Rickettsia OCCURRENCE IN COMMERCIAL PAPAYA (Carica papaya L.) PLANTATIONS WITH BUNCHY TOP DISEASE IN COLIMA, MEXICO

Abstract

Phytoplasmas, viruses, and rickettsiae (Rickettsia spp.) are the etiological agents of the bunchy top disease (BT) in papaya (Carica papaya L.) in several Caribbean countries. In Mexico, phytoplasmas have been reported in papaya plants with BT-like symptoms, but the incidence of Rickettsia is unknown. Considering that Rickettsia is associated with BT in other countries, it was hypothesized that these bacteria are also present in Colima, Mexico, where this disease is a phytosanitary concern. The objective of this work was to determine the incidence of Rickettsia in commercial papaya plantations with BT, as well as weeds and insects related to this crop in Colima. Using polymerase chain reaction (PCR) and sequencing of the rickettsial-specific flavoprotein subunit of the succinate dehydrogenase (sdhA) gene, 28 % (54 out of 192) symptomatic and 23.43 % (15 out of 64) asymptomatic papaya samples, as well as 9.77 % (17 out of 174) and 5.95 % (11 out of 185) weeds and insect morphospecies, respectively, tested positive for Rickettsia. The presence of R. bellii in sdhA-positive samples was confirmed by PCR with R. bellii-specific primers, sequencing and phylogenetic analysis of the citrate synthase (gltA) gene in 5.79 % of symptomatic papaya plants, 82.35 % of weeds, and 45.45 % of insects. Weeds positive for R. bellii were Amaranthus palmeri S. Watson, Euphorbia hirta L., E. hyssopifolia L., Anoda cristata (L.) Schltdl., Zinnia maritima Kunth, Parthenium hysterophorus L., Echinochloa colona (L.) Link., and Richardia scabra L. Insects positive for R. bellii were Balclutha mexicana Blocker (Hemiptera: Cicadellidae) and Chlorotettix emarginatus Baker (Hemiptera: Cicadellidae). This is the first time that Rickettsia species have been reported in commercial papaya plantations with BT in Mexico.