Submitted to: Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/2/2008
Publication Date: 11/1/2008
Citation: Luan, F., Dellanay, I., Staub, J.E. 2008. Melon (Cucumis melo L.) Diversity Analyses Provide Strategies for Germplasm Curation, Genetic Improvement and Evidentiary Support of Domestication Patterns. Euphytica. 164(2)-445-461. Interpretive Summary: Cucumis (taxonomic designation for genus) plant species of the taxonomic family Cucurbitaceae are indigenous to the native flora of Africa, India, and various regions of the Middle East. Two Cucumis species, cucumber and melon are important economically worldwide. While cucumber originated in Asia, likely on the Indian subcontinent, melon is thought to have originated in Africa. Edible melons are divided into six botanical groups. Several of these groups are economically important to developed countries based on their culinary attributes. They also differ markedly in fruit characteristics such as netting, shape, interior texture, flavor, aroma, and shelf life to form specific commercial market classes. A knowledge of the genetic factors controlling these types of differences allows plant breeders to improve melon cultivars. In order to improve the performance of melon of commerce, it is important to know the genetic diversity (GD; genetic variation or differences between plants) of melons from different geographic regions at the DNA level. Alhtough GD of many melon types are known, the GD of Chinese melon types is not known. Obtaining estimates of genetic diversity is extremely important to plant improvement since it increases the efficiency and effectiveness of selection of improved cultivars. Thus, a study was undertaken to define the GD of 68 Chinese accessions in relation to other melon accessions of worldwide origin using DNA analysis. DNA analysis indicated that GD among and between Chinese and other melon accessions was great and allowed for the identification of potential parents for hybrid production to increase yield and quality. Public and private plant breeders can use this information to increase to develop new, more genetically diverse melon varieties more effectively by intercrossing U.S. and Chinese accessions. This information provides for opportunities for growers to increase their global competitiveness through increased yield and quality of the melons that they produce.
Technical Abstract: The genetic diversity of melon market types (Cucumis melo L., 2n = 2x = 24) in China, an important secondary center of diversity, has not been examined. Therefore, reference accessions (India, Africa, Crete/Greece, Japan, Europe, USA, and Spain) and 68 Chinese cultigens (fresh market non-netted thin skinned, non-netted thick skinned, netted thick skinned, and non-netted thin skinned vegetable) were evaluated using 17 10-mer RAPD primers, days to flower, lateral branch number, and fruit number and weight per plant. While Chinese thin-skinned melon differed from vegetable melon types only in sex expression, the U.S. Western Shipping market type reference accession ‘Top Mark’ and Chinese thick-skinned melon were similar for all of the morphological traits examined. The average similarity (Jaccard Coefficient) between any two pairs of accessions examined as estimated by RAPD variation was 0.47 ' 0.14. Within-group genetic similarities ranged between 0.94 (thin skin type) and 0.08 (non-netted thick skin type). The average/standard deviation, maximum, and minimum similarity between any two Chinese reference accessions was 0.41 ' 0.13, 0.75, and 0.12, respectively. Cluster analysis partitioned accessions into two main branches consisting of Group Cantalupensis and Inodorus reference accessions and Chinese accessions. A second cluster analysis partitioned China, India and Africa accessions into a major clade, and accessions from Crete/Greece, Japan, Europe, USA, and Spain into a second major clade. Results indicate that Chinese accessions are a rich source of genetic diversity for plant improvement, and that molecular assessments support previously described theoretical melon domestication patterns constructed from historical and archeological evidence.