Detection and characterization of a phytoplasma associated with frog skin disease in cassava

Abstract

Cassava is one of the main carbohydrate sources in the tropics, and it has worldwide importance as basic food for millions of persons in America and Africa. This root crop is affected by cassava frog skin disease that in Colombia produces yield losses of almost 90%. A phytoplasma was associated with this disease by using a nested-PCR followed by RFLP analyses, cloning and sequencing of 16S ribosomal gene. Sequence analysis showed that the phytoplasma was related to those belonging to 16SrIII ribosomal group, with a 99% sequence homology. Evidence of phytoplasma aetiology for the disease was achieved also by electron microscopy observations, grafting to specific host plants, and by its dodder transmission. Symptoms were reproduced in healthy plants. Symptoms disappearance in leaves was obtained by growing cassava infected plantlets in a chloroxytetracycline solution producing further evidence for the phytoplasma aetiology. This study is the first to report a phytoplasma associated with cassava frog skin disease.