Maintaining genetic stability in sweet potato: epigenetic insights into propagation and drought tolerance

Sweetpotato is propagated vegetatively via traditional vine cutting or tissue culture using node or meristematic tissues, yet phenotypic variations among the plants are observed irrespective of the propagation method due to environmental interactions leading to mutations and/or epigenetic modifications. Methylation-mediated epigenetic modification refers to the addition of methyl groups to DNA, primarily at cytosine bases, which regulates gene expression without altering the DNA sequence. The present study focused on understanding how various propagation methods and environmental stressors (drought) affect DNA methylation patterns and epigenetic stability in commercial varieties and half-sib progenies using bisulfite sequencing. This study revealed genotype-specific DNA methylation responses to tissue culture and drought stress in sweetpotato, reflecting genotype-dependent epigenetic plasticity. Statistical analyses revealed that methylation patterns remained largely stable during tissue culture, with only minor, genotype-specific fluctuations across Meristem initiated and conventional nodal cultures. In contrast, drought stress induced unpredictable, variety-dependent methylation remodeling, reflecting active epigenetic reprogramming. Prolonged tissue culture resulted in DNA methylation enhancement, most likely due to cumulative in vitro stress; varieties maintained as greenhouse mother plants, displayed pronounced drought-induced methylation shifts. The consistent stability observed in clonal in vitro subculture supports the feasibility of long-term in vitro propagation for maintaining epigenetic stability.