Elucidation of the Mechanism Underlying Seedless Blueberry Formation after GA3 Treatment Based on the Phenotype, Physiology, Metabolism and Transcriptome

Blueberry fruits are rich in anthocyanins with antioxidant and antiaging functions. GA3 is a plant growth regulator that can induce seedlessness, that is the seed in the fruit is absent or only a small part of the tissue remains, but there is no complete seed structure. To improve the palatability and fresh food quality of rabbiteye blueberry, on the 5th and 10th days after full bloom, GA3 was applied at concentrations of 25, 50 and 100 mg/L to groups in treatments denoted as GA25, GA50 and GA100, respectively. The high-concentration treatment (GA100) induced the formation of seedless blueberry fruits. Although the seeds did not grow normally, fruit production was not inhibited. The content of IAA hormones in the GA100 group was higher than that in the CK group, while ABA-promoted maturation was weaker than that in the CK group. A total of 946,555,024 clean reads were obtained from the transcriptome of the blueberry fruits treated with different GA3 concentrations. A total of 198 genes were annotated to the plant hormone signal transduction pathway. Among them, 18, 17, and 12 DEGs were involved in this pathway in the CK vs. GA100, GA50 vs. GA25, and GA100 vs. GA25 group comparisons, respectively. Interestingly, the four GA3-related genes were barely expressed in the CK group but were induced by exogenous GA3. This study provides valuable reference data for the production of seedless blueberry fruits, the improvement of fruit quality and related practical applications.