A differential basis of antifungal activity of acylalanine fungicides and structurally related chloroacetanilide herbicides in Phytophthora megasperma f. sp. medicaginis

Davidse, L.C.; Gerritsma, O.C.M.; Velthuis, Grardy C.M.

doi:10.1016/0048-3575(84)90098-1

Cited by 18 publications

(7 citation statements)

References 10 publications

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“…The suggestion that response to metalaxyl is regulated by a single locus exhibiting incomplete dominance is consistent with the proposed mode of action of phenylamide fungicides which are thought to inhibit RNA synthesis by interfering with template-bound a-amanitin-insensitive RNA polymerase activity (Davidse et aL, 1983(Davidse et aL, , 1984. If resistance is caused by a modification of the enzyme resulting in a failure to bind the fungicide, then homozygous resistant isolates with two functional alleles would be expected io grow and reproduee more rapidly in the presence of fungicide than heterozygous isolates with only a single functional allele.…”

Section: Discussionsupporting

confidence: 76%

Studies on the inheritance of resistance to metalaxyl in Bremia lactucae and on the stability and fitness of field isolates

Crute¹,

Harrison²

1988

Plant Pathology

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One hundred and eighty‐one sexual progeny isolates from three F1, one F2, five BC1 and one BC2 generations of crosses involving two metalaxyl‐resistant and two metalaxyl‐sensitive isolates of Bremia lactucae were assessed for response to metalaxyl. In most cases, isolates were also tested for virulence phenotype and sexual compatibility type. Isolates could be classified into three phenotypes (sensitive, resistant and intermediate) on the basis of their response to fungicide. Sensitive progeny isolates were similar to the sensitive parents and did not sporulate on lettuce seedlings grown in the presence of > 1.0 μg/ml metalaxyl. Resistant progeny isolates, in common with the resistant parents, sporulated as readily on lettuce seedlings grown in the presence of 100 μg/ml metalaxyl as on untreated seedlings. Progeny isolates which expressed an intermediate phenotype not observed in field samples were also recovered. This phenotype was more variable but isolates so classified were able to sporulate on seedlings grown in the presence of 100 μg/ml metalaxyl but exhibited a latent period (time from inoculation to appearance of sporulation) which was on average twice as long as that observed on seedlings grown in the absence of fungicide. Segregation patterns suggested that response to metalaxyl is controlled at a single locus exhibiting incomplete dominance but that the expression of response in the heterozygous condition may be affected by modifier genes. There was evidence that the metalaxyl‐resistant parental field isolates were heterokaryotic (possibly carrying nuclei homozygous and heterozygous at the locus controlling metalaxyl response). After 10‐30 asexual generations in the absence of fungicide, the response to metalaxyl of resistant field isolates began to approach that of an intermediate type. This phenomenon did not occur with a resistant sexual progeny isolate (presumed homokaryotic) and is additional evidence for the heterokaryosis of field isolates. The relative fitness of a range of isolates was examined by observing changes in the proportions of spores over three asexual generations after they were initially mixed in a 1:1 ratio with mutant isolates carrying a microscopically visible genetic marker (large lipid droplets). Most field isolates were more fit than the mutant isolates used, regardless of whether they were resistant or sensitive to metalaxyl, and there was no evidence that resistant isolates carried any fitness deficit in comparison with the sensitive isolates examined. In contrast, sexual progeny isolates (particularly from BC1 generations) were often less fit than the mutant isolates used, but there was no evidence that this was associated with response to fungicide. These findings are discussed in relation to the mode of action of metalaxyl and disease control strategy.

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Section: Discussionsupporting

confidence: 76%

Studies on the inheritance of resistance to metalaxyl in Bremia lactucae and on the stability and fitness of field isolates

Crute¹,

Harrison²

1988

Plant Pathology

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“…?- ; 1,08 ± 0,02 1,28 ± 0,02 1,12 ± 0,02 1,17 ± 0,02 1,11 ± 0,02 l.IO ± 0,04 0,69 ± 0,02 0,72 ± 0,02 1,04 ± 0,03 1,02 ± 0,03 1,12 ± 0,06 1,09 ± 0,04 1,26 ± 0.03 '' 1.30 ± 0,04 0,86 ± 0,02 Maintained cryogenically at Cornell University, Ithaca, NY, Mating type determined by pairing with isolates of known Al or A2 mating type on clarified 10 % V8-juice agar, S, growth less than 40 % of control on both 5 and 100 |Ug/l metalaxylj I, growth 40 % or more of control on both 5 and 100 f<g/l metalaxyl; R, growth 40 % or more of control on both 5 and 100 //g/1 metalaxyl (DAVIDSE et al 1984), Mean nuclear DNA content (arbitrary units), plus or minus standard error of the mean (N = 50), Phytophthora infestans in Poland from [1987][1988][1989] ::., Mating type determined by pairing with isolates of known Al or A2 mating type on clarified 10 % V8-juice agar. S, growth less than 40 % of control on both 5 and 100 |Ug/l metalaxyl; I, growth 40 % or more of control on both 5 and 100 ^ug/l metalaxyl; R, growth 40 % or more of control on both 5 and 100 ^wg/l metalaxyl (DAVIDSE et al 1984). Mean nuclear DNA content (arbitrary units), plus or minus standard error of the mean (N = 50).…”

Section: Methodsmentioning

confidence: 99%

“…Since the first report of resistance to the systemic fungicide metalaxyl among field isolates of P. infestans from the Netherlands in 1981 (DAVIDSE et al 1981), resistance to metalaxyl has been reported among populations of the fungus worldwide (DOWLEY and O'SULEIVAN 1981, COHEN and REUVENI 1983, HOLMES and CHANNON 1984, PAPPAS 1985, THERRIEN et al 1990). Furthermore, an increase in the frequency of metalaxyl resistance has been observed in Israel (COHEN and SAMOUCHA 1987), Northern Ireland (COOKE 1988) and England and Wales (SHATTOCK et al 1990).…”

Section: Zusammenfassungmentioning

confidence: 99%

“…'' Mating type determined by pairing with isolates of known Al or A2 mating type on clarified 10 % V8-juice agar. ' S, growth less than 40 % of control on both 5 and 100 fig/\ metalaxyl; I, growth 40 % or more of control on both 5 and 100 fxg/l metalaxyl; R, growth 40 % or more of control on both 5 and 100 ;(g/l metalaxyl(DAVIDSE et al 1984).'' Mean nuclear DNA content (arbitrary units), plus or minus standard error of the mean (N = 50).…”

mentioning

confidence: 99%

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Phytophthora infestans in Poland from 1987–1989; Nuclear DNA Content, Mating Type Distribution and Response to Metalaxyl

Therrien

Ritch

Sujkowski³

et al. 1993

Journal of Phytopathology

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Isolates of Phytophthora infestans were collected from all potato growing regions of Poland during the blight seasons of 1987—1989. All 1987 isolates were of Al mating type and were sensitive to metalaxyl. In 1988 and 1989, 46.5 % and 55.3 % of the isolates were sensitive to metalaxyl, respectively. The percentage of highly resistant (R) isolates increased from 25.6 % in 1988 to 39.5 % in 1989; however the percentage of intermediately resistant (I) isolates decreased during that period from 27.9 % to 5.3 %. A significant association was observed between the A1 compatibility type and metalaxyl resistance. The A2 mating type first appeared in 1988, and its frequency increased from 4.7 % of the population in 1988 to 47.6 % in 1989. Coincident with this change in mating type frequency, changes in ploidy levels of isolates were observed. Whereas 3 % of the 1988 isolates were diploid, 90 % of the 1989 A2 isolates and 28.6 % of the 1989 Al isolates were diploid. The approximate 1:1 ratio of the two mating types encountered in 1989, and the predominance of diploidy, indicates that the Polish population of P. infestans has the potential to become sexual.

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“…tato, tomato, and tobacco (Cohen et al, 1979;Davidse et al, 1984;Sujkowski et al, 1995). As it is a biodegradable product, it can induce selection of the soil microbial population that is able to utilize the pesticide as nutrient and energy source.…”

Section: Degradação Acelerada Do Metalaxil Em Solos Agricultáveis Do mentioning

confidence: 99%

Enhanced degradation of metalaxyl in agricultural soils of São Paulo State, Brazil

Papini

Andréa

2001

Pesq. agropec. bras.

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-This work investigated the effect of repeated applications on enhanced degradation of metalaxyl in two different agricultural soils used for cultivation of orange and lemon from Casa Branca and Itapetininga districts of São Paulo State, Brazil. Soil samples were collected from areas repeatedly treated with commercial ridomil 50GR for six successive years, and from other areas never exposed to this fungicide. At the laboratory, soil samples received a 14 C-metalaxyl solution and its degradation was studied through radiometric techniques to measure biomineralization and recovery of extractable-and soil-bound products. Enhanced degradation was verified only in one soil, although partial degradation and mineralization of the fungicide were detected in both soils. The different rates and patterns of metalaxyl degradation in the soils were probably due to their different physical, chemical, and biological characteristics.

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A differential basis of antifungal activity of acylalanine fungicides and structurally related chloroacetanilide herbicides in Phytophthora megasperma f. sp. medicaginis

Cited by 18 publications

References 10 publications

Studies on the inheritance of resistance to metalaxyl in Bremia lactucae and on the stability and fitness of field isolates

Studies on the inheritance of resistance to metalaxyl in Bremia lactucae and on the stability and fitness of field isolates

Phytophthora infestans in Poland from 1987–1989; Nuclear DNA Content, Mating Type Distribution and Response to Metalaxyl

Enhanced degradation of metalaxyl in agricultural soils of São Paulo State, Brazil

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