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.
Background/Aims: Besides antioxidant vitamins and minerals, fruits and vegetables contain flavonoids and related phenolics. The biological activities of these polyphenols have become well known in recent years evidencing their beneficial effects on human health. In this context, the characterization of the flavonoids present in tomatoes is of great interest. Thus the polyphenol pattern (including flavonols, flavanones and cinnamate derivatives), lycopene and β-carotene concentrations and the total antioxidant activity (TAA) of the phenolic fraction from different tomato lines and cultivars have been determined. Methods: The characterization was obtained by means of spectrophotometry and HPLC analyses. Results: Mean values for single flavonoids were 0.68 ± 0.16 for naringenin, 0.74 ± 0.12 for rutin and 0.32 ± 0.06 for a rutin-pentoside. Mean total polyphenol content was 13.15 ± 1.15 mg/100 g and mean TAA value was 1.3 ± 0.10 mmol/g. The obtained TAA values resulted in good accordance with the total polyphenol content (R2 = 0.7928). The main phenolic acids were chlorogenic (mean ± SE 0.20 ± 0.03) and caffeic acid (mean ± SE 0.03 ± 0.01). Mean levels of lycopene and β-carotene were 5.38 ± 0.90 and 1.18 ± 0.40 mg/100 g, respectively. Conclusions: Almost all the lines characterised by low carotenoid content produce high levels of polyphenols, and consequently have the most powerful antioxidant potential.
We investigated the role of gibberellins (GAs) in the phenotype of parthenocarpic fruit (pat), a recessive mutation conferring parthenocarpy in tomato (Solanum lycopersicum L.). Novel phenotypes that parallel those reported in plants repeatedly treated with gibberellic acid or having a GA-constitutive response indicate that the pat mutant probably expresses high levels of GA. The retained sensitivity to the GA-biosynthesis inhibitor paclobutrazol reveals that this condition is dependent on GA biosynthesis. Expression analysis of genes encoding key enzymes involved in GA biosynthesis shows that in normal tomato ovaries, the GA20ox1 transcript is in low copy number before anthesis and only pollination and fertilization increase its transcription levels and, thus, GA biosynthesis. In the unpollinated ovaries of the pat mutant, this mechanism is de-regulated and GA20ox1 is constitutively expressed, indicating that a high GA concentration could play a part in the parthenocarpic phenotype. The levels of endogenous GAs measured in the floral organs of the pat mutant support such a hypothesis. Collectively, the data indicate that transcriptional regulation of GA20ox1 mediates pollination-induced fruit set in tomato and that parthenocarpy in pat results from the mis-regulation of this mechanism. As genes involved in the control of GA synthesis (LeT6, LeT12 and LeCUC2) and response (SPY) are also altered in the pat ovary, it is suggested that the pat mutation affects a regulatory gene located upstream of the control of fruit set exerted by GAs.
Summary.The parthenocarpic fruit (pat) allele causes a complex syndrome affecting different aspects of tomato reproductive development. This mutation affects stamen (reduced length and carpelloidy), ovule (arrested integument growth and unviability), and ovary (autonomous growth, i.e., parthenocarpy) development; pat mutant plants therefore have reduced male and female fertility. We studied the phenotypic expression patterns of the pat gene after treatments with gibberellie acid (GA3) and under different growth seasons (late spring and autumn) and genetic backgrounds (backcross [BC] population after interspecific cross). GA3 treatments were only effective in restoring carpelloid anthers to the wild-type phenotype. Compared to late spring, mutant plants grown in autumn had a lower frequency of carpelloid anthers and aberrant ovules and a higher seed set. Inflorescence position also affected the pat expression; upper inflorescences had low frequency of short anthers and aberrant ovules and an increased tendency to set seeds.pat expressivity was more variable in BC1 plants segregating after interspecific cross with Lycopersicon pennellii than in the original L. esculentum line. Therefore, a role for minor genes that modify the quantitative expression of the pat mutation is postulated and discussed.
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