disintegration of plant tissue; rotting. (of fungicides, insecticides etc.) failure to control (disease, pest etc.) by dosage or concentration of the material that has previously been effective, e.g. as a result of occurrence of resistant strains of the organism. Note: it is the control that has ` broken down `not the chemical. the occurrence of severe disease in a formerly resistant host variety. A general term describing a condition which may have several alternative causes. It commonly refers to the advent of a race of the pathogen having a gene for virulence corresponding with a particular major gene for resistance in the host, i.e. the change occurs in the pathogen and not in the host. In this sense the word is misleading and should be abandoned. The term may also be applied in circumstances in which resistance (usually field resistance) becomes ineffective, e.g. under adverse environmental conditions, with no change in the virulence of the pathogen. Breakdown, Low Temperature: disintegration of plant tissues (especially fruits etc.) associated with storage at low temperatures.
The condition for a reverse biased semiconductor junction when its high resistance, under the reverse bias, suddenly decreases, causing excessive current. Not necessarily destructive.