There are a number of crops where the plants express a large untapped genetic yield potential.
Well managed cantaloupe plants will regularly pollinate, set, and begin sizing over 20 melons per plant until they are about 2 inches in diameter. Then most of them will abort. Exceptional yields are 10,000 melons per acre from 4000 plants or 2.5 melons per plant.
Grape tomatoes can have as many as 150 blossoms per cluster, yet only produce 35-50 marketable fruit per cluster. Tree fruit and nuts can set many more fruit than they can fill to marketable size. We expect ‘June drop’ as a common phenomenon where trees abort many of the set fruit embryos. (How much calcium and trace minerals are exported from the tree when these fruitlets drop after the cell division stage?)
We know the significant factor that limits the realization of yield potential for many crops is environmental/nutritional stress.
There is another significant factor that is less well understood, partially because many of us have not observed 50+ years of plant breeding work, and the gradual evolution of changing plant expression.
Most modern varieties of the crops I have mentioned, and other crops, have the genetic predisposition to develop many blossoms and set a lot of fruit. And they lack the root system and stem diameter to supply water and nutrients to fill all these fruits.
Many modern cucurbit varieties have comparatively weak root systems when compared with older varieties, and they have thinner diameter vines. The reason some watermelon are grafted on gourd rootstock, and some tomatoes are grafted on cherry tomato rootstock is that the rootstock has a much more robust root system, and delivers more nutrition to the crop through a larger diameter stem.
Ed Curry, the chili pepper breeder I interviewed on the podcast has been able to increase the average yield of chili peppers by more than two times over 40 years of breeding work, largely by focusing on developing varieties with a large stem size, and a robust root system. A narrow diameter stem can not deliver the water and nutrients needed to realize the yields many plants are genetically capable of.
What have you observed about root system size and stem diameter over the years?