Almost all wheat grown today is a ‘semi-dwarf’ breed from a naturally occurring mutant line with an altered giberellic acid (GA) signalling pathway. First developed during the ‘Green Revolution’ of the 1960s, these varieties allow farmers to significantly increase crop yields without increasing land area or fertiliser inputs. This is environmentally beneficial, but has also helped poorer economies to improve food security.
But there is a trade-off. An added benefit of GA-defective semi-dwarf plants is that they also show increased resistance to necrotrophic fungi that kill the plant and feed from dead tissues. However, they are also more prone to diseases caused by biotrophic fungi that feed on living plants.
Research into the genetic improvement of domesticated crops is difficult because they have large, complex genomes, and take up a lot of growing space. Using model species with small genomes and a compact size is useful in helping to understand crop plants, but the question remains: can what we have learned in a model be translated to a more complex species?
New research published in the journal Molecular Plant & Microbe Interactions suggests that yes, the wild grass Brachypodium distachyon is an ideal model for studying disease resistance traits in wheat and barley. John Innes Centre PhD student and lead author Rachel Goddard Rachel Goddard, lead author and PhD student in the lab of Paul Nicholson, said:
“We have been investigating another plant signalling system – the brassinosteroid (BR) signalling pathway – in barley, a close relative of wheat. Like GA-defective plants, barley with a mutated BRI1 gene also seems to be a high yielding semi-dwarf that is more resistant to necrotrophic fungi. But in this case, the plants do not have an increased susceptibility to biotrophic fungal disease.”
Crucially, Rachel and her colleagues have found that when genes in the BR-signalling pathway of B. distachyon are disrupted, the same disease resistance traits as barley are observed. This suggests that the mechanisms associated with this pathway are conserved between barley and its wild relative.
Rachel said:
“The fact that the B. distachyon BR-signalling pathway responds in the same way as barley is exciting because it demonstrates the huge potential for this wild grass as a beautiful model species for wheat and barley breeding research. B. distachyon grows quickly, has a relatively simple genome, and unlike arable crops can be grown in a standard lab growth chamber. Hopefully, by working with this model, plant breeders can identify new targets genes to breed even higher yielding crops".