Selection and parasite evolution: a reproductive fitness cost associated with virulence in the parthenogenetic nematode <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> |
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Authors: | Philippe Castagnone-Sereno Michel Bongiovanni Eric Wajnberg |
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Institution: | (1) UMR1064 Interactions Plantes-Microorganismes et Santé Végétale, INRA/UNSA/CNRS, 400 route des Chappes, BP167 Sophia Antipolis, France;(2) UMR 1112 Réponses des Organismes aux Stress Environnementaux, INRA/UNSA, 400 route des Chappes, BP167 Sophia Antipolis, France |
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Abstract: | Selection in plant parasites for virulence on resistant hosts and the resulting effects on parasite fitness may be considered
as a driving force in host-parasite coevolution. In the present study, we tested the hypothesis that a fitness cost may be
associated with nematode virulence, using the interaction between the parthenogenetic species Meloidogyne incognita and tomato as a model system. The reproductive parameters of near-isogenic lines of the nematode, selected for avirulence
or virulence against the tomato Mi resistance gene, were analysed and combined into a reproductive index that was taken as a measure of fitness. The lower fitness
of the virulent lines on the susceptible tomato cultivar showed for the first time that a measurable fitness cost is associated
with unnecessary virulence in the nematode. Although parthenogenesis should theoretically lead to little genetic variability,
such cost may impose a direct constraint on the coevolution between the plant and the nematode populations, and suggests an
adaptive significance of trade-offs between selected characters and fitness-related traits. These results indicate that, although
plant resistance can be broken, it might prove durable in some conditions if the virulent nematodes are counterselected in
susceptible plants, which could have important consequences for the management of resistant cultivars in the field. |
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Keywords: | Evolution of virulence Fitness Host– Pathogen interaction Plant resistance Root-knot nematode Trade-off |
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