According to the source of origin, toxins are divided into 3 broad classes namely, pathotoxins, vivotoxins and phytotoxins.
- These are the toxins which play a major role in disease production and produce all or most of the symptoms characteristic of the disease in susceptible plants.
- Ex: Victorin: Cochliobolus victoriae (Helminthosporium victoriae), the causal agent of Victoria blight of oats. This is a host specific toxin.
a) Selective :
T- toxin: Helminthosporium maydis race T
HC-toxin: Helminthosporium carbonum
HS- toxin: Helminthosporium sacchari
Phyto-alternarin: Alternaria kikuchiana
PC- toxin: Periconia circinata
b) Non-selective :
Tentoxin: Alternaria tenuis
Tabtoxin or wild fire toxin: Pseudomonas tabaci
Phaseolotoxin: Pseudomonas syringae pv. Phaseolicola
c) Produced by plant or plant X pathogen interaction :
Amylovorin: Erwinia amylovora (Fire blight of apple and pears)
- These are the substances produced in the host plant due to host-pathogen interactions for which a causal role in disease is merely suspected rather than established.
- Ex: Alternaric acid – Alternaria solani
- These are the substances produced in the infected host by the pathogen and / or its host which functions in the production of the disease, but is not itself the initial inciting agent of the disease.
- Fusaric acid – Wilt causing Fusarium sp.
- Lycomarasmin – Fusarium oxysporum f.sp. lycopersici
- Piricularin – Pyricularia oryzae
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