Essential Plant Pathology: Second Edition by Gail L. Schumann & Cleora J. D’Arcy

Author:Gail L. Schumann & Cleora J. D’Arcy [Schumann, Gail L. & D’Arcy, Cleora J.]
Language: eng
Format: epub
Publisher: The American Phytopathological Society
Published: 2021-09-15T00:00:00+00:00

Aboveground Infection Sites on Plants

direct penetration

epidermal cells or spaces between them

indirect penetration

hydathodes

lenticels

stomata

wounds

The surface of the leaf that is influenced by plant exudates and the microclimate at the tissue surface and out to the boundary layer (see below) is called the phylloplane. Epiphytic organisms adapted to living on leaf surfaces are called phylloplane-competent. Some nonpathogenic fungi and bacteria are epiphytic residents of the phylloplane. These organisms compete with pathogens for food and space, produce antagonistic substances, and thus reduce foliar diseases. For example, powdery mildew fungi can germinate in high relative humidity, but they do not require free water as most fungal spores and bacteria do. Powdery mildews are more severe in humid weather without much rainfall, not only because the powdery mildew fungi can grow in these conditions, but also because their epiphytic fungal and bacterial competitors that require free water are less active.

Many pathogenic bacteria exist as epiphytes on plant surfaces and become pathogens only when environmental conditions are favorable for infection. In most field situations, it is highly unlikely that a single bacterial cell will successfully infect a plant, but bacteria on plant surfaces interact with each other through quorum sensing and a variety of signaling mechanisms. Quorum sensing allows a population of bacteria to behave more like a multicellular organism and increases the likelihood of successful infection. Thus, prevention of these diseases depends not on removing all of the epiphytic bacteria, which is too costly and difficult, but on predicting when infection is likely and trying to protect the plant during those events.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.