Genetic dissection of oligogenic resistance to bacterial wilt in tomato.
To study resistance to bacterial wilt (caused by Pseudomonas solanacearum) in tomato, we analyzed 71 F2 individuals from a cross between a resistant and a susceptible parent with 79 DNA markers. F2 plants were inoculated by two methods: bacteria were injected into shoots of cuttings or poured into soil surrounding wounded roots. Disease responses were scored on a scale of 0 to 5. Statistical comparisons between DNA marker genotypes and disease phenotypes identified three genomic regions correlated with resistance. In plants inoculated through roots, genomic regions on chromosomes 6 and 10 were correlated with resistance. In plants inoculated through shoots, a region on chromosome 7 was significant, as were the regions on chromosomes 6 and 10. The relative impact of resistance loci on disease response differed between shoot and root inoculations. To confirm the existence of a partial resistance gene on chromosome 6, an F2 individual homozygous for the resistant parent's alleles on chromosomes 7 and 10, but heterozygous for markers on chromosome 6, was selfed. Analysis of the F3 progeny confirmed that a partial resistance locus was located on chromosome 6, very close to CT184. The presence of a partial resistance locus on chromosome 10 was similarly confirmed by analysis of progeny of another F2 plant chosen on the basis of its marker phenotype.
Danesh
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Department of Plant Pathology, University of Minnesota, St. Paul 55108.
Aarons
S
S
McGill
G E
GE
Young
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ND
D002874:Chromosome Mapping; D003433:Crosses, Genetic; D008040:Genetic Linkage; D005819:Genetic Markers; D007113:Immunity, Innate / Q000235:genetics*; D010935:Plant Diseases / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D011549:Pseudomonas / Q000472:pathogenicity*; D014675:Vegetables / Q000235:genetics*
D005819:Genetic Markers