Detection of phytoplasmas and begomoviruses affecting cassava in Grand-Lahou, Côte d'Ivoire

Cassava in Côte d'Ivoire is currently threaten by the Côte d'Ivoire lethal yellowing disease (CILY), which destroyed over 400 ha of coconut plantations in Grand-Lahou. Due to CILY impact in coconut farms, women coconut farmers planted cassava plots in coconut lands devastated by the disease. Symptoms of leaf mosaic, curling and yellowing were observed in cassava plots after one and a half year from planting. Leaf samples were collected from symptom-bearing and symptomless cassava plants in two coconut-growing villages of Grand-Lahou, and subjected to total DNA extraction. Samples were PCR tested using phytoplasma 16S rRNA universal primers, as well as primers specific for subgroup 16SrXXII-B, ‘Candidatus Phytoplasma palmicola-related strains’, and for African/East African cassava mosaic viruses (ACMV, EACMV). Six out of 12 symptom-bearing samples showed PCR amplicons, five of which co-amplified for viral DNA. Phytoplasma sequences, RFLP and phylogenetic analyses confirmed the identification of phytoplasmas of subgroup 16SrXXII-B in co-infection with ACMV in one cassava plant sample, while either ACMV or EACMV were detected in other four cassava plant samples. Cassava was confirmed as a potential alternative host for the CILY phytoplasma, which may play a role in spreading and worsening the severity of CILY disease in coconut palms. The presence of begomoviruses in mixed infection with the CILY phytoplasma in cassava may increase the difficulty of CILY management and control, and poses a serious food security threat for the livelihoods of smallholder farmers in Grand-Lahou.