For the past two decades, Florida citrus production has undergone a 75% reduction due to Huanglongbing (HLB), a disease caused by Candidatus Liberibacter asiaticus and vectored by the Asian Citrus Psyllid (ACP, Diaphorina citri). To combat this threat, breeding programs have been developing new varieties, seeking those tolerant to HLB while possessing other desirable traits and providing a long-term solution for the citrus industry. The Indian River Research and Education Center is leading this effort by planting new scion and rootstock varieties in four independent trials at the Millennium Block in 2019. One trial consists of 18 grapefruit-pummelo hybrid scions grafted onto three rootstock varieties, totaling 54 combinations (Trial 1). The other three trials are rootstock trials, where ‘Ray Ruby’ grapefruit (Trial 2), ‘Glenn Navel’ sweet orange (Trial 3), and ‘UF-950’ mandarin (Trial 4) varieties are grafted onto 32 rootstocks. The Millennium Block is home to 5,500 trees. Complete data for the 2023/24 season was collected, evaluating fruit yield, weight, size, and juice quality across all trials except for the mandarins, which have yet to set and keep a harvestable crop. Fruits were categorized into “good fruit” (based on shape, size, and maturity) and “bad fruit” (including visually HLB-affected fruit and off-bloom fruit). One of the 18 scions in Trial 1, a grapefruit-orange hybrid with golden flesh and high juice content called ‘Triumph,’ was discovered through a fortuitous mistake, yielding over 19,000 lb/ac of “good fruit” when grafted onto X-639, and had a Brix of 8.18. ’Triumph’ exhibits visual tolerance to HLB, with minimal to no affected fruit and no leaf symptoms. Of the red flesh grapefruit, ‘UF-914’ grafted onto ‘US-942’ and ‘X-639’ yielded close to 12,000 lb/ac of “good fruit” each, with juice Brix between 8-9. The traditional ‘Ray Ruby’ grapefruit has produced more boxes per acre grafted onto UFR-15 (close to 8,000 lb/ac) than US-942 and Sour Orange. Meanwhile, ‘Glenn Navel’ sweet orange yields more boxes when grafted onto US-942 (approximately 3,800 lb/ac), UFR-17, and Kuharske. The rootstock trials reveal that grapefruit and sweet orange scions require distinct rootstock characteristics to achieve the best yields. Data gathered by these trials are essential for growers to make informed decisions about which varieties to plant compared to the available conventional scions.
