New host plants for Liberobacter asiaticum
In Asia, citrus greening bacterium (Liberobacter asiaticum – EPPO A1 quarantine pest) is spread by Diaphorina citri. So far, there has been no data on host plants other than citrus. In Taiwan, studies were done on four Rutaceous plants which are suitable hosts of Diaphorina citri: Murraya paniculata var. paniculata (common jasmin orange), Murraya euchrestifolia (curry leaf), Limonia acidissima (wood apple) and Severinia buxifolia (Chinese box orange). Graft inoculation was used to transmit the bacterium to plants. The presence and multiplication of L. asiaticum in the plants was monitored by dot hybridization tests using a specific DNA probe. Results showed that the bacterium can survive and multiply in S. buxifolia and L. acidissima, but not on M. paniculata var. paniculata and M. euchrestifolia. It was also observed that S. buxifolia is a good host (as good as citrus), whereas L. acidissima is a transient host in which the bacterium exists temporarily and disappears after a few months (5 to 10 months). S. buxifolia is a spinous shrub which is often found in citrus orchards, in India, Malaysia, Vietnam, southern China and Philippines. L. acidissima is commonly grown for ornamental purposes in Thailand, India and Indonesia. Preliminary results obtained by using D. citri to transmit the disease and a more sensitive detection method (PCR) were similar to those presented above. Further studies on host plants of L. asiaticum will continue to better understand the role of alternative hosts in the disease epidemiology.
Sources
Hung, T.H.; Wu; M.L.; Su, H.J. (2000) Identification of alternative hosts of the fastidious bacterium causing citrus greening disease.
Journal of Phytopathology, 148(6), 321-326.