Natural Infection of Murraya paniculata and Murraya sumatrana with CLas in Java.

Abstract

The phloem-limited bacterium, 'Candidatus Liberibacter asiaticus' (CLas), is the putative causal pathogen of the severe Asiatic form of huanglongbing (citrus greening) and is most commonly transmitted by the Asiatic citrus psyllid (ACP), Diaphorina citri. CLas 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 qPCR on 2-4 occasions over 14 months. CLas 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 CLas-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 ITS region. The results indicated that natural infection of M. paniculata and M. sumatrana with CLas can occur in Java. This is the first demonstration of the natural infection of M. sumatrana with CLas. Further studies are required to determine if infections persist in the absence of D. citri.