Skip to main content
ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Citrus and Other Subtropical Products Research » Research » Publications at this Location » Publication #320188
Title: Susceptibility of sixteen citrus genotypes to Candidatus Liberibacter asiaticus

Author
item McCollum, Thomas
item Hilf, Mark
item IREY, MIKE - Us Sugar Corporation
item WEIQU, LUO - North Carolina State University
item Gottwald, Timothy

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2015
Publication Date: 6/1/2016
Citation: Mccollum, T.G., Hilf, M.E., Irey, M., Weiqu, L., Gottwald, T.R. 2016. Susceptibility of sixteen citrus genotypes to Candidatus Liberibacter asiaticus. Plant Disease. 100(6):1080-1086.

Interpretive Summary: Huanglongbing (HLB) disease is the most serious threat to citrus production worldwide and in the last decade has devastated the Florida citrus industry. HLB is associated with Candidatus Liberibacter asiaticus (CLas)a bacterium that lives in citrus phloem and its insect vector the Asian citrus psyllid (Diaphorina citri) (ACP). There is currently no cure for HLB and the only long-term sustainable solution to HLB is citrus varieties that are resistant to the disease. Significant effort is being put forth to develop new citrus varieties that are less susceptible to HLB than are current varieties. Effective methods of screening citrus novel citrus germplasm for susceptibility to CLas is essential to identify selections with potential for improved resistance. In this study we exposed small, grafted, trees of sixteen citrus types to free-ranging ACP vectors and CLas inoculum in the greenhouse. We were able to distinguish statistically significant differences in susceptibility to CLas among the sixteen varieties we studied, suggesting that our approach provides meaningful results. Furthermore, our results showed good agreement with trends observed in the orchard, supporting the validity of our approach for screening citrus germplasm for susceptibility to HLB.

Technical Abstract: Huanglongbing (HLB) disease is the most serious threat to citrus production worldwide and in the last decade has devastated the Florida citrus industry. HLB is associated with a phloem-limited a-proteobacter Candidatus Liberibacter asiaticus (CLas) and its insect vector the Asian citrus psyllid (Diaphorina citri)(ACP). Significant effort is being put forth to develop novel citrus germplasm that has a lower propensity to succumb to HLB than do currently available varieties. Effective methods of screening citrus germplasm for susceptibility to HLB are essential. In this study we exposed small, grafted, trees of sixteen citrus types to free-ranging ACP vectors and CLas inoculum in the greenhouse. During 45 weeks of exposure to ACP the cumulative incidence of CLas infection was 70%. Trees of Citrus macrophylla and C. medica were most susceptible to CLas with 100% infection by the end of the test period in three trials, while the complex genetic hybrids US 1-4-59 and ‘Fallglo’ consistently were least susceptible with ca. 30% infection. Results obtained in this greenhouse experiment showed good agreement with trends observed in the orchard, supporting the validity of our approach for screening citrus germplasm for susceptibility to HLB.