Phenotypic diversity in Greek tomato (Solanum lycopersicum L.) landraces

Landraces are heterogeneous populations, generally have wide intra-population diversity, and require a different approach to population characterization than that used for the homogeneous varieties. Either used per se or as a very interesting genetic resource in breeding programs, investigating the genetic structure of tomato landraces is of significant importance. However, information on variation present within tomato landraces and their genetic structure is limited. The present study was designed to: (a) characterize 34 Greek tomato landraces using 36 morphological traits, (b) estimate phenotypic diversity within and among the landraces, and (c) identify the traits that contributed to landrace heterogeneity. Nei's genetic diversity statistics was applied. Principal component analysis (PCA) was used to classify the landraces. The results showed a wide diversity present in the whole collection for most of the traits analyzed (mean total phenotypic diversity HT = 0.47 with the majority of values around the mean). The mean phenotypic diversity among landraces (GST) was 0.21. Some vegetative traits had GST > 0.56, while for the majority of traits, high degree of variation was observed within landrace populations. Most landrace populations had similar magnitudes of phenotypic diversity (H¯p) ranging from 0.24 to 0.52. In most of the landraces, stem pubescence density, foliage density and plant growth type had the lowest phenotypic diversity within landraces (Hs). The heterogeneity of each population was mainly attributed to various traits related to fruit form. Conclusively, the in depth analysis of the phenotypic diversity revealed the allelic and genotypic richness of the studied tomato landrace populations that can be exploited in tomato breeding programs.

Research highlights▶ Wide phenotypic variation existed in the Greek tomato landraces collection. ▶ Most of the landraces had similar magnitude of phenotypic diversity. ▶ The major part of the variation existed within the landraces.▶ The most homogeneous traits within individual landraces were vegetative traits.▶ Landrace heterogeneity was mainly attributed to the traits related to fruit form.