Styrian oil pumpkin seedlings (Cucurbita pepo L. subsp. pepo var. styriaca GREB: .) were treated for 48 h with 1 mM OTC (L-2-oxothiazolidine-4-carboxylic acid) in order to artificially increase cellular glutathione content. They were inoculated with zucchini yellow mosaic virus (ZYMV) 10 days later. The effects of OTC treatment and ZYMV infection on glutathione levels were examined at the subcellular level by immunogold labeling of glutathione using a transmission electron microscope (TEM). These effects were further tested at the whole-tissue level by high performance liquid chromatography (HPLC). Such tests were carried out a) on roots, cotyledons and the first true leaves immediately after OTC treatment in order to analyze to which extent OTC increases glutathione levels in different cell compartments as well as in the whole organ; and b) in older and younger leaves and in roots three weeks after ZYMV inoculation in order to study how possible effects of OTC on symptom development would correlate with glutathione levels at the subcellular level and in the whole organ. Immunocytological and biochemical investigations revealed that, 48 h after OTC treatment, glutathione content had increased in all investigated organs, up to 144% in peroxisomes of cotyledons. Three weeks after ZYMV inoculation, glutathione labeling density had significantly increased within intact cells of infected leaves, up to 124% in the cytosol of younger leaves. Roots showed decreased amounts of glutathione in the TEM. Biochemical studies revealed that OTC treatment resulted in 41 and 51% higher glutathione content in older and younger ZYMV-infected leaves, respectively, in comparison to untreated and ZYMV-infected plants. Evaluation of symptom development at this point revealed that all untreated ZYMV-infected plants had symptoms, whereas only 42% of OTC-treated ZYMV-infected plants showed signs of symptoms. Quantification of ZYMV particles revealed that all organs of OTC-treated and ZYMV-infected plants contained significantly decreased amounts of ZYMV particles over a period of five weeks when compared to the same organs of untreated ZYMV-infected plants. We can conclude that OTC treatment and subsequently elevated glutathione contents within Styrian oil pumpkin plants led to a strong decrease in virus content, which was accompanied by a suppression of ZYMV-induced symptoms as well as reduced and delayed symptom development within plants exhibiting symptoms.

Consumer expectations of apple fruit quality have been steadily increasing over the last couple of decades. One of the main quality attributes affecting product price is colour, determined primarily by the relative amounts of pigments chlorophylls, carotenoids, and anthocyanins, which can be measured non-destructively by visible spectrophotometry. This paper provides a brief overview of studies dealing with the optical pigment-determination of intact apple fruits in visible part of electromagnetic spectrum. Firstly ripening-associated pigment changes in apples as well as the basics of light interaction and measurements in turbid materials are explained. Subsequently the two most appropriate methods for pigment determination of intact apple fruit are presented along with examples. This is followed by a discussion of the various reflectance and remittance indices for the qualification, as well as quantification, of the main apple pigments. Results are reported regarding studies on the relationships between spectral data and derived indices with various destructive quality and ripening parameters. In the conclusion some of the main findings reviewed in this paper are outlined and discussed briefly.

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