conidial suspension on leaves, (iii) placing colonized agar into lateral slits in leaves and (iv) placing colonized agar into whorls. Analysis of variance revealed a significant effect of genotype and inoculation method on several components of resistance and overall disease severity. Application of conidial suspension while puncturing the whorl was found to be the least laborious method, and it produced characteristic symptoms of gray leaf spot. Consistent trends were observed in classification of inbreds to resistant, susceptible and intermediate classes. Increasing the duration of exposure to high humidity by placing plastic bags over plants for 5 days significantly increased disease severity (P , 0.001). Cercospora zeae-maydis produced conidia in all the lesions examined. Spore production was generally most abundant in lesions on susceptible inbreds that displayed necrotic lesion types (LT) and least abundant in lesions on resistant inbreds that were characterized by chlorotic and fleck LTs. The results demonstrated that inoculations in the greenhouse can provide an indication of inbred responses to C. zeae-maydis and may be useful in evaluating resistance and in studies of host,pathogen interactions. [source]

Isolate specificity of quantitative trait loci for partial resistance of barley to Puccinia hordei confirmed in mapping populations and near-isogenic lines

NEW PHYTOLOGIST, Issue 3 2008
Thierry C. Marcel
Summary ,,Partial resistance is considered race-nonspecific and durable, consistent with the concept of ,horizontal' resistance. However, detailed observations of partial resistance to leaf rust (Puccinia hordei) in barley (Hordeum vulgare) revealed small cultivar × isolate interactions, suggesting a minor-gene-for-minor-gene interaction model, similar to so-called ,vertical' resistance. ,,Three consistent quantitative trait loci (QTLs), labelled Rphq2, Rphq3 and Rphq4, that were detected in the cross susceptible L94 × partially resistant Vada have been incorporated into the L94 background to obtain near-isogenic lines (NILs). Three isolates were used to map QTLs on seedlings of the L94 × Vada population and to evaluate the effect of each QTL on adult plants of the respective NILs under field conditions. ,,Rphq2 had a strong effect in seedlings but almost no effect in adult plants, while Rphq3 was effective in seedlings and in adult plants against all three isolates. However, Rphq4 was effective in seedlings and in adult plants against two isolates but ineffective in both development stages against the third, demonstrating a clear and reproducible isolate-specific effect. The resistance governed by the three QTLs was not associated with a hypersensitive reaction. ,,Those results confirm the minor-gene-for-minor-gene model suggesting specific interactions between QTLs for partial resistance and P. hordei isolates. [source]

Analysis by DC,EPG of the resistance to Bemisia tabaci on an Mi -tomato line

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2001
Y.X. Jiang
Abstract The tomato Mi gene confers resistance to nematodes, Meloidogyne spp., and to the potato aphid, Macrosiphum euphorbiae (Thomas). Previous greenhouse choice assays with Bemisia tabaci (Gennadius) showed that tomato commercial varieties carrying this gene had significantly lower values of host suitability and whitefly reproduction than varieties lacking Mi. This indicated that Mi, or another gene in its region, could regulate partial resistance. In order to characterise this resistance, probing and feeding behaviour of Bemisia tabaci B-biotype was studied with DC Electrical Penetration Graph (EPG) technique on the near-isogenic tomato lines Moneymaker (without Mi) and Motelle (carrying Mi). Significant differences (P < 0.05) between tomato lines were found in EPG parameters related to epidermis and/or mesophyll tissues. On Motelle, a lower percentage of whiteflies achieved phloem phase and they made more probes before attaining first phloem phase, had a higher ratio (number of probes before first phloem phase)/(total number of probes), had a longer total duration of non-probing time, and a longer time before making the first intracellular puncture and before making the first phloem phase. In contrast, most of the parameters related to phloem phase were found not to differ significantly between these near-isogenic lines. The behavioural data strongly suggest that the partial resistance in the variety Motelle is due to factors in the epidermis and/or mesophyll that inhibit the whiteflies from reaching phloem sieve elements. However, once the stylets reach a sieve element, whitefly behaviour did not differ between the two varieties. Thus, phloem sap of the two varieties appears to be equally acceptable to the whiteflies. Further studies are necessary to provide a better understanding of these mechanisms of resistance to whiteflies in tomatoes. [source]

A review of research to address carrot fly (Psila rosae) control in the UK,

EPPO BULLETIN, Issue 2 2009
R. Collier
Carrot fly (Psila rosae) is a serious pest of umbelliferous crops such as carrot, parsnip, celery and parsley. Carrot fly has been studied in the UK for more than 60 years. Whilst some of these studies have been focused on insecticides, others have demonstrated the potential for non-insecticidal methods of control that might contribute to an integrated pest management strategy. These include rotation and spatial separation of susceptible crops; carrot varieties with partial resistance to carrot fly; and crop management strategies to avoid oviposition or the development of severe damage. This paper outlines some of the approaches that have been taken and indicates how these are, or might be, used in practice. [source]

Mice transgenic for exon 1 of the Huntington's disease gene display reduced striatal sensitivity to neurotoxicity induced by dopamine and 6-hydroxydopamine

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2001
Åsa Petersén
Abstract Huntington's disease is an autosomal dominant hereditary neurodegenerative disorder characterized by severe striatal cell loss. Dopamine (DA) has been suggested to play a role in the pathogenesis of the disease. We have previously reported that transgenic mice expressing exon 1 of the human Huntington gene (R6 lines) are resistant to quinolinic acid-induced striatal toxicity. In this study we show that with increasing age, R6/1 and R6/2 mice develop partial resistance to DA- and 6-hydroxydopamine-mediated toxicity in the striatum. Using electron microscopy, we found that the resistance is localized to the cell bodies and not to the neuropil. The reduction of dopamine and cAMP regulated phosphoprotein of a molecular weight of 32 kDa (DARPP-32) in R6/2 mice does not provide the resistance, as DA-induced striatal lesions are not reduced in size in DARPP-32 knockout mice. Neither DA receptor antagonists nor a N -methyl- d -aspartate (NMDA) receptor blocker reduce the size of DA-induced striatal lesions, suggesting that DA toxicity is not dependent upon DA- or NMDA receptor-mediated pathways. Moreover, superoxide dismutase-1 overexpression, monoamine oxidase inhibition and the treatment with the free radical scavenging spin-trap agent phenyl-butyl-tert-nitrone (PBN) also did not block DA toxicity. Levels of the antioxidant molecules, glutathione and ascorbate were not increased in R6/1 mice. Because damage to striatal neurons following intrastriatal injection of 6-hydroxydopamine was also reduced in R6 mice, a yet-to-be identified antioxidant mechanism may provide neuroprotection in these animals. We conclude that striatal neurons of R6 mice develop resistance to DA-induced toxicity with age. [source]

First hybrid plane trees to show resistance against canker stain (Ceratocystis fimbriata f. sp. platani)

FOREST PATHOLOGY, Issue 5 2004
A. Vigouroux
Summary Canker stain, caused by the ascomycete Ceratocystis fimbriata f. sp. platani, is a major threat to plane trees in Europe. The American plane tree (Platanus occidentalis) carries some genetic resistance, but this species is not adapted to the climatic conditions in Europe. Therefore, hybrids between susceptible oriental plane trees (Platanus orientalis) and resistant P. occidendalis were screened for disease resistance in France. Among 960 hybrids, we found 18 individuals which survived two successive inoculations. These putatively resistant trees were cut back and, after 18 months, on each tree 12 of the newly produced shoots as well as two roots, were inoculated again. From these trees, only one showed complete and another one partial resistance. This selection process resulting in the resistant clone ,Vallis clausa' is described in detail. Résumé La maladie du chancre coloré provoquée par l'ascomycète Ceratocystis fimbriata f. sp. platani, constitue une menace majeure pour le platane en Europe. Le platane américain (Platanus occidentalis) recèle une résistance génétique mais est très mal acclimaté aux conditions de milieu de l'Europe. Des hybrides entre le platane d'orient (Platanus orientalis) et des clones résistants de P. occidentalis ont donc été sélectionnés pour la résistance au chancre. Parmi les 960 hybrides, 18 individus ont survécu à deux inoculations successives sur le tronc. Rabattus, ces arbres, après 18 mois, ont été inoculés sur 12 des rejets produits par arbre, ainsi que sur deux de leurs racines. De ces arbres, seul un sujet a montré une résistance totale aux deux niveaux, un autre arbre montrant une résistance un peu moins complète. Zusammenfassung Der Platanenkrebs, verursacht durch den Ascomyceten Ceratocystis fimbriata f.sp. platani ist eine grosse Bedrohung für die Platanen in Europa. Die Amerikanische Platane (Platanus occidentalis) verfügt über eine gewisse Resistenz, aber diese Baumart ist nicht an die klimatischen Bedingungen in Europa angepasst. Deshalb wurden Hybriden zwischen anfälligen Platanen (Platanus orientalis) und resistenten P. occidentalis in Frankreich auf ihre Resistenz geprüft. Von 960 Hybriden überlebten 18 Individuen zwei aufeinander folgende Inokulationen. Diese möglicherweise resistenten Bäume wurden auf den Stock gesetzt und nach 18 Monaten wurden jeweils 12 der Neutriebe und zwei Wurzeln pro Pflanze erneut inokuliert. Hierbei zeigte ein Baum völlige, ein zweiter teilweise Resistenz. Dieser Selektionsprozess, welcher den resistenten Klon ,Vallis clausa' ergab, wird im Detail beschrieben. [source]

Absence of residual effects of a defeated resistance gene in poplar

FOREST PATHOLOGY, Issue 2 2003
K.-S. Woo
Summary In a few plant pathosystems, defeated major genes have been shown to contribute to partial resistance to disease. This hypothesis has never been tested before in a forest tree, but pathogenic variation associated with recent hybridization in poplar rust in the Pacific northwest provided an opportunity. An F2 progeny of 256 poplar clones in the field near Corvallis, Oregon, USA, has been monitored for rust severity and infection type since the advent of the new hybrid rust, Melampsora × columbiana, in the mid-1990s. All 256 clones displayed a susceptible infection type in 1997 and again in 2000, and yet variation in uredinial density (i.e. partial resistance) was still observed. To determine which clones possessed a defeated resistance gene, a greenhouse inoculation was performed with an isolate of M. medusae, one of the parents of M. × columbiana. Clones that would have been resistant to M. medusae, prior to the advent of M. × columbiana, were thus identified. The inoculation resulted in a 1 : 1 segregation (,2=0.772; p=0.38) for resistance, indicating the presence of a major gene. However, the F2 clones possessing the defeated resistance gene displayed the same level of partial resistance in the field in both 1997 and 2000 as their full siblings lacking the gene. Résumé Chez quelques pathosystèmes végétaux, il a été montré que le contournement de gènes majeurs de résistance contribue à une résistance partielle envers la maladie. Cette hypothèse n'a encore jamais été testée chez un arbre forestier, mais le changement de pouvoir pathogène associéà l'hybridation récente de la rouille du peuplier dans le nord-ouest des USA en a fourni l'occasion. Une descendance F2 de 256 clones de peuplier a été suivie au champ près de Corvallis, Oregon, USA, pour la gravité de la rouille et le type d'infection, depuis l'apparition du nouvel hybride Melampsora x columbiana, dans les années 1990. Tous les 256 clones se sont montrés sensibles en 1997 et à nouveau en 2000, et une variation dans la densité des urédies (résistance partielle) a aussi été observée. Pour déterminer quels clones présentaient une résistance contournée, des inoculations ont été réalisées en serre avec un isolat de Melampsora medusae originaire du Kentucky. Des clones qui étaient résistants àM. medusae avant l'apparition de M. x columbiana ont ainsi été identifiés. Les inoculations ont abouti à une ségrégation 1 :1 (,2 = 0,772; P = 0,38) pour la résistance, ce qui indique la présence d'un gène majeur. Cependant, les clones F2 possédant le gène de résistance contourné montraient le même niveau de résistance partielle au champ en 1997 et 2000 que leurs plein-frères qui n'avaient pas ce gène. Zusammenfassung Für einige Pflanzen-Pathosysteme wurde gezeigt, dass unwirksam gewordene Haupt-Resistenzgene immer noch zu einer teilweisen Resistenz beitragen. Für Waldbäume wurde diese Hypothese bisher nie überprüft. Dies wurde jetzt im pazifischen Nordwesten möglich, wo der Pappelrost nach einem rezenten Hybridisierungsereignis stark variierte. An den F2-Nachkommenschaften von 256 Pappelklonen, die unter Freilandbedingungen in der Nähe von Corvallis, Oregon, USA wuchsen, wurde nach dem Auftreten des neuen Hybridrostes (Melampsora × columbiana) ab ca. 1990 die Krankheitsintensität und der Infektionstyp registriert. Alle 256 Klone zeigten einen anfälligen Infektionstyp im Jahre 1997 und dann wieder im Jahre 2000. Dabei wurde eine Variation in der Urediendichte (d.h. partielle Resistenz) beobachtet. Um zu bestimmen, welche Klone ein unwirksam gewordenes Resistenzgen besitzen, wurden Inokulationen im Gewächshaus mit einem Isolat von M. medusae, einem Elter von M. × columbiana, durchgeführt. Damit wurden Klone identifiziert, die vor dem Auftreten von M. × columbiana gegen M. medusae resistent waren. Der Infektionsversuch führte zu einer 1:1 Segregation (,2=0,772; P=0,38) für die Resistenz, was auf das Vorliegen eines Hauptgens hinweist. Die F2-Klone, welche dieses überwundene Resistenzgen besitzen, zeigten jedoch unter Feldbedingungen in den Jahren 1997 und 2000 den gleichen Grad einer Teilresistenz wie ihre Vollgeschwister, welchen dieses Gen fehlt. [source]

The Intracellular Target for the Antiresorptive Aminobisphosphonate Drugs in Dictyostelium discoideum Is the Enzyme Farnesyl Diphosphate Synthase,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2000
Joanna E. Grove
Abstract Aminobisphosphonate (aBP) drugs inhibit osteoclast-mediated bone resorption and also growth of amoebas of Dictyostelium discoideum apparently by interaction with the same intracellular target. Identification of the target in Dictyostelium therefore could also identify the target in osteoclasts. The aBPs (100 ,M alendronate and 30 ,M YM-175) inhibited conversion of [14C]mevalonate into sterols by cultures of Dictyostelium amoebas. One of three enzymes (isopentenyl diphosphate [IDP] isomerase, farnesyl diphosphate [FDP] synthase, and squalene synthase) appeared to be the target for this inhibition because conversion of [14C]IDP into squalene, the immediate precursor for sterol biosynthesis, was inhibited in extracts of wild-type amoebas by alendronate (IC50 = 75 nM) or risedronate (IC50 = 30 nM) whereas, when the extract had been prepared from amoebas of strains selected for having partial resistance to the growth-inhibitory effects of alendronate (strain MR102) or risedronate (strain RB101), the values of IC50 were increased to 700 nM for alendronate (MR102 extract) or 130 nM for risedronate (RB101 extract). Neither IDP isomerase nor squalene synthase was inhibited significantly by alendronate or risedronate but both of these aBP drugs, and all others tested, inhibited FDP synthase. Determination of the nucleotide sequences of complementary DNAs (cDNAs) encoding FDP synthase in the wild-type and aBP-resistant strains of Dictyostelium indicated that there had been no changes in the amino acid sequence of the enzyme in the mutant strains. However, both mutant strains overproduce FDP synthase. It is concluded that FDP synthase is the intracellular target for the aBP drugs. (J Bone Miner Res 2000;15:971,981) [source]

Prediction of the virological response to etravirine in clinical practice: Comparison of three genotype algorithms,,

JOURNAL OF MEDICAL VIROLOGY, Issue 4 2009
Laurent Cotte
Abstract The current Agence Nationale de Recherche sur le SIDA (ANRS)/International AIDS Society (IAS) algorithm predicts resistance to etravirine for viruses harboring ,3 mutations from a list of 13 reverse transcriptase (RT) mutations. Two weighted algorithms, best correlated with fold changes to etravirine, have been described recently. A retrospective virological analysis of a major French city HIV sequences database was undertaken to assess the proportion of etravirine resistant viruses according to these three algorithms and the correlations between them. Two thousand six hundred eighty RT sequences were analyzed, including 749 from naive patients and 926 from patients previously treated with non-nucleoside reverse transcriptase inhibitor (NNRTI). Combinations of mutations associated with etravirine resistance according to the three algorithms were found in 0%, 2.3%, and 3.6% of naive patients, and in 2.4%, 20.4%, and 19.3% of patients previously treated with NNRTIs. Concordance between the algorithms was weak (2,×,2 Kendall's tau: 0.787, 0.395, and 0.584). Most of the discordance was due to the differential weights attributed to Y181C/V, L100I, and K101P in the two weighted algorithms. It is concluded that the current ANRS/ IAS algorithm probably underestimates the proportion of viruses partially resistant to etravirine in NNRTI-experienced patients. Improvements in algorithms are needed to take into account the partial resistance associated with some mutation patterns, and should include either additional mutations to the current list and/or differential weights for specific mutations. Surveys of naive patients should be conducted to estimate the risk of primary resistance to etravirine in a minority of cases. J. Med. Virol. 81:672,677, 2009 © 2009 Wiley-Liss, Inc. [source]

Hyperkeratotic nail discoid lupus erythematosus evolving towards systemic lupus erythematosus: therapeutic difficulties

JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 6 2004
B Richert
ABSTRACT Nail changes occur in about 25% of systemic lupus erythematosus (SLE) cases. Onycholysis has been reported as the most frequent abnormality in SLE. Nailbed hyperkeratosis may be observed in both SLE and discoid lupus erythematosus (DLE). Involvement of the nail apparatus in DLE is extremely uncommon and never restricted to it. We report on a patient in whom the clinical features on the proximal nailfold were similar to those observed on the skin of a patient with typical DLE. This has, to the best of our knowledge, not yet been reported. The patient also exhibited a very distinctive prominent subungual hyperkeratosis. Interestingly, the patient developed biological alterations suggesting a systematization of the disease. Only a combination of systemic corticoids, retinoids and antimalarials was able to achieve nail improvement and this partial resistance to therapy may be explained by the very unusual subungual hyperkeratosis. [source]

Oral and vaginal epithelial cell anti- Candida activity is acid labile and does not require live epithelial cells

MOLECULAR ORAL MICROBIOLOGY, Issue 4 2005
J. Yano
Background:,Candida albicans is the causative agent of oral and vaginal candidiasis. Innate host defenses against C. albicans are important against each infection. Among these are oral and vaginal epithelial cells that have anti- Candida activity. The mechanism of action includes a requirement for cell contact with no role for soluble factors, and a putative role for carbohydrates based on the sensitivity of the activity to periodic acid. Methods:, Periodic acid treatment of epithelial cells as well as the property of partial resistance of antifungal activity to fixation was used to further dissect the mechanism of action. Results:, The results herein effectively now challenge a role for carbohydrates alone. Firstly, the putative carbohydrate(s) released into supernatants of periodic acid-treated epithelial cells could not compete with fresh epithelial cells for activity, and equivalent abrogation of activity was observed by periodic acid-treated cells irrespective of the amount of carbohydrate released. Instead, the similar abrogation of activity following treatment with other acids or when cocultured under acidic conditions suggests that the activity is acid-labile. Finally, while activity requires intact epithelial cells, it does not require live cells; activity was minimally affected by fixing epithelial cells prior to coculture where the majority of cells remained impermeable to Trypan blue but were defined as non,viable by positive nuclear staining with propidium iodide. Conclusion:, These results suggest that antifungal activity is dependent on contact by intact, but not necessarily live, epithelial cells through an acid-labile mechanism. [source]

Isolate specificity of quantitative trait loci for partial resistance of barley to Puccinia hordei confirmed in mapping populations and near-isogenic lines

Are fecundity and longevity of female Aphelinus abdominalis affected by development in GNA-dosed Macrosiphum euphorbiae?

PHYSIOLOGICAL ENTOMOLOGY, Issue 4 2001
A. Couty
Abstract. Snowdrop lectin (Galanthus nivalis agglutinin, GNA) confers partial resistance to several aphid species when incorporated into an artificial diet and/or expressed in transgenic potato. First-tier laboratory-scale experiments were conducted to assess the potential effect of GNA on the longevity and fecundity of female parasitoid Aphelinus abdominalis (Dalman) that had developed in Macrosiphum euphorbiae (Thomas) fed artificial diet containing 0.1% GNA (w/v). In a previous study it was shown that GNA ingested by A. abdominalis larvae is not acutely toxic. It was also shown that GNA has a host-size mediated effect on parasitoid sex ratio and larval development, but no apparent direct effect. In this study, we report that A. abdominalis larvae that developed in GNA-dosed aphids that were smaller than control aphids of the same age, produced smaller adults with a reduced longevity and fecundity. Aphelinus abdominalis larvae that developed in GNA-dosed aphids older than the control but of the same size, produced adults of similar size that lived as long as the control but had a reduced fecundity. Our results suggest that GNA fed to aphids in artificial diet has both a host-mediated effect (via aphid-size) and a direct effect on adult parasitoid fecundity. It is not known how GNA affects parasitoid larval development and subsequently adult fecundity, but it is hypothesized that GNA acted as an antifeedant to parasitoid larvae, thus disturbing nutrient assimilation and conversion necessary for egg maturation. [source]

Molecular and histochemical characterisation of two distinct poplar Melampsora leaf rust pathosystems

PLANT BIOLOGY, Issue 2 2010
B. Boyle
Abstract In this study, we compared interactions of two Melampsora foliar rust species with poplar, which resulted in either limited or abundant pathogen proliferation. In the pathosystem exhibiting limited pathogen growth, a defence response was observed after invasion of poplar leaf tissues by the biotroph, with late and clear production of reactive oxygen species (ROS) and other products. Characterisation of the histological, biochemical and transcriptional events occurring in both pathosystems showed striking similarity with components of plant defence reactions observed during qualitative resistance. Key components associated with development of an active defence response, such as up-regulation of pathogenesis-related (PR) genes, were observed during infection. Moreover, the time course and strength of gene induction appear to be critical determinants for the outcome of the tree,pathogen interaction. This work provides basic biochemical characterisation and expression data for the study of so-called partial resistance in the poplar,rust pathosystem, which is also applicable to other plant,pathogen interactions resulting in quantitative disease resistance. [source]

Preferential expression of a plant cystatin at nematode feeding sites confers resistance to Meloidogyne incognita and Globodera pallida

PLANT BIOTECHNOLOGY JOURNAL, Issue 1 2004
Catherine J. Lilley
Summary The expression patterns of three promoters preferentially active in the roots of Arabidopsis thaliana have been investigated in transgenic potato plants in response to plant parasitic nematode infection. Promoter regions from the three genes, TUB-1, ARSK1 and RPL16A were linked to the GUS reporter gene and histochemical staining was used to localize expression in potato roots in response to infection with both the potato cyst nematode, Globodera pallida and the root-knot nematode, Meloidogyne incognita. All three promoters directed GUS expression chiefly in root tissue and were strongly up-regulated in the galls induced by feeding M. incognita. Less activity was associated with the syncytial feeding cells of the cyst nematode, although the ARSK1 promoter was highly active in the syncytia of G. pallida infecting soil grown plants. Transgenic potato lines that expressed the cystatin OcI,D86 under the control of the three promoters were evaluated for resistance against Globodera sp. in a field trial and against M. incognita in containment. Resistance to Globodera of 70 ± 4% was achieved with the best line using the ARSK1 promoter with no associated yield penalty. The highest level of partial resistance achieved against M. incognita was 67 ± 9% using the TUB-1 promoter. In both cases this was comparable to the level of resistance achieved using the constitutive cauliflower mosaic virus 35S (CaMV35S) promoter. The results establish the potential for limiting transgene expression in crop plants whilst maintaining efficacy of the nematode defence. [source]

Field trial of serially passaged isolates of BYDV-PAV overcoming resistance derived from Thinopyrum intermedium in wheat

PLANT BREEDING, Issue 3 2006
F. Chain
Abstract Barley yellow dwarf disease (BYDD) is one of the main viral diseases of small grain cereals. This disease, reported on numerous plant species of the Poaceae family, is caused by a complex of viral species including the species Barley yellow dwarf virus -PAV (BYDV-PAV, family Luteoviridae, genus Luteovirus), frequently found in western Europe. Resistance sources towards BYDD are scarce. Indeed, breeding-resistant genotypes is a long and expensive process. Thus, estimating the durability of the resistance genes before the achievement of selection would be an asset for breeders. One isolate of BYDV-PAV has been serially passaged on two hosts, ,Zhong ZH' and ,TC14', carrying a gene for partial resistance. The resulting viral population showed an increase of the speed of development of the infection in controlled conditions. In this study, these viral populations were evaluated in a 3-year field trial, including a susceptible host, ,Rendezvous', and a host carrying the resistance gene of ,TC14' in a ,Rendezvous' background, to assess the effect of serial passages in field conditions. Results indicate that isolates issued from serial passages on hosts carrying a gene for partial resistance induced increased damage in field conditions when compared with the initial isolate. Yield losses are mainly due to a decrease of the number of kernels per square metre. The interest on using partial resistance gene to control BYDD is discussed. [source]

Contributions of disease resistance and escape to the control of septoria tritici blotch of wheat

PLANT PATHOLOGY, Issue 5 2009
L. S. Arraiano
The contributions of disease escape and disease resistance to the responses of wheat to septoria tritici leaf blotch (STB) were analysed in a set of 226 lines, including modern cultivars, breeding lines and their progenitors dating back to the origin of scientific wheat breeding. Field trials were located in the important wheat-growing region of eastern England and were subject to natural infection by Mycosphaerella graminicola. STB scores were related to disease-escape traits, notably height, leaf spacing, leaf morphology and heading date, and to the presence of known Stb resistance genes and isolate-specific resistances. The Stb6 resistance gene was associated with a reduction of 19% in the level of STB in the complete set of 226 lines and with a 33% reduction in a subset of 139 lines of semidwarf stature. Greater plant height was strongly associated with reduced STB in the full set of lines, but only weakly in the semidwarf lines. Shorter leaf length was also associated with reduced STB, but, in contrast to earlier reports, lines with more prostrate leaves had more STB on average, probably because they tended to have longer leaves. Several lines, notably cvs Pastiche and Exsept, had low mean levels of STB which could not be explained by either escape traits or specific resistance genes, implying that they have unknown genes for partial resistance to STB. [source]

Identification of isolate-specific and partial resistance to septoria tritici blotch in 238 European wheat cultivars and breeding lines

PLANT PATHOLOGY, Issue 6 2006
L. S. Arraiano
From a total of 238 European cultivars and breeding lines screened for isolate-specific resistance to septoria tritici blotch (STB) with eight Mycosphaerella graminicola isolates from five different countries, 142 lines were resistant to Ethiopian isolate IPO88004, and 43 lines were specifically resistant to IPO323, with little or no leaf area bearing pycnidia of M. graminicola. These lines probably all have the resistance gene Stb6. Specific resistances to isolates CA30JI, IPO001, IPO89011, IPO92006 and ISR398 were less common. Seventy-three per cent of the lines were specifically resistant to at least one isolate and 36 lines were resistant to more than one isolate. The line with the greatest number of specific resistances was the spring cultivar Raffles, with five. The most resistant line in which no specific resistance was identified was the Italian landrace Rieti, an ancestor of many modern European wheat cultivars. There was also a wide range of partial resistance among the lines tested, expressed in detached seedling leaves. Information about the resistance of wheat lines to M. graminicola isolates will assist breeders to choose parents of crosses from which progeny with superior resistance to STB may be selected. [source]

Ovary colonization by Claviceps africana is related to ergot resistance in male-sterile sorghum lines

PLANT PATHOLOGY, Issue 5 2003
B. Komolong
Ergot, caused by Claviceps africana, has emerged as a serious threat to sorghum hybrid seed production worldwide. In the absence of gene-for-gene-based qualitative resistance in commercial cultivars, varieties with high pollen production that can escape ergot infection are preferred. Recent demonstration of differences in ergot susceptibility among male-sterile lines has indicated the presence of partial resistance. Using chitin-specific fluorescin-isothiocyanate-conjugated wheat germ agglutin and callose-specific aniline blue, this study investigated the process of sorghum ovary colonization by C. africana. Conidia germinated within 24 h after inoculation (a.i.); the pathogen was established in the ovary by 79 h a.i., and at least half of the ovary was converted into sphacelial tissue by 120 h a.i. Changes in fungal cell wall chitin content and strategic callose deposition in the host tissue were associated with penetration and invasion of the ovary. The rate of ovary colonization differed in three male-sterile lines that also differed in ergot susceptibility. This work demonstrates a possible histological basis for partial resistance in male-sterile sorghum lines that could lay the foundation for variety improvement through further breeding and selection. [source]

Simple inheritance of partial resistance to leaf rust in two wheat cultivars

PLANT PATHOLOGY, Issue 5 2001
J. A. Kolmer
The wheat cultivars Westphal 12A and BH1146 were characterized in previous studies as having partial resistance to the leaf rust pathogen Puccinia triticina. In the present study, genetic analysis showed that Westphal 12A has three genes that condition resistance in seedling plants, and the gene Lr34, which is optimally expressed in adult plants. The three seedling resistance genes in Westphal 12A may be new leaf-rust resistance genes. BH1146 was shown to have the adult plant resistance genes Lr13 and Lr34. Many wheat cultivars with partial resistance to leaf rust may have Lr13 and/or Lr34, or other previously described Lr genes. [source]