Abstract

Cocoa swollen shoot virus disease (CSSD-badnavirus) is one of the major diseases responsible for the destruction of cocoa plantations. The objective of this study was to determine the genetic diversity of swollen shoot viruses detected in potentially tolerant and sensitive cocoa trees. Scions taken from 320 cocoa accessions established in seven CSSD-badnavirus-infected regions of Côte d'Ivoire were grafted onto Amelonado rootstocks and maintained in an insect-free greenhouse. Total DNA was isolated from 168 cocoa graft accessions that exhibited tolerance and sensitivity to the disease. Badnavirus detection was carried out by polymerase chain reaction (PCR) amplification and DNA sequencing of a cloned fragment of the CSSD-badnavirus movement protein (mp) (650 bp). The results revealed that 6.64% of the potentially tolerant accessions were asymptomatic in the field but, once in the greenhouse, expressed CSSVD symptoms. This new phenotypic group (APT/APS) was found to be a useful indicator of virus presence within APTs and of possible disease tolerance. PCR amplification yielded 32 amplicons of CSSD badnavirus mp, and virus isolates were provisionally identified by BLASTn analysis against available CSSD badnavirus reference sequences based on the closest sequence match. Two badnavirus species were identified: CSSCDV and CSSTBV. This study could lead to further investigation of the molecular characterization of CSSD-badnavirus.

Key words:  Cocoa swollen shoot virus disease (CSSD)-badnavirus, tolerance, Theobroma cacao, Côte d’Ivoire.