IDENTIFICATION OF 2 GENES REQUIRED IN TOMATO FOR FULL CF-9-DEPENDENT RESISTANCE TO CLADOSPORIUM-FULVUM

Mutagenesis was used to identify and characterize plant genes required for fungal disease resistance gene function in tomato. Seed of a stoc k homozygous for the Cf-9 gene for resistance to Cladosporium fulvum w ere treated with ethyl methanesulfonate, and 568 M2 families were scre ened for mutations to C. fulvum sensitivity. Eight mutants with reduce d resistance were isolated. Four mutations, all of which mapped to the Cf-9 gene, lost both resistance and response to the race-specific AVR 9 elicitor. The other four mutations partially lost resistance and res ponse to the AVR9 elicitor. Cytological analysis revealed that a uniqu e host cell staining pattern accompanied the reduced-resistance phenot ype in three mutants. Two of the mutants with reduced resistance mappe d to Cf-9, and two mapped to two distinct loci designated Rcr-1 and Rc r-2 (Required for Cladosporium resistance) that are unlinked to Cf-9.