Parthenocarpy restores fruitfulness in sterile triploid (3x) tomatoes artificially obtained by crossing 4x x 2x somaclones

SummaryTo breed fruitful triploid tomatoes, diploid (2x) and tetraploid (4x) plants were regenerated from hypocotyl explants, using two pairs of near-isogenic lines differing respectively for the parthenocarpic fruit and parthenocarpic fruit-2 mutations. From 626 regenerated shoots, 53 were tetraploid. In the 4x plants, the mean number of fruits was lower than in the 2x class for all the genotypes, but in the two parthenocarpic lines it was higher than in the respective wild-types at the same ploidy level. Compared with 2x, the mean weight of 4x fruits was lower in wild-type and higher in parthenocarpic lines. Out of four cross combinations between tetraploid and diploid plants (within two parthenocarpic and two corresponding wild-type lines), only two yielded seeds (the parthenocarpic fruit line and its near-isogenic wild-type). Triploids were vegetatively propagated and evaluated in a field trial. Whereas wild-type triploids were completely sterile, the 3x parthenocarpic fruit plants had a fruit set tha...