Responsiveness of Lycopersicon pimpinellifolium to acute UV-C exposure: histo-cytochemistry of the injury and DNA damage.

The in vivo and in vitro effects of UV-C (254 nm) exposure (0.039 watt . m(-2) . s for 2 h) of currant tomato (Lycopersicon pimpinellifolium), indigenous to Peru and Ecuador, were assayed. H(2)O(2) deposits, dead cells and DNA damage were localized, 12/24 h after irradiation, mainly in periveinal parenchyma of the 1st and 2nd order veins of the leaves, and before the appearance of visible symptoms, which occurred 48 h after irradiation. Cell death index was of 43.5 +/- 12% in exposed leaf tissues, 24 h after treatment. In currant tomato protoplasts, the percentage of viable cells dropped 1 h after UV-C irradiation from 97.42 +/- 2.1% to 43.38 +/- 4.2%. Afterwards, the protoplast viability progressively decreased to 40.16 +/- 7.25% at 2 h, to 38.31 +/- 6.9% at 4 h, and to 36.46 +/- 1.84% at 6 h after the exposure. The genotoxic impact of UV-C radiation on protoplasts was assessed with single cell gel electrophoresis (SCGE, or comet assay). UV-C treatment greatly enhanced DNA migration, with 75.37 +/- 3.7% of DNA in the tail versus 7.88 +/- 5.5% in the case of untreated nuclei. Oxidative stress by H(2)O(2) used as a positive control, induced a similar damage on non-irradiated protoplasts, with 71.59 +/- 5.5% of DNA in the tail, whereas oxidative stress imposed on UV-C irradiated protoplasts slightly increased the DNA damage (85.13 +/- 4.1%). According to these results, SCGE of protoplasts could be an alternative to nuclei extraction directly from leaf tissues.

Inheritance of Resistance to Two-spotted Spider Mite and Glandular Leaf Trichomes in Wild Tomato Lycopersicon pimpinellifolium (Jusl.) Mill.

Genetics of resistance to Tetranychus urticae Koch and of glandular trichomes of Lycopersicon pimpinellifolium accession TO-937 in a cross between susceptible L. esculentum Mill. `Moneymaker' and resistant TO-937 was studied in a greenhouse experiment. Parents, F1, F2, and two BC1 generations, interspersed with susceptible tomato plants to avoid negative interplot interference, were artificially infested. Mite susceptibility was evaluated by a rating based on plant capacity to support mite reproduction. TO-937, BC1 to TO-937, and F1 were resistant, `Moneymaker' susceptible, and the F2 and the BC1 to `Moneymaker' segregated. Resistance was controlled by a single dominant major locus, but modulated by unknown minor loci. TO-937 presented type IV glandular trichomes, their presence governed by two dominant unlinked loci. Type IV trichome density correlated to resistance; however, a causal relationship between type IV trichomes and mite resistance could not be definitively established. The relatively simple inheritance mode will favor successful introgression of resistance into commercial tomatoes from the close relative L. pimpinellifolium.

Genetic Analysis of Traits Distinguishing Outcrossing and Self-Pollinating Forms of Currant Tomato, Lycopersicon pimpinellifolium (Jusl.) Mill.

The evolution of inbreeding is common throughout the angiosperms, although little is known about the developmental and genetic processes involved. Lycopersicon pimpinellifolium (currant tomato) is a self-compatible species with variation in outcrossing rate correlated with floral morphology. Mature flowers from inbreeding and outcrossing populations differ greatly in characters affecting mating behavior (petal, anther, and style lengths); other flower parts (sepals, ovaries) show minimal differences. Analysis of genetic behavior, including quantitative trait locus (QTL) mapping, was performed on representative selfing and outcrossing plants derived from two contrasting natural populations. Six morphological traits were analyzed: flowers per inflorescence; petal, anther, and style lengths; and lengths of the fertile and sterile portions of anthers. All traits were smaller in the selfing parent and had continuous patterns of segregation in the F2. Phenotypic correlations among traits were all positive, but varied in strength. Quantitative trait locus mapping was done using 48 RFLP markers. Five QTL total were found involving four of the six traits: total anther length, anther sterile length, style length, and flowers per inflorescence. Each of these four traits had a QTL of major (>25%) effect on phenotypic variance.