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1.
Blatter  Brown  & Wolfe 《Plant pathology》1998,47(5):570-579
The genetics of resistance to ergosterol demethylation inhibitor (DMI) fungicides of the triazole (conazole) group was examined in a cross between two isolates of the barley powdery mildew fungus, Erysiphe graminis (=  Blumeria graminis ) f.sp. hordei . One isolate, E1, was previously identified as being resistant to the triazole fungicide triadimenol, while the other, HL3/5, was sensitive. The 56 progeny tested were classified into two distinct groups, either being resistant to triadimenol, like E1, or sensitive, like HL3/5. The segregation ratio was not significantly different from 1:1, consistent with responses to triadimenol being controlled by a single gene. In further tests with cyproconazole, epoxiconazole, propiconazole and tebuconazole, all the progeny classified as resistant to triadimenol were also more resistant to each of these other triazole fungicides than were any of the triadimenol-sensitive progeny. This is consistent with the triadimenol resistance allele also conferring cross-resistance to the other triazoles. The ratio between the responses of the resistant and sensitive progeny (the resistance factor, RF) was greatest for triadimenol, followed by tebuconazole, propiconazole, epoxiconazole and cyproconazole, in that order. The RF for triadimenol was much greater when the fungicide was applied as a seed treatment than when it was sprayed. Five isolates, covering the five levels of responses to triadimenol identified previously in the UK population of E. graminis f.sp. hordei , were used as standards; a triadimenol-sensitive isolate and one with the lowest level of resistance were sensitive to all four of the other fungicides, while three isolates with higher levels of triadimenol-resistance were also more resistant to the other chemicals.  相似文献   

2.
Strains of Pseudocercosporella herpotrichoides collected in France on winter wheat give either fast-growing mycelial colonies with regular margins or slow-growing mycelial colonies with irregular margins. Most of the fastgrowing isolates were sensitive to triadimenol (EC50 below 2mg litre?1), but some of them were resistant to this inhibitor of sterol C-14 demethylation. In contrast, all the slow-growing strains were highly resistant to triadimenol (EC50 greater than 100 mg litre?1). This resistance was also expressed in inhibition of germ-tube elongation. Positive cross-resistance was observed between most of the inhibitors of sterol C-14 demethylation, with the exception of some imidazole derivatives (clotrimazole, prochloraz). All the fast-growing strains were tolerant to fenpropimorph and fenpropidin whereas the slow-growing ones were susceptible; the reverse was true with piperalin and tridemorph. All the field isolates were inhibited to the same extent by the inhibitors of squalene-epoxidase, nafifine and terbinafine. Two types of mutant resistant to triadimenol have been induced under laboratory conditions from sensitive fast-growing strains. The most common mutants were resistant to all the inhibitors of sterol C–14 demethylation and also in some conditions to fenpropimorph, tridemorph and the inhibitors of squalene-epoxidase. The other mutants were characterised by a reduced spectrum of cross-resistance between triadimenol and the other inhibitors of sterol biosynthesis. The field isolates and laboratory mutants resistant to triadimenol and propiconazole were also resistant to each of the four enantiomers of these two fungicides.  相似文献   

3.
Surveys of 528 randomly selected commercial fields in England and Wales in 1983 showed that isolates of Pseudocercosporella herpotrichoides resistant to benomyl were common and widespread on winter wheat and winter barley. During June and July resistant strains were recovered from 16 to 66% of fields and the proportion of resistant isolates was 37–52%. The frequency of occurrence of resistant isolates was positively correlated with the number of applications of carbendazimgenerating (MBC) fungicides during the previous 8 years. Benomyl resistance was found in 21–48% of fields where it was claimed that MBC had never been used, and 7–28% of isolates from those fields, were resistant. Resistance was more frequent in R-type than in W-type isolates of the pathogen. The proportion of R-type isolates decreased as the number of previous winter wheat crops rose and increased with the number of winter barley crops grown and with the number of MBC sprays applied to crops in previous years. The implications of these findings for the control of eyespot in England and Wales are discussed.  相似文献   

4.
A study was conducted on the genetic control of the response of Erysiphe graminis f.sp. hordei , the causal agent of barley powdery mildew, to two fungicides: the hydroxypyrimidine ethirimol, and the triazole, sterol demethylation inhibitor triadimenol. In tests of responses to both fungicides, sets of progeny of various crosses were classified by principal components analysis into discrete resistant and sensitive classes. A single allele controlled the response to ethirimol of the resistant isolate DH14 in crosses with the sensitive isolates CC52 and CC138. The ethirimol-resistance alleles of DH14 and another resistant isolate. CC107, are at the same locus or are closely linked. Alleles at single loci controlled resistance and sensitivity to triadimenol in crosses of DH14 (sensitive) with CC107 (moderately resistant) and CC138 (highly resistant). There was no evidence for polygenic control of response to either fungicide. The ethirimol response locus and the two putative triadimenol response loci are designated Eth1 and Tdl1 and Tdl2 , respectively. There was no evidence for linkage of Eth1 and Tdl2 in the cross CC138 × DH14, in which responses to both fungicides segregated.  相似文献   

5.
A random sample of conidiospores ofErysiphe graminis f.sp.hordei was obtained from the atmosphere above Cambridge, England, by incubating them on barley seedlings exposed on three dates in 1985. The asexual progeny of each spore was tested for its response to a range of doses of a systemic triazole fungicide, triademenol. Principal components analysis of the data revealed that the majority of isolates had a distinct level of response to triadimenol, being resistant to triadimenol at the rate apoplied to seed commercially. The remaining isolates appeared either to be sensitive to the lowest dose of triadimenol used, or to have one of two intermediate levels of resistance. There was a significant increase in the frequency of isolates with higher levels of resistance to triadimenol during 1985. This is likely to have been a response to the continuing widespread use of demethylation inhibitor (DMI) fungicides by British farmers.  相似文献   

6.
In 1992, samples of Rhynchosporium secalis from 19 winter barley crops in England and Wales were examined for carbendazim resistance. Of the 120 isolates obtained, 14·2% were resistant to carbendazim. A larger survey was carried out in England and Wales in 1993 when samples from 74 crops were examined. On this occasion 16·6% of the 639 isolates obtained were resistant to carbendazim, and resistant isolates were detected in 46% of crops.  相似文献   

7.
Isolates of Pyrenophora graminea resistant to organomercury were obtained from barley crops in England and Scotland in 1984–6. Resistant isolates were approximately 100 times less sensitive in vitro than sensitive isolates to phenyl mercuric acetate (PMA), but the difference was only four times for methoxyethyl mercuric acetate (MEMA). In small-plot field trials, seed treatment with either PMA or MEMA gave good control of leaf stripe disease caused by organomercury-sensitive strains of P. graminea but neither compound gave commercially acceptable control of resistant strains. Fungicides with different modes of action (triadimenol + fuberidazole, flutriafol + ethirimol + thiabendazole, carboxin-+- thiabendazole + imazalil, and guazatine + imazalil) were effective against organomercury-sensitive and organomercury-resistant strains. The few cases of resistance found do not justify a change from the use of organomercury as the standard seed treatment for barley.  相似文献   

8.
Sensitivity of field isolates (121) ofBotrytis cinerea from France (1992), Germany (1979–1992), Israel (1990) and the Netherlands (1970–1989) to the triazoles tebuconazole and triadimenol, the benzimidazole benomyl and the dicarboximide vinclozolin were tested in radial growth experiments. Resistance to benomyl (in 21 to 100% of isolates tested) and vinclozolin (in 25 to 71% of isolates tested) was common in most countries. EC50s (concentrations of fungicides inhibiting radial mycelial growth ofB. cinerea on B5-agar by 50%) for tebuconazole and triadimenol ranged between 0.01–1.64 and 0.4–32.6g ml–1, respectively, and were log-normally distributed. The variation factor (ratio between EC50s of the least and most sensitive isolate tested) amounts 164 and 82 for tebuconazole and triadimenol, respectively. These values are comparable to those for azole fungicides applied in control of other pathogens. Hence, variation in sensitivity to triazoles can probably not explain limited field performance of triazoles towardsB. cinerea. Isolates from south west Germany (1992) were significantly less sensitive to tebuconazole than isolates collected earlier in Germany, Israel and the Netherlands. Such less sensitive populations may contribute to the limited field performance of DMI fungicides towardsB. cinerea. The sensitivity of isolates from south west Germany to tebuconazole was similar to that of DMI-resistant mutants generated in the laboratory. These mutants displayed stable resistance with Q-values (ratio between EC50 of resistant mutant and wild type isolate) between 5 and 20. Sensitivity of field isolates and laboratory mutants to tebuconazole and triadimenol was correlated.  相似文献   

9.
The distribution of restriction-fragment-length polymorphisms (RFLPs) among isolates of Erysiphe graminis f.sp. hordei was used to test hypotheses about the structure of the pathogen population. There was a large diversity in the lengths of DNA restriction fragments homologous to E9, a chromosomal fragment of unknown function. It was shown that a large group of isolates, which shared identical or very similar virulence phenotypes, including virulence on the barley cv. Triumph, were members of a single clone. Several other clones were identified, including a second group of identical isolates which were virulent on cv. Triumph but were highly distinct from the more common clone of Triumph-virulent isolates. Isolates which shared the same level of resistance to the triazole fungicide triadimenol were genetically diverse. Such diversity is consistent with triadimenol resistance being under oligogenic, rather than polygenic, control. Conclusions obtained from analysis of the most easily identifiable subset of fragment lengths were very similar to those obtained from analysis of the complete set.  相似文献   

10.
A reservoir of infection of Tapesia yallundae may exist after harvest in bases of cereal stems due to the presence of apothecia capable of discharging infective ascospores. Apothecia of T. yallundae developed in a seasonal pattern on winter barley inoculated with the pathogen, with maximum numbers of apothecia produced on stubble 5–7 months after harvest. A similar pattern of development was observed on infected winter wheat. However, the peak in numbers of mature apothecia was observed 2 months later than in winter barley. Apothecia capable of discharging ascospores were present for up to 6 months on stubble. Apothecia of T. acuformis were not detected on spring or winter barley, or spring or winter wheat stubble, despite inoculation of growing crops with isolates of compatible mating type.  相似文献   

11.
In a survey conducted during 1991–1992, single-spored isolates of the eyespot fungus from the Swartland area were characterized and tested for sensitivity to carbendazim and ergosterol inhibiting fungicides. The 100 isolates tested were all fast growing, even marginate, and designated as Ramulispora herpotrichoides . Fungal growth was completely inhibit on PDA amended with carbendazim (1 μg/ml), indicating that the local population of the fungus is still at baseline sensitivity to benzimidazoles. The mean concentration of prochloraz calculated to inhibited growth by 50% (IC50 value) was 0.043 ± 0.029 μg/ml, which is comparable with the baseline sensitivity reported for European isolates. Of the 36 representative isolates screened against 2 μg/ml triadimenol, 44% were sensitive, while 36% were resistant. The triadimenol-resistant isolates were sensitive to propiconazole and flusilazole. However, four of the triadimenol-resistant isolates were also resistant to tebuconazole. These results indicate that South African isolates of R. herpotrichoides are sensitive towards carbendazim, prochloraz, propiconazole and flusilazole. They were found to differ, however, in sensitivity towards triadimenol and tebuconazole, where some isolates had an IC50 value greater than 2 μg/ml.  相似文献   

12.
ABSTRACT Single-conidial isolates of Uncinula necator from (i) a population representing two vineyards with no previous exposure to sterol demethylation inhibitor (DMI) fungicides ("unexposed," n = 77) and (ii) a population representing two vineyards in which powdery mildew was poorly controlled by triadimefon after prolonged DMI use ("selected," n = 82) were assayed to determine distributions of sensitivities to the DMI fungicides triadimenol (the active form of triadimefon), myclobutanil, and fenarimol. Median 50% effective dose (ED(50)) values (micrograms per milliliter) in the selected versus unexposed populations were 0.06 versus 1.9 for triadimenol, 0.03 versus 0.23 for myclobutanil, and 0.03 versus 0.07 for fenarimol, respectively. Isolates were grouped into sensitivity classes according to their ED(50) values, and those from the selected population were categorized as resistant if the frequency of their sensitivity class had increased significantly relative to levels found in the unexposed population (ED(50) values exceeding 0.56, 0.18, and 0.18 mug/ml for triadimenol, myclobutanil, and fenarimol, respectively). Of the 76 isolates defined as resistant to triadimenol, 64% were classified as cross-resistant to myclobutanil, 18% were classified as cross-resistant to fenarimol, and 17% were classified as resistant to all three fungicides; 25% of the isolates classified as resistant to myclobutanil also were classified as resistant to fenarimol. Similar cross-resistance relationships were revealed when all isolates were examined by regressing log ED(50) values for each fungicide against those for the remaining two fungicides to determine the correlation coefficients (e.g., r = 0.85 for triadimenol versus myclobutanil and 0.56 for triadimenol versus fenarimol). The restricted levels of cross-resistance indicated by these data, particularly between fenarimol and the other two fungicides, is in sharp contrast to the high levels of cross-resistance among DMIs reported for some other pathogens and has significant implications with respect to programs for managing grapevine powdery mildew and DMI resistance.  相似文献   

13.
The susceptibility of 24 winter and 17 summer crops to infection by Bipolaris sorokiniana was tested in a glasshouse experiment by growing them in soil amended with wheat-barley grain colonized by B. sorokiniana (0.2 g per 100 g soil). At anthesis, infection of both lesioned and randomly selected segments of roots and of crowns was determined by plating them on modified Czapek-Dox Agar. Incidence of infection in winter crops was higher than in summer crops. Guar, mung bean, soybean and sunflower were the least infected of the summer crops while chickpeas and safflower were the least infected of the winter crops. Amongst the taxonomic groups tested, the highest incidence of infection occurred in the gramineous species and the lowest in the leguminous species.
Five summer crops growing in the field were sampled and infection by B. sorokiniana confirmed. Cultivars of wheat, barley, triticale and oats were also screened in a field experiment. Amongst these winter cereals, oats was the least susceptible in both field and glasshouse experiments. Differences between cultivars in susceptibility to common root rot, measured by the degree of lesion development in the subcrown internode, were identified in wheat, triticale and oats but not in barley.  相似文献   

14.
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15.
Fifty-seven isolates of Phytophthora infestans from blighted potato foliage were collected in 1995 in southern Germany and analysed for mating type and sensitivity to metalaxyl. Fifty-six of them were characterised as A1 and one as A2 mating types. Resistance to metalaxyl was observed frequently: 53 isolates were resistant, three were partially sensitive, and one was sensitive. In a subsequent field study in 1999, 84 isolates collected from blighted potato and tomato foliage were analysed for mating type. Seventy-two were characterised as A1 and twelve as A2 mating types. The response of 76 isolates to metalaxyl and to propamocarb was tested. The majority (42) of the 76 isolates was classified as resistant to metalaxyl; 31 were partially sensitive and only three isolates were sensitive. The results with propamocarb were less discrete; 10 isolates were classified as resistant and three were clearly sensitive. AFLP fingerprinting was used to examine the genetic structure of the southern German P. infestans population collected in 1999 and indicated that the tested population can be sub-divided into a tomato group, a potato group and a mixed group containing isolates collected from both crops. The presence of Ia and IIa mitochondrial DNA haplotypes indicates that the German P. infestans isolates belong to the new pathogen population that has also been reported in neighbouring regions of Europe. The present study indicates that at the beginning of the season only a few genotypes were present, and the population became genetically more variable at the end of the growing season.  相似文献   

16.
Summary. Spikes oi Agropyron repens (L.) Beauv. were collected from field crops (mostly spring barley and winter wheat) in England and Wales near the time of crop harvest. Seeds per spike were counted and their germination tested in soil in the glasshouse.
About 95% of the samples contained viable seeds; about one third of the samples had fewer than 5 viable seeds/spike, a third between 6 and 15 and a third more than 15. The average number of viable seeds/spike for all samples was 13. Spikes from spring barley (152 samples) had an average of 11 and a maximum of 51 viable seeds and those from winter wheat (42 samples), 20 and 48 respectively. Samples collected within 3 weeks after mid-July had fewer viable seeds/spike than those collected later. Samples containing morphologically-different spikes had more viable seeds/spike than apparently uniform samples, and spikes from dense field populations more seeds than those from sparse populations.  相似文献   

17.
When introduced as a seed treatment 5 years ago, triadimenol (Baytan) was more effective against Erysiphe graminis f. sp. hordei than was the alternative ethirimol (Milstem). This contrasts with the current situation on the powdery mildew-susceptible cv. Golden Promise, where ethirimol is generally better than triadimenol. In part this reflects a decline in the performance of triadimenol seed treatment, as a result perhaps of some decrease in sensitivity to this fungicide. However, laboratory assays of field isolates also revealed that negatively correlated cross-resistance between triadimenol and ethirimol might exist. In field trials the sensitivity of E. graminis to triadimenol was indeed increased after treatment with ethirimol, but triadimenol hardly altered sensitivity to ethirimol. The possible causes of these changes in fungicide sensitivity are discussed.  相似文献   

18.
BACKGROUND: Cucurbit powdery mildew elicited by Podosphaera fusca (Fr.) U Braun & N Shishkoff limits crop production in Spain. Disease control is largely dependent on fungicides such as sterol demethylation inhibitors (DMIs). Fungicide resistance is an increasing problem in this pathogen. To overcome such risk, it is necessary to design rational control programmes based upon knowledge of field resistance. The aim of this study was to investigate the state of DMI sensitivity of Spanish P. fusca populations and provide tools for improved disease management. RESULTS: Using a leaf‐disc assay, sensitivity to fenarimol, myclobutanil and triadimenol of 50 isolates of P. fusca was analysed to determine discriminatory concentrations between sensitive and resistant isolates. As no clearly different groups of isolates could be identified, discriminatory concentrations were established on the basis of maximum fungicide field application rate, 100 mg L?1 for the three fungicides tested. Subsequently, a survey of DMI resistance was carried out in different provinces located in the south central area of Spain during the cucurbit growing seasons in 2002, 2003 and 2004. Examination of a collection of 250 isolates revealed that 23% were resistant to fenarimol and 7% to triadimenol, the provinces of Almería, Badajoz and Murcia being the locations with the highest frequencies of resistance. By contrast, no resistance to myclobutanil was found. CONCLUSION: Results show that fenarimol and, to a lesser extent, triadimenol have become less efficient for controlling cucurbit powdery mildew in Spain. These are important observations that should lead to reconsideration of the current disease management programmes. Copyright © 2010 Society of Chemical Industry  相似文献   

19.
To assess the potential contribution of growing highly competitive crops to control Cyperus esculentus in the Netherlands, the influence of silage maize, hemp, winter barley and silage winter rye on emergence, growth and reproduction of this weed was studied in two field experiments. Growth and reproduction of C. esculentus (determined both as tuber production per plant and density of the weed in the subseuent crop maize) was reduced by each crop, compared to plots in which no crop was grown. In hemp, hardly any tuber production was observed. By growing a green manure crop after harvest of the winter barley the tuber production of the weed was reduced to about 40% of that in winter barley followed by fallow. Decreasing the light regime in a greenhouse experiment in the same order as was observed in the crops winter barley, maize and hemp, caused a similar reduction of tuber production to that found in the field. Therefore, it is suggested that competition for light is the main factor explaining the observed crop effects on the population dynamics of the weed. It is concluded that growing competitive crops as hemp in rotation may effectively complement chemical control of C. esculentus.  相似文献   

20.
Studies of cereal aphids and barley yellow dwarf virus (BYDV) from 1989 to 1992 revealed that Poa annua is an abundant weed of commercial winter barley crops during the summer months. P. annua was frequently infected with BYDV, and there were usually similarities with the BYDV infection of the surrounding barley crop. These P. annua weeds were often infested by cereal aphids both in July (pre-harvest) and in September (in cereal stubble fields). Poa -infested cereal stubbles may be major local sources of viruliferous aphids, increasing the risk of BYDV in nearby winter cereals. P. annua plays an important role in the epidemiology of S. avenae -transmitted BYDV.  相似文献   

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