1 Plant Health Care Bacteria, Virus, PhotoplasmaPresentation Transcript
Plant Health Care Bacteria, Virus and minor Pathogens
Plant Diseases Causes of Plant Diseases
Causes of Plant Diseases
BIOTIC and ABIOTIC .
BIOTIC causes of plant diseases are those that are biological in origin. There are five major biotic causes of plant diseases. These are the fungi, bacteria, viruses, nematodes and phytoplasmas.
ABIOTIC causes of plant diseases are non-biological in origin. Examples include things like adverse weather conditions or environmental pollutants. Often the affects of abiotic factors on plants are referred to as INJURIES .
Largest pathogen group
More than 8000 pathogenic species
Can be seen with the naked eye
Vegetative growth through production of multicellular fungal threads (hyphae)
Reproduce via spores
About 200 pathogenic species
Can be seen with a light microscope
Reproduce b binary fission
Bacterial diseases are virtually impossible to identify definitively based on symptoms
Typically, in order to identify bacterial pathogens, the bacterium must be isolated from diseased tissue and then grown on specialized media.
Bacterial cells are extremely small (see arrow).
Even when magnified to 400 times their normal size (as they are in this photo) they are difficult to distinguish as individual objects
Often one must stain the cells (as in this photo) to see them.
Often spots produced by bacteria have a water-soaked appearance and a well-defined yellow halo
However, be cautious when attempting to distinguish bacterial and fungal spots
Spots produced by bacteria and fungi are typically very similar
Bacterial lesions are often delimited (bordered) by veins (see arrow) and thus often have an angular appearance