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1.
Navas-Cortés JA Landa BB Rodríguez-López J Jiménez-Díaz RM Castillo P 《Phytopathology》2008,98(6):709-718
Fusarium oxysporum f. sp. ciceris, and the root-knot nematode Meloidogyne artiellia, coinfect chickpea crops in several countries of the Mediterranean Basin. The influence of root infection by M. artiellia on the reactions of chickpea genotypes with different reaction to infection with F. oxysporum f. sp. ciceris races 0, 1A, and 2 was investigated under controlled environmental conditions. Results demonstrated that co-infection of chickpea genotypes resistant to specific fungal races by M. artiellia did not influence the Fusarium wilt reaction of the plant, irrespective of the F. oxysporum f. sp. ciceris race assayed. However, in some of the assayed combinations, coinfection by both pathogens significantly affected the level of colonization by the fungus or reproduction of the nematode in the root system. Thus, coinfection of chickpea plants with Foc-0 and M. artiellia significantly decreased the level of colonization of the root system by F. oxysporum f. sp. ciceris in genotypes 'CA 336.14.3.0' and 'PV 61', but not in 'ICC 14216 K' and 'UC 27'. Similarly, the nematode reproduction index was also significantly reduced by coinfection with Foc-0 in the four chickpea genotypes tested and inoculated with this race. Conversely, coinfection of chickpea plants with Foc-1A and M. artiellia significantly increased colonization of the root system by the fungus in all genotypes inoculated with this race, except for line BG 212. Altogether, we confirmed the complete resistance phenotype of 'UC 27' and 'ICC 14216 K' to Foc-0, and of 'ICC 14216 K' to Foc-1A and Foc-2, and demonstrated that this resistance was not modified by coinfection of the resistant plant with M. artiellia. 相似文献
2.
ABSTRACT Fusarium oxysporum f. sp. ciceris and the root-lesion nematode Pratylenchus thornei coinfect chickpeas in southern Spain. The influence of root infection by P. thornei on the reaction of Fusarium wilt-susceptible (CPS 1 and PV 61) and wilt-resistant (UC 27) chickpea cultivars to F. oxysporum f. sp. ciceris race 5 was investigated under controlled and field conditions. Severity of Fusarium wilt was not modified by coinfection of chickpeas by P. thornei and F. oxysporum f. sp. ciceris, in simultaneous or sequential inoculations with the pathogens. Root infection with five nematodes per cm(3) of soil and 5,000 chlamydospores per g of soil of the fungus resulted in significantly higher numbers of propagules of F. oxysporum f. sp. ciceris with the wilt-susceptible cultivar CPS 1, but not with the wilt-resistant one. However, infection with 10 nematodes per cm(3) of soil significantly increased root infection by F. oxysporum f. sp. ciceris in both cultivars, irrespective of fungal inoculum densities (250 to 2,000 chlamydospores per g of soil). Plant growth was significantly reduced by P. thornei infection on wilt-susceptible and wilt-resistant chickpeas in controlled and field conditions, except when shorter periods of incubation (45 days after inoculation) were used under controlled conditions. Severity of root necrosis was greater in wilt-susceptible and wilt-resistant cultivars when nematodes were present in the root, irrespective of length of incubation time (45 to 90 days), densities of nematodes (5 and 10 nematodes per cm(3) of soil), fungal inocula, and experimental conditions. Nematode reproduction on the wilt-susceptible cultivars, but not on the wilt-resistant one, was significantly increased by F. oxysporum f. sp. ciceris infections under controlled and field conditions. 相似文献
3.
ABSTRACT Specific primers and polymerase chain reaction (PCR) assays that identify Fusarium oxysporum f. sp. ciceris and each of the F. oxysporum f. sp. ciceris pathogenic races 0, 1A, 5, and 6 were developed. F. oxysporum f. sp. ciceris- and race-specific random amplified polymorphic DNA (RAPD) markers identified in a previous study were cloned and sequenced, and sequence characterized amplified region (SCAR) primers for specific PCR were developed. Each cloned RAPD marker was characterized by Southern hybridization analysis of Eco RI-digested genomic DNA of a subset of F. oxysporum f. sp. ciceris and nonpathogenic F. oxysporum isolates. All except two cloned RAPD markers consisted of DNA sequences that were found highly repetitive in the genome of all F. oxysporum f. sp. ciceris races. F. oxysporum f. sp. ciceris isolates representing eight reported races from a wide geographic range, nonpathogenic F. oxysporum isolates, isolates of F. oxysporum f. spp. lycopersici, melonis, niveum, phaseoli, and pisi, and isolates of 47 different Fusarium spp. were tested using the SCAR markers developed. The specific primer pairs amplified a single 1,503-bp product from all F. oxysporum f. sp. ciceris isolates; and single 900- and 1,000-bp products were selectively amplified from race 0 and race 6 isolates, respectively. The specificity of these amplifications was confirmed by hybridization analysis of the PCR products. A race 5-specific identification assay was developed using a touchdown-PCR procedure. A joint use of race 0- and race 6-specific SCAR primers in a single-PCR reaction together with a PCR assay using the race 6-specific primer pair correctly identified race 1A isolates for which no RAPD marker had been found previously. All the PCR assays described herein detected up to 0.1 ng of fungal genomic DNA. The specific SCAR primers and PCR assays developed in this study clearly identify and differentiate isolates of F. oxysporum f. sp. ciceris and of each of its pathogenic races 0, 1A, 5, and 6. 相似文献
4.
The effects of temperature and inoculum density of Fusarium oxysporum f. sp. ciceris race 5 on suppression of Fusarium wilt in chickpea (Cicer arietinum) cv. PV 61 by seed and soil treatments with rhizobacteria isolated from the chickpea rhizosphere were studied in a model system. Disease development over a range of temperatures (20, 25, and 30 degrees C) and inoculum densities (25 to 1,000 chlamydospores per gram of soil) was described by the Gompertz model. The Gompertz relative rate of disease progress and final amount of disease increased exponentially and monomolecularly, respectively, with increasing inoculum densities. Disease development was greater at 25 degrees C compared with 20 and 30 degrees C. At 20 and 30 degrees C, disease development was greater at 250 to 1,000 chlamydospores per gram of soil compared with 25 to 100 chlamydospores per gram of soil. At 25 degrees C, increasing inoculum densities of the pathogen did not influence disease. Nineteen Bacillus, Paenibacillus, Pseudomonas, and Stenotrophomonas spp. out of 23 bacterial isolates tested inhibited F. oxysporum f. sp. ciceris in vitro. Pseudomonas fluorescens RGAF 19 and RG 26, which did not inhibit the pathogen, showed the greatest Fusarium wilt suppression. Disease was suppressed only at 20 or 30 degrees C and at inoculum densities below 250 chlamydospores per gram of soil. Bacterial treatments increased the time to initial symptoms, reduced the Gompertz relative rate of disease progress, and reduced the overall amount of disease developed. 相似文献
5.
ABSTRACT Development of 108 epidemics of Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris were studied on cvs. P-2245 and PV-61 in field microplots artificially infested with races 0 and 5 of F. oxysporum f. sp. ciceris in 1986 to 1989. Disease progression data were fitted to the Richards model using nonlinear regression. The shape parameter was influenced primarily by date of sowing and, to a lesser extent, by chick-pea cultivars and races of F. oxysporum f. sp. ciceris. Fusarium wilt reduced chickpea yield by decreasing both seed yield and seed weight. These effects were related to sowing date, chickpea cultivar, and virulence of the prevalent F. oxysporum f. sp. ciceris race. Regression models were developed to relate chickpea yield to Fusarium wilt disease intensity with the following independent variables: time to initial symptoms (t(is)), time to inflection point (t(ip)) of the disease intensity index (DII) progress curve, final DII (DII(final)), standardized area under DII progress curve (SAUDPC), and the Richards weighted mean absolute rate of disease progression (rho). Irrespective of the chickpea cultivar x pathogen race combination, the absolute and relative seed yields decreased primarily by delayed sowing. The relative seed yield increased with the delay in t(is) and t(ip) and decreased with increasing DII(final), SAUDPC, and rho. A response surface as developed in which seed yield loss decreased in a linear relationship with the delay in t(is) and increased exponentially with the increase of rho. 相似文献
6.
Jiménez-Fernández D Montes-Borrego M Jiménez-Díaz RM Navas-Cortés JA Landa BB 《Phytopathology》2011,101(2):250-262
Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris can be managed by risk assessment and use of resistant cultivars. A reliable method for the detection and quantification of F. oxysporum f. sp. ciceris in soil and chickpea tissues would contribute much to implementation of those disease management strategies. In this study, we developed a real-time quantitative polymerase chain reaction (q-PCR) protocol that allows quantifying F. oxysporum f. sp. ciceris DNA down to 1 pg in soil, as well as in the plant root and stem. Use of the q-PCR protocol allowed quantifying as low as 45 colony forming units of F. oxysporum f. sp. ciceris per gram of dry soil from a field plot infested with several races of the pathogen. Moreover, the q-PCR protocol clearly differentiated susceptible from resistant chickpea reactions to the pathogen at 15 days after sowing in artificially infested soil, as well as the degree of virulence between two F. oxysporum f. sp. ciceris races. Also, the protocol detected early asymptomatic root infections and distinguished significant differences in the level of resistance of 12 chickpea cultivars that grew in that same field plot infested with several races of the pathogen. Use of this protocol for fast, reliable, and cost-effective quantification of F. oxysporum f. sp. ciceris in asymptomatic chickpea tissues at early stages of the infection process can be of great value for chickpea breeders and for epidemiological studies in growth chambers, greenhouses and field-scale plots. 相似文献
7.
ABSTRACT A 3-year experiment was conducted in field microplots infested with Fusarium oxysporum f. sp. ciceris race 5 at Córdoba, Spain, in order to assess efficacy of an integrated management strategy for Fusarium wilt of chickpea that combined the choice of sowing date, use of partially resistant chickpea genotypes, and seed and soil treatments with biocontrol agents Bacillus megaterium RGAF 51, B. subtilis GB03, nonpathogenic F. oxysporum Fo 90105, and Pseudomonas fluorescens RG 26. Advancing the sowing date from early spring to winter significantly delayed disease onset, reduced the final disease intensity (amount of disease in a microplot that combines disease incidence and severity, expressed as a percentage of the maximum possible amount of disease in that microplot), and increased chickpea seed yield. A significant linear relationship was found between disease development over time and weather variables at the experimental site, with epidemics developing earlier and faster as mean temperature increased and accumulated rainfall decreased. Under conditions highly conducive for Fusarium wilt development, the degree of disease control depended primarily on choice of sowing date, and to a lesser extent on level of resistance of chickpea genotypes to F. oxysporum f. sp. ciceris race 5, and the biocontrol treatments. The main effects of sowing date, partially resistant genotypes, and biocontrol agents were a reduction in the rate of epidemic development over time, a reduction of disease intensity, and an increase in chickpea seedling emergence, respectively. Chickpea seed yield was influenced by all three factors in the study. The increase in chickpea seed yield was the most consistent effect of the biocontrol agents. However, that effect was primarily influenced by sowing date, which also determined disease development. Effectiveness of biocontrol treatments in disease management was lowest in January sowings, which were least favorable for Fusarium wilt. Sowing in February, which was moderately favorable for wilt development, resulted in the greatest increase in seed yield by the biocontrol agents. In March sowings, which were most conducive for the disease, the biocontrol agents delayed disease onset and increased seedling emergence. B. subtilis GB03 and P. fluorescens RG 26, applied either alone or each in combination with nonpathogenic F. oxysporum Fo 90105, were the most effective treatments at suppressing Fusarium wilt, or delaying disease onset and increasing seed yield, respectively. The importance of integrating existing control practices, partially effective by themselves, with other control measures to achieve appropriate management of Fusarium wilt and increase of seed yield in chickpea in Mediterranean-type environments is demonstrated by the results of this study. 相似文献
8.
The effects of chlamydosporesandconidia of Fusarium oxysporum f sp. tracheiphilum at different initial spore concentrations were compared in the wilt-susceptible cowpea cultivar California Blackeye No. 5 (CB5). In glasshouse experiments with one inoculum density of either Meloidogyne incognita or M javanica, chlamydospores resulted in greater incidence and severity of Fusarium wilt than conidia at the same inoculum densities. Wilt symptoms also increased on wilt-resistant cultivar CB3 as inoculum densities of M. javanica were increased. When three cultivars were infested with moderate or high densities of both F. o. tracheiphilum and M. javanica. only CB5 developed sere wilt at either inoculum density. The wilt-tolerant cultivar Grant had mild wilt symptoms in most plants at moderate inoculum densities, and a tenfold increase in inoculum did not increase wilt ratings. CB3. however, had higher incidence and severity of Fusarium wilt symptoms at high inoculum densities, although 60% of the plants survived for 9 weeks. 相似文献
9.
Germinated seeds of 'kabuli' chickpea cv. ICCV 4 were inoculated with a conidial suspension of the incompatible race 0 of Fusarium oxysporum f.sp. ciceris (Foc) or of nonhost F. oxysporum resistance 'inducers', and 3 days later were challenged by root dip with a conidial suspension of highly virulent Foc race 5. Prior inoculation with inducers delayed the onset of symptoms and/or significantly reduced the final amount of fusarium wilt caused by race 5. However, the extent of disease suppression varied with the nature of the inducing agent; the nonhost isolates of F. oxysporum were more effective at disease suppression than the incompatible Foc race 0. Inoculation with the inducers gave rise to synthesis of maackiain and medicarpin phytoalexins in inoculated seedlings; these did not accumulate in plant tissues but were released into the inoculum suspension. Inoculation with inducers also resulted in accumulation of chitinase, β-1,3-glucanase and peroxidase activities in plant roots. These defence-related responses were induced more consistently and intensely by nonhost isolates of F. oxysporum than by incompatible Foc race 0. The phytoalexins and, to a lesser extent, the antifungal hydrolases, were also induced after challenge inoculation with Foc race 5. However, in this case the defence responses were induced in both preinduced and noninduced plants infected by the pathogen. It is concluded that the suppression of fusarium wilt in this study possibly involved an inhibitory effect on the pathogen of preinduced plant defences, rather than an increase in the expression of defence mechanisms of preinduced plants following a subsequent challenge inoculation. 相似文献
10.
A California isolate of Meloidogyne javanica increased Fusarium wilt symptoms in cowpea cultivars California Blackeye No. 3 (CB3) (resistant to wilt) and Grant (tolerant) inoculated with each of the three races of Fusarium oxysporum f. sp. tracheiphilum. The same isolate of M. javancia did not similarly increase wilt in wilt-resistant cultivar CB7977 inoculated with two isolates of race 3 of F. o. tracheiphilum. Six of seven isolates of M. javanica caused similar increases in vascular discoloration in cultivar CB3. but one isolate of M. javanica and seven of M. incognita did not. Vascular discoloration rating was positively correlated with galling severity. However, increasing the initial inoculum density, and thus galling index, of one isolate of M. incognita did not increase vascular discoloration. The vascular discoloration ratings for the wilt-susceptible CB5 controls in each experiment were higher than those for the wilt-resistant cultivars infected with M. javanica. It is hypothesized that M. javanica but not M. incognita reduces, but does not eliminate, resistance to all races of F. o. tracheiphilum in cultivars CB3 and Grant. 相似文献
11.
ABSTRACT Fusarium wilt, caused by the soilborne pathogen Fusarium oxysporum f. sp. vasinfectum race 1, is a vascular disease in cotton (Gossypium spp.), and is a component of a disease complex with root-knot nematodes (Meloidogyne incognita). Genetic analysis of two interspecific crosses (G. barbadense Pima S-7 x G. hirsutum Acala NemX and Pima S-7 x Acala SJ-2) showed that one major gene (designated Fov1) with allele dosage effect conferred resistance to F. oxysporum f. sp. vasinfectum race 1 in Pima S-7. Two amplified fragment length polymorphism (AFLP) markers were linked to Fov1 in Pima S-7, with genetic distance from the gene of 9.3 and 14.6 centimorgans. Less severe wilt symptoms in Acala NemX than Acala SJ-2 indicated that Acala NemX possesses one or more minor genes contributing to delay of wilt symptoms. Highly resistant plants in F(2) and F(3) (Pima S-7 x NemX) families indicated transgressive segregation effects of minor genes in Acala NemX combined with Fov1 from Pima S-7. The effects of wilt and nematode resistance on the nematode-wilt disease complex were assayed with two inoculation methods. In the presence of both pathogens, wilt damage measured as shoot and root weight reductions was greatest on wilt- and nematode-susceptible Acala SJ-2 and least in root-knot nematode-resistant and wilt-susceptible Acala NemX. Intermediate damage occurred in wilt-resistant and root-knot nematode-susceptible Pima S-7. The results indicated that nematode resistance was more effective than wilt resistance in suppressing wilt symptoms when either resistance was present alone. Nematode resistance combined with intermediate wilt resistance, as in the F(1) (Pima S-7 x NemX), was highly effective in protecting plants from root-knot nematodes and race 1 of Fusarium wilt as a disease complex. 相似文献
12.
ABSTRACT Fusarium wilt of lettuce, caused worldwide by Fusarium oxysporum f. sp. lactucae, is an emerging seed-transmitted disease on Lactuca sativa. In order to develop a molecular diagnostic tool for identifying race 1 (VCG0300) of the pathogen on vegetable samples, an effective technique is presented. Inter-retrotransposon amplified polymorphism polymerase chain reaction (PCR), a technique based on the amplification of genomic regions between long terminal repeats, was applied. It was shown to be useful for grouping F. oxysporum f. sp. lactucae race 1 isolates. Inter-retrotransposon sequence-characterized amplified regions (IR-SCAR) was used to develop a specific set of PCR primers to be utilized for differentiating F. oxysporum f. sp. lactucae isolates from other F. oxysporum isolates. The specific primers were able to uniquely amplify fungal genomic DNA from race 1 isolates obtained in Italy, Portugal, the United States, Japan, and Taiwan. The primers also were specific to pathogen DNA obtained from artificially infected lettuce seed and naturally and artificially infected plants. 相似文献
13.
Devay JE Gutierrez AP Pullman GS Wakeman RJ Garber RH Jeffers DP Smith SN Goodell PB Roberts PA 《Phytopathology》1997,87(3):341-346
ABSTRACT Development of Fusarium wilt in upland cotton (Gossypium hirsutum) usually requires infections of plants by both Meloidogyne incognita and Fusarium oxysporum f. sp. vasinfectum. In this study, the soil densities of M. incognita and F. oxysporum f. sp. vasinfectum and the incidence of Fusarium wilt in three field sites were determined in 1982-1984. Multiple regression analysis of percent incidence of Fusarium wilt symptoms on population densities of M. incognita and F. oxysporum f. sp. vasinfectum yielded a significant fit (R (2) = 0.64) only on F. oxysporum f. sp. vasinfectum. Significant t-values for slope were also obtained for the interaction of M. incognita and F. oxysporum f. sp. vasinfectum, but densities of M. incognita and F. oxysporum f. sp. vasinfectum were also related on a log(10) scale. The physiological time of appearance of first foliar symptoms of Fusarium wilt, based on a degree-days threshold of 11.9 degrees C (53.5 degrees F), was used as a basis for determining disease progress curves and the phenology of cotton plant growth and development. Effects of Fusarium wilt on plant height and boll set were determined in three successive years. Increases in both of these plant characteristics decreased or stopped before foliar symptoms were apparent. Seed cotton yields of plant cohorts that developed foliar wilt symptoms early in the season (before 2,000 F degree-days) were variable but not much different in these years. This contrasted with cohorts of plants that first showed foliar symptoms late in the season (after 2,400 F degree-days) and cohorts of plants that showed no foliar symptoms of wilt. Regression analyses for 1982-1984 indicated moderate to weak correlations (r = 0.16-0.74) of the time of appearance of the first foliar symptoms and seed cotton yields. 相似文献
14.
ABSTRACT Fusarium oxysporum f. sp. melonis is responsible for Fusarium wilt of melon. Race 1.2 strains overcome two dominant resistance genes (Fom-1 and Fom-2) and are further divided into two types depending on the symptoms they cause, yellowing or wilting. Partial resistance to F. oxysporum f. sp. melonis race 1.2 was studied by using a recombinant inbred line (RIL) population that was developed by single seed descent from an F(1) hybrid between 'Isabelle', a partially resistant line, and a susceptible line, 'Védrantais'. Artificial inoculations were performed with a yellowing strain (TST) and a wilting strain (D'Oléon 8) and replicated in six locations. Disease reactions of the parental lines, controls, and RILs were scored using a 1-to-5 scale and by using the area under the disease progress curve (AUDPC). Phenotypic correlations were highly significant between the different locations and experiments. The heritability of the resistance was high, from 0.72 to 0.96, and 4 to 14 genetic factors were estimated to confer resistance to F. oxysporum f. sp. melonis race 1.2. Thirteen other strains were tested with an RILs subset. Some small strainspecific effects may be involved. These results contribute to a better understanding of the polygenic inheritance of the partial resistance to F. oxysporum f. sp. melonis race 1.2. 相似文献
15.
Ploetz RC 《Phytopathology》2006,96(6):653-656
ABSTRACT Fusarium wilt of banana (also known as Panama disease) is caused by Fusarium oxysporum f. sp. cubense. Where susceptible cultivars are grown, management is limited to the use of pathogen-free planting stock and clean soils. Resistant genotypes exist for some applications, but resistance is still needed in other situations. Progress has been made with this recalcitrant crop by traditional and nontraditional improvement programs. The disease was first reported in Australia in 1876, but did the greatest damage in export plantations in the western tropics before 1960. A new variant, tropical race 4, threatens the trades that are now based on Cavendish cultivars, and other locally important types such as the plantains. Phylogenetic studies indicate that F. oxysporum f. sp. cubense had several independent evolutionary origins. The significance of these results and the future impact of this disease are discussed. 相似文献
16.
ABSTRACT Plants exhibiting symptoms of wilt and xylem discoloration typical of Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici were observed in greenhouses of cherry tomatoes at various sites in Israel. However, the lower stems of some of these plants were covered with a pink layer of macroconidia of F. oxysporum. This sign resembles the sporulating layer on stems of tomato plants infected with F. oxysporum f. sp. radicis-lycopersici, which causes the crown and root rot disease. Monoconidial isolates of F. oxysporum from diseased plants were assigned to vegetative compatibility group 0030 of F. oxysporum f. sp. lycopersici and identified as belonging to race 1 of F. oxysporum f. sp. lycopersici. The possibility of coinfection with F. oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici was excluded by testing several macroconidia from each plant. Airborne propagules of F. oxysporum f. sp. lycopersici were trapped on selective medium in greenhouses in which plants with a sporulating layer had been growing. Sporulation on stems was reproduced by inoculating tomato plants with races 1 and 2 of F. oxysporum f. sp. lycopersici. This phenomenon has not been reported previously with F. oxysporum f. sp. lycopersici and might be connected to specific environmental conditions, e.g., high humidity. The sporulation of F. oxysporum f. sp. lycopersici on plant stems and the resultant aerial dissemination of macroconidia may have serious epidemiological consequences. Sanitation of the greenhouse structure, as part of a holistic disease management approach, is necessary to ensure effective disease control. 相似文献
17.
ABSTRACT Fusarium wilt of cotton is a serious fungal disease responsible for significant yield losses throughout the world. Evolution of the causal organism Fusarium oxysporum f. sp. vasinfectum, including the eight races described for this specialized form, was studied using multigene genealogies. Partial sequences of translation elongation factor (EF-1alpha), nitrate reductase (NIR), phosphate permase (PHO), and the mitochondrial small subunit (mtSSU) rDNA were sequenced in 28 isolates of F. oxysporum f. sp. vasinfectum selected to represent the global genetic diversity of this forma specialis. Results of a Wilcoxon Signed-Ranks Templeton test indicated that sequences of the four genes could be combined. In addition, using combined data from EF-1alpha and mtSSU rDNA, the phylogenetic origin of F. oxysporum f. sp. vasinfectum within the F. oxysporum complex was evaluated by the Kishino-Hasegawa likelihood test. Results of this test indicated the eight races of F. oxysporum f. sp. vasinfectum appeared to be nonmonophyletic, having at least two independent, or polyphyletic, evolutionary origins. Races 3 and 5 formed a strongly supported clade separate from the other six races. The combined EF-1alpha, NIR, PHO, and mtSSU rDNA sequence data from the 28 isolates of F. oxysporum f. sp. vasinfectum recovered four lineages that correlated with differences in virulence and geographic origin: lineage I contained race 3, mostly from Egypt, and race 5 from Sudan; lineage II contained races 1, 2, and 6 from North and South America and Africa; lineage III contained race 8 from China; and lineage IV contained isolates of races 4 and 7 from India and China, respectively. 相似文献
18.
ABSTRACT Colonization of watermelon root and stem tissues by Fusarium oxysporum f. sp. niveum race 1 and its relationship to the apparent resistance to Fusarium wilt was investigated. In each of 2 years, 17 differentially susceptible watermelon cultivars and one accession were tested in the greenhouse, and 7 cultivars also were tested in the field. Colonization by a chlorate-resistant marked isolate of the fungus was assayed by plating homogenized tissue samples on a selective medium. Six days after inoculation, seedlings of highly resistant, moderately resistant, and susceptible cultivars had F. oxysporum f. sp. niveum race 1 CFU counts in the lower stems of 10(2), 10(3), and 10(4) CFU/g of fresh tissue, respectively. Percent wilt (Y) of the seedlings was positively correlated with colonization (X) by F. oxysporum f. sp. niveum race 1 in roots (Y = 21.2 ln [X + 1] - 140.7, R(2) = 0.85) or lower stems (Y = 17.3 ln [X + 1] - 78.6, R(2) = 0.86). Percent wilt (Y) also was correlated with the ratio (X(r), 0 to 1 values) of lower stem to root colonization (Y = 34 ln X(r) + 112, R(2) = 0.36). Field evaluations confirmed these relationships, and a link between cultivar resistance and a reduced rate of spread of the fungus in primary stems during a season was observed. Fruit yield decreased with increased tissue colonization at linear rates of 9.9 to 12.7 t/ha per ln (CFU/g + 1) (R(2) >/= 0.58). The greenhouse seedling stem colonization assay described may be utilized as a collaborative method to quantify Fusarium wilt resistance in watermelon. 相似文献
19.
ABSTRACT Fusarium oxysporum f. sp. lactucae, causal agent of Fusarium wilt of lettuce, is a serious pathogen recently reported in Arizona. Sequence analysis of the mitochondrial small subunit (mtSSU), translation elongation factor 1-alpha (EF-1alpha) gene, and the nuclear ribosomal DNA intergenic spacer (IGS) region was conducted to resolve relationships among f. sp. lactucae isolates, F. oxysporum isolates from other hosts, and local non-pathogenic isolates. Analysis of mtSSU sequences provided limited phylogenetic resolution and did not differentiate the lactucae isolates from 13 other F. oxysporum isolates. Analysis of EF-1alpha sequences resulted in moderate resolution, grouping seven formae speciales with the lactucae isolates. Analysis of the IGS region revealed numerous sequence polymorphisms among F. oxysporum formae speciales consisting of insertions, deletions, and single nucleotide transitions and substitutions. Repeat sequence analysis revealed several duplicated subrepeat units that were distributed across much of the region. Based on analysis of the IGS sequence data, lactucae race 1 isolates resolved as a monophyletic group with three other formae speciales of F. oxysporum. In all analyses, lactucae race 2 isolates composed a separate lineage that was phylo-genetically distinct and distantly related to the lactucae race 1 isolates. 相似文献
20.
ABSTRACT Microplots experiments were carried out at Córdoba, southern Spain, from 1986 to 1989 to determine the effects of sowing date in the management of Fusarium wilt of chickpea as influenced by virulence of the pathogen race and by cultivar susceptibility. A total of 108 epidemics of the disease were described, analyzed, and compared to assess the degree of disease control. The epidemics were characterized by five curve elements: final disease intensity index (DII), standardized area under DII progress curve, time to epidemic onset, time to inflection point (t(ip)), and the DII value at t(ip), the last two parameters being estimates from the Richards function adjusted by nonlinear regression analysis. The structure of Fusarium wilt epidemics was examined by conducting multivariate principal components and cluster analyses. From these analyses, three factors accounting for 98 to 99% of the total variance characterized the DII progress curves and provided plausible epidemiological interpretations. The first factor included the t(ip) and the time to disease onset and can be interpreted as a positional factor over time. This factor accounted for the largest proportion of the total variance and may, therefore, be considered as the main factor for analysis of Fusarium wilt epidemics. The second factor concerns the standardized area under DII progress curves and the final DII of the epidemics. The third factor identified the uniqueness of the estimated value for the point of inflection of the DII progress curve over time. Our results indicate that for each year of experiment epidemic development was related mainly to the date of sowing. Thus, for chickpea crops in southern Spain, advancing the sowing date from early spring to early winter can slow down the development of Fusarium wilt epidemics, delay the epidemic onset, and minimize the final amount of disease. However, the net effect of this disease management practice may also be influenced, though to a lesser extent, by the susceptibility of the chickpea cultivar and the virulence and inoculum density of the Fusarium oxysporum f. sp. ciceris race. 相似文献