Identification of restriction fragment length polymorphisms linked to genes controlling soluble solids content in tomato fruit.

Gene(s) conferring high soluble solids (SS) in tomato fruit had been backcrossed previously from a wild tomato species, Lycopersicon chmielewskii LA1028 (∼ 10% SS), into a L. esculentum cultivar, VF36 (∼ 5% SS), to derive a BC5S5 line, LA1563, similar to 'VF 36' but with 7-8% SS. DNAs from these lines and a tomato breeding line, H2038, were screened for restriction fragment length polymorphisms (RFLPs) using four restriction endonucleases and sixty clones chosen at random from a tomato cDNA library. Most of the cDNA clones (56) identified the same RFLP in 'VF 36' and LA1563 and a different RFLP in LA1028. However, two cDNA clones identified the same RFLP in LA1563 and LA1028 and a different RFLP in 'VF36'. To determine whether RFLPs identified by these two cDNA clones were linked to SS genes, a H2038 x LA1563 F2 population was screened for segregation of the RFLPs and for SS content. The segregation ratios of these RFLPs were consistent with ratios expected for codominant alleles at unlinked loci. Analysis of variance of SS content for different RFLP genotypic classes indicated that RFLP alleles at one of the loci were linked to genes controlling SS content. The RFLP allele from the high SS tomato line, LA1563, was associated with significantly higher SS content and, therefore, could be useful in selecting for high SS gene(s) in a tomato breeding program.