Lightroom 3 doesn’t have a dedicated panorama-tracking feature, but you can build a solid workflow with existing tools.

Useful options mentioned by users:

• Keywords or naming: Add a keyword like panorama to source frames, and save stitched files with something identifiable in the filename. Then use Smart Collections to automatically gather stitched panoramas.
• Color labels: Mark source frames used only for panos with a color label (for example, red). You can then filter them out of normal viewing and only show them when needed.
• Stacks: Put the stitched panorama and its original source images in the same stack. This is the clearest way to keep the finished pano linked to the frames it came from.
• Finding panos visually: In Grid view, sorting by aspect ratio can help surface wide panoramas quickly.

So the practical Lightroom 3 answer is: use a combination of labels/keywords + Smart Collections + stacks. That gives you identification, filtering, and linkage without needing a special plugin. If you want tighter integration with AutoPano Pro, a custom plugin may still be worthwhile, but Lightroom’s built-in organization tools already cover most of the need.