Syngenta AG (SYNN.VX) may seek partners to help improve its product lineup after a thorough review in the wake of a rebuffed takeover approach from Monsanto Co (MON.N), the agrichemicals group’s chairman told a Swiss newspaper. Syngenta’s board is under pressure from shareholders to show how it plans to generate value after turning its back on Monsanto’s $47 billion cash-and-share offer, which it said undervalued the company and had too great an execution risk.