GENETIC-VARIATION AMONG TOMATO ACCESSIONS FROM PRIMARY AND SECONDARY CENTERS OF DIVERSITY

The Asian Vegetable Research and Development Center (AVRDC) maintains one of the largest collections of Lycopersicon germplasm. Approximatel y 60% of the collection is from Old World regions; however, it is uncl ear whether these accessions represent unique sources of genetic varia tion compared with accessions from New World regions. The objective of this study was to compare the magnitude and structure of genetic vari ation among tomato accessions collected from Old and New World regions . Forty-one random amplified polymorphic DNA (RAPD) primers generated 98 polymorphic RAPD markers and were used to estimate relationships am ong 96 accessions collected from a wide geographic range. Genetic dist ances, marker frequency, and marker diversity were used to compare sub populations of these accessions. Differences in RAPD marker frequencie s indicated uniqueness of accessions from the New and Old World collec tions. In addition, accessions from Ecuador, Peru, and Chile had a lar ger magnitude of marker diversity than do Old World accessions. Compar ison of sub-populations of L. esculentum and its sub-species, L. escul entum var. cerasiforme, indicated that the two are distinct but have s imilar levels of diversity. Variation among L. esculentum accessions c an be obtained at a faster rate by sampling accessions from the primar y center vs. other geographic regions. Yet Old World accessions comple ment accessions from the New World and are not simply redundant source s of variation.