Physical geography, isolation by distance and environmental variables shape genomic variation of wild barley (Hordeum vulgare L. ssp. spontaneum) in the Southern Levant

Determining the extent of genetic variation that reflects local adaptation in crop-wild relatives is of interest for the purpose of identifying useful genetic diversity for plant breeding. We investigated the association of genomic variation with geographical and environmental factors in wild barley (Hordeum vulgare L. ssp. spontaneum) populations of the Southern Levant using genotyping by sequencing (GBS) of 244 accessions in the Barley 1K+ collection. The inference of population structure resulted in four genetic clusters that corresponded to eco-geographical habitats and a significant association between lower gene flow rates and geographical barriers, e.g. the Judaean Mountains and the Sea of Galilee. Redundancy analysis (RDA) revealed that spatial autocorrelation explained 45% and environmental variables explained 15% of total genomic variation. Only 4.5% of genomic variation was solely attributed to environmental variation if the component confounded with spatial autocorrelation was excluded. A synthetic environmental variable combining latitude, solar radiation, and accumulated precipitation explained the highest proportion of genomic variation (3.9%). When conditioned on population structure, soil water capacity was the most important environmental variable explaining 1.18% of genomic variation. Genome scans with outlier analysis and genome-environment association studies were conducted to identify adaptation signatures. RDA and outlier methods jointly detected selection signatures in the pericentromeric regions, which have reduced recombination, of the chromosomes 3H, 4H, and 5H. However, selection signatures mostly disappeared after correction for population structure. In conclusion, adaptation to the highly diverse environments of the Southern Levant over short geographical ranges had a limited effect on the genomic diversity of wild barley. This highlighted the importance of nonselective forces in genetic differentiation.

Effect of Exogenous Treatment with Nitric Oxide (NO) on Redox Homeostasis in Barley Seedlings (Hordeum vulgare L.) Under Copper Stress

The protective mechanism of nitric oxide (NO) in regulating tolerance to Cu-induced toxicity in shoots of barley (Hordeum vulgare L.) was studied. The experiment consisted of four treatments based on additions to basal nutrient solutions (BNS): control (CTR), Cu (200 µM), SNP (500 µM), and Cu (200 µM) + SNP (500 µM) over a period of 10 days. Treatment with Cu significantly reduced seedling growth and photosynthetic efficiency concomitant with an increase in reactive oxygen species contents, lipid peroxidation markers, and antioxidant enzyme activities, indicating that Cu induced oxidative stress. Furthermore, growth inhibition of Cu-treated plants was associated with a reduction in photosynthetic pigments and maximum photosystem II efficiency as well as a strong decrease in levels of glutathione (GSH) and ascorbate (AsA). Addition of a nitric oxide (NO) donor, sodium nitroprusside (SNP), to the growth medium alleviated Cu toxicity by decreasing Cu uptake and enhancing antioxidant capacity, as indicated by increased contents of GSH and AsA. The application of SNP decreased oxidative stress and lipid peroxidation by suppressing lipoxygenase activity and enhancing some antioxidant enzyme activities. The results obtained indicate the potential of exogenously applied SNP in the management of metal toxicity. Hence, NO generating compounds have potential agronomical applications when cultivating in contaminated areas. Our findings indicate that NO can alleviate Cu toxicity by affecting the antioxidant defense system and maintaining the glutathione-ascorbate cycle status, suggesting that SNP treatment protects proteins against oxidation by regulating the cellular redox homeostasis.

Metabolic activity of Hordeum vulgare, Brassica napus and Vicia faba in Worm and Root type Biopore Sheaths

Aims Biopores offer favorable chemical, biological and physical properties for root growth in untilled soil layers. There they are considered as nutrient “hotspots” with preferential root growth. However, the literature lacks a quantification of metabolic activity due to nutrient acquisition of main crops while growing in the biopore sheath. Methods A pot experiment was performed to map the metabolic activity of roots, as indicated by pH change. The roots of spring barley (Hordeum vulgare L.), spring oilseed rape (Brassica napus L.) and faba bean (Vicia faba L.) were growing through the biopore sheath influenced by an earthworm (Lumbricus terrestris L.) or a taproot (Cichorium intybus L.), in comparison to subsoil without a pore (bulk soil). pH sensitive planar optodes were applied in order to image a planar section of the sheath, while preserving an intact biopore sheath during the experiment. Results Roots were first found in the field of view in worm biopore then root biopore and bulk soil. At time of the first measurement the pH value was highest in worm biopore sheath (LS-Mean±SEM: 7.16a±0.11), followed by root biopore sheath (6.99ab±0.12) and bulk soil (6.61b±0.12). In spring oilseed rape a significant alkalization (+0.80 Δ pH) was found over time in bulk soil. Faba bean significantly acidified the root biopore sheath (-0.73 Δ pH). Spring barley showed no significant pH changes. Conclusions The results of the current study reveal a trend of faster root growth through biopores and a higher initial pH value in the biopore sheaths compared to the bulk soil. Biopores serve not only as an elongation path for roots, but their sheaths also provide an environment for root activity in the subsoil.

Effect of Substrate Properties and Phosphorus-supply on the Rare Earth Element Facilitation in Mixed-culture Cropping Systems of Hordeum Vulgare, Lupinus Albus and Lupinus Angustifolius

This study presents how nutrient availability and intercropping may influence the migration of REE when cultivated under P-deficient conditions. In a replacement model, Hordeum vulgare was intercropped with 11% Lupinus albus cv. Feodora and 11% L. angustifolius cv. Sonate. They were cultivated on two substrates, A (pH = 7.8) and B (pH = 6.6). Two nutrient solutions were supplied, with N, K, Mg and high P-supply (P+), the other with N, K, Mg, and one-third of P-supply (P-, applied to L0 and Lan only). Simultaneously, a greenhouse experiment was conducted to quantify carboxylate release. There, one group of L. albus and L. angustifolius was supplied with 200 µM K2HPO4 (P+) together with the other nutrients while a second group received 20 µM P (P-). L. albus released higher carboxylates at low P-supply than L. angustifolius. Higher P-supply did not influence the P concentrations and contents of H. vulgare neither on substrate A nor on substrate B. However, addition of P decreased the concentrations of REEs, especially in plants cultivated on alkaline soil. Nutrient accumulation decreased in H. vulgare in intercropping with L. angustifolius when cultivated on the alkaline substrate A with high P-supply. In the same conditions, the accumulation of REE in H. vulgare significantly increased. Conversely, on the acidic substrate B intercropping with L. albus decreased REE contents and concentrations in H. vulgare. Intercropping with L. angustifolius opens an opportunity for enhanced phytomining and accumulation of REE. Furthermore, intercropping with L. albus on REE polluted soils may be utilized to restrict REE accumulation in crops used for food production.