What is the most probable genotype for the parents in cross

What is the most probable genotype for the parents in cross #2?

In squash plants, two alleles of one gene determine the co or o to be either orange (0) or yellow (Y). Two alleles of a separate, independent e gene determine the size of the squash to be either large (L) or small (S) The results of 3 matings of squash phenotype are shown below: Determine which alleles are dominant.

Solution

Looking at mating 1, both parents have small size of squash, but the progeny fraction of progeny shows large phenotype as well. This can happen only when large is recessive to small size of squash and is present in one of the parent. So, S allele (small size squash) is dominant over s allele (large size of squash). Looking at mating 1 again, all progeny show organge color of plant irrespective of one of the parent being yellow in color. This can happen only when the orange allele (O) is dominant over yellow (o) allele.
Since all four types of traits are exhibited in the progeny of mating 2, all four alleles should be present in the parent generation. The first parent in mating 2 is orange large (O-ss) and the other parent is yellow small (ooS-). The given four phenotypes can be obtained only when both parents are heterozygous for the dominant trait. So, the genotype of first parent is orange large (Ooss) and the other parent is yellow small (ooSs).