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. 2013 Jun 11;8(6):e66180.
doi: 10.1371/journal.pone.0066180. Print 2013.

Variability in aggressiveness of rice blast (Magnaporthe oryzae) isolates originating from rice leaves and necks: a case of pathogen specialization?

Abhijeet Ghatak  1 , Laetitia Willocquet, Serge Savary, Jatinder Kumar
Affiliations

Variability in aggressiveness of rice blast (Magnaporthe oryzae) isolates originating from rice leaves and necks: a case of pathogen specialization?

Abhijeet Ghatak et al. PLoS One. .

Abstract

Rice blast, caused by Magnaporthe oryzae, causes yield losses associated with injuries on leaves and necks, the latter being in general far more important than the former. Many questions remain on the relationships between leaf and neck blast, including questions related to the population biology of the pathogen. Our objective was to test the hypothesis of adaptation of M. oryzae isolates to the type of organ they infect. To that aim, the components of aggressiveness of isolates originating from leaves and necks were measured. Infection efficiency, latent period, sporulation intensity, and lesion size were measured on both leaves and necks. Univariate and multivariate analyses indicated that isolates originating from leaves were less aggressive than isolates originating from necks, when aggressiveness components were measured on leaves as well as on necks, indicating that there is no specialization within the pathogen population with respect to the type of organ infected. This result suggests that the more aggressive isolates involved in epidemics on leaves during the vegetative stage of the crop cycle have a higher probability to infect necks, and that a population shift may occur during disease transmission from leaves to necks. Implications for disease management are discussed.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Aggressiveness components on rice leaves of Magnaporthe oryzae isolates originating from rice leaves and necks.
In each experiment, each bar represents the mean over 48 measurements made: 12 isolates and 4 replications per isolate. The error bars represent the standard error of the means. In each graph, the three first pairs of bars represent results obtained in each of three independent experiments, and the last pair of bars represents the results obtained from the three combined experiments.
Figure 2
Figure 2. Aggressiveness components on rice necks of Magnaporthe oryzae isolates originating from rice leaves and necks.
In each experiment, each bar represents the mean over 48 measurements made: 12 isolates and 4 replications per isolate. The error bars represent the standard error of the means. In each graph, the three first pairs of bars represent results obtained in each of three independent experiments, and the last pair of bars represents the results obtained from the three combined experiments.
Figure 3
Figure 3. Principal component analysis from components of aggressiveness of Magnaporthe oryzae isolates on leaves and necks.
a: component loadings of the component of aggressiveness. IE: infection efficiency on leaves; LP50: latent period on leaves; LSA: lesion area on leaves; SIL: sporulation intensity per lesion on leaves; INC: neck blast incidence; IP50: incubation period on necks; LLN: lesion length on necks; SIN: sporulation intensity per lesion on necks. b: factor scores of the 24 Magnaporthe oryzae isolates displayed on the two first axes. Black diamonds: isolates originating from leaves; white diamonds: isolates originating from necks.
See this image and copyright information in PMC

References

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