RAP1 Gene Confers Effective, Race-Specific Resistance to the Pea Aphid in Medicago truncatula Independent of the Hypersensitive Reaction

• Published in: Molecular plant-microbe interactions Vol. 22; no. 12; pp. 1645 - 1655
• Main Authors: Stewart, Sophie Alice, Hodge, Simon, Ismail, Nurul, Mansfield, John W, Feys, Bart J, Prospéri, Jean-Marie, Huguet, Thierry, Ben, Cécile, Gentzbittel, Laurent, Powell, Glen
• Format: Journal Article
• Language: English
• Published: St. Paul, MN APS Press 01.12.2009; American Phytopathological Society; The American Phytopathological Society
• Subjects: Acyrthosiphon pisum; Animals; Aphids; Aphids - physiology; Biochemistry, Molecular Biology; Biological and medical sciences; chromosome mapping; forage crops; forage legumes; Fundamental and applied biological sciences. Psychology; genes; Genetic Markers; Genetic Predisposition to Disease; genetic resistance; genetics; Host-Parasite Interactions; Host-Parasite Interactions - genetics; hypersensitive response; inbred lines; induced resistance; insect pests; Life Sciences; loci; major genes; Medicago truncatula; Medicago truncatula - genetics; Medicago truncatula - metabolism; Medicago truncatula - parasitology; metabolism; mortality; necrosis; parasitology; pest resistance; physiology; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases; Plant Diseases - genetics; Plant Diseases - parasitology; plant pathogenic bacteria; plant pests; Pseudomonas syringae pv. phaseolicola; Quantitative Trait Loci; reactive oxygen species; resistance genes; Resistance; Grain legume; Medicago truncatula; Leguminosae; Gene; Microbiology; Dicotyledones; Pisum sativum; Angiospermae; High protein crop; Spermatophyta; CARTOGRAPHIE GENETIQUE; LESIONS; POIS ACYRTHOSIPHON P
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-22-12-1645

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.