Brix Tested My Trichocereus. Only 4 of 20 seem worth growing

So I have a theory that a cactus that produces high brix level despite poor conditions and stress are worth selecting to continue growing when culling.

I started 50 trichocereus seeds and only 20 survived my rough treatment of full sun early on, drought during spring and summer and low fertilizing. Of these 20 If i were to cull my seedlings further I'd only keep growing 4 seedlings which had the highest brix reading despite growing in identical conditions as the others.

I'm unsure if increasing brix level would increase alkalkoid content and am not claiming low brix reading directly translates to low alkaloid content but I do believe that a high brix level does correlate with a high alkaloid content in comparison to lower brix reading. Brix fluctuates in drought, after fertilizing and after watering so I tested them all today after 5pm so there is a small alignment with my previous tests.

Most trichocereus tested at 3 brix with the highest a bridgesii testing at 4.5 and the lowest at a tie between the 4 wind bridgesii and a pachanoi.
My TBM after growing a while with me and having dropped to 3 brix after a drought has returned to 6 brix level in the same conditions as the rest.

This is still theoretical and may prove to be completely wrong or inconsistent. I plan on growing all my seedlings so that I can test this theory in the future comparing the lowest brix seedling with the highest brix seedling.