This dataset describes six traits for polysaccharides extracted from the outer layer of mucilage of 306 natural accessions and 6 control genotypes from Arabidopsis. The natural accessions were obtained from the Versailles Arabidopsis Stock Center (http://publiclines.inra.fr/naturalAccession/index) are listed by their Versailles identification number, with available co-ordinates for the site of collection indicated and classed for their precision using a colour code. Seed lots represent four independent biological repeats produced from different plants. These were produced from plants grown in a chamber with 65% relative humidity and 170 µmol m-2 s-1 during a 16h photoperiod at 21°C and 8h dark at 18°C. Plants were grown in compost (Tref substrates) following a randomised sowing plan in two independent series of plants grown and harvested together, with four plants of each genotype per series. Seed lots were assigned sample codes a1 to a4 and b5 to b8 corresponding to seed lots from series a or b, respectively. Two seed lots from each series were used for subsequent analyses for accessions. Control genotypes cesa5-1 (SALK_125535), myb61, (SALK_106556) in Col-0 background and cesa5mum3-1 and mum5-1 in the Col-2 background were obtained in previous studies (Western et al., 2001; Desprez et al., 2007; Saez-Aguayo et al., 2014), four seed lots were obtained from independent plants grown as described above; data is colour-coded in green. Data for accessions previously shown to be affected in mucilage release, Shahdara, Neo-3, Neo-6 and Sus-1 (Macquet et al., 2007; Saez-Aguayo et al., 2014) or for Dja-5, which has the same haplotype as Dja-1, which shows delayed and incomplete mucilage release in water (Simon et al., 2012; Saez-Aguayo et al., 2013) are colour-coded in red.

Mucilage was extracted from 100 mg of seed with 2 mL of water by head-to tail mixing for 3 h at 20°C. Extracts were then centrifuged at 8000 g for 3 minutes and filtered through a disposable glass microfiber filter (13 mm diameter, 2.7 µm pore size). A 200 µL aliquot was diluted 10-fold in water and analysed (San-System, Skalar) by the automated m-hydroxybiphenyl method and the automated orcinol method to determine uronic acid and neutral sugar contents, respectively (Thibault, 1979; Tollier and Robin, 1979). The remaining extract was heated to 100°C for 5 minutes and stored at -20°C. Just prior to HPSEC analysis, this extract was thawed, heated again to 100°C and filtered through a disposable PVDF filter (13 mm diameter, 0.45 µm pore size). HPSEC analysis was performed at room temperature with a Shodex OH Pak SB-G-6B pre-column and a Shodex OH Pak SB805 HQ column. Elution was carried out with 50mM sodium nitrate at 0.7 mL/min. The following detectors were used, a differential refractometer (Viscotek VE 3580 RI detector) and a dual light scattering detector combined with a differential pressure viscometer (Viscotek 270 Dual detector). Calibration was performed daily with a pullulan standard with a narrow molar mass distribution (Mw 145618D, Mn 139180D, intrinsic viscosity 54 mL/g). The galacturonic acid and neutral sugar contents indicate the amount and composition of outer mucilage polysaccharides, while the molar mass at peak maximum (Mp), intrinsic viscosity (IV), hydrodynamic radius (Rh) and radius of gyration (Rg) provide information about the conformation and size of polymers.