Building a Better Crop

Building a Better Crop is an Institute side quest in Fallout 4.

Detailed walkthrough
During or after Institutionalized speak with Doctor Holdren, he'll mention that Doctor Karlin could use some help. Karlin will explain that they've replaced Roger Warwick with a synth and need seeds delivered to perform an experiment, he'll provide a passphrase.

Warwick homestead is east of Atom Cats garage and south of The Castle. Go there and speak with Roger, giving him the passphrase. Follow Roger on the "tour" of the homestead, then speak to him again to deliver the seeds. Roger will discuss Bill Sutton's actions around the homestead, and voice his concerns that Bill knows that Roger is a synth. Roger will ask the Sole Survivor to investigate and resolve the issue for him, starting by talking to Roger's family.

Wally and Janey won't provide any information without completing a medium persuasion check, at which point they'll mention Cedric going to Goodneighbor. June can be persuaded to give information by telling her she should be grateful or by passing a medium check.

Go to Goodneighbor next and find Cedric in the The Third Rail, all four options lead to the same second stage of the discussion, at that point he can be bribed or hit with a medium persuasion check to... send the player character back to talk to Bill.

On returning Roger is being held up by Bill, the discussion ends up one of two ways, killing Bill, or passing a moderate persuasion check to talk Bill down. Either way the result is 250 caps, Warwick Homestead as a settlement and instructions to return to the Institute and collect your reward.

Bugs

 * If you have already established Warwick Homestead as one of your settlements before this quest, you may run into issues. Any settlers that are in the vicinity of the confrontation between Bill and Roger at the climax of the quest will eventually start attacking Bill. It's possible that they will already be fighting if you fast travel to the Homestead during this stage. Even if you manage to quickly get through the conversation with the peaceful ending before any settler starts fighting, settlers will still attack Bill afterwards at any time (even if the quest has already been completed). A possible workaround for this issue (that works on any platform) is to send all generic settlers to other settlements before leaving to find Cedric in Goodneighbor. Another possible solution if playing on the PC is to simply disable any settler via the console before they have a chance to attack Bill. It should be noted, however, that even if you specifically re-enable the same IDs afterwards, that any settler's appearance and inventory will be randomized and not saved from before.