The purpose of this study was to investigate the mechanism and efficacy of Lvnonglin ^®41 compound microbial fertilizer in mitigating black pepper continuous cropping obstacles from the perspectives of soil nutrients, microbial community structure and diversity, so as to provide technical strategies for the industrial cultivation of black pepper in Hainan. Field experiments were conducted on a plot with a history of severe black pepper Fusarium wilt. Four treatments were designed: water control (CK), Lvnonglin^® 41 compound microbial fertilizer (LNL41), compound microorganisms (CM), and bacterial fertilizer nutrient substrate (NS). The incidence of Fusarium wilt in the rhizosphere, plant growth and soil nutrients were measured. Using 16S rDNA sequencing technology, the differences in the occurrence of black pepper Fusarium wilt and the bacterial community structure in the rhizosphere soil under LNL41 application were explored. The results showed that compared with CK, all treatments exhibited certain effects, with the LNL41 treatment being the most effective. Soil nutrient indicators in the LNL41 and CM treatments were significantly higher than those in CK. The increases in chlorophyll content, spike length and 1000-grain weight under LNL41, CM and NS treatments reached 26.12%-67.87%, 6.20%-18.33% and 1.48%-6.44%, respectively. The incidence rates at different growth stages in the LNL41 treatment were 2.67%-15.67%, with control efficacies of 81.64%-90.06%. The Ace and Chao1 indices of rhizosphere soil bacteria increased by 12.82%-20.28% and 12.89%-18.78%, respectively, and the Shannon diversity index increased by 1.05%-3.53%, while the Simpson index showed no significant difference among treatments. At the order level, Chitinophagales, Rhizobiales and Burkholderiales were the dominant bacterial orders. At the genus level, Gaiella, P3OB 42, Lactobacillus, Pseudolabrys and Terrimonas were the dominant bacterial genera. The abundances of the common dominant genus Bacillus and Candidatus Omnitrophus were similar across treatments. Linear discriminant analysis (LEfSe) results indicated the presence of six indicator bacterial taxa in the LNL41 treatment. Ellin6067 and Tepidisphaera showed significant or highly significant positive correlations with soil pH, organic matter, available potassium, ammonium nitrogen and available phosphorus. Network analysis further revealed that the LNL41 treatment enhanced the complexity and stability of the soil bacterial co-occurrence network. Bugbase functional prediction demonstrated that the abundance of stress tolerant functional groups in the LNL41 treatment increased by 5.38 percentage points, while it decreased by 10.43 and 7.25 percentage points in the CM and NS treatments, respectively. LNL41 significantly improved the ratio of soil nutrients, thereby enhancing the structure and functional characteristics of the soil bacterial community, stimulating bacterial stress tolerance functions, promoting black pepper growth, and reducing the incidence of Fusarium wilt.

Coffee, one of the most important economic crops worldwide, is widely cultivated in tropical and subtropical regions and serves as a major source of income for many countries and regions. Caffeine (1,3,7-trimethylxanthine) is the main metabolite in coffee beans and related products, which not only imparts the characteristic bitter taste and stimulates effect of coffee but also exerts multiple biological functions. The N-methyltransferase (NMT) gene family plays a key role in the caffeine biosynthetic pathway. Therefore, systematic identification of coffee NMT family members and analysis of the expression patterns at different developmental stages are of great importance for investigating caffeine metabolism, improving coffee quality, and breeding stress-resistant varieties. In this study, a total of 27 NMT genes were identified in allotetraploid Coffea arabica, including 14 genes from the C subgenome and 13 from the E subgenome, distributed across 10 chromosomes. Gene structure analysis revealed that family members shared similar motif compositions but differed in intron arrangement and number. Cis-acting element analysis showed that the promoters of C. arabica NMT genes were enriched with various regulatory elements related to light response, stress response and hormone signaling, and contained transcription factor binding sites such as MYB, MYC and W-box. Transcriptome analysis further demonstrated that NMT genes exhibited dynamic expression during fruit development, with the ripening stage showing the highest number of differentially expressed genes (14 703), while the expansion stage showed the lowest (4419). Moreover, C. arabica NMT genes displayed clear temporal and tissue-specific expression patterns. Weighted gene co-expression network analysis (WGCNA) identified 12 co-expression modules, among which the ivory, coral1 and darkolivegreen modules were enriched in pathways related to environmental stress and protein folding, energy metabolism and nucleic acid metabolism, respectively. Core gene network analysis revealed the critical roles of NMT genes in caffeine metabolism, stress response, and developmental regulation. Taken together, this study systematically identified the NMT gene family in allotetraploid C. arabica, characterized the expression patterns during different stages of fruit development, and elucidated the potential functional differentiation, thereby providing a theoretical basis for coffee breeding.