The product backlog is owned by the product OWNER, it is one of the roles in a scrum TEAM and is aligned completely to the product. Per scrum guidelines, the product owner is responsible for maintaining the product backlog. But that doesn't mean Product Owner is only the INPUT source for the product backlog.

Any stakeholders (Business analyst/Tech architect/software architect/tester/developer/customer) in the organization/project can contribute to the product catalog. But Product owner has the ultimate responsibility for prioritizing them (with or without Development Team). It is the responsibility of the product owner to capture and add anything and everything into the backlog. Also, the product owner will make sure that the items in the backlog reflect the prioritization as the market needs. The item delivering the highest value should be at the top. There are several ways a product owner can USE to prioritize the backlog such as – Ranking, Moscow, and Hundred DOLLAR method, etc., the goal is to keep the backlog healthy and prioritized. You can even say that the product owner is the mini CEO for his own area.