The Role of MaFAD2 Gene in Bud Dormancy and Cold Resistance in Mulberry Trees (Morus alba L.)

Bud dormancy is a critical adaptive trait in woody plants, essential for enduring harsh winter conditions. The relationship between bud break timing and cold resistance is complex and has been a subject of debate. This study utilizes a Genome-Wide Association Study (GWAS) on 201 natural mulberry populations to identify the <i>MaFAD2</i> gene, which shows the strongest association with bud break timing. Known for its role in cold resistance, <i>MaFAD2</i>'s link to bud break timing suggests a direct correlation between these traits. Expression analysis of <i>MaFAD2</i> in mulberry trees indicates peak activity in dormant buds, declining as dormancy ends. Selective sweep analysis on germplasms from contrasting climates reveals positive selection in <i>MaFAD2</i> in cold-resistant Uzbek germplasms. Overexpression of <i>MaFAD2</i> in early-budding germplasms significantly delays bud break, confirming its regulatory role. These findings highlight <i>MaFAD2</i> as a key determinant of cold tolerance variability among mulberry germplasms, with its expression directly correlated with bud break timing. This provides a molecular basis for selecting cold-resistant mulberry germplasms based on bud break timing in breeding programs.