Simple Sequence Repeat (SSR) profiling of cultivated Limau Madu (Citrus reticulata Blanco) in Malaysia

Introduction. In Malaysia, Limau Madu (Citrus reticulata Blanco; Citrus suhuiensis Hort. ex Tanaka) is commercially cultivated for local consumption. It is a loose-peel mandarin with fruits that are spherical in shape with shiny green or greenish yellow peel. In Malaysia, Limau Madu is vegetatively propagated, thus it is presumed to exhibit minimal variability. In our study, the genetic variability and genetic relatedness among cultivated samples collected from different states in Malaysia were assessed using Simple Sequence Repeat (SSR) primers. Materials and methods. Thirty pairs of SSR primers derived from Citrus unshiu were screened and 22 SSR primer pairs were utilized to assess genetic variability and relatedness among 118 cultivated samples. Results and discussion. The percentage of SSR transferability from C. unshiu to C. reticulata (Limau Madu) was 73.33%, which indicated that the primer sequences flanking simple sequence repeats were conserved among these Citrus species. Most SSR loci revealed a large excess of heterozygotes. In our study, low allelic diversity was shown, with an average of 5.227 alleles per locus. Polymorphic information content (PIC) ranged from 0.048 to 0.674. Based on UPGMA clustering analysis, four groups were identified from these citrus genotypes with a mean genetic distance of 0.170. Low genetic variability within species was probably due to vegetative propagation or inability to detect differences among samples using these primers.