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United States Department of Agriculture

Agricultural Research Service

Title: Isozyme Variation in Indian and Chinese Melon (Cucumis Melo L.) Germplasm Collections.

Authors
item McCreight, James
item Staub, Jack - USDA, ARS, MADISON
item Lopez-Sese, Anabel - USDA, ARS, MADISON
item Chung, Sang-Min - USDA, ARS, MADISON

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 13, 2004
Publication Date: November 1, 2004
Citation: Mccreight, J.D., Staub, J.E., Lopez-Sese, A., Chung, S. Isozyme variation in indian and chinese melon (cucumis melo l.) germplasm collections.. Journal of the American Society for Horticultural Science. 129(6):811-818.

Interpretive Summary: Germplasm from the centers of origin and diversity are important sources of genes for disease and insect resistance as well as other traits for crop improvement. India is regarded as a primary center of diversity for melon while China is regarded as a secondary center of diversity for melon. Two expeditions to collect melon (cantaloupe and honeydew) germplasm carried-out in 1992 and 1994 added approximately 400 and 30 melon accessions from India and China, respectively, and incorporated into the U.S. National Plant Germplasm System. This study examined the genetic variation among 378 of these accessions using 19 isozyme loci in 13 enzyme systems. These accessions were compared to two U.S. reference cultivars, 'Top Mark' and 'Green Flesh Honeydew' that represent the range of genetic variation in two distinct cultivar-groups: orange flesh cantaloupe and green flesh honeydew. The genetic variation among Chinese accessions was less than that detected in the Indian accessions examined; possible reasons for this are discussed. Additional collections of melon germplasm should be made in eastern and southern India to capture additional genetic variation not present in the U.S. National Plant Germplasm System.

Technical Abstract: Approximately 400 and 30 melon (Cucumis melo L) germplasm accessions collections were recently collected in India (1992) and China (1994), respectively, and incorporated into the U.S. National Plant Germplasm System. Genetic variation among 378 of these accessions was evaluated using 19 isozyme loci in 13 enzyme systems. These accessions were compared to two reference cultivars, 'Top Mark' and 'Green Flesh Honeydew' that represent the range of genetic variation in two distinct cultivar-groups of U.S. C. melo subsp. melo: Canalupensis and Inodorus, respectively. Statistics that define genetic variation (Nei's gene diversity, Shannon's information index, genetic distance, heterozygosity, and polymorphism) were calculated for comparative analysis. An initial cluster analysis resulted in 148 groups of varying size, ranging from two to 47 accessions. An accession from each of the 148 groups was chosen at random and used in a second cluster analysis that identified 11 isozyme groups. Group 1 was unique and consisted on only two C. melo subsp. agrestis accessions. Two large clades were separated at node 2. While one was comprised of three groups of 3, 12 and 34 accessions, the other clade had seven groups of 2 (two groups), 3, 14, 16 and 47 accessions, and included the reference cultivars. Of the 148 accessions, 132 were from 41 sites in Rajasthan and Madhya Pradesh, and were distributed unequally across the 11 groups. The 14 Chinese accessions originating from seven provinces were dispersed unequally in four cluster groups. 'Top Mark' and 'Green Flesh Honeydew' were genetically distinct and uniquely clustered in the same group. The variation among Chinese accessions was less than that detected in the Indian accessions examined; possible reasons for this are discussed. Additional collections of melon germplasm should be made in eastern and southern India.

Last Modified: 10/25/2014