Changes in sensitivity to DMI fungicides in Rhynchosporium secalis

Kendall, S. J.; Hollomon, D. W.; Cooke, L. R.; Jones, Dennis

doi:10.1016/0261-2194(93)90078-w

Cited by 51 publications

(28 citation statements)

References 4 publications

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“…It is not known whether di †erent selection processes exist for M. graminicola within triazoles as has been claimed to occur in Rhynchosporium secalis Davis for triadimenol versus propiconazole. 15 The sensitivity proÐle of azoxystrobin was much wider for P. infestans (Fig. 5) than for M. graminicola populations (Fig.…”

Section: Discussionmentioning

confidence: 98%

Sensitivity profiles ofMycosphaerella graminicolaandPhytophthora infestanspopulations to different classes of fungicides

et al. 1997

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: Prior to the use of fungicides, the baseline sensitivity of individuals in a pathogen population may already di †er by a factor of 10 to 100 between the least and the most sensitive isolates. In Mycosphaerella graminicola populations, this factor, measured in vitro, was 5 to 20 for both the strobilurin analogue azoxystrobin (baseline) and the triazole cyproconazole which has been in use for several years. In Phytophthora infestans populations, this factor, measured in a leaf disc assay, was about 100 for azoxystrobin (baseline), up to 1000 for the cyanoacetamide cymoxanil and [10 000 for the phenylamide oxadixyl ; both of the latter have been used for many years. In M. graminicola, cross-sensitivity was present between all azole fungicides for the majority of the isolates, whereas no correlation was found between triazoles and azoxystrobin. Despite the existence of cross-sensitivity between azoles, "box-and-whiskersÏ plots revealed large variations in the sensitivity proÐles of some triazoles ; isolates resistant to triazoles have not been detected in M. graminicola populations. In P. infestans populations, the proportion of the phenylamide-resistant sub-population increased during the season more rapidly in treated than in untreated Ðelds, but it was low at the beginning of the next season in all Ðelds. During disease epidemics, the Ðtness of phenylamide-resistant P. infestans isolates, as characterised by lesion size, was higher than that of the sensitive isolates, but after the overwintering period, the recovery of resistant isolates was apparently lower. The presence of both A1 and A2 mating types of P. infestans in European populations, although at di †erent frequencies, allows sexual recombination and increased genetic diversity, a †ecting sensitivity and Ðtness. Such mixed populations can still be adequately controlled by using sound anti-resistance strategies.

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Section: Discussionmentioning

confidence: 98%

Sensitivity profiles ofMycosphaerella graminicolaandPhytophthora infestanspopulations to different classes of fungicides

et al. 1997

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“…Under the selection force of a DMI, the fraction of the population with lower sensitivity will gradually be increased and this can lead to unsatisfactory disease control. Despite the early considerations about the probability of resistance development to DMIs (Fuchs & Drandarevski, 1976), to date, resistance to DMIs has been reported for many pathogens (Stanis & Jones, 1985;Kendall et al, 1993;Eckert et al, 1994;Romero & Sutton, 1997).…”

Section: Introductionmentioning

confidence: 99%

Reduced sensitivity of Cercospora beticola isolates to sterol‐demethylation‐inhibiting fungicides

Karaoglanidis

Ioannidis²,

Thanassoulopoulos

2000

Plant Pathology

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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. ED 50 values were calculated for individual isolates by regressing the relative inhibition of colony growth against the natural logarithm of the fungicide concentration. The mean ED 50 values for flutriafol for the Serres, Imathia and Amyndeon populations were 1´07, 0´73 and 0´5 mg mL 21 , respectively (significantly different at P 0´05). For bitertanol the mean ED 50 values for the Serres and Imathia populations were 0´72 and 0´81 mg mL 21 , respectively, which were not significantly different at P 0´05. The mean ED 50 value of the Amyndeon population was 0´48 mg mL 21 , 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 ED 50 values of 60 isolates were subjected to a linear regression analysis (r 0´81).

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“…While it has been possible to produce mutants in vitro with increased resistance to prochloraz, resistance has rarely developed in field populations (17,23,33,35). Indeed, prochloraz has remained effective in situations where a decline in sensitivity to related DMI fungicides has been reported (26). However, in recent years isolates of Tapesia yallundae and Tapesia acuformis (anamorph Pseudocercosporella herpotrichoides), causal agents of eyespot disease of cereals (14,31), with significantly increased levels of resistance to prochloraz have been obtained from field locations in northwestern France and New Zealand (30; P. S. Dyer and R. E. Bradshaw, unpublished data), providing the first indication of a potential reduction in efficacy of control of eyespot disease by DMI fungicides.…”

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confidence: 99%

Genetic Control of Resistance to the Sterol 14α-Demethylase Inhibitor Fungicide Prochloraz in the Cereal Eyespot Pathogen Tapesia yallundae

Dyer

Hansen

Delaney

et al. 2000

Appl Environ Microbiol

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Sexual crosses were used to determine the genetic basis of resistance to the sterol 14 ␣-demethylase inhibitor fungicide prochloraz in the cereal eyespot pathogen Tapesia yallundae. an even number of sensitive and resistant progeny. This indicated the segregation of a single major gene for resistance in each cross, which was confirmed by the use of backcrosses, crosses between F 1 progeny, and control crosses between sensitive parents. However, there was also evidence of additional quantitative genetic components responsible for the increased IG 50 s of the more resistant isolates. A further cross was made between isolate PR11 and an F 1 progeny arising from isolate 11-3-18, and this also yielded progeny which were entirely prochloraz resistant. This suggested that resistance genes were allelic in these two isolates, with resistance conferred by a gene at the same locus (or closely linked loci), despite the fact that the isolates (PR11 and 11-3-18) originated from different continents.A major reason for the continued success of agricultural production in the developed world has been the availability of chemicals to control pests and diseases in crops. Of these, the sterol 14 ␣-demethylase inhibitor (DMI) fungicides represent the largest and most important group of modern antifungal compounds, possessing excellent protectant, curative, and eradicant properties against a wide range of fungal species (35). Most DMI fungicides are derivatives of imidazoles or triazoles and have remained highly effective in most field applications despite many years of intense agricultural use and their singlesite mode of action. However, decreased sensitivity and field resistance to certain DMIs has been reported in at least 13 species of plant pathogen (10).The imidazole prochloraz (1-{N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]carbamoyl}-imidazole; trade name, Sportak) was launched in 1977 and has since been registered for use on more than 30 different crops in 50 countries worldwide (37; Prochloraz-technical information,

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Changes in sensitivity to DMI fungicides in Rhynchosporium secalis

Cited by 51 publications

References 4 publications

Sensitivity profiles ofMycosphaerella graminicolaandPhytophthora infestanspopulations to different classes of fungicides

Sensitivity profiles ofMycosphaerella graminicolaandPhytophthora infestanspopulations to different classes of fungicides

Reduced sensitivity of Cercospora beticola isolates to sterol‐demethylation‐inhibiting fungicides

Genetic Control of Resistance to the Sterol 14α-Demethylase Inhibitor Fungicide Prochloraz in the Cereal Eyespot Pathogen Tapesia yallundae

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