Abstract
BACKGROUND: Vine cutting propagation in yams offers a transformative approach to conventional tuber-dependent cultivation, with enhanced tuber yield and quality. Adventitious root (AR) formation is a critical prerequisite for vine cutting survival, with substantial variability among yam varieties. However, relatively little is known about the regulatory mechanisms that restrict the application of cutting propagation in recalcitrant varieties. In this study, we integrated rooting rate comparisons, anatomical observations, phytohormone content determination, and transcriptomic profiling to elucidate the developmental mechanisms influencing AR formation. RESULTS: The adventitious rooting capacity of Dioscorea polystachya was significantly different from that of Dioscorea alata. Six D. alata cultivars showed rooting efficiencies exceeding 70%. In contrast, D. polystachya variety RuiChang Shan Yao (RCSY) exhibited a recalcitrant phenotype with a rooting rate of less than 5%. Phenotypic evaluation identified the AR formation phase from 0 to 12 days after cutting (DAC). Anatomical observations indicated AR initiation within the phloem tissues by two DAC, followed by complete penetration of the cortical and epidermal layers by four DAC in D. alata. Temporal phytohormone profiling showed higher auxin levels in Gan Bai Yu (GBY) and Gan Zi Yun (GZY) than in RCSY during AR formation. Transcriptomic profiling analysis of GBY and GZY at 0, 2, 4, and 8 DAC identified 9,680 differentially expressed genes (DEGs). Integrated with hormonal and rooting data, weighted gene co-expression network analysis delineated AR-associated modules (saddlebrown, magenta, orange). Kyoto Encyclopedia of Genes and Genomes enrichment underscored starch and sucrose metabolism (31 DEGs) and hormone signal transduction (18 DEGs) as central pathways. Exogenous application of 1-naphthaleneacetic acid enhanced the rooting rate. Sucrose and starch accumulation were positively associated with AR competence in GBY, GZY, and the recalcitrant RCSY. Cross-species analysis identified 39 conserved DEGs in RCSY, including six auxin-responsive genes (one IAA16, one ARF9, two ARR11, one SAUR50, one SAUR32), two cytokinin-responsive genes (two RR9), a GA-related gene (one GID1C), six ABA-related genes (two PYL10, one AHG1, two ABF), and 24 starch and sucrose metabolism-related genes (SUS7, HXK1, FRK2, SS2, TPPs, DPEP, GLUs, and BGLUs), which implied their roles in AR regulation. CONCLUSIONS: These findings identify the key molecular drivers of AR formation in yams, offering new insights into rooting recalcitrance and strategies for optimizing clonal propagation in agricultural species.