Isozyme Variation in Indian and Chinese Melon (Cucumis melo L.) Germplasm Collections

Abstract

Genetic variation among 378 melon (Cucumis melo L.) germplasm accessions collected in India in 1992 and 26 accessions in China in 1994 was evaluated with 19 isozyme loci. `Top Mark' and `Green Flesh Honeydew', which represented two distinct C. melo ssp. melo L. groups, Cantalupensis and Inodorus, respectively, were used as reference cultivars. Genetic distances among accessions were calculated, and an initial cluster analysis using these distances resulted in 148 groups of varying size, ranging from two to 47 accessions. One accession from each of the 148 groups was chosen at random and used in a second cluster analysis that identified 11 accession groups. Group 1 was unique and consisted of only two C. melo ssp. agrestis (Naudin) Pangalo accessions. Two large branches were detected at cluster node 2. One branch was comprised of three groups of 3, 12, and 34 accessions, while the other branch contained seven groups of 2, 3, 14, 16, and 47 accessions, and the reference cultivars. Of the 148 accessions, 132 were from 41 sites in Rajasthan and Madhya Pradesh, India, which were distributed unequally across the 11 groups. The 14 Chinese accessions originating from seven provinces were also dispersed unequally in the four major cluster groups. `Top Mark' and `Green Flesh Honeydew' were genetically distinct and uniquely clustered in the same group. These results indicate that additional collections of melon germplasm should be made in eastern and southern India.