Relative parasitic fitness of isolates of Pyricularia oryzae Cav. with different sensitivities to fungicides     

Yukio Miyagi  Takashi Hirooka  Fujio Araki 《Pest management science》1986,17(6):653-658

The relative parasitic fitness of isolates of Pyricularia oryzae with different sensitivities to isoprothiolane (di-isopropyl 1,3-dithiolan-2-ylidenemalonate) and IBP (S-benzyl O, O-di-isopropyl phosphorothioate) was studied in the absence of fungicides. Four field isolates (S-1,S-2,MR-1 and MR-2) and two in-vitro mutants (Rvt-1 and Rvt-2) were used for disease epidemics. S-l and S-2 were wild types; MR-1 and MR-2 were sensitive to isoprothiolane and moderately resistant to IBP, and Rvt-1 and Rvt-2 were resistant to both fungicides. Twelve epidemics were made by inoculating rice seedlings with mixed conidial suspensions of two isolates or mutants. The value of relative parasitic fitness (W = 0-1.0) was calculated for each isolate and epidemic. S-l and S-2 were stronger (W = 1.0) than MR-2, Rvt-1 and Rvt-2; but weaker (W = 0.75, 0.73, respectively) than MR-1. MR-1 was strongest among all isolates and mutants used. MR-2 was slightly weaker (W = 0.9-1.0) than S-l and S-2, but stronger than Rvt-1 and Rvt-2. Rvt-1 and Rvt-2 had smaller values of W, ranging from 0.25-0.58, in the epidemics with each field isolate. These results suggest that the proportions of in-vitro mutants do not increase unless intensive selection pressure is given, and would be expected to decrease rapidly after the selection pressure is removed. Isolates moderately resistant to IBP, such as MR-1 and MR-2, however, had high values of W, suggesting that they would increase or would not decrease rapidly in the absence of selection pressure. These results may well explain why isolates highly resistant to isoprothiolane and IBP have seldom been found, and why a large number of isolates moderately resistant to IBP but sensitive to isoprothiolane have been observed in the field.  相似文献   

Molecular breeding for virus resistant potato plants     

Marianne J. Huisman  Erik Jongedijk  Dinie Posthumus-Lutke Willink  Frank Van Der Wilk  Ben J. C. Cornelissen 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(2):29-36

To engineer resistance against potato virus X (PVX), the viral coat protein (CP) gene has been introduced into two potato cultivars. Stable expression of the gene in transgenic clones throughout the growing season has been obtained and resulted in considerably increased virus resistance. With varying frequencies depending on the original cultivar used, true-to-type PVX resistant transgenic clones have been obtained. Since deviant light sprout characteristics were invariably associated with aberrations in plant phenotype, they can be used in procedures to early screen for deviations. Furthermore, it has been possible to unequivocally discriminate between the original untransformed and independent transgenic cultivars. Although no relation has been found between the presence, if any, of the CP of potato virus Y (PVY) or potato leafroll virus (PLRV) in CP gene transgenic potato, appreciable levels of resistance to these viruses has been obtained. This suggests that the mechanism by which a viral CP gene in the potato genome evokes resistance, differs amongst various viruses.  相似文献   

Shifts in disease resistance induced by growth regulators     

O. M. van Andel 《European journal of plant pathology / European Foundation for Plant Pathology》1968,74(1):113-120

Experiments on the effect of various compounds with plant growth regulating activity led to the hypothesis that conditions inhibitory to indoleacetic acid (IAA) action or leading to a decrease in the IAA level in cucumber seedlings would be unfavourable for the development of cucumber scab, caused byCladosporium cucumerinum. Susceptibility decreased as the result of treatment with growth retardants, which cause an increase in IAA-oxidase activity in the plants, whereas application of indoleacetic acid or compounds expected to decrease the rate of oxidative breakdown of IAA in the seedlings resulted in an increase of susceptibility. Growing the plants under various periods of illumination also influenced both the susceptibility of the plants and the IAA-oxidase activity in the hypocotyl tissue.To obtain further information about the relation between the increase in resistance and the increase in the rate of IAA oxidation, the effect of one compound, viz. L-threo-β-phenylserine (abbr. phenylserine) was studied in more detail. The rate of oxidative breakdown of IAA was increased in extracts of hypocotyls and cotyledons of plants treated with phenylserine as compared with extracts of tissue of untreated plants. Extracts of phenylserine-treated plants were found to contain a higher cofactor and/or a lower inhibitor content than those of control plants. The substances involved were not identified, but this result may indicate a shift in the concentrations of various phenols in the tissue.The question must remain open whether a shift in the concentration of phenols some-how effected by phenylserine treatment determines both degree of susceptibility and rate of IAA oxidation independently, or whether the rate of IAA breakdown and the resulting change in IAA content in the plants is directly related to the degree of susceptibility.  相似文献   

New potyvirus isolated from <Emphasis Type="Italic">Cryptotaenia japonica</Emphasis>     

Kentaro Okuno  Tomoko Hama  Minoru Takeshita  Naruto Furuya  Yoichi Takanami 《Journal of General Plant Pathology》2003,69(2):138-142

 A potyvirus, for which the name Japanese hornwort mosaic virus (JHMV) is proposed, was isolated from Japanese hornwort plants (Cryptotaenia japonica) with mosaic disease symptoms. The virus was used to inoculate mechanically 34 plants belonging to 33 species of 10 families. Of these species seven from two families were infected. Faint chlorotic spots appeared on the inoculated leaves of Chenopodium quinoa and C. amaranticolor, but no systemic infection occurred in these plants. JHMV systemically infected only Umbelliferae plants; they did not infect 26 other species in eight families. JHMV was transmitted in a nonpersistent manner by aphids (Myzus persicae). The virus was a flexuous rod-shaped particle about 750 nm in length. Sequencing the nucleotides in the 3′ terminal region of JHMV revealed that the coat protein contains 280 amino acids with a molecular mass of 32.2 kDa. The nucleotide sequence of the coat protein of JHMV had the highest similarity with that of Zantedeschia mosaic virus (83.3%) compared to those of other potyviruses (57.0%–64.9%). An antiserum against JHMV reacted strongly with JHMV and weakly with Potato virus Y. These results indicate that JHMV is a new potyvirus. Received: September 9, 2002 / Accepted: November 7, 2002 RID="*" ID="*" The nucleotide sequence determined in this work appears in the DDBJ/EMBL/GenBank nucleotide sequence databases with the accession number AB081518  相似文献   

Increase in oxidized proteins in Theileria sergenti-infected erythrocyte membrane   总被引：1，自引：0，他引：1  

Yagi Y  Thongnoon P  Shiono H  Chikayama Y 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2002,64(7):623-625

As a part of the elucidation of the pathogenesis of anemia in Theileria sergenti infection, oxidized-erythrocyte membrane proteins (OEMPs) collected from T. sergenti-infected calves were examined. The amount of OEMPs were seen to increase with the progress of the anemia and showed a maximum value around the crisis period of the infection. The increase of OEMPs coincided with band Nos. 1, 2, 2.1, 3, 4.1, 5, 6, and 7. The majority of them was located at the Triton X-100 un-extractive phase, and was confirmed as cytoskeletal proteins. This evidence indicates the enhancement of erythrocytic oxidation, and suggests that it might be one of the aggravating factors of anemia in T. sergenti infection.  相似文献   

Note: Pyrethroid resistance and possible involvement of glutathione<Emphasis Type="Italic">S</Emphasis>-transferases in<Emphasis Type="Italic">Helicoverpa armigera</Emphasis> from Turkey     

Sakine Ugurlu  Metin Konus  Belgin Isgor  Mesude Iscan 《Phytoparasitica》2007,35(1):23-26

An introductory study was conducted to investigate the pyrethroid resistance ofHelicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) strains in Turkey, collected from cotton fields in the Adana and Antalya provinces, through two different synthetic pyrethroid insecticides: lambda-cyhalothrin and esfenvalerate. In addition, the roles of glutathioneS-transferases (GSTs) in this resistance mechanism were analyzed. It was found that whereas resistance ratios for lambda-cyhalothrin (LD₅₀ levels) were 3- and 98-fold increased in the Adana and Antalya strains, respectively, esfenvalerate ratios were 3.3- and 92.3-fold increased in the Adana and Antalya strains, respectively, with respect to the susceptible strain. Furthermore, Adana and Antalya strains showed 2.4- and 2.9-fold higher GST activities than the susceptible strain, respectively. In the Antalya field strain, the minor increase in GST activity compared with the resistance levels implies that GSTs may be not greatly involved in this resistance. It also provides evidence that they could not be the only metabolic mechanism responsible for resistance to lambda-cyhalothrin and esfenvalerate inH. armigera from Turkey. http://www.phytoparasitica.org posting Nov. 16, 2006.  相似文献   

Dhan Pal Singh and Arti Singh,Disease and Insect Resistance in Plants     

Christine Struck 《European journal of plant pathology / European Foundation for Plant Pathology》2007,118(1):91-92

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Critical Use Exemption for methyl bromide for soil disinfestation: Italy’s experience with the European union process     

M. Lodovica Gullino  Riccardo Savigliano  Giuliana Gasparrini  Corrado Clini 《Phytoparasitica》2007,35(4):321-329

Methyl bromide (MB) was phased out on January 1, 2005, and a Critical Use Exemption (CUE) process has been established in order to define the rules for allocating the needed amounts of the fumigant. This paper deals with the effects of the CUE process on Italian horticulture. The actual usage of the amounts of MB allocated to Italy for the year 2005 in the different areas and on the economically most important crops was monitored and critically evaluated. The usage pattern monitored shows that already in the first year after MB phaseout, Italy was able to replace it completely on crops such as zucchini, salad greens, basil and watermelon. However, on crops such as tomato, pepper, melon, eggplant, strawberry, and cut flowers, further work is required in order fully to replace MB. The emerging problems and research needs are discussed briefly.  相似文献   

Towards identifying pathogenic determinants of the chickpea pathogen <Emphasis Type="Italic">Ascochyta rabiei</Emphasis>     

David White  Weidong Chen 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(1):3-12

Ascochyta blight is a serious disease of cool-season grain legumes (chickpea, faba bean, lentil and pea) caused by fungal species of the anamorphic genus Ascochyta and related genera. Despite extensive studies on the biology, ecology, epidemiology and management of the disease, little is known about the pathogenic determinants of these pathogens. This research aims at using Ascochyta rabiei as a model for the genus in investigating genetic factors of pathogenicity, with the ultimate goal of elucidating pathogenic mechanisms. Three advances were made: (1) insertional mutants with altered pathogenicity were identified through in vivo screening, and genomic regions adjacent to the insertion sites in selected mutants were determined; (2) a phage library of A. rabiei genomic DNA was constructed, and the library was estimated to provide complete coverage of the A. rabiei genome. This library was used successfully to recover clones with DNA adjacent to insertional mutation sites and to isolate specific genes; (3) DNA probes specific for an acyl-CoA ligase (cps1) and a polyketide synthase gene (pks1) were developed and library clones containing the corresponding genomic regions were identified from the phage library. These advances provide the foundation and necessary tools for experimentation of ectopic complementation assays and targeted mutagenesis to elucidate the genetic mechanisms of pathogenicity of A. rabiei.  相似文献   

Simulating the cumulative effects of multiple forest management strategies on landscape measures of forest sustainability   总被引：1，自引：2，他引：1  

Eric J. Gustafson  David E. Lytle  Randy Swaty  Craig Loehle 《Landscape Ecology》2007,22(1):141-156

While the cumulative effects of the actions of multiple owners have long been recognized as critically relevant to efforts to maintain sustainable forests at the landscape scale, few studies have addressed these effects. We used the HARVEST timber harvest simulator to predict the cumulative effects of four owner groups (two paper companies, a state forest and non-industrial private owners) with different management objectives on landscape pattern in an upper Michigan landscape managed primarily for timber production. We quantified trends in landscape pattern metrics that were linked to Montreal Process indicators of forest sustainability, and used a simple wildlife habitat model to project habitat trends. Our results showed that most trends were considered favorable for forest sustainability, but that some were not. The proportion of all age classes and some forest types moved closer to presettlement conditions. The trend for the size of uneven-aged patches was essentially flat while the average size of patches of the oldest and youngest age classes increased and the size of patches of the remaining age classes decreased. Forest fragmentation generally declined, but edge density of age classes increased. Late seral forest habitat increased while early successional habitat declined. The owners use different management systems that cumulatively produce a diversity of habitats. Our approach provides a tool to evaluate such cumulative effects on other landscapes owned by multiple owners. The approach holds promise for helping landowner groups develop and evaluate cooperative strategies to improve landscape patterns for forest sustainability.  相似文献