IDENTIFICATION, CHARACTERIZATION, AND BIOLOGY OF FOREIGN AND EMERGING INSECT-TRANSMITTED PLANT PATHOGENS
Location: Foreign Disease-Weed Science
Title: The relevance of Murraya paniculata and related species as potential hosts and inoculum reservoirs of Candidatus Liberibacter asiaticus, causal agent of Huanglongbing (HLB)
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 3, 2009
Publication Date: May 1, 2010
Citation: Damsteegt, V.D., Postnikova, E.N., Stone, A.L., Kuhlmann, M., Wilson, C., Sechler, A.J., Schaad, N.W., Brlansky, R.H., Schneider, W.L. 2010. The relevance of Murraya paniculata and related species as potential hosts and inoculum reservoirs of Candidatus Liberibacter asiaticus, causal agent of Huanglongbing (HLB). Plant Disease. 94:528-533.
Interpretive Summary: Huanglongbing (HLB) is considered the most serious insect-transmitted bacterial disease of citrus. It currently threatens the citrus industry in Florida and the vector has been found in Florida, Georgia, Alabama, Louisiana, Texas, and California. Most citrus species are susceptible to the bacterial disease and several species related to citrus are suspected of being hosts for both the insect vector and pathogen. Murraya species are widely grown in Florida and other southern states as ornamentals and as a source of spices. We demonstrated the relationships among three Murraya species, the citrus psyllid vector of the causal bacterium, and the bacterium Candidatus Liberibacter asiaticus. The widely grown ornamental species Murraya paniculata and Murraya exotica were shown to be excellent hosts of the psyllid and transient hosts of the Huanglongbing bacterium. Both species are systemic hosts of the bacterium but do not maintain the bacterium for more than a few months. Therefore they may be good bridging hosts of the vector and bacterium between citrus species. Murraya koenigii, (also, called Bergera koenigii) is an excellent host for the psyllid but does not retain the bacterium and is not considered a host of HLB. The information is useful for developing means to control the spread of HLB.
Huanglongbing (HLB), considered the most serious insect-vectored bacterial disease of citrus, is transmitted in nature by the Asian citrus psyllid Diaphorina citri and the African citrus psyllid Trioza erytreae. Diaphorina citri was discovered in southern Florida in 1998 and the HLB disease in 2005. Both have become established throughout citrus producing areas of Florida. Murraya species are widely grown in southern Florida as ornamental hedges and are preferred colonization hosts of the D. citri psyllid vectors. Colonies of D. citri, isolates of Candidatus Liberibacter asiaticus (Las) from Taiwan and Florida, and the Murraya species were established in the BSL-3 biosecurity facility at Fort Detrick. In controlled inoculation experiments, D. citri transmitted Las into M. paniculata (34/36 plants) and M. exotica (22/23 plants), but not M. koenigii. Disease symptoms rarely developed in Murraya plants; however, positive infections were determined by conventional and real-time PCR. Back-inoculations of Las from M. paniculata to Madam Vinous sweet orange resulted in disease development in 25 percent of the inoculated plants. Considerable variability was observed in infection rates, titer, and persistence of Las in infected Murraya.