If you want to employ the cops to protect all your hard work, work on something that is patentable, copyrightable, or trademarkable. Selective breeding is not

If you want to employ the cops to protect all your hard work, work on something that is patentable, copyrightable, or trademarkable. Selective breeding is not patentable. Literally millennia of prior art. So instead build a brand based around a 10# onion, and protect the trademark rather than the biological variety. When customers demand "Bowling Bulb" branded 10# onions, produce managers will buy yours instead of the generic knockoff, or charge and pay extra for the onions with your logo stickered on them. Or pull a dirty trick, such that there is an external factor to the onion growth, aside from the onion's own DNA, such as saturating the test and production plots with a chemical not normally required for onions, and breeding in dependence on supplementary fertilization, or breed in dependence on a specific pollinator. You have no choice but to sell the onion as is. You don't have to tell anyone else how to successfully grow it, or let them rent your species of onion-pollinating bee.