Characterization of Phytoplasmas associated with cassava (Manihot esculenta Crantz) infection in Southern and Southeastern Côte d'Ivoire

Abstract

In Côte d'Ivoire, cassava is an important source of food and income for the population. However, its development is confronted with the attack of numerous pathogens such as phytoplasmas as observed in several countries in recent years. The main aim of this study is to diagnose cassava leaf infection in Côte d'Ivoire in order to contribute to sustainable production. Thus, cassava leaf samples were collected from nine growing localities. Molecular analyses required the use of the universal primer pairs for the direct PCR and specific primers for Nested PCR in order to detect the presence of phytoplasmas in the DNA extracted from the samples. Mosaic, vein banding, chlorosis, shoestring and witches' broom symptoms were observed, sometimes alone and other times in complex symptoms. The prevalence of leaf infections was over 70%, with average severity scores ranging from 4.29 to 4.74 depending on the cassava variety. Of the samples tested, 42 (19.44%) were positive with the specific primer (AkwaSR/GH813f) and 32 (18.39%) with the universal primer (R16mF2n/R16mR2), thus demonstrating the presence of phytoplasmas in both symptomatic and non-symptomatic cassava leaves. The amplicons obtained with the specific primer pair allowed the detection of the phytoplasma "Candidatus Phytoplasma palmicola" of subgroup XXII-B associated with the coconut lethal yellowing disease in Côte d'Ivoire in cassava grown in the different collection localities.