User:Safflle/Sandbox2

Koch’s postulates.

Plant defence mechanisms.

Genetic variation

The emergence of new diseases and more virulent forms of existing pathogens through natural selection poses a continuing threat to crops and garden plants.

Commonest method to control plant and environment or to control disease using chemical or biological-control methods. The effectiveness of certain controls varies greatly depending upon the situation, for example local weather conditions and the scale and intensity of farming. Our close dependency on plants for food, fiber and wood has occasionally lead to plant diseases having an effect upon human history. Notably, the Irish Potato Famine caused thousands of deaths and extensive de-population of Ireland. Coffee rust also had a large impact on the economy of Sri Lanka, which now primarily grows tea. More recent and current problems include coconut lethal, banana ___ and chestnut blight. Each of these diseases has effect large enough to impact upon the economy and land use of large areas and in some cases whole countries.

Two oomycete diseases: phtytophthora sojae ‘root rot of soybean’. One example of a pathogen which had a positive effect on the horticultural industry – tulip break virus. Also poinsettia plants infected with a virus to make them more ‘bushy’. Challenges to plant pathology include plant and pathogen responses to climate change and how to reduce yield loss and feed an ever-growing human population.

Arms race and implications for understanding of evolution and populations