Cacao Swollen Shoot Virus

Abstract

Cacao swollen shoot virus (CSSV) is a member of the family Caulimoviridae, genus Badnavirus. CSSV is a serious constraint to cocoa production in West Africa, particularly in Ghana. International attempts at crop improvement are hampered by the need to index cocoa germplasm for this virus, particularly if the germplasm is to be moved to where highly susceptible varieties are grown. For a reliable PCR diagnosis, it is necessary to design primers in conserved regions of the genome. Recently, the alignment of the six full-length sequences of CSSV allowed conserved regions to be identified and improved primers (ORF3-CSSV-F and ORF3-CSSV-R) to be designed for the diagnosis of the CSSV. These primers can detect all the isolates tested to date from Togo and Ghana. These improved primers are located in the first part of the ORF3 and amplify a fragment from 721-724 bp, including from isolates having only 70% nucleotide identity. This PCR-based diagnosis is able to detect CSSV, not only in symptomless leaves of symptomatic plants, but also in symptomless plants as early as one week post inoculation. Molecular variability of the CSSV has been studied in two different parts of the genome leading to the separation of CSSV isolates in three groups. Measures to control the disease arediscussed. (Resume d'auteur)