What pathogens are viroids and mycoplasma-like organisms?

Viroids are extremely tiny ribonucleic acid (RNA) units that can infect cells and replicate themselves. They have been reported to harmcultivatedcrops and other plants, but infection has not yet been found inorchids. The molecular weight of viroids is smaller than that of viruses, at about 75,000 to 120,000, whereas viruses reach 1,000,000 to 10,000,000. Mycoplasma-like organisms are a kind of simple organism, lacking a distinct, well-formed nucleus and also lacking a cell wall, instead being surrounded by a three-layered strand. The so-called "cells" of mycoplasma-like organisms are very small, only 175-250 nm in diameter, and contain cytoplasm as well as thread-like bodies and ribosomes equivalent to nuclear material. They may be filamentous, spiral-shaped, oval or spherical. The main transmission vector of plant mycoplasma-like organism pathogens is insects. More than 300 species of plants are known to be infected by mycoplasma-like organisms, mainly causing yellowing diseases or yellowing and stunting type diseases, with only a very few examples relating toorchids. Tetracycline-class antibiotics have an inhibitory effect on mycoplasma-like organisms, but are ineffective against viruses. (Chen Xinqi, Ji Zhanhe)