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1.
Barley yellow dwarf disease is one of the most important problems confronting cereal production in Iran. Barley yellow dwarf virus-PAV (BYDV-PAV) and Cereal yellow dwarf virus-RPV (CYDV-RPV) are the predominant viruses associated with the disease. One isolate of BYDV-PAV from wheat (PAV-IR) and one
isolate of CYDV-RPV from barley (RPV-IR) were selected for molecular characterisations. A genome segment of each isolate was
amplified by PCR. The PAV-IR fragment (1264 nt) covered a region containing partial genes for coat protein (CP), read through
protein (RTP) and movement protein (MP). PAV-IR showed a high sequence identity to PAV isolates from USA, France and Japan
(96–97%). In a phylogenetic analysis it was placed into PAV group I together with PAV isolates from barley and oats. The fragment
of RPV-IR (719 nt) contained partial genes for CP, RTP and MP. The sequence information confirmed its identity as CYDV. However,
RPV-IR showed 90–91% identity with both RPV and Cereal yellow dwarf virus-RPS (CYDV-RPS). Phylogenetic analyses suggested that it was more closely related to RPS. These data comprise the first attempt
to characterise BYD-causing viruses in Iran and southwest Asia.
The nucleotide sequence data reported appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession
numbers AY450425 and AY450454 相似文献
2.
K. S. Kubo J. Freitas-Astúa M. A. Machado E. W. Kitajima 《Journal of General Plant Pathology》2009,75(3):250-255
Brevipalpus-transmitted viruses (BTV) cause chlorotic, necrotic and/or ringspot lesions in leaves and stems of orchids, citrus, coffee
and several other plant species. There are two different types of BTVs, the nuclear and the cytoplasmic, based on maturation
locale in the cell and particle morphology. The orchid fleck virus (OFV) is a BTV that infects orchids. Its short rodlike
particles are 32–40 nm in diameter, 100–150 nm in length. OFV is found in the nucleus and is associated with intranuclear
electronlucent viroplasms. In 1999, transmission electron microscopy analysis revealed a distinct type of virus causing orchid
fleck symptoms. The bacilliform particles, 70–80 nm in diameter and 110–120 nm in length, induced electron-dense viroplasm
inclusions in infected cells and resembled the cytoplasmic type associated with BTV, such as the citrus leprosis virus C.
Our objective in the present study was to verify whether the cytoplasmic type virus found in orchids could be amplified using
primers for other cytoplasmic BTVs, such as CiLV-C and Solanum
violaefolium ringspot virus (SvRSV). Additionally, we aimed to differentiate the two BTVs found in orchids: the nuclear and the cytoplasmic
types of OFV using microscopy and molecular and serological tools. This virus was not amplified by the CiLV-C and SvRSV primers,
and neither the molecular nor the serological tools available to the OFV diagnosis reacted with it, demonstrating that they
are definitely different viruses. 相似文献
3.
4.
<Emphasis Type="Italic">Turnip yellow mosaic virus</Emphasis> isolated from Chinese cabbage in Japan
Namiko Kirino Koji Inoue Koji Tanina Yuya Yamazaki Satoshi T. Ohki 《Journal of General Plant Pathology》2008,74(4):331-334
A virus that caused a distinct yellow mosaic was isolated in Okayama, Japan from Chinese cabbage (Brassica rapa L., Pekinensis group). The virus, with spherical particles ca. 28 nm in diameter, was mechanically transmissible only to
cruciferous species. From the host range, characteristic morphology of virus particles, serology and sequence analysis of
coat protein gene, the causal virus was identified as Turnip yellow mosaic virus (TYMV). Seed transmission of TYMV at 0–2.2% in Chinese cabbage was confirmed. This report is the first of TYMV from Chinese
cabbage and in Japan.
The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases as accessions AB358971 and AB358972. 相似文献
5.
Eduardo Segundo María P. Carmona Elisa Sáez Leonardo Velasco Germán Martín Leticia Ruiz Dirk Janssen Isabel M. Cuadrado 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(4):579-591
A study was conducted to determine the identity and prevalence of viruses in 455 greenhouses in the main Spanish green bean
growing area. Directed surveys were conducted in 422 crops from 2000–2004 to collect samples from diseased plants displaying
symptoms that could be attributed to viruses. The samples were analysed to detect any virus by means of dsRNA extraction,
mechanical inoculation to test plants, as well as ELISA and/or RT-PCR tests to detect potyviruses, geminiviruses and viruses
previously known to infect beans in Spain. Random surveys were conducted in the years 2002 and 2005 (in 21 and 12 greenhouses,
respectively) to study the actual incidence of known viruses in the area. Symptoms were recorded in 23,108 plants from which
664 plants were collected and analysed by ELISA or RT-PCR. The results of the directed surveys showed that all the analyzed
crops carried the cryptic virus Phaseolus vulgaris endornavirus (PVuV), whereas phytopathogenic viruses appeared in smaller percentages of the crops: Tomato yellow leaf curl virus (TYLCV) 20.4%, Southern bean mosaic virus (SBMV) 9.0%, Tomato spotted wilt virus (TSWV) 4.0%, and the new species Bean yellow disorder virus (BnYDV) that broke out in 2004 with occurrence values higher than 34.3% that year. From 2000–2004 an important decrease in
TYLCV was observed, along with a slight increase in SBMV and a consistently low occurrence of TSWV. The results of the random
surveys confirmed the increased occurrence of virus detected during the directed surveys, and furthermore demonstrated the
percentage of incidence for each virus. 相似文献
6.
Friederike Pferdmenges Helmut Korf Mark Varrelmann 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(1):31-43
Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is vectored by Polymyxa betae. The disease can only be controlled by growing partially resistant sugar beets, which quantitatively reduce virus replication
and spread. None of the known major resistance genes (Rz1, Rz2, Rz3), alone or in combination, are able to prevent BNYVV infection entirely. Here we report for the first time the identification
of a Spanish soil, containing an A-type BNYVV with RNA 1-4, displaying Rz1 resistance-breaking abilities comparable to soils from the USA and to those from France containing the French (Pithiviers)
P-type BNYVV with RNA 5. A resistance test with several soil samples vs. different sugar beet cultivars was conducted under
standardised conditions. Sugar beets were analysed after 12 weeks of greenhouse cultivation for taproot weight, BNYVV and
relative P. betae content. The soil samples from Spain, France and the USA produced high virus contents and strong rhizomania symptoms in Rz1 plants, indicative of resistance-breaking abilities. In addition, all resistance-breaking soil samples produced detectable
virus concentrations in plant lateral roots of the Rz1 + Rz2 cultivar, and plants grown in the Spanish soil sample also had reduced taproot weight and displayed severe rhizomania disease
symptoms. Additionally, the main pathogenicity factor P25, responsible for the formation of BNYVV symptoms, showed high sequence
variability in the amino acid tetrad at position 67–70. The results suggest the geographically independent selection of BNYVV
resistance-breaking isolates following the uniform cultivation of Rz1-containing sugar beet cultivars. 相似文献
7.
The rDNA-ITS sequences of ten single-sporangium isolates of Olpidium virulentus (a noncrucifer strain of Olpidium brassicae), which transmits Mirafiori lettuce big-vein virus (MLBVV) and tobacco stunt virus (TStV), were compared with those of six single-sporangium isolates of O. brassicae. The sequence similarity within isolates of O. virulentus or O. brassicae was almost identical (98.5%–100.0%), but was low between the two species (79.7%–81.8%). In a phylogenetic analysis of the
rDNA-ITS region, O. virulentus and O. brassicae fell into two distinct clusters, indicating that O. virulentus, a vector of MLBVV and TStV, is a distinct species rather than a strain of O. brassicae. 相似文献
8.
Friederike Pferdmenges Mark Varrelmann 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(2):231-245
Beet necrotic yellow vein virus (BNYVV) is transmitted by Polymyxa betae to sugar beet, causing rhizomania disease. Resistance-breaking strains of BNYVV, overcoming single (Rz1) or double (e.g. Rz1
+
Rz2) major resistance genes in sugar beet have been observed in France and recently in the USA and Spain. To demonstrate if resistance-breaking
is dependent on inoculum density, the inoculum concentration of BNYVV and P. betae in soil samples where resistance-breaking had been observed was estimated using the most probable number (MPN) method. The
MPN-values obtained displayed highly significant differences with respect to the virus concentration in various soils and
did not correlate with the ability to overcome resistance. Virus quantification in susceptible plants demonstrated that soils
containing resistance-breaking isolates of BNYVV did not produce higher virus concentrations. The MPN assay was repeated with
Rz1
+
Rz2 partially-resistant sugar beets to see if the resistance-breaking is concentration-dependent. There was no correlation between
soil dilution and increased virus concentration in Rz1
+
Rz2 plants produced by BNYVV resistance-breaking strains. Determination of the absolute P. betae concentration by ELISA demonstrated that all resistance-breaking soil samples contained elevated concentrations. However,
the calculation of the proportion of viruliferous P. betae did not show a positive correlation with the resistance-breaking ability. Finally resistance-breaking was studied with susceptible,
Rz1 and Rz1
+ Rz2 genotypes and standardised rhizomania inoculum added to sterilised soil. Results from these experiments supported the
conclusion that resistance-breaking did not correlate with virus concentration or level of viruliferous P. betae in the soil. 相似文献
9.
Anna Johansson Jan-Kees C. Goud Christina Dixelius 《European journal of plant pathology / European Foundation for Plant Pathology》2006,114(2):139-149
Verticillium longisporum is a soil-borne fungal pathogen causing vascular wilt of Brassica crops. This study was conducted to enhance our knowledge on the host range of V. longisporum. Seven crop species (barley, oat, oilseed rape, pea, red clover, sugar beet and wheat) and five weed species (barren brome,
black-grass, charlock, cleavers and scentless mayweed) all common in southern Sweden were evaluated for infection by response
to V. longisporum. Oat, spring wheat, oilseed rape, scentless mayweed and charlock inoculated with V. longisporum in a greenhouse showed stunting to various degrees close to the fully ripe stage. Based on the extent of microsclerotia formation,
explants were separated into four groups: for pea and wheat, <5% of the samples had formed microsclerotia; for scentless mayweed,
5–10%; for oat, 10–20%; and for charlock and oilseed rape >80%. The results suggest that plant species outside the Brassicaceae can act as reservoirs of V. longisporum inoculum. Soil inoculum densities in nine fields were monitored over a period of 12 months, which ranged from 1 to 48 cfu
g−1 soil. Density of microsclerotia was lowest just after harvest, reaching its maximum six months later. No significant correlation
between inoculum density in soil and disease incidence on oilseed rape plants was found. However, the data suggest that a
threshold of 1 cfu g−1 soil is needed to cause disease on oilseed rape. Species identification based on microsclerotia morphology and PCR analysis
showed that V. longisporum dominated in soil of seven, and V. dahliae in two of the nine fields studied. 相似文献
10.
S. Tanguy C.-A. Dedryver 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(3):281-289
The luteovirus Barley yellow dwarf virus–PAV (BYDV–PAV) and its vector, the aphid Sitobion avenae are two major sources of yield losses in cereal crops. We report in this paper the effects of a Triticum monococcum line (TM44), resistant by antibiosis to S. avenae, on the different steps of transmission of one BYDV–PAV isolate by the aphids. First, it was shown that TM44 is strongly resistant
to BYDV–PAV transmission, but exclusively when S. avenae is the vector. Second, that TM44 is resistant (1) to BYDV–PAV acquisition by S. avenae and (2) to its inoculation, whatever the respective duration of these two periods. Third, that both resistances have partially
additive effects. In the discussion, several lines of evidence are given to support the hypothesis that resistance of TM44
to PAV transmission is due to the same disturbances to S. avenae feeding behaviour that are involved in its antibiosis against this aphid species. Reasons for caution in releasing resistant
material in the field are presented. 相似文献
11.
Kazutaka Kido Rie Adachi Masaru Hasegawa Kazutaka Yano Yasufumi Hikichi Shigeharu Takeuchi Tae Atsuchi Yuichi Takikawa 《Journal of General Plant Pathology》2008,74(4):302-312
An internal fruit rot with a malodor was found in netted melons (Cucumis melo L.) in commercial greenhouses in Kochi Prefecture, Japan, in 1998, despite their healthy appearance and lack of water-soaking
or brown spots on the surface. A yellow bacterium was consistently isolated from the affected fruits. To confirm the pathogenicity
of eight representative isolates of the yellow bacterium, we stub-inoculated ovaries (immature-fruits) 5–7 days after artificial
pollination, with a pin smeared with bacteria. After the melon fruits had grown for 60 more days, an internal fruit rot resembling
the natural infection appeared, and the inoculated bacterium was reisolated. The melon isolates had properties identical with
Pantoea ananatis, such as gram-negative staining, facultative anaerobic growth, indole production, phenylalanine deaminase absence, and acid
production from melibiose, sorbitol, glycerol, and inositol. Phylogenetic analysis based on 16S rDNA sequences showed that
the melon bacterium positioned closely with known P. ananatis strains. The melon bacterium had indole acetic acid (IAA) biosynthesis genes (iaaM and iaaH) and a cytokinin biosynthesis gene (etz). The bacterium could be distinguished from the other ‘Pantoea’ group strains by rep-PCR genomic fingerprinting. From these results, the causal agent of internal fruit rot was identified
as a strain of P.ananatis [Serrano in (Philipp J Sci 36:271–305, 1928); Mergaert et al. in (Int J Syst Bacteriol 43:162–173, 1993)].
The nucleotide sequence data reported are available in the DDBJ database under accessions AB297969, AB373739, AB373740, AB373741,
AB373742, AB373743 and AB373744. 相似文献
12.
Forty-five onion (Allium cepa) cultivars were evaluated for disease resistance to the fungal pathogen Pyrenochaeta terrestris (pink root disease). Forty-three Iranian cultivars and two commercially exotic resistant cultivars (Texas Early Grano and
Yellow Sweet Spanish) were grown in a glasshouse for two successive years (2003 and 2004) in Isfahan, Iran. Susceptibility
of the cultivars was determined using a scale of 0–3. Six cultivars had significantly lower susceptibility of pink root compared
to the exotic ones. High susceptibility tended to be associated with high mean scores (2–3), and the highly resistant cultivars
had the lowest scores (0–1). In addition, the 45 examined cultivars were ranked from 1 to 45 according to their markedly differing
reactions to P. terrestris, which differed markedly. Of 32 cultivars that were less resistant, 30 with an intermediate status or tolerance (1–2) differed
considerably in their rank order. No pink root symptoms were seen in the early stages, but on blotter paper or wheat-straw
agar some roots turned pink with no pycnidia formation, whereas on potato dextrose agar medium (PDA) with a few fresh healthy
and sterile onion roots on the surface, mycelia and pycnidia were recovered. Variance and cluster analysis showed similar
results among the cultivars with various levels of resistance, tolerance and susceptibility as determined by scoring scales. 相似文献
13.
Djabbar Hariri Michel Meyer 《European journal of plant pathology / European Foundation for Plant Pathology》2007,118(1):1-10
In April 2001, stunted barley plants bearing mosaic symptoms were observed in a field in France (Marne Department, 51). Rod-shaped
and flexuous particles were visualized by electron microscopy and positive serological reactions were detected by ELISA with
Barley yellow mosaic virus (BaYMV) and Soil-borne cereal mosaic virus (SBCMV) polyclonal antisera. The tubular virus which was soil transmissible to barley cv. Esterel was separated from BaYMV
by serial mechanical inoculations to barley cv. Esterel. This furo-like virus, in contrast to a French isolate of SBCMV, could
be transmitted to Hordeum vulgare, Avena sativa, Beta vulgaris and Datura stramonium. RT-PCR was used to amplify the 3′-terminal 1500 nucleotides of RNA1 and the almost complete sequence of RNA2. Nucleotide
and amino acid sequence analyses revealed that the French virus infecting barley is closely related to a Japanese isolate
of Soil-borne wheat mosaic virus (SBWMV-JT) which was originally isolated from barley. This French isolate was named SBWMV-Mar. The 3′ UTRs of both RNAs can
be folded into tRNA-like structures which are preceded by a predicted upstream pseudoknot domain with seven and four pseudoknots
for RNA1 and RNA2, respectively. The four pseudoknots strongly conserved in RNAs 1 and 2 of SBWMV-Mar show strong similarities
to those described earlier in SBWMV RNA2 and were also found in the 3′ UTR of Oat golden stripe virus RNAs 1 and 2 and Chinese wheat mosaic virus RNA2. Sequence analyses revealed that the RNAs 2 of SBWMV-Mar and -JT are likely
to be the product of a recombination event between the 3′ UTRs of the RNAs 2 of SBWMV and SBCMV. This is the first report
of the occurrence of an isolate closely related to SBWMV-JT outside of Japan. 相似文献
14.
Several new isolates ofBacillus thuringiensis Berliner have shown significantly higher levels of insecticidal activity than the previous best isolates (Bt24-entomocidus and IH-A-aizawai) against bothSpodoptera littoralis Boisd. andSpodoptera exempta Walker. The best ones, in the following descending order of potency, were: againstS. littoralis — K26–21, MF4B–2, MR1–37, K28–30, K26–8; againstS. exempta — Bt-3, K30–3, HD-133, MR1–37, Bt-17, K26–8, K26–21, MF4B-2, HD-593. Larvae ofS. exempta were considerably more susceptible (4.12–1.25 fold) to some of the isolates (Bt-3, K30–3, HD-133, MR1–37, Bt-17, K26–8, HD-593)
thanS. littoralis. 相似文献
15.
Fumiyoshi Fukumoto 《Journal of General Plant Pathology》2008,74(2):164-170
Alfalfa mosaic virus (AMV) belongs to the genus Alfamovirus of the family Bromoviridae, for which the virions are stabilized by dominant protein–RNA interactions. The infectivity of purified AMV preparations
stored frozen at −20°C decreased to 10–20% in 2 years. In addition, the virion peak profiles after sucrose density gradient
centrifugation (SDGC) was reduced to a single, broad peak as a result of virus particle degradation, and the peaks for the
extracted virion RNA decreased. However, additives such as 0.5% peptone or 2.5% sucrose were markedly protective such that
infectivity and the SDGC profiles of the virus particles and virion RNA remained essentially unchanged after 5–8 years of
freezing. Infectivity of the purified AMV decreased to c. 50%, and virus particles deteriorated immediately after freeze-drying.
The addition of 1.0–7.5% sucrose suppressed alterations in infectivity, particle morphology and virion RNA after freeze-drying
and other preservation processes. The characteristics of AMV preservation were similar to those reported in a previous study
on cucumoviruses. Consequently, viruses belonging to the Bromoviridae may preserve well with sucrose in conjunction with freezing or freeze-drying. 相似文献
16.
H. Delatte H. Holota B. Reynaud J. Dintinger 《European journal of plant pathology / European Foundation for Plant Pathology》2006,114(3):245-253
Two wild genotypes from the same species Lycopersicon pimpinellifolium, WVA106 (susceptible) and INRA-Hirsute (so-called ‘resistant’), were compared with respect to their reaction to Tomato yellow leaf curl virus isolate Réunion (TYLCV-Mld[RE]), using both whitefly-mediated inoculation and graft inoculation. Disease incidence and symptom
severity were scored. Presence and quantification of viral DNA were assessed by dot blot hybridisation. Upon insect inoculation,
accession INRA-Hirsute showed a moderate resistance against TYLCV that was overcome by a high inoculation pressure obtained
by increasing the cumulative number of inoculative whiteflies. Temporal analyses of the disease progress in relation to this
criterion exhibited that the protection was quantitative, mainly reducing the TYLCV-Mld[RE] incidence by at maximum 50% at
low inoculation pressure. When graft inoculated, the final TYLCV-Mld[RE] disease incidence was 100% in both susceptible and
resistant genotypes with severe symptoms, suggesting a reduction of virus transmission by a vector resistance as a possible
mechanism. Implications of using such type of resistance in breeding programmes are discussed. 相似文献
17.
Rosemarie Tedeschi Pavel Lauterer Lorenzo Brusetti Federica Tota Alberto Alma 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(3):301-310
Hawthorn (Crataegus monogyna) is one of the natural hosts of Cacopsylla melanoneura, the acknowledged vector of ‘Candidatus Phytoplasma mali’, the causal agent of Apple Proliferation disease, a serious and growing problem for apple production in
Europe, particularly in northern Italy. Wild plants could be important sources of both insects and phytoplasmas, but their
role in the epidemiology of phytoplasma diseases and their insect vectors has never been thoroughly examined. Cacopsylla melanoneura’s primary host is hawthorn, a plant closely related to apple which often grows wild near orchards. Other psyllid species
feed on hawthorn, but no data are available on their possible role as phytoplasma vectors. We investigated the hawthorn’s
psyllid fauna in northwestern Italy using yellow sticky traps, beat trays, and molecular analyses from 2003–2005, to study
the relationship between hawthorn, the phytoplasma and the insect vector. Population dynamics were monitored, and insects
and hawthorn samples were analysed by polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP), and
DNA sequencing for the presence of phytoplasmas. Cacopsylla melanoneura was the dominant psyllid species, followed by C. peregrina, C. affinis and C. crataegi. PCR and RFLP analyses revealed the presence of different fruit tree phytoplasmas in hawthorn plants, and in all four psyllid
species. 相似文献
18.
You-Xiu Zheng Ching-Chung Chen Yuh-Kun Chen Fuh-Jyh Jan 《European journal of plant pathology / European Foundation for Plant Pathology》2008,121(1):87-95
A putative virus-induced disease showing chlorotic spots on leaves of Phalaenopsis orchids was observed in central Taiwan. A virus culture, phalaenopsis isolate 7-2, was isolated from a diseased Phalaenopsis orchid and established in Chenopodium quinoa and Nicotiana benthamiana. The virus reacted with the monoclonal antibody (POTY) against the potyvirus group. Potyvirus-like long flexuous filament
particles around 12–15 × 750–800 nm were observed in the crude sap and purified virus preparations, and pinwheel inclusion
bodies were observed in the infected cells. The conserved region of the viral RNA was amplified using the degenerate primers
for the potyviruses and sequence analysis of the virus isolate 7-2 showed 56.6–63.1% nucleotide and 44.8–65.1% amino acid
identities with those of Bean yellow mosaic virus (BYMV), Beet mosaic virus (BtMV), Turnip mosaic virus (TuMV) and Bean common mosaic virus (BCMV). The coat protein (CP) gene of isolate 7-2 was amplified, sequenced and found to have 280 amino acids. A homology
search in GenBank indicated that the virus is a potyvirus but no highly homologous sequence was found. The virus was designated
as Phalaenopsis chlorotic spot virus (PhCSV) in early 2006. Subsequently, a potyvirus, named Basella rugose mosaic virus isolated
from malabar spinach was reported in December 2006. It was found to share 96.8% amino acid identity with the CP of PhCSV.
Back-inoculation with the isolated virus was conducted to confirm that PhCSV is the causal agent of chlorotic spot disease
of Phalaenopsis orchids in Taiwan. This is the first report of a potyvirus causing a disease on Phalaenopsis orchids. 相似文献
19.
Chetsadaporn Pitaksutheepong Artit Vimoltat Boonyanath Nathwong Supat Attathom 《Journal of General Plant Pathology》2007,73(1):72-75
The DNA-binding activity and DNA-binding domain of Tomato yellow leaf curl Thailand virus coat protein were investigated. A full-length coat protein (CP) and two truncated derivatives lacking the amino (CPΔ1-62)
and carboxyl (CPΔ126-257) termini were produced in Escherichia coli as fusion proteins to glutathione-S-transferase (GST). Southwestern analysis showed that GST-CP bound both single-stranded (ss) and double-stranded (ds) DNA,
while GST-CPΔ126-257 interacted only with ssDNA. Neither ss nor dsDNA bound to GST-CPΔ1-62. The results suggested that a putative
DNA-binding domain is located at the N-terminal 1-62 amino residues.
The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under accession numbers AF141922 (TYLCTHV-[2]),
AF220561 (RTBVCN), X01633 (MSV) and AF295401 (ToLCBV-[Ban5]) 相似文献
20.
Dry mycelium (DM) of killedPenicillium chrysogenum and its water extract (DME) were used to induce resistance in cotton plants againstFusarium oxysporum f.sp.vasinfectum (Fov). Results showed that the efficacy of either DM or DME in controlling the disease depends on both the concentration and the
mode of application. DM amended to the soil at 0.25–2% (w/w) provided 32–75% protection againstFov. Soil drench with 2–5% DME (w/v) and pre-sowing seed soakage with 5–10% DME provided 51–77% and 28–35% protection against
the wilt disease, respectively, whereas no protection was obtained with foliar sprays of 1–10% DME. DM and its water extract
had no direct antifungal activity on growth ofFov in vitro, suggesting that disease control with DM or DME resulted from the induction of natural defense mechanisms in the cotton plants.
Soil drench with 5% DME was as effective as 2% DM powder in inducing resistance againstFov, implying that the resistance-inducing substances were mostly water-soluble. Four cotton cultivars with various genetic resistance
levels againstFov were tested at the seedling stage: two resistant ‘Pima’ cultivars and two susceptible ‘Acala’ cultivars. The level of protection
achieved in the two susceptible cultivars with DME was equal to, or higher than, that of the two resistant cultivars treated
with water. Innate and induced peroxidase activity in cotyledons or hypocotyls and roots coincided with the level of genetic
resistance and DME-induced resistance, respectively. Based on our results, an integrated control strategy ofFov with both genetic resistance and induced resistance is suggested. 相似文献