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Unexpected variations in flowering and fruiting occur in clonally propagated, purple-fruited pitanga (Eugenia uniflora ‘Zill Dark’) grown in Kona, Hawai’i USA

Griffis, J. L. Jr., McDonald, T. G., Tuncay, O., Manners, M. M.
Acta horticulturae 2018 no.1216 pp. 65-72
Eugenia uniflora, breeding, clones, cultivars, flowering, fruit crops, fruit trees, fruiting, harvesting, horticulture, nutrition, planting, ripening, rootstocks, seedlings, tropical and subtropical fruits, Brazil, Florida, Israel
Many tropical fruits such as the Brazilian purple-fruited pitanga (Eugenia uniflora) are not well known or widely produced outside of their countries of origin. The reasons many of these minor fruit crops do not become more widely available are complex. However, many of the reasons revolve around a lack of research into appropriate horticultural practices such as propagation, nutrition, pest and disease management, and proper harvesting, handling and processing. Another major missing component is cultivar improvement. The purple-fruited pitanga has several named selections available in Brazil, Israel and the USA, but difficulties with clonal propagation have severely limited their availability. Breeding trials using the purple-fruited pitanga ‘Zill Dark’ were initiated in Florida and seedling fields were planted out for further evaluation in both Florida and Hawai’i where the crop is already known. Additionally, twenty veneer-grafted ‘Zill Dark’ pitanga were also planted in the Hawaiian field to provide production data and to serve as comparisons to the seedlings. Scionwood was all obtained from the same ‘Zill Dark’ plant and seedling rootstocks were all grown from seed produced by the same plant that provided the scionwood, as there are no clonal rootstocks available for pitanga. In 2013, five years after the planting of the veneer-grafted ‘Zill Dark’ pitanga, collection of flowering and fruit production data from both the grafted trees of ‘Zill Dark’ and the seedlings was initiated. As a rule, clonally propagated fruit trees of the same cultivar that are the same age, planted in the same field and fertilized, irrigated and pruned in the same manner are expected to produce similar fruiting and flowering results. However, in the Hawaiian field there were statistically significant differences in both times of flowering and ripening of fruit among the ‘Zill Dark’ clones. Why these clonally propagated fruit trees do not have well-synchronized production schedules is unclear; possible causes for this dissimilarity are examined.