As an cultivated aquatic vegetable, the long-term continuous monocropping of water oat results in the frequent occurrence of diseases, the deterioration of ecological system and decreased quality of water oat. In this study, real-time quantitative PCR (qPCR) and Illumina high-throughput sequencing were used to determine the dynamic changes in bacterial and fungal communities in rhizosphere soil under continuous cropping of water oat for 1, 5, 10, 15 and 20 years (Y1, Y5, Y10, Y15 and Y20), and soil properties and enzyme activities were also determined. Results showed that the contents of soil organic carbon (SOC), total nitrogen (TN), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP) and the activities of four soil enzymes increased in Y5 and Y10 and then decreased in Y15 and Y20. Spearman correlation analysis identified SOC, TN, AP and AN as the main factors that affect the four enzyme activities. The qPCR results showed that there was no significant difference in bacterial abundance between the different planting years, while the fungal abundance first increased and then decreased. The long-term continuous planting of water oat (Y15 and Y20) significantly reduced the operational taxonomic unit numbers and the Shannon, Chao1, and ACE indices of rhizosphere bacteria and fungi. The bacterial and fungal community compositions were markedly affected by the continuous planting year. The relative abundances of Bacteroidetes and Firmicutes decreased significantly in Y10 and Bacteroidetes increased significantly in Y15. Relative abundances of dominated Mortierellomycota and Ascomycota phyla increased with the continuous cropping years, while Rozellomycota presented the opposite trend. The AK, AN, and SOC were the main factors that changed the bacterial community, while AK and AP significantly shifted the fungal community. Thus, long-term continuous planting of water oat resulted in the deterioration of soil nutrients and microbial communities. The results provided a reference for the remediation of soil under continuous water oat planting and sustainable development of water oat industry.

Golden2-like (GLK) genes positively regulate chloroplast development, increase crop yields, and improve fruit quality. However, there has been no comprehensive identification and characterization of GLKs in watermelon. In this study, a total of 48 ClGLKs were identified in the watermelon genome. Based on phylogenetic analysis, they were divided into five groups. ClGLKs within the same group showed a similar gene structure and conserved motif compositions. Promoter analysis indicated that cis-elements responsive to light were the most abundant, though cis-elements associated with hormones, stress, and developmental regulation were also identified in ClGLKs promoters. Expression analysis indicated significant responses of some ClGLKs to drought and CGMMV stress, suggesting that these genes may participate in responses to biotic and abiotic stresses. Phenotypic analyses revealed enhanced chloroplast development and increased thylakoid density and chlorophyll content in the pericarp of a “dark green” watermelon cultivar. ClGLK8 was identified as the homolog of GLK1-2, the genes that promote chloroplast development and chlorophyll biosynthesis in fruits, and showed significantly increased expression in accordance with chloroplast development and chlorophyll accumulation. Our results provide detailed knowledge of the ClGLKs, which will enhance efforts to further improve the fruit quality of watermelon.

The purple leaves of Brassica juncea are abundant in anthocyanins that confer stress tolerance, nutritional benefits, and ornamental value. In this study, we constructed F₂ and BC₁ segregating populations by crossing the purple leaf inbred line (ZY) with the green leaf inbred line (LY) to investigate the genetic basis of leaf pigmentation. Bulked segregant analysis sequencing (BSA-Seq) and map-based cloning localized the BjZY locus to a 162.08 kb interval on chromosome BB_Chr05. Based on sequence alignment and homology analysis, an R2R3 MYB transcription factor, BjMYB113 (BjuVB05G51160), was identified as a strong candidate gene, with 3 SNPs and 25 bp insert variants in the promoter region. The expression of BjMYB113 in purple leaves was significantly higher than that in green leaves, leading to anthocyanin biosynthesis and accumulation. The transient expression of BjMYB113 in tobacco leaf confirmed that BjMYB113 positively regulates anthocyanin biosynthesis. RNA-seq analysis revealed that BjMYB113 was involved in flavonoid and anthocyanin biosynthesis pathways and regulated the expression of anthocyanin-related genes, such as BjCHS, BjDFR, and BjANS. Yeast one-hybrid assays showed that BjMYB113 activated the expression of BjDFR by directly binding to its promoter. These results provide further understanding of the genetics of purple leaf and potential applications for marker-assisted breeding in B. juncea.