Japan's cultured pearls have grown to occupy 60% of the world pearl market.
Literal
Japan [possessive-の] cultured pearls [topic-は] world [possessive-の] pearl market [possessive-の] 60% [object-を] occupy [until-まで] [to-に] became.
~までになった (has reached the point of / has grown to) marks an impressive achievement. 養殖真珠 (cultured pearls) is an industry compound: 養殖 (aquaculture/farming) + 真珠 (pearl). ６割 uses 割 (tenths) as a counter — 6割 = 60%. 占める (to occupy/account for) is standard for market share.