A Phytoplasma Belonging to a 16SrIII-A Subgroup and dsRNA Virus Associated with Cassava Frogskin Disease in Brazil

Abstract Cassava frogskin disease (CFSD) is a particular threat in cassava because symptoms remain hidden until harvest and losses can be total. The information related to the etiological agent of this disease is contradictory, because some authors believe it is caused by phytoplasmas while others believe that it is caused by a virus. In order to refine detection protocols and to characterize organisms associated with CFSD in Brazil, 32 symptomatic and 20 asymptomatic cassava plants were collected in Minas Gerais state. Total DNA was extracted and used for nested polymerase chain reaction (PCR) to detect phytoplasmas. Because endophytic Bacillus spp. led to false positives, primers were designed to facilitate the detection of phytoplasma in the presence of bacteria. In addition, double-stranded (ds)RNA was extracted from tubers and used in reverse-transcription PCR for the detection of the RNA-dependent RNA polymerase gene from Cassava frogskin virus segment 4. The detected phytoplasma was identified as b...