Released
The USDA Agricultural Research Service released US SuperSour 4 in September 2023, according to the CRDF Project 21-008 quarterly report dated 2024-05-15. Bowman’s 2023 article also lists its release year as 2023. The CRDF report says the two newest USDA rootstocks were propagated for upcoming demonstration plantings and field trials.
- USDA Agricultural Research ServiceReleasing Organization