shaneatwell, I believe the quality of rootstock is judged on the ability to transmit food/juice to the budwood, and the ability to fend-off/keep-at-bay nematodes (root eating worms).
'South Florida - Winter Avocado Void' (S.FL-WAV') Update:
Today I spoke with the person who Dr. Balerdi said was able to come up with a new avocado cultivar that produces mature/ripe fruit in the 'South Florida - Winter Avocado Void' ('S.FL-WAV') months in South Florida (February, March, April, May).
This person (whom I'll call T.P. to respect his privacy) said to have sold the patent to another individual, and because it was a legal matter, couldn't go into details.
When I told T.P. that he probably planted hundred(s) or thousand(s) of seedlings, to accomplish this feat of filling the 'S.FL-WAV' with a cultivar that produced ripe/mature avocados during this time, surprisingly, T.P. replied "None of that," T.P. said that it was "just a luck of the draw." T.P said that he just grew a seedling avocado that produced ripe/mature fruit during the 'S.FL-WAV.'
Planting a seedling(s) is a valid means to develop a new avocado cultivar that 'fills-in' the 'S.FL-WAV.'
The only problem is, that when an individual solves/fills-in the 'S.FL-WAV,' by the 'Seedling Method,' he/she immediatly realizes that a lot of money can be made and patents the cultivar, effectively removing it from the general population.
This leads me to conclude that the quickest way to solve/fill-in the 'S.FL-WAV,' and then have it become immediatly available to the general population, is by field trying all the avocado cultivars in the “Watch” List. Is it possible that one of these avocado cultivars will solve/fill-in the ‘S.FL-WAV?’ I for one am very inclined to believe so.
Most of these potential ‘S.FL-WAV’ candidates on the “Watch” List were expertly chosen by Carlos. He’s doing an excellent job field-testing many of them.
But, to make good progress in this quest, we really need ‘all of them’ to be presently being field tested.
"Watch" List
We're in the process of confirming that at least one (or more) of the following avocado cultivars, will fill in the 'SFL-WAV' months of March, April and May:
Group 1: 'Sharwil', 'Fujikawa', 'Utuado', 'Jan-Boyce,' ‘Reed,’ ‘Green-Gold,’ ‘Linda,’ 'Fuerte' and 'Wurtz.'
Group 2: ‘Winter-Mexican’ and ‘Winter-Mexican-Seedling’ (per CTMIAMI: that should be good for February and Early March). Also,
Group 3: ‘Don-Carlitos,’ ‘Vero-Beach’ Avocado and ‘Cellons’ Avocado.
Group 4: Hawaiians like, ‘San Miguel,’ ‘Kalahuu,’ ‘Malama,’ ‘Muragishe-Plus.’ And,
Group 5: Californians like, ‘Gwen,’ ‘Santa-Ana-Hass,’ ‘Lamb-Hass,’ ‘Sir-Prize,’ and ‘Holiday.'