Random amplified polymorphic DNA (RAPD) markers were used to detect chimerism of citrus cultivars. Polymerase chain reaction conditions suitable for discriminating citrus chimeras were determined. Primers that produced consistent and repeatable bands that differed between the parental cultivars were chosen to create discriminating band patterns. Our results show that selected 12-mer primers can be useful for identifying the four citrus chimeras tested using RAPD technology.
Randomly amplified polymorphic DNA (RAPD) analysis was used to investigate the histogenic structure of leaf and fruit tissues in four graft chimeras, two intentional chimeras that were produced in combination with `Hamlin' orange [Citrus sinensis (L.) Osbeck] and `Satsuma' mandarin (C. unshiu Marc.), and two naturally occurring periclinal chimera cultivars, Kobayashi Mikan (a graft chimera of C. unshiu and C. natsudaidai Hayata), and Kinkoji Unshu (a graft chimera of C. unshiu and C. obovoidea hort. ex Takahashi). RAPD profiles of the lamina epidermis and the mesophyll cells of specific individuals indicated that the four graft chimeras were interspecific monekto chimeras, whose outermost layer (histogenic layer L-1) of the shoot apical meristem consisted of a species that was different from that in the inner layers (histogenic layers L-2 and L-3). Moreover, juice vesicles, which develop from the inside cells of the pericarp and become the main edible parts of Citrus fruit, were a mixture of the cells from both parental source cultivars. Therefore, the vesicles were at least composed of L-1 and subepidermal inner L-2 cells. This determination of interspecific chimeral construction (which was made possible by molecular techniques) is a valuable finding, in terms of improving Citrus through intentional use of periclinal chimerism.