|Graft and psyllid transmissions indicate resistance to ‘CandidatusLiberibacter asiaticus’ is expressed in the citrus relative orange jasmine|
M. E. HILF (1), D. G. Hall (2). (1) USDA ARS USHRL, Ft Pierce, FL, U.S.A.; (2) USDA ARS USHRL, Fort Pierce, FL, U.S.A.
Huanglongbing (aka citrus greening) is a systemic bacterial disease of citrus associated with infection by the phloem-colonizing bacteria ‘<i>Ca</i>. Liberibacter asiaticus’, (CLas) which is transmitted to non-infected trees by the Asian citrus psyllid (<i>Diaphorina citri, </i>Kuwayama<i>)</i> or by grafting with infected budwood. The rutaceous flowering ornamental plant, <i>Murraya exotica</i> L., commonly called orange jasmine (aka orange jessamine) is a preferred host for <i>D</i>. <i>citri</i> and is a popular landscape ornamental. Experiments were done to evaluate its susceptibility to infection with CLas by psyllid and graft transmission. Transmission experiments with <i>D. citri</i> and <i>M. exotica</i> seedlings conducted in fall 2012 and summer 2013 yielded 1/16 and 5/80 infected seedlings respectively. Grafting experiments done to transmit CLas from citrus to <i>M. exotica</i> showed a significant difference in the survival of budwood which was dependent on the budwood source, with survival of 80% of budwood from non-infected trees and of only 32% of budwood from CLas-infected trees. The psyllid transmission data suggest <i>M. exotica</i> seedling populations are heterozygous for susceptibility to infection and that these results are compatible with a model where resistance is a dominant trait controlled by two genes. The results from grafting experiments suggest this is an active resistance to infection and that resistant <i>M. exotica</i> seedlings can be identified by grafting with budwood from infected citrus trees.