Identification of Rapeseed ( Brassica napus ) Cultivars With a High Tolerance to Boron-Deficient Conditions.

Abstract

Boron (B) is an essential micronutrient for seed plants. Information on B-efficiency mechanisms and B-efficient crop and model plant genotypes is very scarce. Studies evaluating the basis and consequences of B-deficiency and B-efficiency are limited by the facts that B occurs as a trace contaminant essentially everywhere, its bioavailability is difficult to control and soil-based B-deficiency growth systems allowing a high-throughput screening of plant populations have hitherto been lacking. The crop plant Brassica napus shows a very high sensitivity towards B-deficient conditions. To reduce B-deficiency-caused yield losses in a sustainable manner, the identification of B-efficient B. napus genotypes is indispensable. We developed a soil substrate-based cultivation system which is suitable to study plant growth in automated high-throughput phenotyping facilities under defined and repeatable soil B conditions. In a comprehensive screening, using this system with soil B concentrations below 0.1 mg B (kg soil)-1, we identified three highly B-deficiency tolerant B. napus cultivars (CR2267, CR2280 and CR2285) amongst a genetically diverse collection comprising 590 accessions from all over the world. The B-efficiency classification of cultivars was based on a detailed assessment of various physical and high-throughput imaging-based shoot and root growth parameters in soil substrate or in in vitro conditions, respectively. We identified cultivar-specific patterns of B-deficiency-responsive growth dynamics. Elemental analysis revealed striking differences only in B contents between contrasting genotypes when grown under B-deficient but not under standard conditions. Results indicate that B-deficiency tolerant cultivars can grow with a very limited amount of B which is clearly below previously described critical B-tissue concentration values. These results suggest a higher B utilization efficiency of CR2267, CR2280 and CR2285 which would represent a unique trait amongst so far identified B-efficient B. napus cultivars which are characterized by a higher B-uptake capacity. Testing various other nutrient deficiency treatments, we demonstrated that the tolerance is specific for B-deficient conditions and is not conferred by a general growth vigor at the seedling stage. The identified B-deficiency tolerant cultivars will serve as genetic and physiological ‘tools’ to further understand the mechanisms regulating the B nutritional status in rapeseed and to develop B-efficient elite genotypes.

Plant phenotyping relevance

土壌B条件を制御した自動ハイスループット表現型解析システムを開発し、画像ベースの生長形質で590系統を評価しており、表現型取得基盤が研究の中心的役割を担う。

Code and data availability

The paper's phenotyping measurements (590-accession B-efficiency screen, root cessation assay, imaging-derived traits, substrate nutrient quantification) are distributed as Supplementary Data Sheets S1–S5, publicly available via the Frontiers article's supplementary material page. No author analysis code or trained模型的专