Guangxi Academy of Agricultural Science

Abstract Strigolactones (SLs) are an important class of plant hormones that play crucial roles in regulating plant branching, root architecture, and organ development. However, the regulatory mechanisms underlying the crosstalk between SLs and other plant hormones remain largely unclear, particularly regarding the key regulatory genes that integrate and coordinate multiple hormonal signaling pathways. In this study, secondary cup seedlings of the Pisang Awak banana cultivar ‘Yufen 6’ at the eight-leaf stage were used as experimental materials. The roots were treated with a nutrient solution containing 30 μmol/L exogenous SLs, while a nutrient solution supplemented with water served as the control. Tissues near the corm growth point were collected at 0, 15, 30, 60, 90, and 120 days after treatment to measure corm weight, height, and diameter, and transcriptome sequencing was performed using the collected tissues. Differentially expressed genes (DEGs) at different treatment stages were identified, followed by Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses to systematically investigate the crosstalk between SLs and endogenous hormone metabolism and signaling during corm development in Pisang Awak banana. The results showed that SL treatment significantly inhibited the weight, height, and diameter of the corm. The regulatory effect of SLs on Pisang Awak banana corm development exhibited a clear temporal dynamic pattern, representing a gradual accumulation process that ultimately triggers key developmental transitions. The highest number of DEGs was detected at 15 days after treatment, including 3943 upregulated genes and 3704 downregulated genes, indicating that this stage represents a critical phase for SL response initiation. GO enrichment analysis revealed that the DEGs were mainly involved in metabolic processes, biological regulation, response to stimulus, and regulation of biological processes. KEGG pathway analysis indicated that these DEGs were significantly enriched in pathways related to plant hormone signal transduction, starch and sucrose metabolism, and secondary metabolite biosynthesis. Further analysis revealed that the crosstalk between SLs and multiple hormone metabolic and signaling pathways is mediated by the SPL15 gene, involving auxin (IAA), cytokinin (CTK), abscisic acid (ABA), brassinosteroids (BRs), gibberellins (GA), and jasmonic acid (JA) pathways. This study reveals the molecular mechanism by which SLs regulate Pisang Awak banana corm development through SPL15-mediated integration of multiple hormonal signals, providing new insights into the role of SLs in regulating the development of underground organs in banana.

Compost-derived humic acids (HAs) and fulvic acids (FAs) play an essential role in enhancing soil microbial diversity and activity by facilitating metabolic processes through electron transfer. Herein, the effect of bioleaching dewatered sludge (BDS) in comparison with filter press dewatered sludge (FDS) on the electron transfer capacity (ETC) of humic substances during composting was investigated as a novel attempt. A variety of characterization methods including UV-Vis, FTIR, 3D-EEM, and electrochemical measurements, were used to explore the change in humic substances during composting. The results indicated that bioleaching treatment significantly influenced the organic matter composition and hindered the accumulation of redox-active functional groups during composting. Notably, the ETC of HA increased by 24.07% in the FDS group but declined by 40.62% in the BDS group. This divergence stemmed from the organic matter loss during bioleaching, leading to reduced quinone-like and tryptophan-like substances associated with electron transfer in HA during composting. Furthermore, BDS showed lower pH, water content, and organic matter, but higher concentrations of ammonium nitrogen (NH4+-N) and ammonia nitrogen NH3−-N, all of which potentially influenced humification efficiency. These findings not only clarify the electron-transfer dynamics of humic fractions but also highlight the importance of optimizing sludge pretreatment for improved composting performance and resource recovery.

Abstract (1) Background: The rhizosphere microbiome, as the “second genome” of plants, plays a crucial role in nutrient acquisition, stress resistance, and soil health maintenance. Polyploidization is a key breeding strategy for watermelon: triploids are valued for seedlessness and high stress resistance, while tetraploids serve as important parental materials for triploid hybridization. However, how ploidy level (diploid, triploid, tetraploid) shapes the micro-ecological environment and microbial community assembly remains unclear. This study aims to elucidate the link between ploidy and rhizosphere microbiota, providing a theoretical basis for optimizing breeding and cultivation practices. (2) Methods: High-throughput sequencing (Illumina MiSeq PE300 for bacteria, PE250 for fungi) targeting the bacterial 16S rRNA gene (primers 338F/806R) and fungal ITS region (primers ITS1F/ITS2R) was used to analyze rhizosphere microbial communities of diploid (HLL40-3), triploid (Guixi No.5), and tetraploid (MT410n-1) watermelons. Alpha diversity (Shannon/Chao1/ACE/Simpson), beta diversity (PCoA/PLS-DA), taxonomic composition (phylum/genus level), and functional prediction (PICRUSt2/Tax4Fun/FUNGuild) were performed to compare differences among groups. (3) Results: Triploid watermelons exhibited significantly higher bacterial and fungal alpha diversity (Shannon/Chao1) than diploid and tetraploid varieties. Beta diversity analysis confirmed distinct separation of microbial communities across ploidy levels ( p < 0.05). Taxonomically, diploid rhizospheres were enriched in Proteobacteria, Melanconiella, and Hypomyces ; triploids were enriched in Bacteroidota, Microvirga , Mortierellomycota, Cercophora , and Neocosmospora ; tetraploids were specifically enriched in Patescibacteria , Gaiella , Trichoderma , and Papiliotrema . Functional prediction showed diploids were dominated by plant/wood saprotrophs; triploids harbored diverse functional guilds (animal pathogens, endophytes, soil saprotrophs, etc.); tetraploids had the highest relative abundance of undefined saprotrophs. (4) Conclusions: Ploidy level is a key determinant of watermelon rhizosphere microbial structure and function. Triploid watermelons assemble a more diverse and functionally versatile microbial community through selective recruitment, which may contribute to their superior agronomic traits. These findings deepen our standing of plant-microbe interactions and provide new insights for integrating polyploid breeding with rhizospheric microecological regulation in sustainable watermelon production.

Citrus, a globally significant fruit crop, is predominantly cultivated on sloping land in China with a large amount of resource input and incurs high environmental costs. Current research often relies on general parameters and rarely simultaneously assesses carbon footprint (CF) and water footprint (WF) to reveal the synergistic effects in emission reduction strategies. To address knowledge gaps, we conducted a 2-year county-scale survey and a 3-year field experiment in Zhongxian County, Chongqing, China. We optimized five nutrient management schemes, chemical fertilizer (Che), chemical fertilizer + organic manure (Che+Org), chemical fertilizer + cover crops (Che+CC), chemical fertilizer + organic manure + cover crops (Che+Org+CC), and optimized management (OPT), and analyzed them using the life cycle assessment (LCA) framework. The results showed that OPT achieved dual benefits of high productivity and low carbon-water cost, with a CF reduction of 26.9%-64.6% and a WF reduction of 75.7%-92.1% compared with other treatments. Nitrogen fertilizer production and application were the primary CF sources, whereas cover crop integration markedly decreased WF. A significant positive correlation between CF and grey WF (p < 0.05) indicates that cover crops simultaneously mitigated carbon emissions and reduced nitrogen/phosphorus runoff. While achieving these environmental benefits, the citrus yield of the OPT was 33.57% higher than that of the Che, and the economic returns were 45.51% higher. This study demonstrates that in the sloping land environment, selectively combining organic fertilizers and cover crops can transform the contradiction between yield and the environment into a synergistic effect, thereby deepening the understanding of sustainable nutrient management. The research results show that the OPT system is a superior nutrient management strategy for sloping citrus orchards. The research results also provide reliable and specific evidence to support the optimization of the "organic substitution" policy and offer a feasible approach for low-carbon, high-efficiency citrus production in ecologically fragile regions.

Bacterial diseases pose a serious threat to horticultural crops, necessitating the exploration of biocontrol resources for sustainable agricultural development. This study characterises Burkholderia arboris M13, a novel biocontrol strain exhibiting broad-spectrum antagonism in vitro against major phytopathogenic bacteria of horticultural crops, including Pseudomonas syringae pv. tomato, Ralstonia solanacearum, Paracidovorax citrulli, and Xanthomonas campestris pv. campestris. Applications of its bacterial suspension or culture supernatant significantly suppressed tomato bacterial speck, bacterial wilt, watermelon bacterial fruit blotch, and cabbage black rot in greenhouse and field trials. The strain also induced plant systemic resistance and promoted plant growth. Genomic analysis revealed significant novelty, as B. arboris M13 possesses two unique plasmids and harbours 20 biosynthetic gene clusters for secondary metabolites, with several showing weak collinearity to close relatives, indicating genetic determinants for its expanded functionality. Furthermore, B. arboris M13 demonstrated compatibility with the plant growth regulator (24-epibrassinolide) but incompatibility with the copper-based bactericide copper hydroxide, which enhances its practical integration into existing crop management strategies. This combination of effective biocontrol, plant growth promotion, distinct genomic features, and chemical compatibility establishes B. arboris M13 as a versatile and promising candidate for sustainable agriculture.