Hopefully I can simplify what happens with fig breeding and that will clear it up.
So, common figs are persistent because they carry the gene “P”, it is the same for persistent caprifigs, they have the gene “P” in their DNA. It is a dominant gene, so figs need only one “P” in order to be persistent, in fact, no fig can have “PP” because when the seed embryo has a P it kills the seed, only the pollen parent can pass the gene “P” to the offspring. The other gene is just called “+”, Smyrnas have 2 of them: “++” and common figs/persistent caprifigs have one along with their gene for persistence: “P+”. So to get common/persistent females you must use a persistent male “P+” as their father, if not and you use a caprifig that does not have the gene it means none of the seedlings will either, they will all be “++”. Smyrna figs/caprifigs are called homozygous because they have 2 of the same genes that result in dropping figs that are not pollinated “++”, Common figs/persistent caprifigs are heterozygous because they have one gene for persistence (that is dominant) and one for dropping fruit “P+”, homo means the same; hetero means different, zygous just means it has to do with genetics
Herman2 was talking about how Condit initially worked with Gillette as the pollen parent but switched to a different one because there is very little pollen in Gillette’s stamens.