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Efficient protocols for in vitro shoot growth and ex vitro root formation from in vitro-derived shoots under light-emitting diodes (LEDs) with simple ventilation were developed for rabbiteye blueberry cv. ‘Titan’. Red LEDs promoted shoot elongation while blue LEDs induced short shoots with enhanced accumulation of leaf chlorophyll contents. A combined treatment of 80% red with 20% blue LEDs was found the most suitable for plant growth, and more effective than 50% red mixed with 50% blue LEDs or fluorescent lamps as the control treatment. The use of ventilated vessels with ambient CO2 enrichment from a growth chamber resulted in healthy plants having greatly improved shoot length, leaf expansion, leaf chlorophyll contents and dry weight of both shoots and roots. In vitro-cultured shoots could be directly rooted at 100% under non-sterile conditions using a perlite-peat mixture with careful controls of high humidity. These results suggest that LEDs, particularly when coupled with ventilated vessels, should be used as a primary light source for replacing conventional fluorescent tubes in large-scale production of rabbiteye blueberries.

Light-emitting diodes (LEDs) are useful for the growth of many plants, but not known for blueberry species. This study examined the effects of fluorescent lamps and 100 % red, 80 % red plus 20 % blue, 50 % red plus 50 % blue, and 100 % blue LEDs on the growth and development of highbush blueberry shoots under aseptic and non-aseptic conditions. Results revealed that monochromatic blue LEDs accumulated the highest contents of leaf chlorophylls. In contrast, monochromatic red LEDs inhibited chlorophyll accumulation, but produced the longest shoots and roots and provided high percentages of side shoot formation from ex vitro plants. Mixed LEDs, particularly 50 % red plus 50 % blue light, improved plant growth with respect to notably increased shoot and root biomass. Direct rooting of in vitro shoots under non-aseptic conditions was readily achieved using a commercial mixture of perlite and peat moss with high humidity controls. These findings obviously suggest the efficient use of LEDs to replace traditional fluorescent lamps in large-scale propagation of the highbush blueberry, and also pave the way for future studies on LEDs for standardizing micropropagation protocols to shrub crops and woody plants.