Is there a list being developed of heat tolerant Ocas that may grow okay in the southern USA? Anyone growing out mass seedlings in hot conditions to see what survives?
This depends on what you mean by heat tolerant. Many ocas will survive hot temperatures, but they tend not to yield well. A few yield reasonably well in climates that climb frequently into the 90s. None will flower reliably in hot weather.
We try to get people in hot climates for our variety evaluations and the varieties that we have released fall into two categories: those that perform better than average in warmer climates and those that form tubers early. Redshift, Sockeye, and Longview all have performed well in pretty hot summers in the San Joaquin valley. They don’t yield as well there as they do here, but they outperform the heirloom varieties with the possible exception of Mexican Red. Longview has flowered at unusually warm temperatures for oca.
One of our members, Rowan, grows oca from seed in Australia and has reported good results in getting better adapted varieties.
The focus of my breeding so far is to identify heat tolerant ocas to expand the range south and earlier varieties to expand the range north. If I can make enough progress at this to get reliable flowering in more diverse climates, those of you who actually grow in those climates ought to be able to take over and make faster progress.