PHYLOGENETIC-RELATIONSHIPS AMONG SELECTED CITRUS GERMPLASM ACCESSIONSREVEALED BY INTER-SIMPLE SEQUENCE REPEAT (ISSR) MARKERS

ISSR markers were analyzed to study phylogenetic relationships among 4 6 Citrus L. accessions representing 35 species. A dendrogram based on the unweighted pair-group method, arithmetic average cluster analysis was constructed using a similarity matrix derived from 642 polymorphic ISSR fragments generated by 10 primers. These 46 accessions could be classified into five major groups: 1) C. indica Tan.; 2) C. maxima (Bu rm.) Merrill; 3) lemon [C. limon (L.) Burm.] or lime [C. aurantifolia (Christm.) Swingle] type accessions; 4) C. halimii B.C. Stone; and 5) sour orange (C. aurantium L.), mandarins and their hybrids. Group 5 wa s further divided into three subgroups. Although some previous work ha d grouped it with mandarins, C. indica appeared to be a distinct genot ype or species that was not close to mandarins. C. tachibana Tan. grou ped closely to mandarins. C. vulgaris Risso was not related to sour or ange but was similar to accessions usually classified in the lime or l emon group. Sour orange and its hybrids, C. nippokoreana Tan, C. hanay u Hort. ex Shirai, C. sudachi Hort. ex Shirai, and C. yuko Hort, ex Ta n. had close phylogenetic relationships with mandarins. Although the m andarin accessions studied were divergent in morphology, the genetic d istances among them were relatively small. Relationships among these C itrus accessions revealed by ISSR markers were generally in agreement with previous taxonomic classifications.