The symbiotic association of fungi and algae is called

• A lichen is not a single organism; it is a stable symbiotic association between a fungus and algae and/or cyanobacteria. 
• The lichen symbiosis is thought to be a mutualistic one since both the fungi and the photosynthetic partners are benefitted as algae are responsible for the synthesis of food meanwhile fungi provide protection to the algae. 
• Mycorrhiza is a symbiotic association between a green plant and a fungus. 
• Mycoplasma is a genus of bacteria that lacks a cell wall. Mycoplasmas are the smallest free-living microbes known. 
  

So, the correct answer is 'Lichen'