Anna Oliva

Invited Paper: Chemicals from nature for weed management

Abstract Natural products represent a vast repository of materials and compounds with evolved biological activity, including phytotoxicity. Some of these compounds can be used directly or as templates for herbicides. The molecular target sites of these compounds are often unique. Strategies for the discovery of these materials and compounds are outlined. Numerous examples of individual phytotoxins and crude preparations with weed management potential are provided. An example of research to find a natural product solution of a unique pest management problem (blue-green algae in aquaculture) is described. Finally, the problems associated with natural products for pest control are discussed.

A new and efficient Baeyer–Villiger rearrangement of flavanone derivatives by the methyltrioxorhenium/H2O2 catalytic system

Abstract The catalytic Baeyer–Villiger rearrangement of flavanones is described by the use of the homogeneous methyltrioxorhenium (MTO)/H2O2 system. In these experimental conditions 3,4-dihydro-4-phenyl-1,5-benzodioxepin-2-ones and previously not reported para-quinone derivatives have been obtained in mild experimental conditions from acceptable to good yields.

Fungistatic Activity of Ruta graveolens Extract and Its Allelochemicals

The biological activity of an extract of Ruta graveolens and its allelochemicals [8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP) and 4-hydroxycoumarin] (previously isolated) was evaluated gainst pathogenic fungi: Fusarium solani, Pyrenochaeta lycopersici, and Trichoderma viride. In addition a rue lyophilized extract was also tested against Penicillium sp., Thielaviopsis basicola, and Verticillium dahliae. We determined that 5 g rue lyophilized extract/liter, the lowest concentration tested, inhibited the mycelial growth of P. lycopersici and V. dahliae by 63.6% and 47%, respectively, with IC50 (the concentration required to inhibit growth 50%) values of 4.16 and 6.5 g/liter, respectively. Moreover, the rue lyophilized extract was shown to reduce radial growth of all six fungal species significantly at concentrations ranging from 5.0 to 40.0 g/liter. Mycelial growth of Penicillium sp. was promoted at 5.0 g lyophilized rue extract/liter and inhibited at higher concentrations. 4-OH coumarin had no effect on the growth of these fungi at concentrations ranging from 0.32 to 2.60 mg/liter, whereas 8-MOP and 5-MOP inhibited the mycelial growth of F. solani and T. viride with IC50 values of 6 mg/liter (5-MOP) and 27 mg/liter (8-MOP) for both fungi, respectively. A mixture of 5-MOP and 8-MOP, tested at 64.8 mg/liter (as they naturally occur in the crude rue extract) significantly inhibited the growth of all tested fungal species. These results suggest potential role for the rue extract and its allelochemicals in controlling pathogenic fungal infections.

Molecular and physiological characterization of Italian isolates of Pyrenochaeta lycopersici

Corky root of tomato caused by Pyrenochaeta lycopersici is a disease of concern in Italy and for many tomato growing areas in the world. Isolates of the fungus were characterized at both the physiological and molecular level. The optimal in vitro growth temperature for all isolates was 23 degrees C. All Italian isolates of P. lycopersici showed similar RAPD and esterase banding patterns. No relevant polymorphisms were detected after enzymatic digestion of PCR-amplified ITS and IGS regions. The overall results indicate a low degree of genetic variability within a collection of 43 Italian isolates. These data are of interest in breeding programs for resistance against corky root of tomato and they provide useful information for the development of molecular diagnostic tools for the rapid identification and detection of P. lycopersici.

Cyto-physiological events during radish germination in the presence of a Ruta graveolens L. infusion

ABSTRACT An infusion of Ruta graveolens L. was tested for its inhibitory effects upon radish germination at the cyto-physiological level. Radish seeds were placed under optimum conditions for germination either in water (control) or in the presence of rue infusion (treated seeds). Morpho-physiological observations indicate that in treated radish seeds the inhibition of germination is accompanied by reduced water uptake and delayed reactivation of the outermost living layer, i.e. the aleurone cells. Compared to the control, aleurone cells of treated seeds present many large lipid droplets and protein bodies, without differentiated organelles. Moreover, chemical and biochemical analyses show that the treatment impairs the metabolic pathways of germination, such as the mobilization and utilization of seed reserves, and the loosening of cell walls. In fact, in treated seeds we found i) increased contents of glucose and galactose, ii) higher concentration of malic acid and iii) lower activities of some glycosidases compared to the control. Results suggest that aleurone cells may play an active part in controlling the embryos metabolism.