The RAP1 gene confers effective, race-specific resistance to the pea aphid in Medicago truncatula independent of the hypersensitive reaction.
Plant resistance to pathogens is commonly associated with a hypersensitive response (HR), but the degree to which the HR is responsible for incompatibility is subject to debate. Resistance to aphids is likely to share features with resistance to pathogens but is less well understood. Here, we report effective resistance to the pea aphid Acyrthosiphon pisum in Medicago truncatula. Aphids lost weight and died rapidly (within two days) on the resistant genotype Jemalong, which developed necrotic lesions following infestation. Lesions were induced by nonvascular intracellular stylet punctures by aphids, remained localized to the site of stylet entry, stained for the presence of reactive oxygen species, and were similar to the HR induced by the bacterial pathogen Pseudomonas syringae pv. phaseolicola. The implication that aphid-induced lesions confer resistance was tested by quantitative trait loci analysis using recombinant inbred lines derived from a cross between Jemalong and the susceptible genotype DZA315.16. One major locus, RAP1, was identified that was sufficient to confer race-specific resistance against the pea aphid and was mapped to the middle of chromosome 3. Surprisingly, a separate locus, mapping to the top of chromosome 3, governed aphid-induced HR, indicating that the HR-like lesions are not required for RAP1-mediated aphid resistance.
Stewart
Sophie Alice
SA
Division of Biology, Imperial College London, South Kensington Campus, London, UK.
Hodge
Simon
S
Ismail
Nurul
N
Mansfield
John W
JW
Feys
Bart J
BJ
Prospéri
Jean-Marie
JM
Huguet
Thierry
T
Ben
Cécile
C
Gentzbittel
Laurent
L
Powell
Glen
G
D000818:Animals; D001042:Aphids / Q000502:physiology*; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease; D006790:Host-Parasite Interactions / Q000235:genetics; D046913:Medicago truncatula / Q000235:genetics* / Q000378:metabolism / Q000469:parasitology*; D010935:Plant Diseases / Q000235:genetics / Q000469:parasitology; D040641:Quantitative Trait Loci
D005819:Genetic Markers