Molecular discrimination of lemon cultivars

Some lemon [Citrus Union (L.) Burm. f.] cultivars present compatibility problems with commonly used citrus rootstocks. Therefore, assessing trueness-to-type of lemon mother trees is needed by growers. Morphological differentiation of lemon cultivars is not precise because they present high phenotypic plasticity. The objective of this paper is to contrast the discriminatory ability of several molecular marker systems for lemon. Three marker types were used: randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeats (ISSR) and inter-retrotransposon amplified polymorphism (IRAP). The molecular variability found in C. limon is larger than that reported for C. clementina, another vegetatively propagated citrus species. This difference in variability content might be explained by differences in the distribution and age of both cultures. Similar to clementines, polymerase chain reaction (PCR) markers using primers anchored in copya-like retrotransposons resulted in a higher rate of polymorphisms (36.4%) than did primers of random sequence (27.3%) or those anchored at simple sequence repeats (0%), indicating a higher molecular variability at the locations where these retrotransposons inserted. Primers anchored in gypsy-like retroelements did not yield polymorphisms. Lemon cultivars from important groups such as 'Eureka', 'Fino', and 'Verna' could be distinguished using all polymorphisms.