Transcriptome based WGCNA analysis reveals the mechanisms underlying corolla abscission in blueberry (Vaccinium...

Corolla abscission is an important agronomic trait that affects fruit quality and disease susceptibility in blueberry. However, the underlying molecular mechanisms remain poorly understood. This study aimed to investigate the molecular and physiological factors associated with corolla abscission by comparing two blueberry cultivars with contrasting corolla abscission characteristics: the caducous 'Magica' ('F6') and the persistent 'Eureka-Sunrise' ('L25').

Cytological analysis revealed distinct structural differences in the abscission zone (AZ) between the two cultivars. In 'F6', cell separation occurred after full bloom, whereas AZ cells in 'L25' remained intact and gradually resembled adjacent tissues. To explore the molecular basis of these differences, transcriptome analysis was performed at three developmental stages. Differential expression and enrichment analyses indicated that genes related to plant hormone signaling, cell wall organization, and oxidative stress response were consistently involved. Weighted gene co-expression network analysis further identified modules associated with cultivar-specific traits, with genes related to ethylene and abscisic acid pathways showing higher expression in 'F6', while those associated with auxin metabolism and stress-related processes were more active in 'L25'. To validate these findings, the activities of cell wall-related enzymes were measured. Polygalacturonase activity increased at the stage corresponding to abscission initiation in 'F6', while remaining relatively low in 'L25'. In addition, cellulase activity was consistently higher in 'F6' than in 'L25'.

These results indicate that corolla abscission in blueberry is associated with coordinated changes in hormone-related pathways and cell wall modification. Differences in the regulation of these processes between cultivars may contribute to variation in abscission behavior.