Flowering response of the uniflora:blind:self-pruning and jointless:uniflora:self-pruning tomato (Solanum lycopersicum) triple mutants.

Tomato (Solanum lycopersicum) is a day-neutral plant with a sympodial growth habit. Triple mutants were produced in order to investigate the genetic interactions in the flowering regulation of this species in the initial and sympodial segments. The jointless:uniflora:self-pruning and uniflora:blind:self-pruning triple mutants were produced by crossing the jointless:uniflora and uniflora:blind double mutants with the uniflora:self-pruning double mutant. The phenotype of the triple mutants was characterized and the expression of the affected genes was studied in the uniflora (uf) mutant through semi-quantitative reverse transcriptase polymerase chain reaction (PCR). The triple mutants produced solitary flowers, as their uf parent, instead of inflorescences. They were both late flowering in the initial segment with a flowering time intermediate between their parental double mutants. The flowering time of the sympodial segments was delayed in the jointless:uniflora:self-pruning triple mutant while the uniflora:blind:self-pruning triple mutant did not initiate sympodial segments. The expression of the studied genes was not markedly affected by the uf mutation. These results suggest that floral transition of the primary shoot and of sympodial segments is regulated differently in tomato. The UNIFLORA (UF) gene acts upstream of the other investigated genes in controlling reproductive structure and flowering time of the initial segment although their expression does not seem to be affected by the uf mutation. In the sympodial segments, the self-pruning determinate phenotype is strengthened by the blind mutation and suppressed by the jointless mutation.