Indigo Ag, a Boston-based developer of crop yield improvement solutions, raised $250 million in Series E funding at what Axios has learned is a $3.5 billion post-money valuation. Return backers include Ballie Gifford, Investment Corp. of Dubai, the Alaska Permanent Fund and Flagship Pioneering. Why it matters: The company is using microbes to fight hunger, and is also seeking to upend the entire grains industry with an online marketplace that allows for buy-side quality specifications and identity preservation.