Relevance of grain number and grain weight on barley yield responses to environmental and genetic factors

Global food demand is projected to rise, making it essential to enhance agricultural production to ensure food security while minimizing environmental impacts, particularly in the face of climate change challenges. Understanding the determination of grain yield (GY) in barley is crucial for future advancements in this crop. This study examines the relationships between the two major components of GY (grain number-GN and grain weight-GW), when driven by genetic and environmental factors. We compiled data of GY and its numerical components (i.e. GN and GW) to generate a large and unbiased database from every single paper having the word “barley” in the title published over 25 years in four prestigious international journals: Field Crop Research, European Journal of Agronomy, Crop Science and Crop and Pasture Science (formerly Australian Journal of Agricultural Research) between January 1996 and December 2021, both inclusive. GN was significantly better correlated with GY than GW, accounting for 86 % of the variation in GY compared to just 13 % for GW. The changes in GY responsiveness to environmental and genetic factors were mainly due to variations in GN, especially in scenarios with high responsiveness. In contrast, low-responsiveness cases showed trade-offs between GN and GW, suggesting compensatory mechanisms that may not accurately reflect competition for resources. The potential to increase barley GY relies heavily on GN, emphasizing the need to optimise conditions during the critical period of GN determination. Barley crops under typical field conditions are generally not limited by resource availability during grain filling. • We quantified barley grain yield numerical components depending on genetic and/or environmental source of variation. • Grain number was the main component regardless of the source of variation, especially in scenarios with high responsiveness. • In low-responsiveness scenarios, there was a trade-off between grain number and grain weight. • Barley crops under typical field conditions are generally not limited by resource availability during grain filling.