National Australia Bank plans to sell a stake of around 30 per cent of National Asset Servicing to BNY Mellon Asset Servicing, I&T News reported.The executive general manager of National AS, Leigh Watson, is said to have signed a heads of agreement on a joint venture deal with his BNY Mellon AS counterpart, Timothy Keaney, in London last month, the newsletter reported yesterday. BNY Mellon is global custodian for NAB, a role filled since 1996. NAB is the dominant custodian in Australia with almost $600 billion under custody for local investors at the end of 2009, according to I&T News.