Dodd, I. C. | bioRxiv Science

bioRxiv2024

The ideotype for drought tolerance in bioenergy Populus nigra

Fast-growing perennial trees such as Populus nigra L. are important species for wood, plywood, pulp, and bioenergy feedstock production, yet tree vigor in a changing climate is poorly understood. This research aimed to identify breeding targets for yield in water-limited environments, alongside unraveling the relationship between drought, yield, and glucose release in P. nigra. A diversity panel of 20 P. nigra genotypes, selected from a wide natural association population, was grown at three divergent European sites. Through extensive phenotyping of physiological and morphological productivity and water-use traits, under irrigated conditions and when exposed to a progressive drought, we elucidated the adaptive and plastic drivers underlying tree productivity. We have identified the underpinning traits for drought tolerance, whereby high yields can be maintained under water deficit, in this key species. This highlighted the importance of examining the yield stress index (YSI) over the drought resistance index (DRI) to assess genotypes for performance under moderate drought. In this way, we found genotypes with high hydraulic capacity, and large leaves made up of many cells to be best suited to multiple European environments, with contrasting water availability. Moreover, we identified genotypes that combine yield and water use efficiency, with good glucose release potential, which will be important traits for the future of poplar as a bioenergy crop. Vigorous poplar genotypes, which are adapted to wet climates showed high environmental plasticity. However, in European drought scenarios, these trees outperform drought resistant genotypes, and some exhibit good glucose release. These trees are a valuable resource for the future.

plant biology↗

bioRxiv2021

A soil-binding polysaccharide complex released from root hairs functions in rhizosheath formation

To elucidate factors involved in rhizosheath formation, wild type (WT) barley (Hordeum vulgare L. cv. Pallas) and a root hairless mutant, bald root barley (brb), were investigated with a combination of physiological, biochemical and immunochemical assays. When grown in soil, WT barley roots bound [~]5-fold more soil than brb per unit root length. High molecular weight (HMW) polysaccharide exudates of brb roots had less soil-binding capacity than those of WT root exudates. Carbohydrate and glycan monoclonal antibody analyses of HMW polysaccharide exudates indicated differing glycan profiles. Relative to WT plants, root exudates of brb had reduced signals for arabinogalactan-protein (AGP), extensin and heteroxylan epitopes than brb. In contrast, the brb root exudate contained [~]25-fold more detectable xyloglucan epitope relative to WT. Epitope detection chromatography indicated that the increased detection of xyloglucan in brb exudates was due to enhanced abundance of a neutral polymer. Exudate preparations from brb had decreased amounts of an acidic form of xyloglucan associated with root-hair located glycoprotein and heteroxylan epitopes and with soil-binding properties. Therefore, in addition to physically structuring soil particles, root hairs facilitate rhizosheath formation by releasing a soil-binding polysaccharide complex. One sentence summaryThe root exudate of a root hairless mutant of barley, relative to wild type, has an altered pattern of polysaccharide epitopes and lesser amounts of an acidic soil-binding polysaccharide complex.

plant biology↗