The 2012 ASHS Annual Conference

The objective of this study was to evaluate vegetative growth of highbush blueberry plants derived from micropropagation and softwood cuttings under field conditions. The experiment was conducted at two locations with different average chill hour accumulation per season (temperatures from 0–7 °C): Citra, FL (420-540 chill hours) and Haines City, FL (110–220 chill hours) respectively.  ‘Emerald’, ‘Jewel’, and ‘Primadonna’ were planted in a completely randomized block design with six treatments and five replications. Whole plants were harvested at four biologically significant points during the study: at planting, after the first growing season, after the first harvest, and after the second growing season. Average plant height and width, number major canes, and total shoot number were determined from 10 plants per treatment at planting and from one plant per replication at the other sampling dates. Stems arising from the first 12 cm above the soil line with a minimum diameter of 7 mm were recorded as major canes. Subsequently, plants were divided into roots, crowns, canes, shoots, and leaves, and dry weights were obtained for each. Results were evaluated by analysis of variance and treatments were compared using Tukey’s HSD test at 5% significance level (SAS 9.2). Micropropagated plants of the three cultivars had more major canes and greater plant dry weight than plants from rooted cuttings at planting and after the first growing season. Location by propagation interaction was not significant, except for plant width and root to shoot ratio, and differences among propagation types were observed in Citra but not in Haines City. After the first harvest, treatment means across locations showed a significant increase in height, width, volume, number of canes and shoots, and cane and plant dry weights for micropropagated ‘Emerald’ and ‘Jewel’ compared to cutting-derived plants, but there was no significant effect on size or dry weight of ‘Primadonna’. By November 2011, cane and total shoot dry weights of micropropagated 'Emerald' and 'Jewel' plants were greater than plants from softwood cuttings, but plant dry weight was only greater for micropropagated 'Jewel' plants. Micropropagation resulted in higher leaf dry weight at the end of each growing season in Citra but not in Haines City. After the second growing season, micropropagated plants of all cultivars had more canes, total shoot number was greater only for micropropagated ‘Jewel’ plants, and there was no significant effect of propagation method on total shoots, size, or dry weight for 'Primadonna'.