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Two Loci from Lycopersicon hirsutum LA407 Confer Resistance to Strains of Clavibacter michiganensis subsp. michiganensis

May 2002 , Volume 92 , Number  5
Pages  504 - 510

E. Kabelka , B. Franchino , and D. M. Francis

Department of Horticulture and Crop Science, The Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Ave., Wooster 44691

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Accepted for publication 17 January 2002.

We used molecular markers to identify quantitative trait loci (QTL) that contribute to resistance to bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis. Resistance was first identified as a marker-trait association in an inbred backcross (IBC) population derived from crossing Lycopersicon hirsutum accession (LA407) with L. esculentum. Single-marker QTL analysis suggested that at least two loci originating from L. hirsutum LA407, Rcm 2.0 on chromosome 2 and Rcm 5.1 on chromosome 5, contribute to resistance in replicated trials. Two segregating F2 populations were developed by crossing resistant inbred backcross lines (IBLs) to elite L. esculentum lines and used to confirm QTL associations detected in the IBC population. In these populations, realized heritability estimates were higher for selection based on maximal disease than for selection based on disease progression. Realized heritability in the population carrying Rcm 2.0 was 0.63 and 0.14, respectively, for each selection criteria. Realized heritability estimates were 0.85 for selection based on maximal disease and 0.37 for selection based on disease progression in a population carrying Rcm 5.1. The disease response of F3 families selected for resistance suggested that both Rcm 2.0 and Rcm 5.1 confer resistance to bacterial strains in the repetitive sequence-based polymerase chain reaction DNA fingerprint classes A and C. Markers linked to Rcm 2.0 explained up to 56% of the total phenotypic variation for resistance in one population, and markers linked to Rcm 5.1 explained up to 73% of the total phenotypic variation for resistance in a separate population.

Additional keywords: inbred backcross breeding method.

The American Phytopathological Society, 2002