Phytocercomonas venanatans, a New Species of Cercozoa Associated with Chlorotic Streak of Sugarcane

Abstract

Chlorotic streak is a global disease of commercial sugarcane (Saccharum spp. hybrids). The disease is transmitted by wet soil, water, as well as in diseased planting material. Although first recognized almost 90 years ago and despite significant research effort, the identity of the causal agent has been elusive. Metagenomic high throughput sequencing (HTS) facilitated the discovery of novel protistan ribosomal and nuclear genes in chlorotic streak-infected sugarcane. These sequences suggest a possible causal agent belonging to the order Cercomonadida (Rhizaria, phylum Cercozoa). An organism with morphological features similar to cercomonads (=Cercomonadida) was isolated into pure axenic culture from internal stalk tissues of infected sugarcane. The isolated organism contained DNA sequences identical to those identified in infected plants by HTS. The DNA sequences and the morphology of the organism did not match any known species. Here we present a new genus and species, Phytocercomonas venanatans, which is associated with chlorotic streak of sugarcane. Amplicon sequencing also supports that P. venanatans is associated with this disease. This is the first reported member from Cercomonadida showing a probable pathogenic association with higher plants.