Application of DNA Based Molecular Marker for the Assessment of Genetic Transformation in Citrus Sinensis

In the present study, Random amplified polymorphic DNA (RAPD) and Simple Sequence Repeat (SSR) markers were used to study the occurrence of graft transformation in Citrus sinensis plants. Elite Citrus sinensis scion plants were grafted to wild Citrus sinensis plants collected from Manipur region. Ten decamer oligonucleotide primers along with two SSR primers were used to amplify genomic DNA extracted from leaf samples. A total of 17 strong, unambiguous amplicons were generated. Primer OPAT04 detected one amplicon (1350 bp) in grafts which is present in rootstock but not in scions. This is an instance of transmission of genetic material from stock to scion. OPAD10 primer amplified one excess amplicon of 1000 bp, not found in scion or stock but only noticed in grafts. SSR primer CCSM147 with AG repeat revealed the absence of a 100 bp amplicon in two graft plants which was present in scions. The result indicated that after grafting the genetic fidelity is not maintained in the grafts. The absence of amplicons may be explained as gene silencing by transcriptional down regulation. Genetic transformation may be used for improvement of horticultural and agronomic traits of agriculturally important fruit crops by correlating the molecular marker and phenotypic manifestations.