Building a Better Crop

Building a Better Crop is a faction quest in Fallout 4.

Quick walkthrough

 * Talk to Clayton Holdren.
 * Talk to Isaac Karlin.
 * Go to Warwick homestead and speak to Roger.
 * Speak to Roger's family and get information.
 * Go to Goodneighbor and speak with Cedric.
 * Go back and deal with Bill.
 * Turn in the quest to Isaac Karlin.

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
On multiple occasions if there were other settlers in the area they would attack Bill once he pulls his gun on Roger. Talk to Bill and try to save him by sending all settlers to other locations before talking to Cedric. If playing on PC, first disable combat AI before fast traveling to the Homestead by bringing up the console and entering "tcai" without quotes. The settlers won't draw their weapons, and the scene will play out as it's intended to.