Adaptive resistance in Peronosporales to metalaxyl

Bruin, G. C. A.; Edgington, L. V.

doi:10.1080/07060668109501348

Cited by 47 publications

(15 citation statements)

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“…Even so, several regions have reported resistance to mefenoxam in isolates of P. erythroseptica (Goodwin and McGrath 1995;Lambert and Salas 1994;Salas et al 1998). Soil applications of persistent fungicides are known to increase the selection pressure for resistant strains, especially where microniches containing sublethal concentrations of the fungicide are formed (Bruin and Edgington 1981). Shew (1985) found that consecutive soil applications of metalaxyl to control tobacco black shank led to a reduction in sensitivity of the causal agent, Phytophthora parasitica Dast.…”

Section: Discussionmentioning

confidence: 99%

Use of mefenoxam to control pink rot [Phytophthora erythroseptica] of potato in Prince Edward Island

Peters

Arsenault

Sturz³

2003

Canadian Journal of Plant Pathology

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Pink rot of potato, caused by Phytophthora erythroseptica, causes yield losses in the field and in storage. Surveys were conducted in Prince Edward Island (P.E.I.) during 1999-2001 to determine the sensitivity of local isolates of the pathogen to mefenoxam (Ridomil  ). In addition, field trials were established to test the efficacy of foliar applications of Ridomil to control pink rot in stored progeny tubers. Of 47, 24, and 4 samples of infected tubers collected from harvested fields or warehouses across P. E.I. in 1999, 2000, and 2001, respectively, 15 (32%), 2 (8%), and 2 (50%) contained tubers showing symptoms of pink rot. Tissues excised from infected tubers of samples showing symptoms of pink rot yielded 62, 7, and 8 field isolates of P. erythroseptica in 1999in , respectively. In 1999 and 17 single-zoospore isolates were also generated, respectively, for testing of sensitivity to mefenoxam. An assay on agar amended with mefenoxam revealed that all field and single-zoospore isolates collected from P.E.I. were highly sensitive to mefenoxam (EC 50 < 0.5 µg mefenoxam/mL). By contrast, tester isolates of P. erythroseptica from Maine were either sensitive, moderately resistant, or highly resistant to mefenoxam. Tubers ('Russet Burbank' and 'Kennebec') harvested from field plots managed with foliar applications of mefenoxam were inoculated with selected isolates of P. erythroseptica. Isolates that were inhibited on agar medium amended with mefenoxam were also suppressed in tubers from plants treated with foliar applications of the chemical. One foliar application of mefenoxam at tuber initiation was often sufficient to provide a significant (P = 0.05) reduction in pink rot incidence and severity. In some instances, two foliar applications (at tuber initiation and 2 weeks thereafter) reduced disease incidence and severity significantly (P = 0.05) more than a single application. By contrast, tester isolates of P. erythroseptica from Maine designated as either moderately or highly resistant following the amended-agar assay, also infected tubers from plants treated with mefenoxam. Fungicide efficacy was found to vary between cultivars and among years of study; suppression of pink rot was greater in 'Kennebec' than 'Russet Burbank', and fungicide efficacy was reduced in drier years. Management of resistance to mefenoxam and application scheduling are discussed.

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Section: Discussionmentioning

confidence: 99%

Use of mefenoxam to control pink rot [Phytophthora erythroseptica] of potato in Prince Edward Island

Peters

Arsenault

Sturz³

2003

Canadian Journal of Plant Pathology

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“…In the field, the rapid appearance of new races of P. infestans has made single major resistance genes useless in potato (23). Resistance against the fungicide metalaxyl has arisen rapidly in P. infestans and other oomycetes (24)(25)(26). In P. sojae, changes from avirulence to virulence and vice versa were observed among two generations of single zoospore lines (27).…”

mentioning

confidence: 99%

High frequency mitotic gene conversion in genetic hybrids of the oomycete Phytophthora sojae

Chamnanpunt

Shan

Tyler

2001

Proc. Natl. Acad. Sci. U.S.A.

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Microbial populations depend on genetic variation to respond to novel environmental challenges. Plant pathogens are notorious for their ability to overcome pesticides and host resistance genes as a result of genetic changes. We report here that in particular hybrid strains of Phytophthora sojae, an oomycete pathogen of soybean, high frequency mitotic gene conversion rapidly converts heterozygous loci to homozygosity, resulting in heterokaryons containing highly diverse populations of diploid nuclei. In hybrids involving strain P7076, conversion rates of up to 3 ؋ 10 ؊2 per locus per nucleus per generation were observed. In other hybrids, rates were of the order of 5 ؋ 10 ؊5 . Independent gene conversion was observed within a selected linkage group including loci as close as 0.7 kb apart and in unlinked markers throughout the genome. Gene conversions continued throughout vegetative growth and were stimulated by further sexual reproduction. At many loci, conversion showed extreme disparity, with one allele always being lost, suggesting that conversion was initiated by allele-specific double-stranded breaks. Pedigree analysis indicated that individual loci undergo multiple independent conversions within the nuclei of a vegetative clone and that conversion may be preceded by a heritable ''activation'' state.

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“…However, after 12 consecutive transfers on non-amended medium, all the isolates lost most of this resistance returning to EC 50 values of 0.8, not determined, 28, and 2, respectively. However, when three isolates of P. capsici were tested using the same methods as Table 4 Year and field identification number, county and state where field was located, total Pythium population and level of metalaxyl resistance, level of metalaxyl sensitivity, species identification of metalaxyl-resistant isolates, and percentage of the population resistant from fields cropped to potato from 2004 (Bruin and Edgington 1981). In addition, in field tests of isolates of Phytophthora parasitica var nicotianeae exposed to metalaxyl over a 3 year period, EC 50 values steadily increased over the 3 year period as isolates of P. nicotianeae were continuously exposed to metalaxyl in the soil.…”

Section: Discussionmentioning

confidence: 99%

“…Research assessing the development of metalaxyl resistance by MS Pythium isolates under laboratory conditions has previously been assessed (Bruin and Edgington 1981). Single isolates of P. aphanidermatum, P. arrhenomanes, P. graminicola, and P. vexans were exposed to varying concentrations of metalaxyl from 0.1µg/ml to 300µg/ml and the isolates were maintained on metalaxyl-amended agar and transferred 12 times over an 8 month period.…”

Section: Discussionmentioning

confidence: 99%

“…Development of resistance to metalaxyl in commercial agricultural fields or orchards has been confirmed in at least seven species of Phytophthora (Bruin and Edgington 1981;Ferrin and Kabashima 1991;Taylor et al 2002;Timmer et al 1998;Chauhan and Singh 1987;and Seemuller and Sun 1989); and in six other genera in the order Peronosporales including Pythium (Taylor et al 2002;Mazzola et al 2002;Falloon et al 2000;Wiglesworth et al 1988;Schettini et al 1991;Herzog and Schuepp 1985;Molinero-ruiz 2003;Mazzola et al 2002;White et al 1988;Cook et al 1983;Hamm et al 2004). Since the development of metalaxyl resistance is common among oomycete plant pathogens, it is important to assess the Pythium population in potato production areas where metalaxyl is used, to determine the current and future opportunity to effectively use this fungicide not only to help manage Pythium leak on potato but Pythium damping off on other crops in rotation with potato.…”

Section: Introductionmentioning

confidence: 90%

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Metalaxyl-M-Resistant Pythium Species in Potato Production Areas of the Pacific Northwest of the U.S.A.

Porter¹,

Hamm

David

et al. 2009

Am. J. Pot Res

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Several Pythium species causing leak on potato are managed by the systemic fungicide metalaxyl-M. Metalaxyl-M-resistant (MR) isolates of Pythium spp. have been identified in potato production areas of the U.S.A., but information is lacking on the distribution of MR isolates in the Pacific Northwest. Soil samples from numerous fields (312) cropped to potatoes in Idaho (140), Oregon (59), and Washington (113) were assayed using metalaxyl-Mamended agar for the presence of MR isolates of Pythium in 2004 to 2006. Altogether, 1.4%, 42.4% and 32.7% of the fields from these states, respectively, were positive for MR Pythium. Isolates of Pythium ultimum that were highly resistant to metalaxyl were recovered from 53 fields representing ID, OR, and WA. Greater than 50% of the Pythium soil population consisted of MR isolates in ten of 64 fields from Oregon and Washington. Nine species of Pythium were recovered from soil samples, of which MR P. ultimum and P. spinosum were identified. Isolates of MR P. ultimum recovered from soil were pathogenic on potato tubers and may pose a serious threat to the management of Pythium leak and seed rot of diverse crops rotated with potato.Resumen Varias especies de Pythium que causan la pudrición acuosa en papa son controladas por el fungicida sistémico metalaxilo-M. Cepas de metalaxilo-M-resistente (MR) de Pythium spp. han sido identificadas en áreas de producción de papa de los Estados Unidos, pero no hay información de la distribución de cepas MR en el Pacifico Noroeste. Muestras de suelo de numerosos campos (312) cultivados con papa, en Idaho (140), Oregon (59), y Washington (113) fueron ensayadas utilizando agar metalaxilo-M-enmendado para la presencia de Pythium MR del 2004 al 2006. En total, 1.4%, 42.4% y 32.7% de los campos de estos estados, respectivamente, dieron positivo a Pythium MR. Cepas de Pythium ultimum altamente resistentes al metalaxilo fueron recuperadas de 53 campos representando a Idaho, Oregon y Washington. Más del 50% de la población de Pythium del suelo, consistió de cepas MR en 10 de los 64 campos de Oregon Am.

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Adaptive resistance in Peronosporales to metalaxyl

Cited by 47 publications

References 3 publications

Use of mefenoxam to control pink rot [Phytophthora erythroseptica] of potato in Prince Edward Island

Use of mefenoxam to control pink rot [Phytophthora erythroseptica] of potato in Prince Edward Island

High frequency mitotic gene conversion in genetic hybrids of the oomycete Phytophthora sojae

Metalaxyl-M-Resistant Pythium Species in Potato Production Areas of the Pacific Northwest of the U.S.A.

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