14.5 Pathogens that produce haustoria (Ascomycota and Basidiomycota)

14.5 Pathogens that produce haustoria (Ascomycota and Basidiomycota)

Flax rust (Melampsora lini, Basidiomycota) and barley powdery mildew (Blumeria graminis (also known as Erysiphe graminis), Ascomycota), share the ability to produce specialised feeding structures called haustoria which penetrate the living cells of their host plant. This gives them intimate contact with live host cell membranes through which they can extract nutrients and suppress plant defences. Smut fungi (species of Ustilago, Basidiomycota) are particularly important pathogens of cereal crops. They do not form haustoria but nevertheless make close contact with living host cells through intracellular hyphae which invaginate the host cell membrane.

All these pathogens are of major importance to agriculture and comparison of the ways in which they interact with their hosts in terms of cross-recognition and cross-signalling, and the virulence and resistance genes involved in these interactions is seen as a way of improving understanding of the biology of their relationships with their host plants and a way to improve food production (Ellis et al., 2007). Haustoria are the key features of these extremely successful plant pathogens, the obligate biotrophs.

The broad phylogenetic range of organisms that produce haustoria suggests that these structures are specific adaptations to close exploitation of their respective host plants that have arisen many times during evolution. Since it became possible to analyse haustorial function at a molecular level a picture began to emerge indicating that haustoria not only function in nutrient uptake but also synthesise and secrete a panel of virulence factors. Proteins called effector proteins, which manipulate the physiological and immune responses of host cells, redirecting the host’s metabolic flows to the benefit of the pathogen (Voegele & Mendgen, 2003; Garnica et al., 2014).

All of these pathogens are of major importance to agriculture and comparison of the ways in which they interact with their hosts in terms of cross-recognition and cross-signalling, and the virulence and resistance genes involved in these interactions is seen as a way of improving understanding of the biology of their relationships with their host plants and a way to improve food production (Ellis, Dodds & Lawrence, 2007).

Resources Box 14.1

Where to find more information about crop diseases, crop losses, plant pathogens and food and agriculture statistics

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Updated July, 2018