Assessment of clonal fidelity of micro-propagated guava (Psidium guajava) plants by ISSR markers

Inter-simple sequence repeat (ISSR) was used to assess the genetic stability of micro-propagated plantlets of guava. Thirty one plantlets were chosen from a clonal collection of shoots that originally from a single mother plant. Out of 21 ISSR primers screened, 16 primers were found to produce clear, reproducible bands resulting in a total of 93 distinct bands with an average of 6.5 bands per primer. Of these 93 bands, 84 were monomorphic across all 31 of the plants tested and 9 showed polymorphisms (9.67% polymorphisms). Based on the ISSR band data, similarity indicators between the progenies and the mother ranged from 0.92 to 1.0, such a similarity indicated a very low polymorphism. These similarities indices were used to construct an UPGMA dendrogram and demonstrated that all 31 micro-propagated plants grouped together in one major cluster with a similarity level of 92%. A total of 2356 scorable bands were obtained from the full combination of primers and plantlets and only 39 (1.65%) were polymorphic across the plantlets which indicated that the micro-propagated guava is genetically stable.