EFFECTS OF THE LYCOPERSICON-CHMIELEWSKII SUCROSE ACCUMULATOR GENE (SUCR) ON FRUIT YIELD AND QUALITY PARAMETERS FOLLOWING INTROGRESSION INTOTOMATO

A gene controlling fruit sucrose accumulation, suer, was introgressed from the wild tomato species Lyco-persicon chmielewskii into the genet ic background of a hexose-accumulating cultivated tomato, L. esculentu m. During introgression, the size of the L. chmielewskii chromosomal s egment containing suer was reduced by selection for recombination betw een RFLP markers for the sucr gene and flanking loci. The effects of s ucr on soluble solids content, fruit size, yield and other fruit param eters were studied in the genetic background of the processing tomato cultivar 'Hunt100'. In a segregating BC5F2 generation, the smallest in trogression containing sucr-associated markers was necessary and suffi cient to confer high-level sucrose accumulation, the effects of which were completely recessive. Fruit of sucr/sucr genotypes were smaller t han those of +/sucr or +/+ genotypes at all stages of development. The timing of sugar accumulation and total sugar concentration were unaff ected by sugar composition. No differences in total fruit biomass (fre sh weight of red and preen fruit) at harvest were observed between the genotypes, and sucrose accumulators produced greater numbers of fruit than hexose accumulators in one family. However, the proportion of ri pe fruit at harvest, and hence yield of ripe fruit, as well as average ripe fruit weight and seed set were reduced in sucr/sucr genotypes. S ucrose accumulation was also associated with increased soluble solids content, consistency, serum viscosity, predicted paste yield and acidi ty, and decreased color rating. In the first backcross to L. chmielews kii, hexose accumulators (+/sucr) had larger fruit than sucrose accumu lators (sucr/sucr), while no difference in soluble solids was detected .