Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2002
Publication Date: 4/5/2002
Citation: Kim, M.S., Moore, P.H., Zee, F.T., Fitch, M.M., Steiger, D.L., Manshardt, R.M., Paull, R.A., Drew, R.A., Ming, R. 2002. Genetic diversity of carica papaya as revealed by aflp markers. Genome. 45:503-512. Interpretive Summary: To determine patterns of genetic relationship in a large collection of Caricaceae (5 genera, 34 species) spanning different geographic origins, compare results with previous papaya characterization research and discover the intravarietal variation in papaya. Also, because it has demonstrated a common phylogenetic origin with the Brassicaceae, and consequently with the completely sequenced model plant Arabidopsis. The differences between papaya and six other Carica species were substantial, with the average genetic similarity 0.432, ranging from 0.296 to 0.545. The average genetic similarity between the six Carica species was 0.729 ranging from 0.634 to 0.87. Carica papaya appears to be significantly different from other Carica species. The impact of inbreeding on narrowing the germplasm diversity evaluated among diverse materials can be used in germplasm management, varietal protection and papaya improvement by helping to point to related materials if something interesting is found in standard evaluation trials. The 10% of the papaya germplasm tested from the National Clonal Germplasm Repository indicate the collection preserves the vast majority of the natural variation found in papaya. The estimates of genetic similarity are particularly useful in choosing widely divergent parents with desirable traits for genetic mapping and selection.
Technical Abstract: Genetic relationships among Carica papaya cultivars, breeding lines, unimproved germplasm, and related species were established using amplified fragment length polymorphism (AFLP) markers. Seventy-one papaya accessions and related species were analyzed with nine EcoRI-MseI primer combinations. A total of 186 informative AFLP markers was generated and analyzed. Cluster analysis suggested limited genetic variation in papaya, with an average genetic similarity among 63 papaya accessions of 0.880. Genetic diversity among cultivars derived from the same or similar gene pools was smaller, such as Hawaiian Solo hermaphrodite cultivars and Australian dioecious cultivars with genetic similarity at 0.921 and 0.912, respectively. The results indicated that self- pollinated hermaphrodite cultivars were as variable as open-pollinated dioecious cultivars. Genetic diversity between C. papaya and six other Carica species was also evaluated. Carica papaya shared the least genetic similarity with these species, with an average genetic similarity of 0.432; the average genetic similarity among the six other species was 0.729. The results from AFLP markers provided detailed estimates of the genetic variation within and among papaya cultivars, and supported the notion that C. papaya diverged from the rest of Carica species early in the evolution of this genus.