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1.
Citrus tristeza virus replicates and forms infectious virions in protoplasts of resistant citrus relatives 总被引:1,自引:0,他引:1
Albiach-Marti Maria R. Grosser Jude W. Gowda Siddarame Mawassi Munir Satyanarayana Tatineni Garnsey Stephen M. Dawson William O. 《Molecular breeding : new strategies in plant improvement》2004,14(2):117-128
Citrus tristeza virus (CTV) is the most economically important viral disease of citrus worldwide. Cultivars with improved CTV tolerance or resistance are needed to manage CTV-induced diseases. The citrus relatives Poncirus trifoliata (L.) Raf., Swinglea glutinosa (Blanco) Merr., and Severinia buxifolia (Poir) Ten. are potential sources of CTV resistance, but their resistance mechanisms are poorly characterized. As a first step to examine the mechanisms of resistance to CTV in these citrus relatives and selected Citrus × Poncirus hybrids, it was necessary to develop methods for protoplast isolation and viral inoculation to allow examination of CTV multiplication in this range of citrus varieties and relatives. Leaf and/or cultured cell protoplasts were isolated and inoculated with four biologically distinct CTV isolates. Northern-blot hybridization analyses for progeny RNAs and immuno-electron microscopy assays for newly produced virions showed that CTV replicated and produced infectious particles in protoplasts from all of the resistant plants tested. These results suggest that resistance to CTV observed at the plant level results from a lack of virus movement and/or some induced resistance response, rather than lack of viral multiplication at the cellular level. 相似文献
2.
3.
New gene(s) involved in the resistance of Poncirus trifoliata (L.) Raf. to citrus tristeza virus 总被引:3,自引:0,他引:3
P. F. Mestre M. J. Asíns E. A. Carbonell L. Navarro 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(4):691-695
Citrus tristeza virus (CTV) causes important economic losses in the citrus industry worldwide. Resistance to CTV is present
in Poncirus trifoliata and is known to be controlled by a dominant gene at the Ctr locus. Short-distance movement of CTV around the inoculum, as well as passive movement through the phloem vessels, were studied
in segregant plants derived by self-pollination from P. trifoliata var. “Flying Dragon” in order to genetically analyze the mechanism of CTV resistance. Accumulation of CTV in the vicinity
of the inoculum and in new flushes was studied by means of a direct tissue-blot immunoassay (DTBIA). CTV is able to passively
move with the phloematic flux from inoculated resistant genotypes Ctr-Rr and Ctr-RR up to a susceptible scion cultivar (Ctr-rr). Differences regarding CTV accumulation around the inoculum were found among Ctr-Rr individuals of the progeny. Bulked segregant analysis identified five RAPD markers linked to a locus (Ctm), or a genomic region, involved in short-distance accumulation of CTV but located in a different linkage group from Ctr. This result indicates that Ctr is not the only locus responsible for resistance to CTV in P. trifoliata, and that at least one other gene is involved. Given that citrus is a perennial crop, breeding for durable disease resistance
should take into account selection at both the Ctr and Ctm loci.
Received : 13 March 1996 / Accepted : 18 April 1997 相似文献
4.
Citrus tristeza virus (CTV) resistance in transgenic citrus based on virus challenge of protoplasts 总被引:2,自引:0,他引:2
Summary A strategy for the sereening of candidate virus-derived sequences to provide RNA-mediated citrus tristeza virus (CTV) resistance
and early selection of virus-resistant citrus is presented. The system is based on the polyethylene glycol-(PEG) mediated
cotransformation of protoplasts using virus-derived sequences and green fluorescent protein as a single selectable marker,
followed by an in vitro assay of virus inoculation into transgenic protoplasts to determine the level of citrus tristeza virus replication. A cotransformation
rate higher than 20% allowed selection of several clones carrying the desired transgenes. Efficient in vitro inoculation of virus in transgenic protoplasts was performed. Tobacco mosaic virus virions were used as a control in order
to check eitrus protoplast viability. Different CTV replication levels were detected in transgenic clones. Only one clone
showed no replication of CTV. Considerations regarding selection of candidate virusderived sequences and virus challenge of
transgenic cells are presented. 相似文献
5.
Polyamines in plants infected by citrus exocortis viroid or treated with silver ions and ethephon 总被引:3,自引:2,他引:1 下载免费PDF全文
The levels of polyamines in leaves of Gynura aurantiaca DC and tomato, Lycopersicon esculentum Mill. cv Rutgers, infected with citrus exocortis viroid (CEVd) or treated with silver nitrate or ethephon (2-chloroethylphosphonic acid) were measured by HPLC in relation to development of symptoms. Previously it had been demonstrated that treatment of G. aurantiaca plants with silver nitrate or ethephon closely mimicked the effects of viroid infection in the plants. In the studies reported here, a marked decrease in putrescine level was observed in plants infected by CEVd or treated with silver ions or ethephon. There was no significant change in either spermidine or spermine levels. Treatment of G. aurantiaca plants with specific inhibitors of ethylene biosynthesis (aminoethoxyvinylglycine, Co2+) or ethylene action (norbornadiene) prevented the decrease of putrescine associated with silver nitrate treatment and had no effect on spermidine or spermine levels. The development of viroid-like symptoms, the production of associated pathogenesis-related proteins, and the rise in protease activity induced by silver nitrate, were all suppressed by exogenous application of putrescine. The decreased level of putrescine as an ethylene-mediated step in the transduction of the viroid and silver or ethephon signaling is discussed. 相似文献
6.
Susanne Stöcker Marie-Christine Guitton Angela Barth Hans-Peter Mühlbach 《Plant cell reports》1993,12(11):597-602
Photosynthetically active callus and cell suspension cultures were established from uninfected Lycopersicon peruvianum plants and from uninfected and potato spindle tuber viroid (PSTVd) infected plants of Lycopersicon esculentum cv. Rutgers. Viroid infection was maintained in photoheterotrophic culture on media containing 3% sucrose, but during continuous photo-mixotrophic culture in low sucrose media (1% sucrose), the level of PSTVd accumulation decreased. Photoautotrophic cell suspensions could be established with uninfected, but not with viroid infected tomato cells. As compared to uninfected cells, PSTVd infected cells grew slowly, were morphologically different in size and shape, and formed tight cell aggregates. Electronmicroscopy showed that starch accumulation in chloroplasts, deformation of the chloroplast envelope and irregular plasmalemmasomes at the cell membrane were associated with PSTVd infection.Abbreviations 2,4-D
2,4-Dichlorophenoxyacetic acid
- BAP
6-benzylaminopurine
- CEVd
citrus exocortis viroid
- CSVd
chrysanthemum stunt viroid
- PSTVd
potato spindle tuber viroid
- TMV
tobacco mosaic virus
- phc
photoheterotrophic cell culture
- mcc
photomixotrophic cell culture
- pcc
photoautotrophic cell culture 相似文献
7.
Expressed sequence enrichment for candidate gene analysis of citrus tristeza virus resistance 总被引:7,自引:0,他引:7
Bernet GP Bretó MP Asins MJ 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2004,108(4):592-602
Several studies have reported markers linked to a putative resistance gene from Poncirus trifoliata (Ctv-R) located at linkage group 4 that confers resistance against one of the most important citrus pathogens, citrus tristeza virus (CTV). To be successful in both marker-assisted selection and transformation experiments, its accurate mapping is needed. Several factors may affect its localization, among them two are considered here: the definition of resistance and the genetic background of progeny.Two progenies derived from P. trifoliata, by self-pollination and by crossing with sour orange (Citrus aurantium), a citrus rootstock well-adapted to arid and semi-arid areas, were used for linkage group-4 marker enrichment. Two new methodologies were used to enrich this region with expressed sequences. The enrichment of group 4 resulted in the fusion of several C. aurantium linkage groups. The new one A(7+3+4) is now saturated with 48 markers including expressed sequences. Surprisingly, sour orange was as resistant to the CTV isolate tested as was P. trifoliata, and three hybrids that carry Ctv-R, as deduced from its flanking markers, are susceptible to CTV. The new linkage maps were used to map Ctv-R under the hypothesis of monogenic inheritance. Its position on linkage group 4 of P. trifoliata differs from the location previously reported in other progenies. The genetic analysis of virus-plant interaction in the family derived from C. aurantium after a CTV chronic infection showed the segregation of five types of interaction, which is not compatible with the hypothesis of a single gene controlling resistance. Two major issues are discussed: another type of genetic analysis of CTV resistance is needed to avoid the assumption of monogenic inheritance, and transferring Ctv-R from P. trifoliata to sour orange might not avoid the CTV decline of sweet orange trees.Communicated by C. Möllers 相似文献
8.
Systemic interactions of long duration among the Group I] Citrus Viroids, CVd-IIa and CVd-IIb were investigated by grafting buds from established citron (Citrus medica L.) sources containing single viroids to a common healthy seedling. In healthy tissues, the two viroids became established in approximately equal titres as a mixed infection. By contrast, tissues that grew from the CVd-IIa or CVd-IIb source buds contained only trace amounts of the heterologous invading viroids. This interference between CVd-IIa, a mild exocortis agent, and CVd-IIb, the cachexia agent, was also demonstrated in the presence of CEVd, the severe exocortis agent but not a Group II viroid. When a CVd-IIb bud was propagated on a citron containing CVd-IIa, a dramatic reduction in the titre of CVd-IIb was observed. The interference between CVd-IIa and CVd-IIb indicates that the mild and relatively innocuous isolate, CVd-IIa, can interfere with the replication and/or accumulation of the severe cachexia agent, CVd-IIb, in citrus. This offers a potential practical approach for the control of cachexia in commercial plantings by “viroid interference”. 相似文献
9.
Systemic invasion of plants by viruses is thought to involve two processes: cell-to-cell movement between adjacent cells and long-distance movement that allows the virus to rapidly move through sieve elements and unload at the growing parts of the plant. There is a continuum of proportions of these processes that determines the degrees of systemic infection of different plants by different viruses. We examined the systemic distribution of Citrus tristeza virus (CTV) in citrus species with a range of susceptibilities. By using a "pure" culture of CTV from a cDNA clone and green fluorescent protein-labeled virus we show that both cell-to-cell and long-distance movement are unusually limited, and the degree of limitation varies depending on the citrus host. In the more-susceptible hosts CTV infected only a small portion of phloem-associated cells, and moreover, the number of infection sites in less-susceptible citrus species was substantially decreased further, indicating that long-distance movement was reduced in those hosts. Analysis of infection foci in the two most differential citrus species, Citrus macrophylla and sour orange, revealed that in the more-susceptible host the infection foci were composed of a cluster of multiple cells, while in the less-susceptible host infection foci were usually single cells, suggesting that essentially no cell-to-cell movement occurred in the latter host. Thus, CTV in sour orange represents a pattern of systemic infection in which the virus appears to function with only the long-distance movement mechanism, yet is able to survive in nature. 相似文献
10.
Molecular markers flanking citrus tristeza virus resistance gene from Poncirus trifoliata (L.) Raf. 总被引:2,自引:0,他引:2
P. F. Mestre M. J. Asíns J. A. Pina E. A. Carbonell L. Navarro 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(3-4):458-464
Two segregating populations for citrus tristeza virus (CTV) resistance derived from Poncirus trifoliata var ‘Flying Dragon’ by self-pollination and pollination to Citrus medica L. var ethrog ‘Arizona’ were inoculated with a common CTV isolate. The presence of virus was checked by the Double Antibody
Sandwich Enzyme-Linked Assay and Direct Tissue Blot Inmunoassay at 3, 6, and 12 months after inoculation. Seven RAPDs were
found linked to the CTV resistance gene by bulked segregant analysis. The closest linked RAPDs were cloned to obtain linked
codominant RFLPs and to increase the precision of the genetic distance estimation. The CTV resistance gene seems to be located
between cW18 and cK16. Differences in genetic distances among progenies are large and can be explained by genome-wide reduction
in the recombination of progeny derived from male versus female gametes.
Received: 5 June 1996 / Accepted: 26 July 1996 相似文献
11.
Sílvia de Oliveira Dorta Juliana Balbinotte Rose Monnerat Joo Roberto Spotti Lopes Tatiane da Cunha Odimar Zanuzo Zanardi Marcelo Pedreira de Miranda Marcos Antonio Machado Juliana de Freitas‐Astúa 《Insect Science》2020,27(3):519-530
Bacillus thuringiensis (Bt) toxins are effective in controlling insect pests either through the spraying of products or when expressed in transgenic crops. The discovery of endophytic Bt strains opened new perspectives for studies aimed at the control of sap‐sucking insects, such as the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae), a vector of “Candidatus Liberibacter spp.,” associated with citrus huanglongbing (HLB). In this study, translocation of endophytic Bt strains in citrus seedlings inoculated with Bt suspension delivered by soil‐drench, and their systemic pathogenicity to D. citri nymphs were investigated. The pathogenicity of three wild‐type Bt strains against D. citri third‐instar nymphs was demonstrated. Among the 10 recombinant strains tested (each of them harboring a single cry or cyt gene), 3 can be highlighted, causing 42%–77% and 66%–90% nymphal mortality at 2 and 5 d after inoculation, respectively. The isolation of Bt cells from young citrus shoots and dead nymphs, and PCR performed with specific primers, confirmed the involvement of the Bt strains in the psyllid mortality. This is the first report showing the translocation of Bt strains from citrus seedling roots to shoots and their potential to control D. citri nymphs that fed on these soil‐drench inoculated seedlings. The Bt strains that caused the highest mortality rates have the potential to be used as bioinsecticides to control D. citri and the identified genes can be used for the production of transgenic Bt citrus. 相似文献
12.
Efficient production of transgenic citrus plants expressing the coat protein gene of citrus tristeza virus 总被引:15,自引:0,他引:15
A. Domínguez J. Guerri M. Cambra L. Navarro P. Moreno L. Peña 《Plant cell reports》2000,19(4):427-433
The coat protein gene of citrus tristeza virus (CTV) has been introduced into Mexican lime (Citrus aurantifolia Swing.) plants by using an improved Agrobacterium-mediated genetic transformation system. Internodal stem segments from greenhouse-grown seedlings were co-cultivated with
A. tumefaciens strain EHA 105 carrying the binary plasmid pBI 121/CTV-CP in a medium rich in auxins that provided the explant cells with the proper treatment to shift them to a competent state for
transformation. The transformation frequency was enhanced, and this allowed us to recover 42 transgenic plants from 1200 explants.
Regenerated shoots were identified as transformants by performing β-glucuronidase (GUS) assays and subsequently by PCR amplifications
of the CTV-CP transgene. Southern analyses revealed that at least one copy of the CTV-CP gene was integrated in all PCR positive plants. Interestingly, 70% of them had linked T-DNAs arranged at one locus. Copy
number of the CTV-CP gene varied from one to six among the transgenic lines. Half of them showed truncated T-DNAs in which the left border was
lost. Expression of the CTV-CP transgene was demonstrated in 38 out of 42 plants by western analysis and DASI-ELISA. No correlation was found between coat
protein expression and transgene copy number or integration pattern.
Received: 7 April 1999 / Revision received: 17 June 1999 · Accepted: 24 June 1999 相似文献
13.
Efficient search for new resistant genotypes to the citrus tristeza closterovirus in the orange subfamily Aurantioideae 总被引:2,自引:0,他引:2
P. F. Mestre M. J. Asíns J. A. Pina L. Navarro 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(8):1282-1288
Virulent isolates of the citrus tristeza virus (CTV) are continuously arising and their spread threatens the world citrus
industry. Methods for effective utilization of material conserved in germplasm banks are needed in plant improvement. Two
objectives are pursued in the present paper: a search for new CTV-resistant genotypes and tests of two strategies for this
search. One of these tests is based on a study of genetic relationships among genera and species of the orange subfamily and
the other on scores of molecular markers known to be linked to the CTV-resistant locus.
Sampled plants were graft-inoculated with a mild CTV isolate (T-346) and two virulent ones (T-388 and T-305). Susceptible
plants were those where CTV multiplication was detected beyond 4 months after inoculation. All cultivars of Poncirus trifoliata tested, as well as Severinia buxifolia and Atalantia ceylanica, were resistant to the three CTV isolates; Fortunella crassifolia (Meiwa kumquat) resists two of them. The finding of CTV resistance in this species, closely related to cultivated Citrus species, opens a new arena for CTV-resistance improvement of oranges and mandarines by sexual hybridization.
The searching strategy based on phylogenetic data has been successful, whereas the other one may be worthwhile only when the
search is restricted to the species where linkage analysis is available. A good documentation system that allows quick sampling
of accessions to build up core collections and where the location of new and useful genes could be easily worked out, is suggested
to enhance germplasm utilization.
Received: 27 April 1997 / Accepted: 5 June 1997 相似文献
14.
Citrus viroids (CVds) were used to limit citrus tree size ('dwarfing'). It
is hypothesized that changes also occur in the hydraulic properties of the
conducting system, thereby affecting water relations. Grapefruit trees
(var. Star Ruby on Troyer Citrange rootstock) in northern Israel were
infected with citrus exocortis viroid (CEVd). The orchard was drip
irrigated. The infected (I) and apparently healthy (H) control plots were
subdivided into wet (W) and dry (D) irrigation treatments receiving 100%
and 70% of the recommended irrigation quantity for the region. Soil water
content, soil temperature, water uptake, leaf and stem water potential, and
leaf conductance were measured in addition to climatic variables. Water
uptake response to increasing spring-time soil temperatures was greater in
healthy than in infected trees. Leaf conductance in the infected trees was
lower than the non-infected trees only in the sixth year after inoculation.
Stem water potential was significantly lower in the CEVd-infected trees
than in the control trees. Water uptake was lower and hydraulic resistance
higher in infected than in healthy trees. It was concluded that CEVd causes
a reduction in the water uptake ability of the root and canopy system.
Possible mechanisms for this are discussed. 相似文献
15.
Rizza S Conesa A Juarez J Catara A Navarro L Duran-Vila N Ancillo G 《Molecular Plant Pathology》2012,13(8):852-864
Viroids are small (246-401 nucleotides), single-stranded, circular RNA molecules that infect several crop plants and can cause diseases of economic importance. Citrus are the hosts in which the largest number of viroids have been identified. Citrus exocortis viroid (CEVd), the causal agent of citrus exocortis disease, induces considerable losses in citrus crops. Changes in the gene expression profile during the early (pre-symptomatic) and late (post-symptomatic) stages of Etrog citron infected with CEVd were investigated using a citrus cDNA microarray. MaSigPro analysis was performed and, on the basis of gene expression profiles as a function of the time after infection, the differentially expressed genes were classified into five clusters. FatiScan analysis revealed significant enrichment of functional categories for each cluster, indicating that viroid infection triggers important changes in chloroplast, cell wall, peroxidase and symporter activities. 相似文献
16.
QTL analysis of citrus tristeza virus-citradia interaction 总被引:2,自引:0,他引:2
Asins MJ Bernet GP Ruiz C Cambra M Guerri J Carbonell EA 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2004,108(4):603-611
Citrus tristeza virus (CTV) has caused the death of millions of trees grafted on sour orange (Citrus aurantium). However, this rootstock is very well adapted to the Mediterranean, semi-arid conditions. The aim of the present research is to genetically analyze the accumulation of CTV in a progeny derived from the cross between C. aurantium and Poncirus trifoliata, both resistant to CTV isolate T-346. Graft propagation of 104 hybrids was done on healthy sweet orange as a rootstock. Three months later, each rootstock was graft inoculated with two patches of infected tissue (isolate T-346). One, 2, and sometimes, 3 and 4 years after inoculation, hybrids and infected patches were tested for CTV by tissue-blot immuno-assay. Additionally, CTV multiplication was evaluated every year as the optical density of double-antibody sandwich enzyme-linked immuno-sorbent assay reactions. Linkage maps for P. trifoliata based on 63 markers, and for C. aurantium based on 157 markers, were used. Most molecular markers were microsatellites and IRAP (inter-retrotransposon amplified polymorphisms). Some analogues of resistance and expressed sequences were also included for candidate gene analysis.Resistance against CTV was analyzed as a quantitative trait (CTV accumulation) by QTL (quantitative trait loci) analysis to avoid the assumption of monogenic control. Three major resistance QTLs were detected where the P. trifoliata resistance gene, Ctv-R, had been previously located in other progenies. Up to five minor QTLs were detected (Ctv-A
1
to Ctv-A
5
). A significant epistatic interaction involving Ctv-R
1
and Ctv-A
1
was also found. An analogue of a resistance gene is a candidate for Ctv-A
3
, and two expressed sequences are candidates for Ctv-A
1
and Ctv-A
5
. Single-strand conformational polymorphism analysis of CTV genes QTL P20 and P25 (coat protein) in susceptible hybrids, was carried out to test whether or not any QTL accumulation was a defeated resistance gene. Since the same haplotype of the virus was visualized independently on the CTV titer, differences in the amount of virions are not explained through the selection of CTV genotypes by the host, but through differences among citradias in CTV replication and/or movement.Communicated by C. Möllers 相似文献
17.
F. G. Gmitter Jr S. Y. Xiao S. Huang X. L. Hu S. M. Garnsey Z. Deng 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(6):688-695
A localized genetic linkage map was developed of the region surrounding the citrus tristeza virus (CTV) resistance gene (designated Ctv) from Poncirus trifoliate L., a sexually compatible Citrus relative. Bulked segregant analysis (BSA) was used to identify potential resistance-associated RAPD fragment markers in four intergeneric backcross families that were segregating for CTV resistance. Eight RAPD fragments were found that were consistently linked to Ctv in the four families. Map distances and locus order were determined with MAPMAKER 3.0, using the results obtained from 59 individuals in the largest family. Also, a consensus map was constructed with JOINMAP 1.3, using pooled results from the four backcross families. Marker orders were identical, except for 1 marker, on these independently developed maps. Family-specific resistance-associated markers were also identified, as were numerous susceptibility-associated markers. The identification of markers tightly linked to Ctv will enable citrus breeders to identify plants likely to be CTV-resistant by indirect, marker-assisted selection, rather than by labor-intensive direct challenge with the pathogen. These markers also provide a basis for future efforts to isolate Ctv for subsequent genetic manipulation.Florida Agricultural Experimental Station Journal Series No. R-04491 相似文献
18.
Summary Bacteria, isolated from roots (xylem tissue) of healthy and Young Tree Decline (YTD, Blight)-affected citrus trees, and also from nursery seedlings, were screened for potential pathogenicity by the tobacco hypersensitive reaction (HR). A majority (>75%) of the HR positive strains were classified as nonfluorescent pseudomonads. These HR positive strains were subsequently inoculated into rough lemon (Citrus jambhiri Lush.) and sweet orange (C. sinsensis Osbeck) seedlings or into Valencia sweet orange budded on rough lemon root-stock. Many of the HR positive pseudomonads reduced fresh weights (up to 94%) of roots and shoots and some reduced xylem water conductance and caused scion dieback. There was no evidence of necrosis or root rot in inoculated roots. A few HR negative Pseudomonas and Enterobacter strains significantly, but less severely, inhibited (to 43%) root growth of sweet orange seedlings. HR negative mutants derived from HR positive strains were considerably less inhibitory. Postinoculation stresses (dark and cold) markedly decreased susceptibility of seedlings to bacterial-induced inhibition. Evidence of cultivar-specific effects was obtained in comparable inoculations of rough lemon and sweet orange seedlings. Soil application of a fluorescent pseudomonad, which alone was growth stimulatory, intensified inhibitory effects of nonfluorescent, growth inhibitory, psuedomonads. This study demonstrates that many rhizobacteria isolated from xylem tissue of roots have detrimental effects on citrus. 相似文献
19.
Riad Sedki Riad El-Mohamedy 《Archives Of Phytopathology And Plant Protection》2013,46(9):819-828
Abstract The efficiency of two biocontrol agents (Trichoderma harzianum NB and Bacillus subtilis NB) and two commercial biocides (Plant Guard and Rhizo-N) in controlling Fusarium root rot disease on some citrus rootstocks was evaluated under artificially infested soil in green house. Fusrium root rot on citrus rootstocks seedlings i.e. sour orange (SO), volkamer lime (VL), rangpur lime (RP) and cleopatra mandarin (CL) was successfully controlled by dipping the root system of such seedlings in water suspensions of each biological treatment i.e. Trichoderma harzianum (spore suspension 5×106 spore/ml), Bacillus subtilis (cell suspension 8×107 cell/ml), Plant Guard (3 g/l) and Rhizo-N (4 g/l), then transplanted into artificially infested soil with Fusarium solani and drenched with enough water suspension of such biological treatments. Plant Guard (3 g/l) and Rhizo-N (4 g/l) were highly effective treatments in decreasing infection and severity of the disease, Fusarium density in rhizosphere soil and colonization of Fusarium solani in the roots of all tested seedlings. Meanwhile, root dipping or soil drenching with the same treatments individually gave the least effect in reducing root rot incidenceon all tested rootstocks compared with application of the two methods together. It should be noted that using biocontrol agents and commercial biocides could be successfully used in controlling root rot pathogens on citrus in commercial greenhouses or under field conditions before transplanting in new reclaimed lands in the desert. 相似文献
20.
Z. Deng Q. Tao Y.-L. Chang S. Huang P. Ling C. Yu C. Chen F. G. Gmitter Jr. H.-B. Zhang 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(8):1177-1184
A BAC library was constructed from the genomic DNA of an intergeneric Citrus and Poncirus hybrid. The library consists of 24,576 clones with an average insert size of 115 kb, representing approximately seven haploid
genome equivalents and is able to give a greater than 99% probability of isolating single-copy citrus DNA sequences from this
library. High-density colony hybridization-based library screening was performed using DNA markers linked to the citrus tristeza
virus (CTV) resistance gene and citrus disease resistance gene candidate (RGC) sequences. Between four and eight clones were
isolated with each of the CTV resistance gene-linked markers, which agrees with the library’s predicted genome coverage. Three
hundred and twenty-two clones were identified using 13 previously cloned citrus RGC sequences as probes in library screening.
One to four fragments in each BAC were shown to hybridize with RGC sequences. One hundred and nine of the RGC BAC clones were
fingerprinted using a sequencing gel-based procedure. From the fingerprints, 25 contigs were assembled, each having a size
of 120–250 kb and consisting of 2–11 clones. These results indicate that the library is a useful resource for BAC contig construction
and molecular isolation of disease resistance genes.
Received: 22 May 2000 / Accepted: 25 September 2000 相似文献