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Inoculated Plants (inoculated + plant)
Selected AbstractsVector within-host feeding preference mediates transmission of a heterogeneously distributed pathogenECOLOGICAL ENTOMOLOGY, Issue 3 2010MATTHEW P. DAUGHERTY 1. Ecological theory predicts that vector preference for certain host species or discrimination between infected versus uninfected hosts impacts disease incidence. However, little information exists on the extent to which vector within-host feeding preference mediates transmission. This may be particularly important for plant pathogens, such as sharpshooter transmission of the bacterium Xylella fastidiosa, which are distributed irregularly throughout hosts. 2. We documented the within-host distribution of two vector species that differ in transmission efficiency, the leafhoppers Draeculacephala minerva and Graphocephala atropunctata, and which are free to move throughout entirely caged alfalfa plants. The more efficient vector D. minerva fed preferentially at the base of the plant near the soil surface, whereas the less efficient G. atropunctata preferred overwhelming the top of the plant. 3. Next we documented X. fastidiosa heterogeneity in mechanically inoculated plants. Infection rates were up to 50% higher and mean bacterial population densities were 100-fold higher near the plant base than at the top or in the taproot. 4. Finally, we estimated transmission efficiency of the two leafhoppers when they were confined at either the base or top of inoculated alfalfa plants. Both vectors were inefficient when confined at the top of infected plants and were 20,60% more efficient when confined at the plant base. 5. These results show that vector transmission efficiency is determined by the interaction between leafhopper within-plant feeding behaviour and pathogen within-plant distribution. Fine-scale vector and pathogen overlap is likely to be a requirement generally for efficient transmission of vector-borne pathogens. [source] The development and endophytic nature of the fungus Heteroconium chaetospiraFEMS MICROBIOLOGY LETTERS, Issue 2 2005Teruyoshi Hashiba Abstract The root endophytic fungus Heteroconium chaetospira was isolated from roots of Chinese cabbage grown in field soil in Japan. This fungus penetrates through the outer epidermal cells of its host, passes into the inner cortex, and grows throughout the cortical cells, including those of the root tip region, without causing apparent pathogenic symptoms. There are no ultrastructural signs of host resistance responses. H. chaetospira has been recovered from 19 plant species in which there was no disruption of host growth. H. chaetospira has a symbiotic association with Chinese cabbage. The fungus provides nitrogen in exchange for carbon. These associations are beneficial for the inoculated plants, as demonstrated by increased growth rate. When used as a preinoculum, H. chaetospira suppresses the incidence of clubroot and Verticillium yellows when the test plant is post-inoculated with the causal agents of these diseases. H. chaetospira is an effective biocontrol agent against clubroot in Chinese cabbage at a low to moderate soil moisture range and a pathogen resting spore density of 105 resting spores per gram of soil in situ. Disease caused by Pseudomonas syringae pv. macricola and Alternaria brassicae on leaves can be suppressed by treatment with H. chaetospira. The fungus persists in the roots and induces systemic resistance to the foliar disease. [source] Pathogenicity of fungi isolated from Quercus suber in Catalonia (NE Spain)FOREST PATHOLOGY, Issue 5 2000J. Luque Summary Thirty-four fungal species isolated from cork oak (Quercus suber) in Catalonia (NE Spain) during 1992,95 were tested for pathogenicity either in stem, leaf or root inoculations. Eleven species were found to be pathogenic on stem: Biscogniauxia mediterranea, Botryosphaeria stevensii, Diatrype cf. stigma, Endothia gyrosa, Fusarium solani, Graphium sp., Ophiostoma quercus, Phomopsis sp., Phytophthora cinnamomi, Sporendocladia bactrospora and an unidentified Coelomycete. Three fungi showed pathogenic effects on leaves: Dendrophoma myriadea, Lembosia quercina and Phomopsis quercella. No clear pathogenic effects were detected in the root inoculation experiment. Trunk pathogens were differentiated into two groups according to the effects induced in the inoculated plants; B. stevensii, Phomopsis sp. and P. cinnamomi caused the death of the inoculated plants and induced the formation of large cankers and vascular necroses. The other pathogenic species also produced severe cankers and vascular lesions, but no significant mortality was detected. Water stress increased the lesions caused by B. mediterranea and Phomopsis sp., but limited those of P. cinnamomi and the rest of the inoculated fungi. However, water stress did not significantly affect the damage caused by B. stevensii, which was the most virulent of the species tested. Leaf pathogens only showed their effects if the leaf cuticle was previously damaged. Lembosia quercina caused small dark lesions whereas D. myriadea and P. quercella produced large necrotic areas in well-watered plants. The lesions caused by the last two fungi were reduced by water stress. Résumé Le pouvoir pathogène de trente-quatre espèces fongiques isolées de chêne liège en Catalogne (nord-est de l'Espagne) de 1992 à 1995 a été testé par inoculation sur tronc, feuilles et racines. Onze espèces se sont montrées pathogènes sur tronc: Biscogniauxia mediterranea, Botryosphaeria stevensii, Diatrype cf. stigma, Endothia gyrosa, Fusarium solani, Graphium sp., Ophiostoma quercus, Phomopsis sp., Phytophthora cinnamomi, Sporendocladia bactrospora et un Coelomycète non identifié. Trois champignons ont eu un effet pathogène sur feuilles: Dendrophoma myriadae, Lembosia quercina et Phomopsis quercella. Aucun effet clair n'a été détecté chez les inoculations de racines. Les pathogènes de tronc se répartissaient en deux groupes selon leurs effets en inoculation; B. stevensii, Phomopsis sp. et P. cinnamomi provoquaient la mort des plants et induisaient le formation de grands chancres et des nécroses vasculaires. Les autres espèces pathogènes produisaient aussi des chancres graves et des lésions vasculaires, mais pas de mortalité significative. Un stress hydrique augmentait les lésions provoquées par B. mediterranea et Phomopsis sp. mais limitait ceux de P. cinnamomi et des autres champignons inoculés. Cependant, le stress hydrique n'affectait pas significativement les dégâts par B. stevensii qui était la plus agressive des espèces testées. Les pathogènes foliaires n'avaient d'effet que si la cuticule foliaire était préalablement endommagée. Lembosia quercina provoquait de petites lésions sombres et D. myriadea et P. quercella provoquaient de grandes plages nécrotiques chez les plants bien arrosés; les lésions causées par ces deux derniers champignons étaient réduites par le stress hydrique. Zusammenfassung Die Pathogenität von 34 Pilzarten, die im Zeitraum 1992,1995 von Korkeichen (Quercus suber) in Katalonien (NO-Spanien) isoliert wurden, wurden mit Hilfe von Trieb-, Blatt- oder Wurzelinokulationen untersucht. Am Stamm erwiesen sich 11 Arten als pathogen: Biscogniauxia mediterranea, Botryosphaeria stevensii, Diatrype cf. stigma, Endothia gyrosa, Fusarium solani, Graphium sp., Ophiostoma quercus, Phomopsis sp., Phytophthora cinnamomi, Sporendocladia bactrospora und ein nicht identifizierter Coelomycet. Drei Arten verursachten Symptome auf Bla¨ttern: Dendrophoma myriadea, Lembosia quercina und Phomopsis quercella. Bei den Wurzelinokulationen wurden keine pathogenen Effekte beobachtet. Bei den Stammpathogenen wurden nach den von ihnen an den inokulierten Pflanzen verursachten Symptomen zwei Gruppen unterschieden: B. stevensii, Phomopsis sp. und P. cinnamomi verursachten den Tod der Pflanzen und induzierten die Bildung von grossen Rinden- und Xylemnekrosen. Die anderen pathogenen Arten verursachten ebenfalls starke Rindennekrosen und Gefa¨ssla¨sionen, es wurde jedoch keine auffallende Mortalita¨t beobachtet. Unter Wasserstress war die durch B. mediterranea und Phomopsis sp. induzierte Nekrosebildung versta¨rkt, dagegen war sie bei P. cinnamomi und den u¨brigen inokulierten Pilzen reduziert. Wasserstress beeinflusst jedoch das Ausmass der Scha¨digung durch B. stevensii, der virulentesten der untersuchten Arten, nicht. Die Blattpathogene verursachten nur dann Symptome, wenn zuvor die Blattcuticula bescha¨digt worden war. Lembosia quercina verursachte kleine dunkle La¨sionen, wa¨hrend D. myriadea und P. quercella bei gut bewa¨sserten Pflanzen grosse Nekrosen verursachten. Diese Symptome waren unter Wasserstress weniger stark ausgepra¨gt. [source] Biological Control of Fusarium oxysporum f.sp. lycopersici on Tomato by Brevibacillus brevisJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2010Sunita Chandel Abstract The ability of Brevibacillus brevis to influence development of disease on tomato caused by Fusarium oxysporum f.sp. lycopersici was investigated using plants raised in Petri dish microcosms and in pots in the glasshouse. Development of symptoms on both microcosm- and glasshouse-raised tomato plants was markedly reduced in co-inoculations of F. oxysporum f.sp. lycopersici with B. brevis, compared with inoculations with the pathogen alone. Moreover, co-inoculations resulted in significant growth boosting effects on the plants, with increases in plant height in microcosms and in total root lengths in glasshouse-raised plants. In microcosm-raised plants, the carrier used to inoculate seed with B. brevis, either carboxymethyl cellulose (CMC) or vermiculite, had no effect on the persistence of the biological control agent on roots in the absence of inoculation with the pathogen. By contrast, numbers of B. brevis recovered from the rhizosphere and rhizoplane of inoculated plants in microcosms were four orders of magnitude lower than in plants treated with B. brevis alone. Moreover, higher numbers of B. brevis CFU were re-isolated from the rhizosphere of plants arising from CMC-coated seed, than vermiculite-coated seed. The carrier had no effect on disease control. Inhibition of conidial germination and germ-tube extension of F. oxysporum f.sp. lycopersici by cell-free filtrates of B. brevis cultures varied significantly depending on the culture medium used for suspension. These results indicate that B. brevis is a potential biological control agent for reducing the impact of F. oxysporum f.sp. lycopersici on tomato. [source] Monitoring the colonization of sugarcane and rice plants by the endophytic diazotrophic bacterium Gluconacetobacter diazotrophicus marked with gfp and gusA reporter genesLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2010L.F.M. Rouws Abstract Aims:, To evaluate the colonization process of sugarcane plantlets and hydroponically grown rice seedlings by Gluconacetobacter diazotrophicus strain PAL5 marked with the gusA and gfp reporter genes. Methods and Results:, Sugarcane plantlets inoculated in vitro with PAL5 carrying the gfp::gusA plasmid pHRGFPGUS did not present green fluorescence, but ,-glucuronidase (GUS)-stained bacteria could be observed inside sugarcane roots. To complement this existing inoculation methodology for micropropagated sugarcane with a more rapid colonization assay, we employed hydroponically grown gnotobiotic rice seedlings to study PAL5,plant interaction. PAL5 could be isolated from the root surface (108 CFU g,1) and from surface-disinfected root and stem tissues (104 CFU g,1) of inoculated plants, suggesting that PAL5 colonized the internal plant tissues. Light microscopy confirmed the presence of bacteria inside the root tissue. After inoculation of rice plantlets with PAL5 marked with the gfp plasmid pHRGFPTC, bright green fluorescent bacteria could be seen colonizing the rice root surface, mainly at the sites of lateral root emergence, at root caps and on root hairs. Conclusion:, The plasmids pHRGFPGUS and pHRGFPTC are valid tools to mark PAL5 and monitor the colonization of micropropagated sugarcane and hydroponic rice seedlings. Significance and Impact of the Study:, These tools are of use to: (i) study PAL5 mutants affected in bacteria,plant interactions, (ii) monitor plant colonization in real time and (iii) distinguish PAL5 from other bacteria during the study of mixed inoculants. [source] Pyramiding of genes conferring resistance to Tomato yellow leaf curl virus from different wild tomato speciesPLANT BREEDING, Issue 6 2008F. Vidavski Abstract Tomato (Solanum lycopersicum) production in tropical and subtropical regions of the world is limited by the endemic presence of Tomato yellow leaf curl virus (TYLCV). Breeding programmes aimed at producing TYLCV-resistant tomato cultivars have utilized resistance sources derived from wild tomato species. So far, all reported breeding programmes have introgressed TYLCV resistance from a single wild tomato source. Here, we tested the hypothesis that pyramiding resistances from different wild tomato species might improve the degree of resistance of the domesticated tomato to TYLCV. We have crossed TYLCV-resistant lines that originated from different wild tomato progenitors, Solanum chilense, Solanum peruvianum, Solanum pimpinellifolium, and Solanum habrochaites. The various parental resistant lines and the F1 hybrids were inoculated in the greenhouse using viruliferous whiteflies. Control, non-inoculated plants of the same lines and hybrids were exposed to non-viruliferous whiteflies. Following inoculation, the plants were scored for disease symptom severity, and transplanted to the field. Resistance was assayed by comparing yield of inoculated plants to those of the control non-inoculated plants of the same variety. Results showed that the F1 hybrids between the resistant lines and the susceptible line suffered major yield reduction because of infection, but all hybrids were more resistant than the susceptible parent. All F1 hybrids resulting from a cross between two resistant parents, showed a relatively high level of resistance, which in most cases was similar to that displayed by the more resistant parent. In some cases, the hybrids displayed better levels of resistance than both parents, but the differences were not statistically significant. The F1 hybrid between a line with resistance from S. habrochaites and a line with resistance from S. peruvianum (HAB and 72-PER), exhibited the lowest yield loss and the mildest level of symptoms. Although the resistance level of this F1 hybrid was not statistically different from the level of resistance displayed by the 72-PER parent itself, it was statistically better than the level of resistance displayed by the F1 hybrids between 72-PER and any other resistant or susceptible line. [source] Induction of root-mat symptoms on cucumber plants by Rhizobium, but not by Ochrobactrum or Sinorhizobium, harbouring a cucumopine Ri plasmidPLANT PATHOLOGY, Issue 6 2005S. A. Weller Ochrobactrum CSL 2573, Rhizobium CSL 2411 and Sinorhizobium CSL 2611 strains harbouring the Agrobacterium cucumopine Ri plasmid (pRi), previously were shown to induce root-mat symptoms in an in vitro cucumber cotyledon assay. In whole-plant, rockwool-grown cucumber host tests Rhizobium CSL 2411 was shown to be as efficient an inducer of root-mat symptoms as the virulent Agrobacterium radiobacter strain NCPPB 4042, which also harbours a cucumopine pRi. Conjugal transfer of pRi to ingressing, avirulent Agrobacterium isolates was observed within root tissues with symptoms. Ochrobactrum CSL 2573 and Sinorhizobium CSL 2611 were not able to induce root-mat symptoms on plants. Rhizobium CSL 2411 and Ochrobactrum CSL 2573 were reisolated from inoculated plants, but Sinorhizobium CSL 2611 was not detected or isolated from inoculated plants 68 days after inoculation. It was postulated that the differences in pathogenicity observed between the in vitro and in situ host tests were caused by a lack of proper attachment to inoculated root tissues by pRi-harbouring Ochrobactrum and Sinorhizobium in the whole-plant host tests. [source] Effects of foliar- and root-applied silicon on the enhancement of induced resistance to powdery mildew in Cucumis sativusPLANT PATHOLOGY, Issue 5 2005Y. C. Liang Two cucumber (Cucumis sativus) cultivars differing in their resistance to powdery mildew, Ningfeng No. 3 (susceptible) and Jinchun No. 4 (resistant), were used to study the effects of foliar- and root-applied silicon on resistance to infection by Podosphaera xanthii (syn. Sphaerotheca fuliginea) and the production of pathogenesis-related proteins (PRs). The results indicated that inoculation with P. xanthii significantly suppressed subsequent infection by powdery mildew compared with noninoculation, regardless of Si application. Root-applied Si significantly suppressed powdery mildew, the disease index being lower in Si-supplied than in Si-deprived plants, regardless of inoculation treatment. The resistant cultivar had a more constant lower disease index than the susceptible cultivar, irrespective of inoculation or Si treatment. Moreover, with root-applied Si, activities of PRs (for example peroxidase, polyphenoloxidase and chitinase) were significantly enhanced in inoculated lower leaves or noninoculated upper leaves in inoculated plants of both cultivars. Root-applied Si significantly decreased the activity of phenylalanine ammonia-lyase in inoculated leaves, but increased it in noninoculated upper leaves. However, Si treatment failed to change significantly the activity of PRs in plants without fungal attack. Compared to the control (no Si), foliar-applied Si had no effects either on the suppression of subsequent infection by P. xanthii or on the activity of PRs, irrespective of inoculation. Based on the findings in this study and previous reports, it was concluded that foliar-applied Si can effectively control infections by P. xanthii only via the physical barrier of Si deposited on leaf surfaces, and/or osmotic effect of the silicate applied, but cannot enhance systemic acquired resistance induced by inoculation, while continuously root-applied Si can enhance defence resistance in response to infection by P. xanthii in cucumber. [source] Comparison of viral RNA populations of pathogenically distinct isolates of Citrus tristeza virus : application to monitoring cross-protectionPLANT PATHOLOGY, Issue 3 2002A. Sambade The population of sequence variants of Citrus tristeza virus (CTV) isolates of different geographic origins and pathogenicity properties was characterized by single-strand conformation polymorphism (SSCP) analysis of cDNA of the genes p18, p13, p20 and p23. The mild isolates analysed here usually yielded a SSCP profile with two DNA bands, suggestive of a predominant sequence variant, whereas the SSCP profile of the most virulent isolates contained more than two DNA bands, indicating that their viral populations are likely to be more complex. The set of SSCP profiles of the four genes allowed identification of individual isolates, but no profile characteristic of a geographic area or a biogroup was found. Sweet orange plants singly inoculated with a mild or with a severe isolate yielded the SSCP profile characteristic of each isolate, whereas the SSCP profile of plants successively inoculated with both isolates was a composite of the two individual profiles. The SSCP profile of plants singly inoculated remained constant, but the profile of doubly inoculated plants varied with time. Plants in which the SSCP profile of the severe isolate became predominant showed stem pitting, and those in which the predominant profile corresponded to the mild isolate remained symptomless. The results indicate that SSCP analysis can be used to study changes in RNA populations of doubly inoculated plants and to monitor cross-protection between mild and severe isolates. [source] Production of Phytophthora infestans oospores in planta and inoculum potential of in vitro produced oospores under temperate highlands and subtropical plains of IndiaANNALS OF APPLIED BIOLOGY, Issue 3 2004B P SINGH Summary High moisture content of the host tissue ( 88%) and low ambient r.h. (50-54%) favoured oospore formation under controlled environments. It took 14,16 days for oospores to develop; thereafter the number of oospores increased with time and decreased with moisture content of host tissue. High ambient r.h. (> 80%) did not favour oospore formation under field or controlled conditions. Oospore formation was detected in inoculated plants grown in the field when the ambient r.h. declined to 74% and moisture content of host tissue decreased to 83.7,85.6%. It took 8 days (cv. Kufri Chandramukhi) to 13 days (cv. Kufri Jyoti and Kufri Badshah) for oospores to develop. Cultivars also differed in their response to oospore production, cv. Kufri Chandramukhi being more responsive (4800 oospores g,1 f wt) than cv. Kufri Jyoti and Kufri Badshah (1320 and 390 oospores g,1 f wt respectively). Oospores produced in vitro remained viable when buried in soil in the temperate highlands of Himachal Pradesh and sub-tropical plains of Uttar Pradesh, India for more than 150 days, i.e. beginning of the next crop season. The oospores germinated and initiated late blight infection at the base of the stems after 21,30 days of incubation of the potato plants raised in oospore-infested soil. It took 2 days for newly formed oospores to germinate and this delay time increased to 75,77 days after 180-days burial. It took 15 days for their germination (47%) in soil extract as compared to 50 days in sterilised distilled water. [source] | ||||||||||||||||||||||