I also found it quite interesting hearing Dr. Manners state in his GROTW presentation that many older roses which had "lost vigor", regained it after being treated to remove the RMV they were infected with. There ARE degenerative sports (mutations) as well as deleterious effects from the various viruses which comprise Rose Mosaic Virus. Who knows which is the case with a particular rose, unless it is treated?

Due to the method the US rose industry produced their product for most of the past century, it was very easy (and fast) for a variety to pick up multiple types of viruses, both RMV as well as many others. It's entirely possible the "degrading" of rose varieties which has so often been attributed to "over propagation", was, to a large part, due to stacked viral infections over powering the rose's immune system. It's also entirely possible by eliminating the infections possible through the treatment process, the genetic immunity of the roses so treated have been permitted to function properly, producing plants more the quality in vigor and performance the old descriptions indicate. The only logical explanation for the "over propagation" claims would be stacked and intensified viral load types.

Yes, "over propagation" claims can be made about any rose which appears to have become weaker or less productive compared to the original descriptions. You have to be careful there aren't other explanations for the 'change'. Early writers praised many of the Hybrid Perpetual and Bourbon roses because of their wonderful performance in gardens of the time. As the Nineteenth Century progressed, many were found to have "degenerated" and the "over propagation" explanation was frequently used. However, something else completely unrelated to the actual roses themselves was happening. High sulfur oils and coals were used for power and heat, releasing sulfur, a very good fungicide, into the air where it would combine with the fog, dew and rains, then bathe the roses (and everything else!) nightly with a sulfur bath. As lower sulfur fuel sources were discovered and pressed into use, suddenly the old "tried and true favorites" began suffering from fungal issues. "Over propagation" was often blamed as the culprit.

And, yes, like isolating a mutation or sport, if a degenerative mutation which results in a reduction in vigor is isolated through any method of propagation, it can result in a degenerated line or strain of the particular rose. Similar things have happened. Angel Face, Circus and French Lace (the ones I know about) had mutated to more vigorous forms with significantly degraded flower colors. All three were "muddier", "dirtier" colored than the originals. All three were also more vigorous, producing greater quantities of buds available for production. Since these degraded growths were more vigorous, those selecting material for propagation were naturally drawn to collect them for use. I haven't read of complaints about the inferior coloring in any French Lace or Circus lines in many years, but I do still see examples of the degraded Angel Face in gardens and stores. Peace mutated to a miniature (Baby Peace). It's possible there were partial mutations along the way which were propagated in the effort to isolate the miniature form. Some of those could well have resulted in plants which were genetically smaller and perhaps, weaker. Mutations are not always an "on or off" situation. Often, they occur along a continuum, resulting in plants which express the mutation to varying degrees.