The genetic control of stem mechanical properties in Brassica Napus and Wheat
Understanding what contributes to the genetic control of stem mechanical strength in important crop species, has potential for the improvement of lodging resistance. This may be particularly important given the recent interest in the exploitation of crop residues as feedstock for lignocellulosic ethanol production, where the manipulation of cell wall chemical composition to improve feedstock processibility may lead to reduced stem strength. Lodging is a widespread problem in both Brassica napus (B. napus) and wheat, and is a key contributor to yield loss. The development of genetic markers that could be used in the selection of elite accessions with high stem mechanical strength is an approach that could compliment current strategies in place for lodging control. The level of genetic variation available for stem mechanical strength and related traits was assessed across wheat and B. napus diversity panels. Following the detection of high levels of variation, these traits were analysed using Associative Transcriptomics. Important variation at both the sequence and the gene expression level was identified. This analysis revealed a potential importance of xylan acetylation in wheat. For B. napus a subset of candidate genes were validated in an Arabidopsis thaliana mutant screen, which revealed GAUT5, SAUR72 and a pectin methylesterase (AT3G12880), as key contributors to stem mechanical strength. Xylan acetylation and pectin methylesterification are both known to impair saccharification efficiency of lignocellulosic biomass, suggesting that there may be conflict between feedstock processibility and stem mechanical strength. A subset of markers detected through Associative Transcriptomics were further tested an independent panel of B. napus and wheat breeding material. Through genotyping and subsequent mechanical testing, markers with high durability for the selection of stem mechanical strength were identified in both crop species. These experiments demonstrate the power of Associative Transcriptomics for the identification of durable markers for complex traits of agronomic importance.
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