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1.
The effects of a range of concentrations of four nutrients – nitrogen, phosphorus, potassium and calcium – in fertilizer solutions on the severity of anthracnose on strawberry cv. Nyoho cultivated under a noncirculation hydroponics system were determined after inoculation with Colletotrichum gloeosporioides . Crop growth and tissue nitrogen, phosphorus, potassium and calcium contents of the entire above-ground parts of the plant were also investigated. Elevated nitrogen and potassium concentrations in the fertilizer solution increased disease severity in contrast to phosphorus and calcium. Treatment with either NH4 or NO3 nitrogen was not significantly different. The dry weight of the strawberry plants increased significantly with elevated concentrations of nitrogen ( R 2 = 0·9078) and phosphorus ( R 2 = 0·8842), but was not influenced by the elevated amounts of potassium ( R 2 = 0·8587) and calcium ( R 2 = 0·6526) concentrations.  相似文献   

2.
The Rdm4 gene from soybean cv. Hutcheson has been extensively used to incorporate resistance to soybean stem canker (SSC), caused by Diaporthe phaseolorum var . meridionalis (Dpm), into soybean commercial cultivars. The objective of this work was to characterize the inheritance of the Rdm4 locus in different populations derived from the cross: J77-339 ( rdm / rdm , susceptible) × Hutcheson ( Rdm4 / Rdm4 , resistant) in independent interactions with two local isolates of Dpm. Four F2 populations were obtained and two were advanced to the F3 generation as separate F2:3 families to perform progeny tests. Each population was inoculated with the CE109 and/or CE112 isolates of Dpm. Within each plant–pathogen interaction, the resistance gene segregated as completely dominant. However, cross resistance, or opposite disease reactions, to CE109 and CE112 isolates of Dpm were observed in four F2:3 families, indicating an intergenic recombination event between two nonallelic genes interacting specifically with each isolate of Dpm. The distance between them, estimated as the recombination fraction, was 29%, suggesting that both genes were not tightly linked, but close enough to segregate together in most crosses. Results indicated the existence of a genomic region in cv. Hutcheson composed of race-specific resistance loci with at least two Rdm genes: the previously recognized Rdm4 and a novel gene, tentatively named Rdm5 , conferring specific resistance to Dpm isolates CE109 and CE112.  相似文献   

3.
The differential genotypes R1, R10 and R11, as originally defined by Black, were crossed with R-gene-free cultivars and the progenies divided into two subpopulations comprising those which had inherited the R-gene and those which had not. The underlying level of field resistance of the two groups was compared in a field trial in which they were inoculated with an isolate that could overcome the relevant R-genes. The R-gene-bearing group was significantly ( P  < 0·001) more resistant than the R-gene-free group, with mean scores over four dates in 2000 of 4·86 and 4·09, respectively, on a 1–9 scale of increasing resistance, and of 4·10 and 2·35 on one date in 2001. However, the magnitude of the effect depended on the R-gene and the year of the trial. Data from a progeny of cv. Stirling (with an R-gene and a high level of field resistance) were examined and the same effect of an R-gene found. Fewer of the R-gene-bearing group of clones were highly susceptible, and more were resistant. The most resistant clones always bore the R-gene. It is concluded that increased resistance is conferred by the defeated R-gene or linked genes for field resistance.  相似文献   

4.
Transfer of factors for resistance to white blister disease caused by Albugo candida between Brassica species involving two genotypes each of B. juncea and B. rapa was studied in hybrids. More hybrids were obtained by in vivo than in vitro techniques, although an in vitro phase was a prerequisite for the establishment of in vivo hybrids. Hybrids were identified by PCR-based inter-simple sequence repeat (ISSR) markers with both male and female species-specific bands being identified. There was a positive correlation between disease severity and number of days after sowing ( r  > 0·93), the highest being towards pod formation and plant maturity at 110 days after sowing. The plants from F2 and BC1 progeny showed higher resistance to A. candida than either of the parents. Plants of B. juncea and B. rapa with high field resistance (disease index < 1·0) were selected from BC2 and F2BC1 generations. The frequency of plants classified as resistant in BC2 progeny ranged from 4·5 to 39·0% in cross-combinations involving B. juncea genotypes as female parent, compared with 100% in the reciprocal cross involving B. rapa as female parent.  相似文献   

5.
The sensitivity of 127 Phytophthora infestans isolates to flumorph was determined in 2003 and 2004. The isolates originated from two geographical regions and showed similar levels of sensitivity in both years. Baseline sensitivities were distributed as a unimodal curve with EC50 values for growth of mycelia ranging from 0·1016 to 0·3228  µ g mL−1, with a mean of 0·1813 (± 0·0405) µ g mL−1. There was no cross-resistance between flumorph and metalaxyl. Laboratory studies were conducted to evaluate the risk of P. infestans developing resistance to flumorph. Mutants resistant to metalaxyl or flumorph were obtained by treating mycelium of wild-type isolates with ultraviolet radiation. Metalaxyl-resistant mutants were obtained with a high frequency and exhibited resistance factor values (EC50 resistant/EC50 sensitive phenotypes) of more than 100, while flumorph-resistant mutants were obtained at much lower frequencies and had very small resistance factors (1·5–3·2). There was cross-resistance between flumorph and dimethomorph, but not with azoxystrobin or cymoxanil. Most flumorph-resistant mutants showed decreases in hyphal growth in vitro and in sporulation both in vitro and on detached leaf tissues. These studies suggested that the risk of resistance developing was much lower for flumorph than metalaxyl. However, as P. infestans is a high-risk pathogen, appropriate precautions against resistance development should be taken.  相似文献   

6.
A new selective medium (APCA medium) was developed for the isolation of Burkholderia caryophylli , the causal agent of carnation bacterial wilt, from both plants and soil. The optimal concentration and combination of antibiotics was investigated to determine the most selective condition for growing B .  caryophylli . The resultant composition of the medium per litre was: 0·79 g (NH4)2SO4, 1·0 g KH2PO4, 0·5 g MgSO4 · 7H2O, 0·2 g KCl, 2·0 g D-arabinose, 5 mg crystal violet, 50 mg cycloheximide, 50 mg polymyxin B sulphate, 50 mg ampicillin sodium, 10 mg chloramphenicol, 25 mg blue tetrazolium, and 15 g agar. Plating efficiency ranged from 119 to 174% with an average of 141% compared to that of nutrient agar. The bacterium was successfully isolated from contaminated soil and plant tissues with this medium. Moreover, the medium almost completely inhibited the growth of other plant pathogenic bacteria and soil saprophytes. This selectivity was high enough to detect B . caryophylli in contaminated soil.  相似文献   

7.
Host–parasite relationships in root-knot disease of spinach caused by Meloidogyne incognita race 1 were studied under glasshouse conditions. Nematode-induced mature galls were large and usually contained one or more females and egg masses with eggs. Feeding sites were characterized by the development of giant cells containing granular cytoplasm and many hypertrophied nuclei. The cytoplasm in these giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P i) in a series from 0–128 eggs and second-stage juveniles per cm3 soil and growth of spinach cv. Symphony F1 seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m  + (1 −  m ) z P–T ] was fitted to fresh top- and total plant-weight data for inoculated and control plants. Tolerance limits ( T ) of spinach cv. Symphony F1 to M. incognita race 1 for fresh top and total plant weights were 0·25 and 0·5 eggs and second-stage juveniles per cm3 soil, respectively. The minimum relative values for fresh top and total plant weights were zero in both cases at P i ≥ 32 eggs and second-stage juveniles per cm3 soil. Root galling was least at low initial population densities and greatest at 16 eggs and second-stage juveniles per cm3 soil. Maximum nematode reproduction rate was 33·1-fold at the lowest P i.  相似文献   

8.
The susceptible rose cv. Madelon and the partially resistant cv. Sonia both responded with reduced development of rose powdery mildew when they were treated with the synthetic inducer 2,6-dichloroisonicotinic acid (INA). The EC50 for number of colonies cm−2 was approximately 0.4 mg L−1 in both cultivars when treated 4 days prior to inoculation. However, conspicuous differences were observed with respect to number of spores per cm2. For sporulation, the EC50 was 0.37 mg L−1 in cv. Madelon and only 0.08 mg L−1 in cv. Sonia. A comparison with the pathosystems cucumber/ Sphaerotheca fuliginea and red cabbage/ Peronospora parasitica is made and the importance of the observed phenomenon for the selection of parents in a breeding programme for (partial) resistance is discussed.  相似文献   

9.
Twenty-two cotton varieties were screened for resistance to cotton leaf curl disease (CLCuD), a disease of viral origin, using three procedures: field evaluation, whitefly transmission assay and graft inoculation. Viral infection of cotton varieties was determined by visual symptom assessment as well as dot-blot and multiplex PCR diagnostic techniques. Crosses were made between the most susceptible variety (S-12) and highly resistant varieties (CP-15/2, LRA-5166 and CIM-443). All F1 plants of these crosses were resistant, showing dominant expression of the resistance as well as the absence of extrachromosomal inheritance. The F2 plants of the crosses CP-15/2 × S12, LRA-5166 × S-12 and CIM-443 × S12 exhibited a ratio of 13 resistant (symptomless) to three susceptible (with symptoms). Screening of the F2 generation for virus infection by multiplex PCR further subdivided the resistant class into those exhibiting a high level of resistance (HR; PCR-negative) and those exhibiting resistance (R; symptomless, yet showing virus replication by PCR analysis). Hence, the final ratio was 3:10:3 (HR:resistant:susceptible). The F3 progeny of susceptible F2 plants segregated for resistance, indicating the probable presence of a suppressor gene ( S ). These findings are consistent with three genes being involved in G. hirsutum resistance to CLCuD, two for resistance ( R 1CLCuDhir and R 2CLCuDhir ) and a suppressor of resistance ( S CLCuDhir ).  相似文献   

10.
Sensitivity of Botrytis cinerea from vegetable greenhouses to boscalid   总被引：4，自引：1，他引：4  
Between 2004 and 2006, 228 isolates of Botrytis cinerea from two regions in China were characterized for baseline sensitivity to boscalid, a new active ingredient that interferes with succinate ubiquinone reductase in the electron transport chain. The isolates showed similar sensitivity in different years and regions. Baseline sensitivities were distributed as unimodal curves with mean EC50 values of 1·07 (± 0·11) and 0·42 (± 0·05) mg L−1 for inhibition of mycelial growth and conidial germination, respectively. Laboratory studies were conducted to evaluate the risk of development of resistance to boscalid. Boscalid-resistant mutants were obtained by UV-treatment at lower frequencies and with smaller resistance factors than pyrimethanil-resistant mutants. All boscalid-resistant mutants were also significantly more sensitive to Qo inhibitors than their wild-type parents and showed reduced sporulation in vitro and pathogenicity on aubergine leaves. The results suggested that the risk of resistance developing for boscalid was lower than for pyrimethanil. However, as B. cinerea is a high-risk pathogen, appropriate precautions against resistance development should be taken. Synergism between the activity of boscalid and that of kresoxim-methyl was observed.  相似文献   

11.
Pan  Wang  & Tanisaka 《Plant pathology》1999,48(2):288-293
Blast, caused by Pyricularia grisea , is a major constraint on rice production. To widen genetic diversity for disease resistance, the Indian native rice cultivar Aus373 was screened by F2 segregation analyses to investigate the genetic basis of its high resistance. Aus373 was crossed with a series of Japanese differential cultivars (JDCs) and the Chinese susceptible cultivar Lijiangxintuanheigu (LTH). The resistance ratios of subsequent F2 progenies were used to determine the number of blast-resistance loci present as well as allelic relationships with known loci. Resistance of Aus373 was governed by dominant alleles at two loci, one at the Pi-k locus and the second apparently at a new locus linked to an isozyme gene Amp-1 with a recombination fraction of 37.9 ± 3.0% on chromosome 2. This putative new locus and allele were designated Pi16 (t).  相似文献   

12.
Genetic analysis of resistance of wheat seedlings to two races of Puccinia striiformis was conducted on F1, F2 and F3 generations from crosses Carstens V (CV) × Lee, Spaldings Prolific (SPA) × Lee and CV × SPA. F2 generations from crosses of CV and SPA with Strubes Dickkopf (SD) were also studied. The plants were classified into six resistance classes and analysed by factorial correspondence analysis and nonhierarchical classification. The two P. striiformis isolates tested were a French isolate of race 43E138 and a Lebanese isolate of race 2E16, selected for the differences in their virulence spectra for the common differential cultivars Strubes Dickkopf and Nord Desprez. Resistance of CV and SPA was recessive and dominant to races 43E138 and 2E16, respectively. CV possessed three or four resistance genes, one of them being expressed with both races. Two genes of CV had a cumulative effect for resistance to 43E138 and two or three gave dominant resistance to 2E16. SPA had three resistance genes, all of which gave resistance to 2E16 and two of which also gave resistance to 43E138. SPA had one gene in common with CV for resistance to both races. Furthermore, the gene for resistance to race 2E16 in CV and SPA was allelic with a gene in SD, and was probably Yr25 .  相似文献   

13.
In late 2003, nine populations of Sclerotinia homoeocarpa in Ontario Canada (seven of which had been previously sampled in early 1994, prior to the registration of sterol demethylation-inhibiting (DMI) fungicides for turf disease control in Canada) were sampled and tested for sensitivity to propiconazole. Four of the nine populations had not been treated with DMI fungicides during the intervening years, and isolates from these locations were sensitive to propiconazole (geometric mean EC50 values of 0·005–0·012 µ g mL−1, compared with 0·005–0·008 µ g mL−1 for the original 1994 populations). Among the five populations from 2003 that had been exposed to DMI fungicides, mean EC50 values were significantly greater, ranging from 0·020 to 0·048 µ g mL−1. A significant correlation of determination was found between estimated number of fungicide applications and log EC50 ( R 2 = 0·832, P  = 0·0001), and the equation predicted that 42·3 applications of propiconazole would be needed to bring a sensitive population (EC50 < 0·01  µ g mL−1) to a resistant level (EC50 > 0·10  µ g mL−1). Fungicide sensitivity vs. duration of fungicide efficacy was also tested, and it was found that isolates with decreased sensitivity were able to more quickly overcome the inhibitory effects of fungicide application, reducing the duration of control from 3 weeks to 2 weeks.  相似文献   

14.
Control of Penicillium expansum by plant volatile compounds   总被引：1，自引：0，他引：1  
Nine plant volatiles were tested for their activity in vitro and in vivo against Penicillium expansum , the cause of blue mould of pear. In vitro spore germination and mycelial growth assay showed a consistent fungicidal activity by trans -2-hexenal, carvacrol, trans -cinnamaldehyde and citral, while hexanal (-)- carvone, p -anisaldehyde, eugenol and 2-nonanone exhibited a progressively lower inhibition. trans -2-Hexenal was the best inhibitor of conidial germination [MIC (minimum inhibitory concentration) = 24·6  µ L L−1; ED50 = 10·2  µ L L−1], while carvacrol was the best inhibitor of mycelial growth (MIC = 24·6  µ L L−1; ED50 = 9  µ L L−1). The four most active compounds in in vitro studies were tested in vivo as fumigants against blue mould on pear cv. Conference. Best control was achieved by trans -2-hexenal vapour treatments (12·5  µ L L−1) when applied over a 24-h period, beginning 24 h after inoculation. In contrast, carvacrol (12·5–200  µ L L−1), and trans -cinnamaldehyde (50–400  µ L L−1) were ineffective and citral (200  µ L L−1) showed only slight effect.  相似文献   

15.
A total of 651 isolates of cucumber corynespora leaf spot fungus ( Corynespora cassiicola ) collected from cucumber in Japan, either with (438 isolates) or without (213 isolates) a prior history of boscalid use, were tested for their sensitivity to boscalid by using a mycelial growth inhibition method on YBA agar medium. Additionally, seven isolates of C. cassiicola obtained from tomato, soybean, eggplant (aubergine) and cowpea in different locations in Japan were tested before boscalid registration. Minimum inhibitory concentration (MIC) and 50% effective concentration (EC50) values for 220 isolates from crops without a prior history of boscalid use ranged from 0·5 to 7·5 μg mL−1 and from 0·04 to 0·59 μg mL−1, respectively. Two hundred and fourteen out of 438 isolates collected from ten cucumber greenhouses in Ibaraki Prefecture, Japan, which received boscalid spray applications showed boscalid resistance, with MIC values higher than 30 μg mL−1. Moreover, resistant isolates were divided into two groups: a moderately resistant (MR) group consisting of 189 isolates with EC50 values ranging from 1·1 to 6·3 μg mL−1, and a very highly resistant (VHR) group consisting of 25 isolates with EC50 values higher than 24·8 μg mL−1. MR isolates were detected from all ten greenhouses, but VHR isolates were detected from only three. As a result of fungus inoculation tests which used potted cucumber plants, control failures of boscalid were observed against resistant isolates. Efficacy of boscalid was remarkably low against VHR isolates in particular. This is the first known report on boscalid resistance in Japan.  相似文献   

16.
Elemental sulphur levels, sulphur localization in stems, and levels of sulphate, glutathione and cysteine were studied in pepper ( Capsicum annuum ) cvs Yolo Wonder (higher resistance) and Luesia (lower resistance) after inoculation with Verticillium dahliae , the cause of vascular wilt. Accumulation of elemental sulphur (S0) was first detected 10 days after inoculation in Yolo Wonder (mean S0 level 7·3  µ g g−1 DW), and 15 days after inoculation in Luesia (mean S0 level 3·3  µ g g−1 DW). The maximum level was reached 21 days after inoculation in Yolo Wonder (14·1  µ g g−1 DW). In control plants, elemental sulphur was not detected. SEM-EDX (scanning electron microscopy-energy dispersive X-ray microanalysis) indicated that the sulphur was not restricted to a specific location, but was dispersed throughout the vascular tissue. Sulphate levels showed a decline at the end of the experiment in inoculated plants, possibly related to the increase in sulphur levels seen in the two cultivars. The differences in sulphate levels between the two cultivars may be due to faster sulphate breakdown in cv. Yolo Wonder.  相似文献   

17.
In a survey conducted during October 1995, single-lesion isolates of the sugar beet leaf-spot fungus, Cercospora beticola , were tested for sensitivity to the sterol demethylation inhibiting fungicides (DMIs) flutriafol and bitertanol. The isolates were collected from fields in three different areas of northern Greece. Fields at Serres and Imathia had been sprayed with DMIs for about 15 years to control sugar beet leaf-spot. At the third site, Amyndeon, DMI fungicides had not been used. From each area 150 isolates were tested. ED50 values were calculated for individual isolates by regressing the relative inhibition of colony growth against the natural logarithm of the fungicide concentration. The mean ED50 values for flutriafol for the Serres, Imathia and Amyndeon populations were 1·07, 0·73 and 0·5 µg mL−1, respectively (significantly different at P  = 0·05). For bitertanol the mean ED50 values for the Serres and Imathia populations were 0·72 and 0·81 µg mL−1, respectively, which were not significantly different at P  = 0·05. The mean ED50 value of the Amyndeon population was 0·48 µg mL−1, which was significantly lower than those of the other two populations ( P  < 0·05). A cross-resistance relationship was found to exist between the two triazole fungicides tested when log transformed ED50 values of 60 isolates were subjected to a linear regression analysis ( r  = 0·81).  相似文献   

18.
Host–parasite relationships and pathogenicity of Meloidogyne javanica on potatoes (newly recorded from Malta) were studied under glasshouse and natural conditions. Potato cvs Cara and Spunta showed a typical susceptible reaction to M. javanica under natural and artificial infections, respectively. In potato tubers, M. javanica induced feeding sites that consisted of three to four hypertrophied giant cells per adult female. Infection of feeder roots by the nematode resulted in mature large galls which usually contained at least one mature female and egg mass. In both tubers and roots, feeding sites were characterized by giant cells containing granular cytoplasm and many hypertrophied nuclei. Cytoplasm in giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P ) [0–64 eggs + second-stage juveniles (J2s) per cm3 soil] and growth of cv. Spunta potato seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m  + (1 −  m ) z ( P − T )] was fitted to fresh shoot weight and shoot height data of nematode-inoculated and control plants. Tolerance limits ( T ) for fresh shoot weight and shoot height of cv. Spunta plants infected with M. javanica were 0·50 and 0·64 eggs + J2s per cm3 soil, respectively. The m parameter in that model (i.e. the minimum possible y -values) for fresh shoot weight and shoot height were 0·60 and 0·20, respectively, at P  = 64 eggs + J2s per cm3 soil. Root galling was proportional to the initial nematode population density. Maximum nematode reproduction rate was 51·2 at a moderate initial population density ( P  = 4 eggs + J2s per cm3 soil).  相似文献   

19.
The essential oil of Chrysanthemum coronarium flowerheads showed strong nematicidal activity in vitro and in growth-chamber experiments. Essential oil concentrations of 2, 4, 8 and 16  µ L mL−1, significantly reduced hatch, J 2 survival (determined by final value and area under curves of cumulative percentage hatch or mortality) and reproduction rate of Meloidogyne artiellia in vitro , with the lowest values occurring at 16  µ L mL−1. In pot trials with chickpea cv. PV 61, essential oil concentrations of 10–40  µ L per 500 cm3 soil, applied on sterile cotton pellets, also significantly reduced the nematode's reproduction rate. The biological processes of mortality and hatching/reproduction were adequately described by the monomolecular and expanded negative exponential models, respectively. Effectiveness of soil amendment with either flowers, leaves, roots or seeds of C. coronarium , and flowers from several species of Asteraceae ( Chrysanthemum segetum , Calendula maritima , Calendula officinalis and Calendula suffruticosa ) at 5 g per 500 cm3 soil was tested for suppression of M. artiellia and growth of chickpea cv. PV 61 under growth-chamber conditions. In these tests, flowers of all five Asteraceae species and various parts of C. coronarium significantly reduced reproduction rates of M. artiellia , by 83·0–95·9%, with the minimum rates occurring in infected chickpea plants amended with flowers of C. officinalis and C. suffruticosa . The in vitro and in planta results suggest that the essential oil of C. coronarium and organic amendments from Asteraceae species may serve as nematicides.  相似文献   

20.
The inheritance of tolerance to the herbicide metribuzin was studied in two durum wheat cultivars, one of which, 'Anton', is resistant and one, 'Nita', susceptible. Parents, F1, F2 and F3 of the crosses 'Anton' × 'Nita' and 'Nita' × 'Anton' were tested for herbicide response. The character evaluated was the increase in weight of plants treated with the herbicide. As there were no significant differences between progenies of reciprocal crosses, cytoplasm was not involved in tolerance. Tolerance was semi-dominant with means values of F1, F2 and F3 progenies in the range of mid-parent. The heritability of this trait estimated by regression of the average of progeny F3 in their parent F2 had a value of 0.23 ± 0.063 and a value of 0.52 ± 0.150 estimated by the relation V G/ V P for full-sib F2 families.  相似文献   

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