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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC IMPROVEMENT OF CITRUS

Location: Subtropical Insects and Horticulture Research

Title: Incidence and severity of huanglongbing and Candidatus Liberibacter asiaticus titer among field-infected citrus cultivars

Authors
item Stover, Ed
item McCollum, Thomas

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 27, 2011
Publication Date: October 11, 2011
Citation: Stover, E., McCollum, G. 2011. Incidence and severity of huanglongbing and Candidatus Liberibacter asiaticus titer among field-infected citrus cultivars. HortScience. 46:1344-1348.

Interpretive Summary: Huanglongbing (HLB) disease was assessed in eight citrus varieties representing diverse fruit types growing in commercial groves in Florida’s Indian River region, an area with high incidence of HLB. Twenty trees of each cultivar were rated for visual HLB symptoms and leaves were collected to assess the level of the bacterium associated with HLB. There was a strong correlation between HLB symptoms and levels of bacteria detected. Although incidence and severity of HLB varied considerably among the groves, differences in HLB among the varieties were found, even when grove differences were excluded in the analyses. ‘Temple’ tangor showed the most consistently low incidence of HLB symptoms and CLas titer; in contrast, ‘Murcott’ tangor and ‘Minneola’ tangelo had the highest incidence of HLB symptoms and highest levels of the HLB bacteria. These results suggest useful resistance to huanglongbing may be found in conventional citrus cultivars and further work is needed to assess this potential and its commercial value.

Technical Abstract: Incidence and severity of Huanglongbing (HLB) disease were assessed in April, 2010 among eight citrus cultivars representing diverse scion types growing in commercial groves in Florida’s Indian River region, an area with high incidence of HLB. Twenty trees of each cultivar were rated for visual HLB symptoms and leaves were collected for quantification of Candidatus Liberibacter asiaticus (CLas), presumptive causal agent of HLB. There was a strong correlation between HLB incidence and CLas titer, whether on a grove basis or a cultivar basis. Although incidence and severity of HLB varied considerably among the groves, differences among the scions were apparent, even when analyses excluded differences between groves. ‘Temple’ tangor showed the most consistently low incidence of HLB symptoms and CLas titer; in contrast, ‘Murcott’ tangor and ‘Minneola’ tangelo had the highest incidence of HLB symptoms and highest CLas titer. These results suggest useful resistance to huanglongbing may be found in conventional scion cultivars and further work is needed to assess this potential and its commercial value.

Last Modified: 7/31/2014
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