Milkweed yellows phytoplasma
Milkweed yellows phytoplasma is a strain of phytoplasma in the class Mollicutes, a class of bacteria distinguished by the absence of a cell wall. The phytoplasma strain is denoted by the acronym MW1.
Source: Wikipedia — Milkweed yellows phytoplasma (CC BY-SA 4.0)