Surveys on ‘Candidatus Liberibacter asiaticus’ and ‘Candidatus Liberibacter americanus’ in Murraya exotica in Brazil
In the state of São Paulo (BR), two surveys were conducted, to investigate the incidence of 'Candidatus Liberibacter asiaticus' and 'Ca. L. americanus' (both EPPO A1 List - associated with citrus huanglongbing) in orange jasmine (Murraya exotica*, Rutaceae). Orange jasmine is a preferred host of Diaphorina citri (vector of huanglongbing and it is a widespread ornamental tree in Brazilian cities, towns and villages. During these surveys, the presence of Liberibacter spp. was detected by PCR in 91 of the 786 sampled M. exotica plants (in 10 of the 76 sampled locations). The presence of Liberibacter spp. was also detected in urban citrus. Although citrus and M. exotica were found to host Liberibacter spp. in the cities, their responses to infection were very different. Damage to M. exotica was much less severe than on citrus. It is noted that although M. exotica is less conducive to liberibacter multiplication than citrus, its importance in the huanglongbing epidemics should not be underestimated. M. exotica plants growing in cities are not treated against D. citri and in most cases they are not subject to eradication campaigns. It is noted that the survey area was located within the main citrus-growing regions of the state of São Paulo and coincides with an area of high incidence of huanglongbing in commercial citrus orchards. It is suspected that M. exotica trees in Brazilian cities might have been continually serving as sources of Liberibacter spp. and D. citri.
* Often considered as synonym of Murraya paniculata.
Lopes SA, Frare GF, Camargo LEA, Wulff NA, Teixeira DC, Bassanezi RB, Beattie GAC, Ayres AJ (2010) Liberibacters associated with orange jasmine in Brazil: incidence in urban areas and relatedness to citrus liberibacters. Plant Pathology 59(6), 1044-1054.