Effect of explant type, culture medium, and BAP concentration on in vitro shoot development in highbush blueberry (Vaccinium corymbosum L.) cultivars

Blueberry (Vaccinium corymbosum L.) is an important horticultural crop with many nutraceutical values. With increasing market demand, high-quality virus-free planting materials are critical for growers. As such, micropropagation techniques that produce a greater number of shoots and subsequently plantlets can meet the needs of growers and provide materials for gene editing and genetic transformation. Therefore, a study was conducted to compare the effect of three factors: explant type (shoot tip and two-node explants obtained from in vitro grown plants), culture medium (Chee and Pool (C2D) and Lloyd and McCown Woody Plant Medium (WPM)), and 2.0, 4.0, 6.0, or 8.0 mg L-1 6-benzylaminopurine (BAP) on shoot production from two highbush blueberry cultivars, "Farthing" and "Legacy." The results showed that WPM was better than the C2D medium for both cultivars. For the "Farthing" cultivar, WPM supplemented with 6.0 mg L-1 or 8.0 mg L-1 of BAP produced higher number of shoots when shoot tips and two-node shoot explants were used, respectively. For the "Legacy" cultivar, WPM supplemented with 4.0 mg L-1 of BAP was ideal media for either shoot tip or two-node explant. Although shoot production from the C2D medium was lower than from WPM, the ability of the C2D medium to proliferate shoots from explants could indicate a possibility for its optimization. Shoots obtained from all treatments produced roots on rooting media. Results from this research establish a starting point for the selection of optimum conditions for greater shoot production when different explant types, culture media, and BAP concentrations are used.