Genetic analysis of the trait of sucrose accumulation in tomato fruit using molecular marker

The trait of sucrose accumulation in some wild species of tomato such as L. chmielewskii, L. hirsutum and L. peruvianum is thought to be monogenic and recessive. We hypothesized that this trait may be linked to acid invertase activity, and examined the relationship between sucrose accumulation and the acid invertase gene. We previously cloned a cell wall-bound form of acid invertase cDNA in tomato (L. esculentum) fruit. As a result of PCR analysis of the acid invertase gene in L. esculentum and L. chmielewskii, a difference in amplified fragment length was detected using one pair of primers. Each fragment was cloned and sequenced, identifying a difference in the sequence of the sixth (last) intron of the invertase gene. A total deletion of 11 bp was found in L. chmielewskii including the continuous sequence of the 10bp long ''AAAAGGTTTT''. PCR analysis enabled us to characterize and distinguish the invertase allele between these species. In the F-2 population, all the sucrose accumulating plants were homozygous for the L. chmielewskii allele. This strongly suggested that the trait of sucrose accumulation was determined by the acid invertase gene at the molecular level. Another possible enzyme linked to the trait of sucrose accumulation, sucrose synthase, was esamined, but no relationship was detected.