INTRODUCTION TO PLANT PATHOLOGY CHAPTER 1 INTRODUCTION TO PLANT PATHOLOGY

Objectives To define plant pathology To define plant disease To classify plant diseases To identify the main causal agent of plant disease

Plant Pathology Also be referred as ‘Phytopathology’ A science that study plant disease The diseases are caused by pathogens (infectious diseases) and environmental conditions (physiological factors) Improve the chances of plant survival

What is actually plant disease?

‘A malfunctioning process that is caused by continuous irritation and produce symptoms’ Horsfall & Cowling ‘A deviation from normal growth or structure of plants that is sufficiently pronounced and permanent to produce visible symptoms or to impair quality and economic value’ Stakman & Harrar

Healthy plant : The ability to carry out normal physiological functions at a acceptable level consistent to genetic potential Sick plant : A malfunctioning process that is caused by continuous irritation and produce symptoms

Healthy Plant

Healthy Plant Normal physiological functions include: Normal cell division, differentiation & development Absorption of water and minerals from the soil and translocation Photosynthesis and translocation of photosynthates Utilization and storage of photosynthates Reproduction Storage of reserves for overwintering or reproduction.

Diseased Plant A plant would not have all of these at once Plant disease is any disruption (biotic or abiotic) of the plants normal metabolism.

“ The malfunctioning of host cells and tissues that results from their continuous irritation by a pathogenic agent or environmental factor and leads to the development of symptoms. Disease in a condition involving abnormal changes in the form, physiology, integrity, or behavior of the plant. Such changes may result in partial impairment or death of the plant or its parts” George N. Agrios

Classification of plant disease Infectious Non-infectious

Infectious Disease A disease that is caused by a pathogen that can spread from a diseased to healthy plant Disease that is caused by living organism

Non-infectious Disease Disease that is caused by non living organism Could not be spread to other healthy plant Example factors: Too low/high temperature Lack/excess of soil moisture Air pollution Nutrient deficiencies Mineral toxicities Soil acidity or alkalinity

Causes of plant disease Biotic factors - any living factors that could cause disease Fungi Bacteria Virus Nematodes

Causes of plant disease Abiotic factors - any non-living factors that could cause disease Nutrient deficiencies Toxicities Environmental stress ( drought; heat; cold )