Presence of triploid cytotypes in the common fig (Ficus carica L.)

Abstract

Ficus carica (2n = 26) is one of the oldest fruit trees of the Mediterranean basin. Recently there has been increasing interest in this species, in particular for questions related to germplasm such as genetic diversity and cultivar identification. This study was undertaken to gain more knowledge of F. carica cytogenetics and provide data useful for the characterization of its germplasm. Karyomorphological analysis and physical mapping of 18S-25S and 5S rRNA genes by the FISH technique contributed to defining the basic traits of the chromosome complement of F. carica. However, the most interesting result was the discovery of triploid (2n = 39) cytotypes of the cultivated common fig. This result demonstrates the importance of cytogenetic investigations in studies of fig germplasm and emphasizes the role of cross-fertilization as a source of variability not only in wild populations but also in cultivated forms. The results of pollen analysis suggest spontaneous sexual polyploidization as a possible origin of triploid cytotypes. Further studies are necessary to clarify the origin and effective spreading of polyploidy, the presence of other ploidy levels, and their distribution in wild and cultivated forms.