These genes influence the size and shape of the fruit.

Keeping in mind that all tomatoes evolved from the pea-sized common ancestor of Solanum pimpinellifolium (Currant tomato), each variation in shape is from a different gene.

The first shape genes were ovate

(which actually has an effect on firmness and shelf-life),

and lc (locules, more) and fas (fasciated, merged locules) all pre-European, and then sun (and sun plus fas = heart-shape) post-European.

globe

sov-1

sov-2

It’s apparent from detailed genetics studies that track effects of (hundreds of genes) that it’s a bit simplistic to attrtibute too much to a partciular geens,

QTL quantitative trait loci assign percentage determination for each gene, so that the role of each gene can be understood more holistically, keeping in mind that other genes are in play, and that they can have additive or multiplicative effects.