Reproductive Growth and Yield of Three Southern Highbush Blueberry Cultivars Obtained from Micropropagation and Softwood Cuttings in Two Florida Locations

The objective of this study was to evaluate reproductive growth and yield of southern highbush blueberry plants derived from micropropagation and softwood cuttings during the initial field establishment years. The experiment was conducted at two locations with different average chill hour accumulation per season (temperatures from 0 °C to 7 °C): Citra, FL (420–540 chill hours) and Haines City, FL (110–220 chill hours), respectively.  ‘Emerald’, ‘Jewel’ and ‘Primadonna’ were planted in March (Citra) and April (Haines City) 2010 in a completely randomized block design, with five replications. Two plants per replication were selected and total number of canes, total shoots, and flower buds per plant were recorded in December 2010 (Haines City) and January 2011 (Citra). The same plants were harvested from March 28, 2011, to June 6, 2011, and total fruit yield and berry weight were calculated. One plant per replicate was selected the second year, and total flower buds per plant were estimated by counting the flower buds on two to four representative major canes and visually estimating what percentage of the whole plant the sample represented. Results were evaluated by analysis of variance and treatments were compared using Tukey’s HSD test at a 5% significance level (SAS 9.2). Location by propagation was not significant and means compared are averages of both sites.   Micropropagated ‘Emerald’ plants had significantly more flower buds during the first reproductive season. Propagation method had no effect on flower bud numbers for the other two cultivars. Micropropagation resulted in 42 and 58% yield increase for 'Emerald' and 'Jewel' plants, respectively. Total number of shoots per plant and yield of both micropropagated ‘Emerald’ and ‘Jewel’ plants were significantly greater  than for softwood cutting- derived plants, with no significant effect of propagation type on yield of ‘Primadonna’. Linear regression analysis showed a positive correlation between total number of shoots per plant and yield for 'Emerald' and 'Jewel' in both locations and for all three cultivars in Haines City. Location did not significantly affect total flower buds per plant during the second reproductive season, but there was a significant location by cultivar interaction: in Haines City, ‘Jewel’ and ‘Emerald’ had more flower buds per plant than ‘Primadonna’, with no significant difference between cultivars in Citra. 'Emerald' and 'Jewel' micropropagated plants had significantly more flower buds than plants derived from softwood cuttings, with no effect of propagation method on flower buds for 'Primadonna'.