Conditions for plant regeneration from explants of tomato (Lycopersicon esculentum) cv. UC82B were studied for optimizing transformation procedure. The best regeneration rate was obtained from cotyledon explants from 8–10-d-old seedlings on a modified Murashige and Skoog medium (1962) with 0·5 mg dm⁻³ zeatin and 0·5 mg dm⁻³ indolylacetic acid. Tomato cultivars (UC82B, Castone, Fl Ferline, Monalbo) and a Lycopersicon peruvkmum ‘CMV sel. INRA’ were studied. The cultivarUC82B and the wild Lycopersicon species showed an efficient shoot regeneration potential. Early events in the transformation of tomato cotyledons were analysed using an Agrobacterium tumefaciens strain carrying a binary vector with an nptII (pnos) gene and a reporter GUS-intron (p35S) chimeric gene. Two days after infection, GUS activity appeared specifically at the cut surface. Subepidermal cells were more susceptible to transformation than epidermal cells. When selection for kanamycin resistance was applied 2 d after inoculation, transformed cells were efficiently recovered. Preculture with feeder cells stimulated cell transformation, but reducedregeneration capacity from transformed cells. The optimal transformation rate was observed witha time of preculture of 1 and 2 d. Transformation events for two tomato cultivars (UC82B and Monalbo) occurred at the same rate as 55% of the inoculated explants developed kanamycin resistant calli. However, transformed plants were obtained at different rates of 8% and 14% for cv. Monalbo and cv. UC82B.

Background: Tunisia is considered a secondary center of diversification of durum wheat and has a large number of abandoned old local landraces. An accurate investigation and characterization of the morphological and genetic features of these landraces would allow their rehabilitation and utilization in wheat breeding programs. Here, we investigated a diverse collection of 304 local accessions of durum wheat collected from five regions and three climate stages of central and southern Tunisia.Results: Durum wheat accessions were morphologically characterized using 12 spike- and grain-related traits. A mean Shannon-Weaver index (H′) of 0.80 was obtained, indicating high level of polymorphism among accessions. Based on these traits, 11 local landraces including Mahmoudi, Azizi, Jneh Khotifa, Mekki, Biskri, Taganrog, Biada, Badri, Richi, Roussia and Souri were identified. Spike length (H′ = 0.98), spike shape (H′ = 0.86), grain size (H′ = 0.94), grain shape (H′ = 0.87) and grain color (H′ = 0.86) were the most polymorphic morphological traits. The genetic diversity of these accessions was assessed using 10 simple sequence repeat (SSR) markers, with a polymorphic information content (PIC) of 0.69. Levels of genetic diversity were generally high (I = 0.62;He = 0.35). In addition, population structure analysis revealed 11 genetic groups, which were significantly correlated with the morphological characterization. Analysis of molecular variance (AMOVA) showed high genetic variation within regions (81%) and within genetic groups (41%), reflecting a considerable amount of admixture between landraces. The moderate (19%) and high (59%) levels of genetic variation detected among regions and among genetic groups, respectively, highlighted the selection practices of farmers. Furthermore, Mahmoudi accessions showed significant variation in spike density between central Tunisia (compact spikes) and southern Tunisia (loose spikes with open glume), may indicate an adaptation to high temperature in the south.Conclusion: Overall, this study demonstrates the genetic richness of local durum wheat germplasm for better in situ and ex situ conservation and for the subsequent use of these accessions in wheat breeding programs.