Determination of germplasm diversity and genetic relationships among breeding materials is an invaluable aid in crop improvement strategies. This study assessed the breeding value of tomato source material. Two commercial hybrids along with an experimental hybrid and four cultivars were assessed with cluster and principal component analyses based on morphophysiological data, yield and quality, stability of performance, heterosis, and combining abilities. The assessment of commercial hybrids revealed a related origin and subsequently does not support the identification of promising offspring in their crossing. The assessment of the cultivars discriminated them according to origin and evolutionary and selection effects. On the Principal Component 1, the largest group with positive loading included, yield components, heterosis, general and specific combining ability, whereas the largest negative loading was obtained by qualitative and descriptive traits. The Principal Component 2 revealed two smaller groups, a positive one with phenotypic traits and a negative one with tolerance to inbreeding. Stability of performance was loaded positively and/or negatively. In conclusion, combing ability, yield components, and heterosis provided a mechanism for ensuring continued improvement in plant selection programs. 1. Introduction Knowledge about levels and patterns of genetic diversity can be an invaluable aid in crop breeding for diverse applications [1], including analysis of genetic variability in cultivars [2, 3], identifying diverse parental combinations to create segregating progenies with maximum genetic variability for further selection [4], and introgressing desirable genes from diverse germplasm into the available genetic base [5]. An understanding of the genetic relationships among lines can be particularly useful in planning crosses, in assigning lines to specific heterotic groups, and in precise identification with respect to plant varietal protection [6]. Study of genetic diversity is the process by which variation among individuals or groups of individuals or populations is analyzed. Data often involves numerical measurements and, in many cases, combinations of different types of variables. Phylogenetic relationships based on morphophysiological data provide a way of making a relatively rapid assessment of the diversity present, so that a greater number of related operational taxonomic units (OTUs) [7] can be subsequently tested. It is wellknown that maintenance or preservation of germplasm involves two principal considerations: (1) avoiding loss of
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