Survey of 16SrIX phytoplasmas associated with HLB-symptoms in weeds and leafhoppers at citrus orchards

Citrus plants presenting the typical huanglongbing (HLB) symptoms have been associated to 16SrIX phytoplasma in the States of Sao Paulo (SP), Minas Gerais (MG), Bahia (BA) and, more recently, Distrito Federal (DF), Brazil. Although in SP and MG states ‘Candidatus Liberibacter asiaticus’ is more commonly associated with HLB, single infection by phytoplasmas also occurs. To date, only 16SrIX phytoplasma induces HLB symptoms in BA and DF, a region free of ‘Ca. Liberibacter spp.’. The objective of this work was to survey for alternative hosts and potential vectors of the 16SrIX phytoplasma in citrus orchards from DF using quantitative real-time PCR (qPCR) detection. Fifty-three specimens encompassing fifteen species of weeds were collected from three Tahiti lime (Citrus latifolia Tanaka) and Ponkan mandarin (Citrus reticulata Blanco) orchards. Only five plants, one Euphorbia sp., one Sida sp., and three Bidens pilosa were positive for the presence of the 16SrIX phytoplasma. Regarding the leafhoppers, 16SrIX phytoplasma was detected in 11/ 38 specimens of Scaphytopius sp. and not detected in 32 specimens of Planicephalus flavicosta. These results suggest that spontaneous vegetation and the leafhoppers Scaphytopius may harbor 16SrIX phytoplasma that can further infect citrus orchards. The capacity of Scaphytopius insects to vector the phytoplasma to citrus plant should be better investigated.