Increased consumption of blueberries has led to a prominent rise in demand. However, Georgia blueberry production is limited by challenges including short orchard life of southern highbush (SHB; tetraploid) and fruit quality issues associated with rabbiteye (RE; hexaploid) varieties. Interspecific hybridization can bring in beneficial alleles to improve the local adaptability and fruit quality of commercial varieties. Many of the wild blueberry germplasm with valuable soil adaptability and fruit quality traits such as V. fuscatum are diploids. Heteroploid crossings between SHB and diploid wild blueberry were shown to have a very low level of success. Ploidy induction through tissue culture is promising to circumvent the ploidy barrier and improve the efficiency of wide-hybridization. The objective of this research focuses on developing a ploidy induction protocol using two SHB varieties ‘Emerald’ and ‘Rebel’. SHBs previously initiated in tissue culture, were treated with 0%, 0.02% and 0.2% colchicine. SHBs were segmented into single and double node segments and put into woody plant medium (WPM) culture media containing either 6-(γ,γ-Dimethylallylamino)Purine (2iP) or trans-Zeatin. The treatments, along with non-treated control, were grown in a growth chamber of 26°C with 16/8 day and night cycles. The number and length of new shoots were recorded 35 and 50 days after treatment (DAT). Significant longer axillary stem growth was observed in the non-treated control compared to that of colchicine-treated segments for both SHBs indicating the suppressive effect of stem growth from colchicine treatments. Several Octo- and mix ploidy-shoots of ‘Emerald’ and ‘Rebel’ were identified among colchicine-treated SHB explants after ~ 21 weeks using a flow cytometer. Both levels of colchicine treatments generated octoploids. These new synthetic octoploid blueberries will be useful to cross with SHB and RE blueberries. The established ploidy induction protocol will be utilized to double the chromosomal levels of diploid V. fuscatum species and make them cross-compatible with SHB varieties.
