The study of phenotypic and genetic diversity in landrace collections is important for germplasm conservation. In addition, the characterisation of very diversified materials with molecular markers offers a unique opportunity to define significant marker-trait associations of biological and agronomic interest. Here, 50 tomato landraces (mainly collected in central Italy), nine vintage and modern cultivars, and two wild outgroups were grown at two locations in central Italy and characterised for 15 morpho-physiological traits and 29 simple sequence repeat (SSR) loci. The markers were selected to include a group of loci in regions harbouring reported quantitative trait loci (QTLs) that affect fruit size and/or shape (Q-SSRs) and a group of markers that have not been mapped or shown to have a priori known linkage (NQ-SSRs). As revealed by univariate and multivariate analyses of morphological data, the landraces grouped according to vegetative and reproductive traits, with emphasis on fruit size, shape and final destination of the product. Compared to the low molecular polymorphism reported in tomato modern cultivars, our data reveal a high level of molecular diversity in landraces. Such diversity has allowed the inference of the existence of a genetic structure that was factored into the association analysis. As the proportion of significant associations is higher between the Q-SSR subset of markers and the subset of traits related to fruit size and shape than for all of the other combinations, we conclude that this approach is valid for establishing true-positive marker-trait relationships in tomato.

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The dependence of the Maki-Thompson and of the density of states (DOS) depletion contributions from superconducting fluctuations to nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) relaxation is derived in the framework of the diagrammatic theory, applied to layered three-dimensional (3 -D) high-T superconductors. The regularization procedure devised for the conductivity (A. I. Buzdin, A. A. Varlamov: Phys. Rev. B 58, 14195, 1998) is used in order to avoid the divergence of the DOS term. The theoretical results are discussed in the light of NMR-NQR measurements in YBCO and compared with the recent theory (M. Eschrig et al.: Phys. Rev. B 59, 12095, 1999), on the basis of the assumption of a purely 2 -D spectrum of fluctuations.