Assessing the impact of traits on wheat yield and stability under climate change.

Wheat is a staple food that provides 20% of all calories and protein worldwide. While the primary objective of wheat selection has been to enhance yield levels to meet the needs of a growing population, ensuring stability in yield production is also of utmost importance.

Variability in yield production from year to year have a direct impact on farmers’ income and, particularly for staple crops, contribute to food insecurity at both national and household levels, according to the FAO. Climate change increases yield variability by

  • making the environments in which plants are grown less predictable – conditions that breeders typically target may no longer be consistent or reliable due to climate fluctuations and
  • altering regional productivity – yield in different areas may change due to shifts in temperature, rainfall patterns, or other climatic factors. This can further complicate breeding efforts, as the traits that were previously beneficial in one region may no longer be as successful.

There is a need to identify novel cultivars with enhanced productivity that also have high stability under future climates. However, it is challenging to identify superior traits because the traits of plants (phenotypes) are influenced by both their genetic makeup (genotypes) and the environmental conditions they grow in. Crop models can support crop improvement by providing a way to quantify the interactions between crop traits and climate factors affecting yield under future conditions.

In light of this, a new study delves into the examination of yield stability in high yielding wheat lines in the face of climate change. Dr. Heidi Webber of the Leibniz Centre for Agricultural Landscape Research (ZALF) and colleagues used a crop simulation model solution in the SIMPLACE framework to explore yield sensitivity to select trait characteristics across 34 locations representing the world’s wheat-producing environments.

The 34 sites considered in the study

They focused on the influence of three traits known to increase yield potential: radiation use efficiency, light extinction coefficient, and fruiting efficiency.

  • Radiation use efficiency refers to the efficiency with which plants capture and utilize solar radiation for photosynthesis and subsequent growth. This, in turn, translates into higher yields.
  • The light extinction coefficient represents the rate at which light intensity decreases as it travels through the plant canopy. By increasing this coefficient, more light can reach lower leaf layers, promoting photosynthesis, and ultimately leading to improved yield.
  • Fruiting efficiency refers to the number of grains produced per spike.

To identify potential candidates for targeted breeding in different climatic scenarios, researchers employed a simulation approach to model the growth and development of wheat. They created 1782 virtual genotypes per site by combining various trait values, and then identified which genotypes were best suited to specific locations and environmental conditions.

In one experiment, the researchers examined the impact of different trait values on both yield and yield stability under current climate conditions. Among different locations, increased radiation use efficiency had the greatest effect on the yield of the virtual genotypes, followed by increased fruiting efficiency, then increased light extinction coefficient. Generally, increased trait values resulted in higher yields but also increased yield variability.

Magnitude of yield and inter-annual yield variability under base climate for select sites. Standard deviation was used to quantify temporal yield variability.

In another experiment, the researchers tested the influence of trait values on yield and yield stability under future climate conditions. They found that projected climate change led to an overall improvement in average yield and decreased yield stability of the virtual genotypes for about half of the sites.

A figure showing that for the highest yielding genotype, like most of the genotypes, showed an increase in average yield and variability in about half of irrigated sites and one third of the rainfed sites.
Changes in yield and yield stability between future and baseline climate scenarios for the highest yielding genotype across the 34 test locations.

The authors identified a single trait combination (a 34 % increase in radiation use efficiency, a 10% increase in fruiting efficiency, and a 20 % increase in light extinction coefficient) that had the highest yield of all the virtual genotypes in most of the sites under baseline and scenario climates.

While higher yields resulting from improved traits often correlated with increased year-to-year yield variability, there was no notable difference in yield variability between the base genotypes and the improved genotypes. This implies that the improved genotypes did not demonstrate a disproportionately higher degree of yield variability compared to the base genotypes, even though they achieved higher yields. This observation held true for both present and projected future climate conditions.

Webber concludes, “our study suggests that increasing the expression of traits in wheat to achieve higher yields would not pose additional climate risks for farmers in terms of warmer temperatures and drought. Furthermore, adopting cultivars with these traits would not result in increased yield variability.”

READ THE ARTICLE:

Tommaso Stella, Heidi Webber, Ehsan Eyshi Rezaei, Senthold Asseng, Pierre Martre, Sibylle Dueri, Jose Rafael Guarin, Diego N L Pequeno, Daniel F Calderini, Matthew Reynolds, Gemma Molero, Daniel Miralles, Guillermo Garcia, Gustavo Slafer, Francesco Giunta, Yean-Uk Kim, Chenzhi Wang, Alex C Ruane, Frank Ewert, Wheat crop traits conferring high yield potential may also improve yield stability under climate change, in silico Plants, Volume 5, Issue 2, 2023, diad013, https://doi.org/10.1093/insilicoplants/diad013

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