The original cardboard tomato contained the rin gene. This completely shutdown the production of ethylene. These tomatoes never turned red until ethylene gas was applied externally.
These types fell out of favor when varieties with down regulated ethylene response and production were developed. These types will turn red but are always firm and mostly flavorless.
Store tomatoes are bred for firmness.
The original cardboard tomato contained the rin gene. This completely shutdown the production of ethylene. These tomatoes never turned red until ethylene gas was applied externally.
These types fell out of favor when varieties with down regulated ethylene response and production were developed. These types will turn red but are always firm and mostly flavorless.