Submitted to: Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/15/2003
Publication Date: 7/15/2005
Citation: Nakata, E., Staub, J.E., Lopez-Sese, A.I. 2005. Genetic diversity in japanese melon (cucumis melo l.) as assessed by random amplified polymorphic dna and simple sequence repeat markers. Euphytica. Interpretive Summary: Plant species differ genetically for visual (phenotype) and cellular (pertaining to the cell) traits. Fruit yield and fruit quality are examples of phenotypic traits. The analysis of DNA (contained in the cell) of organisms is now used to determine differences between plants. The biotechnological tool associated with the analysis of DNA is called molecular marker analysis. Molecular markers are segments of DNA used to identify differences in DNA between organisms. Melon varieties differ in their plant habit (stature as small or large) and their DNA. Although Japanese melons differ in phenotype from U.S. melon types, the extent of differences in their DNA is not known. There are many attributes in Japanese melon types that might be used to improve U.S. melon (e.g., pest and disease resistance, fruit quality, and long self life). However, in order for U.S. public and private plant breeders to utilize Japanese melon types in their plant improvement programs, the DNA variation (differences) among Japanese types must be characterized and compared to the U.S. melon types. Therefore, an experiment was designed and executed to determine the DNA variation among Japanese melon types and contrast them with the DNA of U.S. melon market classes (i.e., Western Shipping and Eastern Market types). The data indicate that U.S. and Japanese melon are very different in both phenotype and DNA. The data also provide the plant breeder with working strategies for the incorporation of genes from Japanese melon into U.S. melon types. This will allow the plant breeder to work more efficiently and effectively, and thus shortened the time to develop improved melon varieties for U.S. consumption. Improved melon varieties will in turn make the U.S. grower more competitive while providing an unique product to the U.S. consumer.
Technical Abstract: The genetic diversity among 67 melon (C. melo L.) cultivars from five Japanese seed companies was assessed using 25 10-mer RAPD primers (56 bands) and 9 SSR (36 alleles) markers. These cultivars belong to three botanical varieties (groups) spanning eight melon cultivar-groups: Group Cantalupensis (cultivar-group Earl's, House, Galia, Charentais, and Ogen), Group Inodorus [cultivar-group Honeydew and Casaba (cultivars Amarillo, Piel de Sapo, Rochet, Negro, Crenshaw, and Tendral)], and Group Conomon (cultivar-group Oriental). Genetic variation among these cultivars was compared to variation in a reference array (RA) consisting of 34 selected melon accessions from previous studies. This RA characterized the genetic diversity in U.S. and European cultivar-groups mostly in Group Cantalupensis (Galia, Ogen, Charentais, and U.S. and European Shipper) and Group Inodorus [Honeydew and Casaba (Piel de Sapo, Rochet, and Amarillo)], as well as African germplasm. While 11 of 15 Japanese Oriental accessions formed one grouping with South African accessions in the RA after cluster analysis, the other Group Conomon Japanese accessions grouped either with Casaba or with Honeydew cultivars. Japanese Group Conomon accessions and South African accessions in the RA formed a genetic group that was distinct from all other accessions studied, and suggests an Asiatic origin for South African melon germplasm. The majority of Japanese House and Earl cultivar-group accessions shared genetic affinities and were genetically different from the Japanese Group Inodorus accessions examined. These Japanese accessions were most similar to Casaba RA accessions. Japanese Galia accessions were similar to either House and Earl's cultivar-goups or Galia, Ogen, Casaba, and Honeydew RA accessions. Genetic analysis indicates that the Japanese melon germplasm studied can provide opportunities for broadening the genetic base of melon cultivars of western origin