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The microbiota thriving in the rhizosphere, the thin layer of soil surrounding plant roots, plays a critical role in plant's adaptation to the environment. Domestication and breeding selection have progressively differentiated the microbiota of modern crops from the ones of their wild ancestors. However, the impact of eco-geographical constraints faced by domesticated plants and crop wild relatives on recruitment and maintenance of the rhizosphere microbiota remains to be fully elucidated. Here we performed a comparative 16S rRNA gene survey of the rhizosphere of 4 domesticated and 20 wild barley (Hordeum vulgare) genotypes grown in an agricultural soil under controlled environmental conditions. We demonstrated the enrichment of individual bacteria mirrored the distinct eco-geographical constraints faced by their host plants. Unexpectedly, Elite varieties exerted a stronger genotype effect on the rhizosphere microbiota when compared with wild barley genotypes adapted to desert environments with a preferential enrichment for members of Actinobacteria. Finally, in wild barley genotypes, we discovered a limited, but significant, correlation between microbiota diversity and host genomic diversity. Our results revealed a footprint of the host's adaptation to the environment on the assembly of the bacteria thriving at the root–soil interface. In the tested conditions, this recruitment cue layered atop of the distinct evolutionary trajectories of wild and domesticated plants and, at least in part, is encoded by the barley genome. This knowledge will be critical to design experimental approaches aimed at elucidating the recruitment cues of the barley microbiota across a range of soil types. [ABSTRACT FROM AUTHOR]

Purpose: Silicon improves plants' ability to tolerate stresses. It is taken up by roots as silicic acid, transported via the transpiration stream, and is unloaded in the shoot by specific silicon transporters. In grasses, silicon deposits may reach 10 % of the leaf dry weight. However, no molecular mechanism is known to control the deposition. Our purpose thus was to identify a sorghum mutant unable to absorb silicic acid and use it to study leaf silicification. Methods: We generated and characterized a Sorghum bicolor knockout mutant in a root silicon transporter, SbLsi1, and followed leaf epidermal silicification, using an airSEM (air-scanning electron microscope). Results: The mutant contained 40 times less silica than the wild type (about 0.01 % per dry weight, compared to 3.7 %). The base of wild type leaf blades contained very few, partially silicified dumbbell-shaped silica cells. The silicification intensified towards the leaf tip. Contrary to this, the mutant leaf epidermis displayed empty and probably non-turgid dumbbells. Mature mutant leaves supplied with silicic acid through their base, accumulated silica in the cell walls along the vasculature. No specific dumbbell silicification was detected. Conclusions: The loss of turgor may indicate that cell death is part of the development of dumbbell-shaped silica cells. These cells do not accumulate silica after turgor loss, suggesting that a biological process may be involved in their silicification. [ABSTRACT FROM AUTHOR]

Harvest index, defined as the ratio of reproductive yield to total plant biomass, and early ripening are traits with important agronomic value in processing tomatoes. The Solanum pennellii introgression-line (IL) population shows variation for harvest index and earliness. Most of the QTL mapped for these traits display negative agronomic effects; however, hi2- 1 is a unique QTL displaying improved harvest index and earliness. This introgression was tested over several years and under different genetic backgrounds. Thirty-one nearly isogenic sub-lines segregating for the 18 cM TG33-TG276 interval were used for fine mapping of this multi-phenotypic QTL. Based on this analysis the phenotypic effects for plant weight, Brix, total yield and earliness were co-mapped to the same region. In a different mapping experiment these sub-lines were tested as heterozygotes in order to map the harvest index QTL which were only expressed in the heterozygous state. These QTL mapped to the same candidate region, suggesting that hi2- 1 is either a single gene with pleiotropic effects or represents linked genes independently affecting these traits. Metabolite profiling of the fruit pericarp revealed that a number of metabolic QTL co-segregate with the harvest index trait including those for important transport assimilates such as sugars and amino acids. Analysis of the flowering pattern of these lines revealed induced flowering at IL2-1 plants, suggest that hi2- 1 may also affect harvest index and early ripening by changing plant architecture and flowering rate. [ABSTRACT FROM AUTHOR]