PLANT PATHOLOGY
Introduction
Plants provide energy and food to almost all living organisms
including human beings. They plays an important role in balancing the
environment as they are primary
producers in the ecosystem hence the health of plants is very essential to
mankind
·
The
study of disease causing agents, symptoms caused due to infection,
physiological effects, prevention and control of disease known as plant pathology (or) phytopathology (study of plant
diseases)
·
An
organism able to cause disease in a particular host known as pathogen.
·
The
complete process of disease development in the host from initial infection to
production of symptoms known as pathogenesis.
·
The
capability of the pathogen to cause disease in the host known as pathogenecity.
·
The
malfunctioning process due to continues irritation of host known as disease.
·
An
external manifestation of invisible, improper functioning of plants known as symptom.
The diseases in plants caused either by physical, chemical or biological
agents. The diseases may be:
·
Infectious disease: These are caused by biotic agents
like bacteria, fungi,viruses,mycoplasms,nematodes,protozoans and parasites.
·
Non-infectious disease: These are caused by abiotic agents
like air, water, soil,frost,pollutants,mineral nutrition and adverse
environmental conditions.
Plants
diseases are of two types based on the position of the pathogen as follows:
·
Systemic pathogen: If the pathogen affect the whole
plant
·
Localized pathogen:If the pathogen affects certain
parts.
Classification of Plant diseases
In 1969, Wheeler
proposed the classification of plant diseases caused by fungus, bacteria and viruses.
Plant diseases can be classified in various ways basis of casual organism or pathogen,
symptoms caused by pathogen, degree of prevalence of a disease, method of infection,occurance,perpetuation
and mode of transmission in nature.
Examples:
· Blast of Paddy
is a fungal disease caused by Pyricularia
oryza.
· Redrot of sugarcane is a fungal disease caused by
Colletotricum falcatum.
· Tikka disease of groundnut is a fungal disease caused by Cercospora personata.
· Leaf rust of wheat is a fungal disease caused by
Puccinia recondita.
· Leaf blight of Paddy is a bacterial disease caused by
Xanthomonas oryza.
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