Researchers find a potential control for leaf blotch disease in wheat

Scientists have found a genetic mechanism that could stop the spread of a “devastating” disease threatening wheat crops.

Source: Rothamsted Research

Septoria leaf blotch (STB) is caused by a fungus and is seen as the most significant threat to wheat yields in Europe, and most other wheat growing regions, as currently available fungicides become less effective against resistant strains of the disease. Rothamsted Research scientists, working with partners from Newcastle University on a study led by Durham University, have now found a way that could potentially be used to stop extensive spreading of STB disease. The findings are published in the journal New Phytologist.

A key feature of STB is the long symptomless growth of the fungus – called Zymoseptoria tritici – which can affect the host plant’s cells before it switches to the visible disease phase that eventually destroys the plant’s leaves. The researchers found that a wheat protein, TaR1, was key in enabling Zymoseptoria tritici to maintain this symptomless growth.

By manipulating TaR1 protein levels in wheat, either by conventional breeding or genetic modification in plants grown in laboratory controlled environments, the researchers demonstrated that they could activate the plant’s defences earlier. Early activation of the plant’s defences means that symptoms of the disease are displayed at an earlier stage when the fungus does not have the capacity to spread any further. This potentially allows for more effective control of the disease, the researchers added.

More than a third of wheat yield can be lost due to STB and it is the most significant disease of wheat in Europe and many other temperate climates.

Lead author Dr Ari Sadanandom, in the Durham Centre for Crop Improvement Technology, Durham University, said: “The foundation of global food security is built on three cereals, wheat, rice and maize, and wheat is the leading source of vegetable protein in human food.

“STB drastically affects yield by destroying the leaves on wheat plants, reducing their capacity to carry out the photosynthesis needed for grain production. It’s a significant threat as the fungicides that are currently the only control for this disease become less effective. However our findings show that by manipulating the TaR1 protein we can create unfavorable conditions preventing the spread of STB in the plant, potentially providing a new strategy for combating this devastating disease.”

Professor Kim Hammond-Kosack, leader of the Wheat Pathogenomics team at Rothamsted Research, commented: “The Durham group came to us to be trained by Dr Kostya Kanyuka in the Virus-Induced Gene Silencing (VIGS) technology adapted to study the wheat – Zymoseptoria tritici interaction. This technology was then used to manipulate the expression levels of the TaR1 gene and thereby explore the in planta function of the wheat TaR1 protein. In this joint project, the Durham group explored some of the earliest gene leads arising from our STB-wheat transcriptome study led by Dr Jason Rudd recently published in Plant Physiology.”

The researchers added that their goal now would be to find out if manipulating TaR1 could boost resistance against STB in field grown wheat.

The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Syngenta and the European Research Council (ERC).

Article reference:  ‘Functional analysis of a Wheat Homeodomain protein, TaR1, reveals that host chromatin remodeling influences the dynamics of the switch to necrotrophic growth in the phytopathogenic fungus Zymoseptoria’. Lee, J, et al, New Phytologist (2015)

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