Well, there is a genetic black back yes. Selective breeding can also reproduce the trait. I have a lovely banded normal girl with a partial black back, when I bred her with my husband's spider, she produced 2 very reduced spiders, 3 normals and a lesser all with a black back. She also produced a woma who was not a black back. If the same breeding produces the same results this season, I would say she carried the black back as a fixed trait.
Selective breeding can fix many traits. Banding for example, as well as reduced patterns, even blushing. There is a fine line between true genetic and simply a fixed trait, but I'm not technical enough to explain it correctly.
I guess what I'm trying to say is, even if Bryan is not considered a genetic black back, by breeding him to the right females, his babies are more likely to carry the black back like dad.
Gale
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