Micrografting cacti is not suitable for random sampling

Way back 2015, I tried implementing random sampling among certain gymnocalycium and astrophytum batches to see if the crosses I've chosen eventually made significant progress.

To achieve this, Micro grafting (can be referred to as seedling graft) via pereskiopsis became my main tool.

Initally, the outcomes were noteworthy and in a way quenched my thirst for positive results. However, there were some things I've realized in course of time which consequently led me to discontinue.

One of them is, grafting somehow manipulated the natural growth of the specimens. Like there were some specimens that had enormous thorns during the early stages, which I think was not usual as compared with a normally grown cacti from seeds. 

Some have been producing pups even at a very small size. I wanted to know how seedlings would realistically look like when they grow mature but grafting sways away from that.

On more thing, I find many gymnos and astros to be surprisingly heterogeneous and crossing one cultivar from another one would give you several features among batches.

To illustrate, in a sample population of 100 seedlings, some would have 5 ribs, some more than that. There will be a tiny percentage of variegated plants but most would be plain green. Some will have different stress colors when hey grow, many would stick to their greenish skin. Some will exhibit long spines while others won't. And so on and so forth.

Perhaps the most consequential discovery I learned out of this is that grafted specimens won't necessarily represent the totality of the general population/batch insofar as sampling is concerned - unless otherwise the subjects came from a very pure and stable materials.