Breeding blueberries for the Florida climate.

Abstract

R. H. Sharpe and G. M. Darrow1 When Coville wrote his classic article (1) on early development of blueberries from the wild to the cultivated state, brief mention was made of the ease of crossing the southern species Vaccinium myrsinites with the northern highbush species. Both were tetraploid with 48 chromosomes in somatic cells. Attempts to cross northern highbush with two northern 24-chromosome or diploid species resulted in complete failures or weak, unproductive plants. Identification of V. ashei, the rabbiteye blue berry of northern Florida and south Georgia, as a hexaploid with 72 chromosomes, and crosses of it with northern highbush and 24chromosome species have been described by Darrow et al (2). The 24-chromosome Florida evergreen species, V. darrowi, was thought to be of particular interest in breeding blueberries for Florida because of its blue fruit, drought resistance and far southern range (3). Suc cess in combining qualities from the highbush, rabbiteye, and Florida evergreen species, al1 Associate Horticulturist, University of Florida, and Prin cipal Horticulturist, U.S.D.A. retired, respectively. Florida Agricultural Experiment Station Journal Series. No. 954. though not yet final, is far enough along to warrant a progress report of this work. Highbush x Florida Evergreen Forty seedlings of highbush by V. myrsi nites were observed at Gainesville in 1952 and did not look impressive. Growth was badly delayed, not starting until after April 15, while adapted kinds were in growth by Febru ary 15. The limited fruits produced were black and unattractive. Further breeding may be useful if the V. myrsinites parents are care fully selected, but this has not yet been done. Rabbiteye x Darroufs Evergreen Blue-fruited plants with a minimum winter cold requirement for use in breeding appeared to be best found amongst native plants of the Winter Haven, Lake Wales, Orlando areas. Hence, collections were made during the fruit ing season in 1951 and 31 selected plants were established at Gainesville. These appeared to be the 24-chromosome species V. darrowi, so it was planned to cross them first with V. ashei to obtain tetraploid plants with 48 chromosomes. These should then cross readily with the northern, tetraploid, highbush type to give blue-fruited plants with good drought