Natural variation in the Arabidopsis thaliana root and shoot response to boron deficiency reveals sensitive and responsive phenes and phylogenetic and geographic clustering of boron efficiency adaptations

Boron (B) is an essential plant micronutrient with a crucial role in cell wall stability. To improve plant tolerance to suboptimal B-availability, it is crucial to understand the mechanisms plants have evolved to tolerate B-limited conditions. We assessed temporal physiological, ionomic and molecular responses to B-deficiency across a diversity panel of 185 Arabidopsis thaliana accessions. Plants were characterised in soil-substrate in an automated phenotyping system to track shoot performance, and on agar plates to track root traits. Accessions varied widely in their response to B-deficiency. Rosette area decreased by 50% under B-deficiency across all accessions on average but by less than 15% in B-efficient accessions alone. Most root traits suffered under B-deficiency but lateral root length increased in 20% of accessions. The B-uptake and B transporter expression response of B-efficient and B-inefficient accessions was similar, suggesting increased B-use rather than B-uptake efficiency in efficient accessions. Phylogenetic analysis demonstrated enrichment of B-efficient accessions within a clade containing accessions originating from areas characterised as B-deficient. K-means clustering revealed increased lateral root length was associated with efficient shoot growth under B-deficiency. The results demonstrate different response strategies to B-deficiency, indicating target traits to improve the performance of plants grown under B-limiting conditions.