Hamlin N13-32: A Somaclone Under Observation for Huanglongbing Tolerance

Huanglongbing (HLB) has devastated citrus production in Florida, with juice orange production down approximately 90% as measured by boxes of fruit per year. Sweet orange (Citrus sinensis) scions are highly susceptible to HLB and the disease causes severe problems for tree growth, yield, and fruit quality. There have been major efforts to produce HLB tolerant sweet oranges using biotechnological approaches. Utilizing somaclonal variation of ‘Hamlin’ sweet orange has been one of these approaches to select for tolerance. During the 2022–23 season, a ‘Hamlin’ somaclone named ‘N13-32’ on the UFR-4 rootstock has been noted to display plant health that has been described as indicative of HLB tolerance at multiple sites. ‘Hamlin N13-32’ is a somaclone (protoclone), one of three selected from 1000 clones under evaluation. This study collected fruit quality and health data from these trees to determine the potential of this clone for crop production in the HLB environment. Data collected included tree height, yield, Brix, titratable acidity, sugar to acid ratio, fruit size, fruit mass, Candidatus Liberibacter asiaticus (CLas) titer, and health based on hyperspectral drone imagery. Conventional ‘Hamlin’ trees on an industry standard rootstock were compared to ‘N13-32’ on the UFR-4 rootstock. There was evidence for statistically significant differences between scion-rootstock combinations for yield, fruit quality, and tree health. Further evidence is needed to determine the level of HLB tolerance of this promising somaclone.