By Natalia Zinets KYIV (Reuters) -Heavy Russian strikes hit the southern Ukrainian port city of Mykolaiv overnight and early on Sunday, killing the owner of one of the country’s largest grain producing and exporting companies, the local governor said. Oleksiy Vadatursky, founder and owner of agriculture company Nibulon and his wife, were killed in their home, Mykolaiv Governor Vitaliy Kim said on Telegram. Headquartered in Mykolaiv, a strategically important city that borders the mostly Russia-occupied Kherson region, Nibulon specializes in the production and export of wheat, barley and corn, …