Frequency of avirulence alleles in field populations of Leptosphaeria maculans in Europe

Stachowiak, A.; Olechnowicz, J.; Jędryczka, M.; Rouxel, Thierry; Balesdent, Marie‐Hélène; Happstadius, I.; Gladders, P.; Latunde‐Dada, A. O.; Evans, N. J.

doi:10.1007/1-4020-4525-5_6

Cited by 24 publications

(40 citation statements)

References 27 publications

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“…100-200 isolates) can allow a first description of the race structure in a given country, should the information be completely lacking. Such a survey is currently being done in additional European countries (Stachowiak et al, 2004(Stachowiak et al, , 2006 and in Australia (M. Barbetti, pers. comm.).…”

Section: Discussionmentioning

confidence: 98%

A Large-Scale Survey of Races of Leptosphaeria maculans Occurring on Oilseed Rape in France

Balesdent¹,

et al. 2006

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Nine avirulence genes (AvrLm1-AvrLm9) were identified in Leptosphaeria maculans, the causal agent of stem canker of oilseed rape (OSR), combinations of which could theoretically generate up to 512 different races of the fungus. L. maculans displays a high evolutionary potential to adapt to novel resistance genes as illustrated by the Rlm1 breakdown in France, where virulent populations became prevalent within three growing seasons. An improved knowledge of the race structure of the fungal population is therefore needed to ensure a better use of available major resistance genes. The objective of this study was to characterise the L. maculans population structure in France using a large-scale, rationalised sample of isolates. Experimental fields, planted with ''trap plants'' harbouring no major resistance gene, were sown at 20 locations. Single-pycnidium isolates were collected from leaf lesions that developed in early autumn and 1797 isolates were genotyped at Avr loci. The frequency of AvrLm6 and AvrLm7 was higher than 99%, whereas avrLm2 and avrLm9 alleles were fixed in the population. AvrLm1, AvrLm4, AvrLm5 and AvrLm8 were polymorphic. AvrLm3 isolates were detected at a very low frequency (less than 1%). Only 11 races were identified in France, with one race prevalent, namely Av5-6-7-(8) (i.e. virulent on Rlm1, Rlm2, Rlm3, Rlm4 and Rlm9), representing around 65% of the population. Disparities between the locations sampled were evident at all scales analysed. Some virulent races, such as those harbouring avrLm5, were present before the introduction of the corresponding resistance gene in the commercial OSR crop.

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Section: Discussionmentioning

confidence: 98%

A Large-Scale Survey of Races of Leptosphaeria maculans Occurring on Oilseed Rape in France

Balesdent¹,

et al. 2006

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“…At least nine corresponding L. maculans Avr genes have been genetically characterised (AvrLm1-AvrLm9) and AvrLm1, AvrLm4, AvrLm6 and AvrLm7 have now been cloned (Gout et al 2006;Fudal et al 2007;Parlange et al 2009). The surveys suggest that there is no fitness cost of virulence at the AvrLm2 and AvrLm3 loci since avirulent alleles AvrLm2 or AvrLm3 are very rare or completely absent in European populations (Rouxel et al 2003;Balesdent et al 2006;Stachowiak et al 2006). By contrast, they suggest that there may be a fitness cost at AvrLm1 and AvrLm4 loci since AvrLm1 and AvrLm4 are still present in L. maculans populations, although cultivars with R genes Rlm1 and Rlm4 have been used commercially for >10 years.…”

Section: Introductionmentioning

confidence: 91%

Fitness cost of virulence differs between the AvrLm1 and AvrLm4 loci in Leptosphaeria maculans (phoma stem canker of oilseed rape)

Huang

Balesdent

et al. 2009

Eur J Plant Pathol

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???The original publication is available at www.springerlink.com??? Copyright Springer [Full text of this article is not available in the UHRA]To investigate whether the reported fitness cost of virulence at the AvrLm4 locus in Leptosphaeria maculans is common to other loci, near-isogenic (NI) isolates differing at AvrLm1 locus were produced in vitro. Fitness of virulent (avrLm1) or avirulent (AvrLm1) isolates on Brassica napus without the corresponding R (resistance) gene Rlm1 was investigated in controlled environment (CE) and field experiments. Results indicate that there is a measurable fitness cost for avrLm1 compared to AvrLm1 isolates in terms of number of lesions, size of lesions, distance grown through leaf tissue towards the petiole in CE experiments and systemic growth from leaf lesions to stems in field experiments. There were differences in fitness cost between the AvrLm1 and AvrLm4 loci. There was a cultivar effect on fitness cost of virulence at the AvrLm1 locus but not at the AvrLm4 locus. In CE experiments, the optimal temperature for leaf infection was greater for AvrLm4 isolates than for AvrLm1 isolates. Field experiment results suggest that on the same host AvrLm4 isolates are more fit than AvrLm1 isolates in warmer seasons. The fitness cost at the AvrLm4 locus was generally greater than at the AvrLm1 locus, suggesting that the corresponding R gene Rlm4 may be more suitable than Rlm1 for redeployment in commercial cultivars after an interval of a few years

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“…The L. maculans-Brassica napus pathosystem confirmed a fitness cost of virulence at the AvrLm4 locus in L. maculans on hosts without the corresponding R gene Rlm4 (Huang et al, 2006). Studies suggest that there is no fitness cost for virulence at the AvrLm2 and AvrLm3 loci because the avirulent alleles AvrLm2 or AvrLm3 are very rare or completely absent in European populations (Rouxel et al, 2003;Balesdent et al, 2006;Stachowiak et al, 2006). In contrast, there may be a fitness cost at the AvrLm1 and AvrLm4 loci because AvrLm1 and AvrLm4 are still present in L. maculans populations, although cultivars containing R genes Rlm1 and Rlm4 have been used commercially for over 10 years.…”

Section: Discussionmentioning

confidence: 97%

Assessment of sensitivity and virulence fitness costs of the AvrPik alleles from Magnaporthe oryzae to isoprothiolane

Wu¹,

Wang²,

Zhang³

et al. 2014

Genet. Mol. Res.

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ABSTRACT. The in vitro sensitivity of AvrPik allele isolates of Magnaporthe oryzae to isoprothiolane was examined and the virulence fitness costs of AvrPik allele isolates to isoprothiolane were assessed. Isoprothiolane was found to suppress the radial growth of AvrPik allele isolates at all concentrations (1, 5, 10, 15, and 20 µg/mL). Generally, a higher isoprothiolane concentration has a stronger inhibitory effect on mycelial growth in AvrPik allele isolates at 6 and 10 days after inoculation. The inhibitory effect of isoprothiolane also increased with treatment time. To determine whether a correlation existed between the in vitro sensitivity of AvrPik allele isolates and virulence, the halfmaximal inhibitor concentration and 75% of the maximum inhibitor concentration were calculated for each mutation isolate and wild-type isolate. Based on these values and virulence, no significant correlation between the susceptibility of AvrPik allele isolates and virulence was detected. In summary, no fitness costs were associated with sensitivity of blast isolates carrying specific AvrPik alleles to different virulence.

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Frequency of avirulence alleles in field populations of Leptosphaeria maculans in Europe

Cited by 24 publications

References 27 publications

A Large-Scale Survey of Races of Leptosphaeria maculans Occurring on Oilseed Rape in France

A Large-Scale Survey of Races of Leptosphaeria maculans Occurring on Oilseed Rape in France

Fitness cost of virulence differs between the AvrLm1 and AvrLm4 loci in Leptosphaeria maculans (phoma stem canker of oilseed rape)

Assessment of sensitivity and virulence fitness costs of the AvrPik alleles from Magnaporthe oryzae to isoprothiolane

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