An in vitro method for screening for the presence of the pat-2 gene in tomatoes (Lycopersicon esculentum Mill.)

Under field conditions, pat-2, the gene which conditions parthenocarpy in tomatoes, is recessive. A simple method has been devised for distinguishing the heterozygote from the two homozygotes using tissue culture. Ovaries of plants segregating for the pat-2 gene were excised and cultured on a medium containing 100 ppm gibberellic acid. After three weeks in culture, three distinct ovary sizes could be seen. It was shown, using F₃ progeny tests, that the largest ovaries corresponded to those plants homozygous for the pat-2 gene, the smallest ovaries corresponded to those plants homozygous for the wild type allele, and the intermediate sized ovaries were the heterozygotes. The ability to identify the heterozygote would greatly simplify a backcross breeding program aimed at incorporating the pat-2 gene into commercial cultivars by eliminating the need for an F₃ progeny test to determine the genotype of a plant.