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The aim of the study was to evaluate the antifungal activity of extracts of 10 plant species used in traditional Uruguayan medicine against the phytopathogenic fungus Alternaria spp. The plants were selected on the basis of their reported ethnobotanical uses. Aqueous, saline buffer and acid extracts of different plant species were screened in vitro for their antifungal activity against Alternaria spp. For the antifungal evaluation we used a microspectrophotometric assay. Minimal inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the extracts were determined. Three solvents were assayed on different tissues of the plants and among the 29 evaluated extracts, 31% of the extracts inhibited growth, similar to the effects of a chemical fungicide. Acid extracts of the plants were more effective than the aqueous or buffer extracts against Alternaria spp. The MIC values of the extracts were determined ranging between 1.25 and 25 µg mL -1 . The MFC values of the extracts ranged between 1.25 µg mL -1(Rosmarinus officinalis L.) and 10 µg mL -1 (Cynara scolymus L.). MICs and MFCs values obtained from leaves (Salvia officinalis L. and R. officinalis) and seeds extracts (Salvia sclarea L.) were quite comparable to values obtained with the conventional fungicide captan (2.5 µg mL -1 ). The extracts of Salvia sclarea, S. officinalis and R. officinalis could be considered as potential sources of antifungal compounds for treating diseases in plants. These extracts showed maximum activity, even at very low concentrations, and the same fungicide effects as chemical fungicide. We conclude from this that these extracts exhibit amazing fungicidal properties that support their traditional use as antiseptics.

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A novel protein factor, named PcF, has been isolated from the culture filtrate of Phytophthora cactorum strain P381 using a highly sensitive leaf necrosis bioassay with tomato seedlings. Isolated PcF protein alone induced leaf necrosis on its host strawberry plant. The primary structure and cDNA sequence of this novel phytotoxic protein was determined, and BLAST searches of Swiss-Prot, EMBL, and GenBank TM /EBI data banks showed that PcF shared no significant homology with other known sequences. The 52-residue PcF protein, which contains a 4-hydroxyproline residue along with three S-S bridges, exhibits a high content of acidic sidechains, accounting for its isoelectric point of 4.4. The molecular mass of isolated PcF is 5,622 ؎ 0.5 Da as determined by mass spectrometry and matches that calculated from the deduced amino acid sequence with cDNA sequencing. The cDNA sequence indicates that PcF is first produced as a larger precursor, comprising an additional N-terminal, 21-residue secretory signal peptide. Maturation of this protein involves the hydroxylation of proline 49, a feature that is unique among other known secreted fungal phytopathogenic proteins.In modern agriculture, the selection of pathogen-resistant cultivars remains of the utmost importance. Conventional breeding selection protocols are relatively inefficient as a consequence of the general lack of genetic variability in cultivated plants as well as the inability to keep pace with the rapid adaptation of pathogen genotypes. New strategies, aimed at achieving resistant plants through gene engineering, require an in depth knowledge of the mechanism of pathogenesis at the molecular level. Host-pathogen interactions can result in either "incompatibility" (resistance) or "susceptibility" (pathogenesis). In either case, mounting evidence suggests that the process is mediated by the production of so-called elicitor-and toxinsignaling molecules (1-3). Signal recognition at the plant cell surface triggers an ordered cascade of downstream events, leading to a range of host-cell responses (4 -7). Because elicitor and toxic mediators play a central role, elucidation of the mechanism of plant-pathogen interactions promises to provide insights about strategies for incorporating pathogen resistance in cultivated plants.The European cultivated strawberry plants (Fragaria vesca ϫ ananassa Duch.) are mostly susceptible to attack by Phytophthora cactorum (8, 9), a pathogenic oomycete for many herbaceous and woody plants because of its wide range host specificity. This pathogen is the causal agent of the "leather rot" and "root rot" diseases in strawberry plants, whose morphological symptoms are recognized by rotting of root, crown, and fruit tissues (10). Plich and Rudnicki (11) first reported that culture filtrates of P. cactorum possessed phytotoxins with action on tomato and involvement in the development of apple tree diseases. Most of these metabolites, however, have not been purified and characterized. The exception is "cactorein" from P. cactorum, a secreted pr...

Bacterial wilt (BW) caused by Ralstonia solanacearum is responsible for substantial losses in cultivated potato (Solanum tuberosum) crops worldwide. Resistance genes have been identified in wild species; however, introduction of these through classical breeding has achieved only partial resistance, which has been linked to poor agronomic performance. The Arabidopsis thaliana (At) pattern recognition receptor elongation factor-Tu (EF-Tu) receptor (EFR) recognizes the bacterial pathogen-associated molecular pattern EF-Tu (and its derived peptide elf18) to confer anti-bacterial immunity. Previous work has shown that transfer of AtEFR into tomato confers increased resistance to R. solanacearum. Here, we evaluated whether the transgenic expression of AtEFR would similarly increase BW resistance in a commercial potato line (INIA Iporá), as well as in a breeding potato line (09509.6) in which quantitative resistance has been introgressed from the wild potato relative Solanum commersonii. Resistance to R. solanacearum was evaluated by damaged root inoculation under controlled conditions. Both INIA Iporá and 09509.6 potato lines expressing AtEFR showed greater resistance to R. solanacearum, with no detectable bacteria in tubers evaluated by multiplex-PCR and plate counting. Notably, AtEFR expression and the introgression of quantitative resistance from S. commersonii had a significant additive effect in 09509.6-AtEFR lines. These results show that the combination of heterologous expression of AtEFR with quantitative resistance introgressed from wild relatives is a promising strategy to develop BW resistance in potato.