Crop diseases and pests
Fusarium Ear Blight
Julia Halder: Grantham funded doctoral researcher, Imperial College London
The disease Fusarium Ear Blight is a problem for farmers across the globe who produce staple crops including wheat, maize and rice, and is caused by pathogenic (disease causing) fungi. Like many plant pathogens, its life cycle is highly influenced by the weather, meaning the risk of the disease could change as the result of climate change.
Computer models of the disease have been used with climate model output to estimate any change in risk for the 2020s and the 2050s, for a small number of geographic regions. Results of these so far broadly indicate that there will be an increased risk of the disease over the first half of this century. However, most computer models show that fusarium ear blight is highly influenced by rainfall in short critical time periods around a certain growth stage of the crop. Given that projections of future rainfall patterns are highly uncertainty, it is difficult to say for certain whether the risk of fusarium ear blight will increase. This suggests it may be wise to build in resilience – to many pathogens and different weather patterns - rather than focusing on preparing for increased incidence/severity of this or any other individual pathogen.
As with other microorganisms, there is the potential for these fungi to evolve new strains relatively quickly. Their life cycle is such that many generations of huge numbers can be produced in a short period of time. There are mechanisms which can generate new versions of genes and new combinations of genetic material with each generation. This can result in fungi with an increased ability to grow at extreme high temperatures, or to survive a period of drought. New characteristics such as resistance to treatments, or growth on a new host, can also arise. Fungi can respond rapidly to changing weather patterns, new fungicide treatments and other agricultural tools, because their genetic diversity means it is likely that at least part of the population can already survive these changes. This is the same situation we are seeing with human diseases and antibiotic resistance; strains of pathogens which have evolved to be resistant to previously useful antibiotics are an increasing problem.
Analysis of the genetic diversity of current fungal populations can provide some information as to the potential for evolution, especially when this is done in conjunction with studying the variation in particular characteristics. We are analysing fusarium ear blight fungi from across the globe with this aim in mind. One fungus which has already been examined in this manner is the barley pathogen Rhynchosporium commune. The study revealed that the pathogen was unlikely to be limited by higher temperatures. Fungi have demonstrated that they have the potential to evolve in response to stresses such as heat. Pathogens and pests are a constant threat to food crops; a changing climate is unlikely to present any obstacle to these organisms.
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Steffanson, McDonald, and Willi 2013 http://onlinelibrary.wiley.com/doi/10.1111/eva.12039/full