As an important halophyte in the Yellow River Delta, the Amaranthaceae C3 Suaeda salsa (L.) Pall. has attracted much attention for the “red carpet” landscape, and could be simply divided into red and green phenotypes according to the betacyanin content in the fleshy leaves. However, S. salsa has not been sequenced yet, which limited people’s understanding at the molecular level. We constructed a high-quality chromosome-level reference genome by combining high-throughput sequencing, PacBio Single Molecule Real-Time (SMRT) sequencing, and Hi-C sequencing techniques with a genome size of 445 MB and contigs N50 of 2.94 Mb. Through the annotation of the reference genome, a total of 288.23 Mb of the repeating elements (64.76% of the total genome size) and 23,965 protein-coding genes were identified. Comparative genomics indicated that S. salsa undergone a WGD event about 146.15 million years ago (mya), and the estimated divergence time between S. salsa and S. aralocaspica was about 16.9 mya. A total of four betacyanins including betanidin, celosianin II, amaranthin and 6’-O-malonyl-celosianin II were identified and purified in both phenotypes, while two significantly up-regulated betacyanins (celosianin II and amaranthin) may be the main reason for the red color in red phenotype. In addition, we also performed transcriptomics and metabolomics in both phenotypes to explore the molecular mechanisms of pigment synthesis, and a series of structural genes and transcription factors concerned with betacyanin production were selected in S. salsa.

The effects of different straw returning and nitrogen addition levels on soil quality are important for proper coastal saline soil remediation. Two maize/wheat straw returning levels (1.0 × 10 4 kg ha -1 (2S) and 5.0 × 10 3 kg ha -1 (S)) and three inorganic nitrogen addition levels (300 kg ha -1 (N2), 150 kg ha -1 (N) and 75 kg ha -1 (N1/2))—were studied, with 150 kg ha -1 inorganic nitrogen and without straw addition treatment as the control (CK), to elucidate the response of soil physical and chemical properties to the two factors. Dry-sieving technique was applied to fractionate the soils into silt-plus-clay particles (< 0.053 mm, CS), microaggregates (0.053–0.25 mm, MI), small macroaggregates (0.25–2.0 mm, SM), and large macroaggregates (> 2 mm, LM). After four consecutive wheat-maize cycles, different straw and N fertilizer treatments obviously decreased the salinity contents, increased the total nutrient contents, and optimized the soil structure of the saline soil. The saline soil reclamation effects showed significant distinctions among the different straw and N fertilizer treatments. The 2SN2 treatment displayed the greatest effects in regard to decreasing salinity, increasing the total soil nutrient contents and optimizing the soil structure, which resulted in the best remediation effect. Straw returning play a major role in decreasing soil salinity and enhancing saline soil aggregate formation. N fertilizer addition supplies rich nutrients for straw decomposition, and promotes soil microbial growth and reproduction, which brought about C sequestration in coastal saline soil. During the coastal saline soil remediation process in the Yellow River Delta, it is suggested to prioritize straw returning and moderate N fertilizer addition, and live together with moderate P fertilizer application.

The effects of different straw returning and nitrogen addition levels on soil quality are important for proper coastal saline soil remediation. Two maize/wheat straw returning levels (1.0 × 10 4 kg ha -1 (2S) and 5.0 × 10 3 kg ha -1 (S)) and three inorganic nitrogen addition levels (300 kg ha -1 (N2), 150 kg ha -1 (N) and 75 kg ha -1 (N1/2))—were studied, with 150 kg ha -1 inorganic nitrogen and without straw addition treatment as the control (CK), to elucidate the response of soil physical and chemical properties to the two factors. Dry-sieving technique was applied to fractionate the soils into silt-plus-clay particles (< 0.053 mm, CS), microaggregates (0.053–0.25 mm, MI), small macroaggregates (0.25–2.0 mm, SM), and large macroaggregates (> 2 mm, LM). After four consecutive wheat-maize cycles, different straw and N fertilizer treatments obviously decreased the salinity contents, increased the total nutrient contents, and optimized the soil structure of the saline soil. The saline soil reclamation effects showed significant distinctions among the different straw and N fertilizer treatments. The 2SN2 treatment displayed the greatest effects in regard to decreasing salinity, increasing the total soil nutrient contents and optimizing the soil structure, which resulted in the best remediation effect. Straw returning play a major role in decreasing soil salinity and enhancing saline soil aggregate formation. N fertilizer addition supplies rich nutrients for straw decomposition, and promotes soil microbial growth and reproduction, which brought about C sequestration in coastal saline soil. During the coastal saline soil remediation process in the Yellow River Delta, it is suggested to prioritize straw returning and moderate N fertilizer addition, and live together with moderate P fertilizer application.