Allium White Rot Suppression with Composts and Trichoderma viride in Relation to Sclerotia Viability.

ABSTRACT Allium white rot (AWR) is a serious disease of Allium spp. caused by the sclerotium-forming fungus Sclerotium cepivorum. This work has examined the effects of onion waste compost (OWC) and spent mushroom compost (SMC), with and without Trichoderma viride S17A, on sclerotia viability and AWR in glasshouse and field experiments. Incorporation of OWC into soil reduced the viability of sclerotia and the incidence of AWR on onion plants in glasshouse pot bioassays, whereas SMC or T. viride S17A only reduced incidence of AWR. In two field trials, OWC reduced sclerotia viability and was as effective in reducing AWR as a fungicide (Folicur, a.i. tebuconazole). Field application of SMC had no effect on sclerotia viability and did not control AWR. However, the addition of T. viride S17A to SMC facilitated proliferation of T. viride S17A in the soil and increased the healthy onion bulb yield. The results indicate two mechanisms for the suppression of AWR: (i) reduction in the soil population of viable sclerotia, which may be due to volatile sulfur compounds detected in OWC but absent in SMC, and (ii) prevention of infection of onion plants from sclerotia following amendment of soil with OWC, SMC, or T. viride S17A.

Subcritical water extraction of nutraceuticals with antioxidant activity from oregano. Chemical and functional characterization.

In the present work, oregano leaves (Origanum vulgare L.) are explored as natural source of nutraceuticals with antioxidant activity. To do this, subcritical water extraction (SWE), a new environmentally friendly technique, is employed as extraction procedure and HPLC coupled to DAD is used for the chemical characterization of the extracts. Moreover, the radical scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) method and the determination of the total phenolic content (measured with the Folin test) are applied to evaluate the antioxidant activity of the extracts. The extraction of antioxidants from oregano leaves by SWE is studied considering different temperatures (25, 50, 100, 150 and 200 degrees C) to investigate the selectivity of the process. The highest antioxidant activity is observed for the extract obtained at the highest temperature, 200 degrees C (EC(50) equal to 10 microg/ml). Moreover, the extraction yield was also the highest (54% dry weight) at these extraction conditions. The total phenolic content showed no differences among the different extracts, concluding that the amount of phenolic compounds extracted was similar but the type and structure of the phenolics was different, providing in this way different antioxidant activity. Some compounds could be tentatively identified, proposing some probable chemical structures for some of them, such as flavanones, dihydroflavonols, favonols and flavones.

Selection of hybrids and edible citrus species with a high content in the diosmin functional compound. Modulating effect of plant growth regulators on contents.

The purpose of this study is to identify species, hybrids, and cultivars of edible Citrus species with high contents of diosmin as a functional compound and also to identify the developmental progress of the fruit in which it reaches maximum levels; these findings would be useful for extraction purposes and for the modulating effect of plant growth regulators on diosmin content to increase the level of this flavone. The results obtained reveal that the highest contents of diosmin are present in immature fruits of certain varieties of citron (Buda's finger) and lemon (Meyer), whereas the contents in the edible parts of the fruits are irrelevant from a pharmacological point of view. Similarly, it is shown that it is possible to increase the content of this flavone using hormonal treatments (6-benzylaminopurine and 2,4-dichlorophenoxyacetic acid) during the early stages of fruit growth.

Distribution of flavone glycoside diosmin in Hyssopus officinalis plants: changes during growth.

A study of the flavonoid composition of Hyssopus officinalis L. (Lamiaceae) plants using high-performance liquid chromatography and NMR spectroscopy revealed the presence of diosmin as the major flavone. The maximum levels of this secondary compound are located in sepals and leaves, which represent 51 and 40.5%, respectively, of the total content of diosmin in whole plant. The presence of isoferulyl D-glucose ester in this plant material was also revealed.

Bioproduction of neohesperidin and naringin in callus cultures of Citrus aurantium.

The accumulation of both neohesperidin and naringin as major flavonoids in callus cultures of bitter orange (Citrus aurantium) was demonstrated using high performance liquid chromatography with a diode-array detector. The identity of both compounds was confirmed by their corresponding nuclear magnetic resonance spectra. The levels of neohesperidin are higher than those of naringin in callus culture, as they are in immature fruit, and high concentrations of both are found in young tissues such as immature fruits and the outer zone of calli.