Loading...On paper, optimising photosynthesis looks like a game changer. Some plants, like tobacco, potatoes and wheat, can produce 10-40% more under experimental conditions, while barley with reduced chlorophyll content sees its transpiration decrease by 40-50% under water stress. But can these results, obtained in the laboratory through genome modification, be reproduced through conventional breeding? In France, the Greenscale project aims to evaluate the benefits of “pale” barley with reduced chlorophyll level. This is an avenue still largely unexplored in breeding, as lighter coloured plants are often discarded due to their association with deficiencies or diseases.
“The scientific literature shows that when this paleness is due solely to chlorophyll levels, yields can remain stable or even improve,” notes Fabien Chardon, project co-ordinator and a researcher at the Institut Jean-Pierre Bourgin (IJPB) in France. “In modern crops, the upper leaves often receive more light than they can use, while those at the bottom operate below theiroptimum,” he adds. At the crop stand scale, a less pigmented canopy could lead to increased light availability for the lower leaves.
The literature suggests that by limiting chlorophyll just enough so as not to affect yield, we can expect nitrogen savings of 5-10% in cereals.
Dr. Fabien Chardon
Two key stakes
The field trials launched this year by the Arvalis institute partner in the Greenscale project aim to test low chlorophyll lines across a variety of nutrient, water and climatic conditions. This data will allow simulation through modelling of crop behaviour and its impact on the ecosystem in multiple scenarios. The ambition is twofold. Firstly, to identify lines that are potentially more resistant to drought, since beyond the optimal chlorophyll level, the plant dissipates excess light as heat. “The hope is that by slightly reducing pigmentation, we can lower the canopy temperature a little, and therefore evapotranspiration.”
The second objective is to reduce nitrogen requirements. During the vegetative phase, half of the nitrogen in the leaves is invested in proteins that form light-harvesting complexes, which bind with chlorophyll molecules. The hypothesis is that a less green plant will also use fewer proteins to produce these complexes. “We want to determine whether this will actually lead to lower nitrogen uptake, but also to understand how these proteins will be reallocated during grain growth and filling.” This could lead to a reduction in carbon footprint and fertiliser costs. “The literature suggests that by limiting chlorophyll just enough so as not to affect yield, we can expect nitrogen savings of 5-10% in cereals,” says Fabien.