Natural Infection of Murraya paniculata and Murraya sumatrana with ' Candidatus Liberibacter asiaticus' in Java.

The phloem-limited bacterium ' Candidatus Liberibacter asiaticus' ( C Las) is the putative causal pathogen of the severe Asiatic form of huanglongbing (citrus greening) and is most commonly transmitted by the Asiatic citrus psyllid Diaphorina citri . C Las severely affects many Citrus species and hybrids and has been recorded in the Citrus relative, orange jasmine, Murraya paniculata (L.) Jack (syn. M . exotica L.). In this study, 13 accessions of three Murraya species ( M. paniculata , M. sumatrana Roxb., and M. lucida [G.Forst.] Mabb.) and the Papuan form of a putative hybrid ( M. omphalocarpa Hayata) were identified morphologically and molecularly based on sequence identity of the matK-5'trnK region of the chloroplast genome, and infection on these plants under field conditions was determined by PCR and quantitative real-time PCR (qPCR) on two to four occasions over 14 months. C Las was repeatedly detected in leaflet midribs by PCR and qPCR on four and three accessions of M . paniculata and M. sumatrana , respectively. It was not detected in leaflet midribs of single accessions of M. lucida and M. omphalocarpa . The species identification of the C Las-positive accessions was further confirmed using all the molecular taxonomic markers consisting of the six fragments of the maternally inherited chloroplast genome and part of the nuclear-encoded internal transcribed spacer (ITS) region. The results indicated that natural infection of M. paniculata and M. sumatrana with C Las can occur in Java. To our knowledge, this is the first demonstration of the natural infection of M. sumatrana with C Las. Further studies are required to determine whether infections persist in the absence of D. citri .