Building a Better Crop

You can get this quest from Dr. Karlin in the Institute during or right after the quest "Institutionalized". Since the reward for this quest is Warwick Homestead as a settlement and the quest requires the NPC Bill Sutton, the quest may not trigger if you already have this settlement under your control prior to entering the Institute and/ or if Bill is killed (by supermutant or raider invasion)

You need to deliver the seeds you acquired from Dr. Karlin to Roger Warwick. Upon reaching the location, talk to Roger and follow him as he tours you around. Talk to him again to hand over the seeds. Roger will also mention about how one of the settlers, Bill Sutton is increasingly suspicious that Roger is a synth. The player will be asked to resolve the issue.

The investigation involves more talking and successful passing of charisma speech checks. Talk to Roger's family members until you learn that Cedric has gone to Goodneighbor.

Travel to Goodneighbor and find Cedric in the Third Rail. Talk to him to update your objective, then travel back to the settlement. Upon arriving, you'll find Roger held up by Bill. From hereon, you have the option to kill Bill or persuade him to calm down.