Study On Citrus Identification And Taxonomy By Using AFLP Markers

Study on Citrus Identification and Taxonomyby using AFLP markersCandidate: Xiong Guangming Supervisor: Pro. Liang GuoluCitrus is the. major commercial fruit crop in the world. The taxonomic relationships of the species of the genus Citrus, however, have given rise to a certain amount of confusion since they produce both sexual and asexual progenies called "nucellar" embryos. Two taxonomic systems have been generally proposed for this genus: one is Swingle s system including 16 species and the other is Tanaka s system including 162 species. In recent years, several numerical taxonomic studids, biochemical studies on isozyme patterns, RFLP and RAPD have been carried out enable the identification and classification of the species of the genus Citus. Based on some of these experimental systematic analyses, only three basic taxa in the subgenus Citrus of the genus Citrus have been identified: C.grandis, C.reticulata and C.medico.The document of morphological, palynological is used in the old taxonomic study. However, new plant taxonomy has studied genetic strusture and physiological function from molecular level, and associated with cytogenetics, biochemistry and mathematics.A novel multilocus DNA fingerprinting technique, named AFLP, has been proven its potential for systematic botany. In the study, 87 biotypes (16 species in Swingle system ) were evaluated by AFLPs to estimate genetic relationships within the genus, and the position of ichangensis in Citrus classification was discussed, raising that it will be more reasonable to put Citrus ichangensis Swingle into section Pepeda . The possible ancestors of some biotypes were postulated. On the polyphenetic tree of cluster analysis, the evolutionary tendency of Citrus plant can been found according to the distance similarity confficients among sections. At the systematic development of subgenus Citrus, this experiment assists to the "thee basic species" hypothesis. Finally, proposing that only when molecular systematic study was associated with morphological taxonomic, palynological taxonomic, numerical taxonomic, chemitaxonomic and cytotaxonomic studies, then we will draw a good conclusion on Citrus.