Mycology and Plant Pathology: Fungi as Friends and Foes
Fungal biology
Know the major fungal groups - Chytridiomycota, Zygomycota, Ascomycota, Basidiomycota and the deuteromycetes - by their spore types and sexual structures. Understand mycelium, hyphae, septa, coenocytic forms, haustoria and lichens. Learn fungal nutrition, saprophytism, symbiosis and reproduction.
Disease and defence
Master the disease triangle: susceptible host, virulent pathogen and favourable environment. Know the major pathogen groups - fungi, bacteria, viruses, nematodes and phytoplasmas - and classic diseases such as rusts, smuts, blights, wilts and mildews. Understand infection, incubation, symptoms and signs, and the difference between them. Learn plant defence: preformed barriers, hypersensitive response, systemic acquired resistance and phytoalexins.
Traps
Examiners confuse symptoms (the plant's response) with signs (the pathogen's structures). Another trap is attributing a disease to the wrong pathogen group, or assuming all wilts are fungal. Watch for questions on the disease cycle where the overwintering stage is asked.
Rule of thumb
For any disease, name the pathogen, the host, the symptom, the sign and the control strategy. If control is asked, match it to the disease cycle stage it interrupts.
Worked example
A leaf shows powdery white growth on the surface. The white growth is a sign (mycelium and conidia), while yellowing is a symptom; the pathogen is an obligate biotroph of the Erysiphales.