Environmental Changes and Plant Disease Epidemics

what are some greenhouse gases that have increased levels due to human emissions?

carbon dioxide, methane, nitrous oxide

what are some ways that climate change can affect the severity of plant epidemics?

1. changing the environment to be more favorable to the development of severe epidemics

2. indirectly affecting epidemic severity by affecting host resistance (such as temperature-sensitive resistance)

3. affecting virulence of pathogens by selecting for pathogen races that are adapted to new climates

4. allowing pathogens to become established in new regions because of changing climates

effects of temperature

both plants and pathogens have a range between a given min and max temperature in which it is best for them to grow

effects of moisture

climate change impacts moisture distribution (increasing occurrences of extreme rainfall or leading to droughts)

interactions betweentemp and duration of wetness on severity and range of plant disease epidemics

difference between wind and water dispersal

wind disperses inoculum further with shallower dispersal gradient

water or rain splash has a steeper dispersal gradient

is light exposure impacted by climate change?

no

what is the impact of light exposure on plants?

reduced light intensity makes plants more etiolated, more susceptible to nonobligate fungal pathogens and viruses

increased light intensity can exacerbate symptoms of some diseases like barley ramularia leaf spot

effects of soil pH and structure

soil acidity can weaken host through nutrient deficiencies, affect incidence and severity of some diseases

soil structure influences water holding capacity which influences disease development

effects of host-plant nutrition

affects rate of growth and plant’s ability to defend themselves against pathogens

change in host susceptibility depends on nutrient and pathogen

what impact does nitrogen abundance have on plants?

production of young succulent growth and delays maturity

makes plants more susceptible for longer periods of time to pathogens that attack young tissues (especially obligate biotrophs)

lack of nitrogen causes weak, slow-growing plants that senesce faster, susceptible to different pathogens

effect of phosphorus

increases plant resistance by improving balance of nutrients or accelerating crop maturity

potassium effects

promotes wound healing, increases resistance to frost injury and therefor infections that begin from frost-damaged tissue.

delays maturity and senescence which gives more time for infection by certain facultative parasites

calcium effects

strengthens cell wall composition and resistance to penetration by pathogens

decrease in calcium concentration increases susceptibility to pathogen penetration during crop storage

addition of what micronutrients caused reduction in disease severity?

iron, copper, manganese, magnesium, molybdenum

severity of a couple diseases increased due to added micronutrients

silicon effects

reduces disease severity when added to soil

application of various different grades increased amount of silicon uptaken by plant

some silicon treated plants produced specific defense reactions upon pathogen innoculation (formation of papilla, production of callose, release of phenolic compounds

irrigation effects

will become increasingly important as more areas face water shortages due to climate change

can be a pathogen vector and influence disease severity, means of pathogen dispersal

overhead irrigation favors foliar pathogen dispersal

flood irrigation favors soilborne pathogen dispersal

farmers must evolve to low input water use strategies like drip irrigation which is also better at controlling pathogens

reduction of water can induce plant stress and weaken plant defenses against pathogens

effects of changes in trade patterns

human global trade is a major vector for plant disease transmission outside of natural geographic area

effect of nitrous oxides (NOx)

N2O is potent greenhouse gas with long half life, concentration has been increasing due to human activity

phytotoxic, can cause stunting, cell death, lipid peroxidation, protein mods, signalling changes

can affect plant susceptibility by:

1. influencing a plant’s nutritional value to pathogens

2. may effect biotic and abiotic stress responses

effects of CO2

most plant diseases increase in severity in CO2 rich environments, can change inducible defense responses

can increase host resistance in some pathogens by reducing leaf stomatal density and opening, shortening growth period, and increase in root biomass

effects of ozone (O3)

air pollutant affecting plant productivity, concentration has continued to increase under climate change

phytotoxic

reduces crop and timber yields by damaging cells, causing destruction of leaf tissue, reduces ability of plants to photosynthesize

causes plants to grow more leaves, reducing stored carbs in roots and stems, makign them more susceptible to pathogens

effects of sulfur dioxide (SO2)

human-made emission, can harm crop physiology, morphology and biochemical processes which reduces plant growth and makes them more susceptible to pathogens

changes what pathogens infect plants

danger of withdrawing harmful pesticides?

reduces availability of reliable chemical pesticides and increases risk of pesticide resistance