Very interesting question yours, I try to answer you based on my experiences, then if any reader has to say about it I leave the comment form open below.
How to make a cutting
Being a public answer, I start from afar, to allow even beginners to understand what we are talking about. The cutting consists in obtaining a new plant starting not from the germination of a seed but by removing a part of a part of the existing plant and making it root. This can also be done by growing tomatoes: some tomato branches have the possibility of forming autonomous roots giving life to new plants.
In particular, it is customary for tomatoes that are growing to remove the axillary shoots (also called female or cacchi). Females that are detached can be rooted to obtain plants from cuttings. To take root the detached branch must be placed with one end in water or in a jar of soil to be kept very moist for a couple of weeks. Rooting axillary shoots can be useful for having late tomato seedlings.
Productivity of tomato cuttings
Now that we have seen what it means to make a tomato cutting, let's move on to answer Massimo. Plants obtained by cuttings have the same genetic heritage as the mother plant, so on paper they can be equally productive and will bear fruit of the exact same variety. However, it often happens that the rooted females produce less than the original plant, the reasons that I identify are basically two:
- Late transplant and therefore too short a useful period. Since the cutting is obtained from an existing plant, it is often ready in a non-optimal period for transplanting tomato seedlings. In fact, in order to obtain the cutting, it is first necessary to plant the mother plant, wait for it to grow enough to form suitable females, prune and root the branch. These operations take time, it is likely that the cutting will be ready later than the best time to grow tomatoes and therefore find an unsuitable climate in the garden.
- Inadequate rooting. It is not certain that the cutting is perfect and if the plant develops its root system slowly it may be inadequate compared to the size of the stem and therefore have a lower capacity to find resources, which then translates into less fruit production.