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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Molecular Plant Pathology Laboratory » Research » Publications at this Location » Publication #333033

Research Project: GENOME SEQUENCE-BASED STRATEGIES FOR DETECTION & IDENTIFICATION OF PLANT PATHOGENIC PHYTOPLASMAS & SPIROPLASMAS, & VASCULAR WALLED BACTERIA

Location: Molecular Plant Pathology Laboratory

Title: 'Candidatus Phytoplasma brasiliense’-related strains associated with papaya bunchy top disease in northern Peru represent a distinct geographic lineage

Author
item Wei, Wei
item Perez-lopez, Edel - Auburn University
item Davis, Robert
item Bermudez-diaz, Ludisleydis - Universidad Privada Atenor Orrego
item Granda-wong, Carlos - Universidad Nacional De Piura
item Wang, Jiawei - Shangdong Institute Of Pomology
item Zhao, Yan

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2016
Publication Date: 2/1/2017
Citation: Wei, W., Perez-Lopez, E., Davis, R.E., Bermudez-Diaz, L., Granda-Wong, C., Wang, J., Zhao, Y. 2017. 'Candidatus Phytoplasma brasiliense’-related strains associated with papaya bunchy top disease in northern Peru represent a distinct geographic lineage. Crop Protection. 92:99-106. doi: 10.1016/j.cropro.2016.10.024.

Interpretive Summary: Papaya is a widely cultivated tropical fruit tree with high nutritional value, and the papaya fruit has become the fourth most traded tropical fruit in the world after banana, mango, and pineapple. However, the production of papaya fruit is hindered by diseases associated with infection by phytoplasmas, a group of cell wall-less bacteria that invade nutrition-conducting vessels of diseased plants. During the 2015-2016 fruit production season, a papaya disease was observed in a papaya production farm located in northern Peru. Affected plants exhibited symptoms of excessive proliferation of auxiliary shoots at the top or near top of the main stem, shortening of internodes, leaf yellowing, and necrosis of leaf veins. The symptoms suggested possible infection by a phytoplasma. Molecular diagnostic assays for phytoplasma detection were therefore employed. DNA finger printing analysis of phytoplasma-unique genetic markers confirmed that the diseased papaya plants were indeed infected by a phytoplasma. This is the first documented case of a papaya phytoplasmal disease in northern Peru. Further genotyping of the phytoplasma revealed that the papaya disease agent is affiliated with ‘Ca. Phytoplasma brasiliense’, a species that had previously never been implicated in a papaya disease anywhere in the world. The study also revealed that the papaya-infecting phytoplasma is closely related to a phytoplasma associated with the first grapevine yellows disease that we recently identified in Peru. The papaya- and grapevine- infecting phytoplasma strains in Peru represent an emerging geographic lineage that is distinct from those of all other known ‘Ca. Phytoplasma brasiliense’ strains in the Americas. The findings of this study are important to the farmers and extension personnel who are concerned with phytoplasmal disease diagnosis and management. The information is also critical to regulatory agencies for preventing exotic pathogens from being introduced into the U.S. and other papaya production countries.

Technical Abstract: During the 2015-2016 fruit production season, a papaya bunchy top (BPT) disease was observed in a papaya production farm located at Region de Piura, northern Peru. Affected plants exhibited symptoms of excessive proliferation of auxiliary shoots at the top or near top of the main stem, shortening of internodes, leaf yellowing, and necrosis of leaf veins. The symptom syndrome suggested possible infection by a phytoplasma, and the recent discovery of a phytoplasmal disease in a nearby vineyard also indicated that a phytoplasma reservoir and potential vector(s) were present in the area. Molecular diagnostic assays for phytoplasma detection were therefore employed. Nested polymerase chain reactions and subsequent nucleotide sequence analysis confirmed that phytoplasma infection did occur in the papaya production farm. The phytoplasma strains found to be associated with the PBT disease are affiliated with ‘Candidatus Phytoplasma brasiliense’, a species that had previously never been implicated in a papaya disease anywhere in the world. We provide molecular evidence to suggest that the papaya-infecting phytoplasma strains identified in this study are closely related to a phytoplasma associated with the first grapevine yellows (GY) disease that we recently identified in Peru. The results of our study indicate that these PBT and GY phytoplasma strains in Peru represent an emerging geographic lineage that is distinct from those of all other known ‘Ca. Phytoplasma brasiliense’ strains in the Americas.