In vitro antioxidant, antimicrobial, and antiviral activities of the essential oil and various extracts from herbal parts and callus cultures of Origanum acutidens

The essential oil and various extracts obtained from Origanum acutidens and methanol extracts (MeOH) from callus cultures have been evaluated for their antioxidative, antimicrobial, and antiviral properties. The essential oil exhibited strong antimicrobial activity with a significant inhibitory effect against 27 (77%) of the 35 bacteria, 12 (67%) of the 18 fungi, and a yeast tested and moderate antioxidative capacity in DPPH and beta-carotene/linoleic acid assays. GC and GC-MS analyses of the oil resulted in the identification of 38 constituents, carvacrol being the main component. The MeOH extracts obtained from herbal parts showed better antioxidative effect than that of butylated hydroxytoluene (BHT), whereas callus cultures also exhibited interesting antioxidative patterns. Concerning antiviral activity, none of the extracts inhibited the reproduction of influenza A/Aichi virus in MDCK cells. The MeOH extracts from herbal parts inhibited the reproduction of HSV-1, and also callus cultures exerted slight antiherpetic effect.     

Potassium and stress alleviation: Physiological functions and management of cotton

Potassium (K) plays a major role in the basic functions of plant growth and development. In addition, K is also involved in numerous physiological functions related to plant health and resistance to biotic and abiotic stress. However, K deficiency occurs widely resulting in poor growth, lost yield, and reduced fiber quality. This review describes the physiological functions of K and its role in stress relief and also provides some agronomic aspects of K requirements, diagnosis of soil and plant K status, and amelioration. The physiological processes described include enzymes and the regulation of organic‐compound synthesis, water relations and stomates, photosynthesis, transport, cell signaling, and plant response to drought stress, cold stress, salt stress, as well as biotic stresses. The agronomic aspects of K fertilization include the K requirements of cotton, K uptake, and soil characteristics, genotypic variation in K uptake and use, and characteristics of K deficiency in cotton. In addition, diagnosis and amelioration of K soil and plant status is discussed.     

Biological and molecular characterization of laboratory mutants of Cercospora beticola resistant to Qo inhibitors

The resistance to strobilurin-related fungicides and its molecular basis in laboratory mutant isolates of Cercospora beticola was investigated. After ultraviolet mutagenesis, mutants with high, moderate or low resistance levels to pyraclostrobin were isolated from a wild-type strain of C. beticola. Fungitoxicity tests on the response of resistant isolates on medium containing pyraclostrobin and salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration, indicated that the biochemical mechanism of alternative oxidase was not responsible for the reduced sensitivity to pyraclostrobin for half of the mutants. Cross-resistance studies with other inhibitors of the cytochrome bc ₁ complex of the mitochondrial respiratory chain showed that the mutation(s) for resistance to pyraclostrobin also reduced the sensitivity of mutant strains to other Qo inhibitors such as azoxystrobin and fenamidone, but not to the Qi inhibitor cyazofamid. No effect of pyraclostrobin-resistant mutation(s) on fungitoxicity of the carboxamide boscalid, the triazoles epoxiconazole and flutriafol and to the benzimidazole benomyl, which affect other cellular pathways or other steps of the respiratory chain, was observed. Study of fitness parameters showed that most mutants had a significant reduction in sporulation and pathogenicity compared to the wild-type parental isolate. However, experiments on the stability of the resistant phenotype did not show a significant reduction of the resistance for half of the mutants when grown for at least four generations on pyraclostrobin-free medium. Molecular analysis of cytochrome b cDNA, isolated from the wild-type and the pyraclostrobin-resistant mutant isolates, revealed two novel amino acid replacements at positions involved in Qo resistance in other species. The glycine (GGT) to serine (AGT) replacement at position 143 (G143S) was found in the isolate with the highly resistant phenotype. The second amino acid change was the replacement of phenylalanine (TTC) by valine (GTC) at position 129 (F129V), which was found in a mutant strain with the moderately resistant phenotype. Four additional mutations located in conserved regions of the mitochondrial cytochrome b gene (I154L, N250D, E256G and V261D) were detected in some mutant isolates of C. beticola but their possible role in Qo-resistance needs further investigation. This is the first study reporting C. beticola strains resistant to Qo inhibitor fungicides due to the biochemical mechanism of target-site modification, resulting from amino acid changes in the mitochondrial cytochrome b␣gene.     

Rapid method for simultaneous quantitative determination of four major essential oil components from oregano (Oreganumsp.) and thyme (Thymus sp.) using FT-Raman spectroscopy

A simple and rapid method for the quantitative determination of four major components found in oregano and thyme essential oils is presented. The method correlates the Raman peak intensity in the spectral region from 1800 to 600 cm(-1) and the concentration percentage of each particular constituent in the sample. To achieve accurate quantification results and avoid the risk of overlapping peaks of unknown Raman-active substances in natural essential oils, the peaks must be analyzed. For this purpose, PEAKSOLVE software (Ver. 1.0.5) was used. Unknown samples were measured with the FT-Raman method, and the results were compared to those of the gas chromatographic (GC) analysis. The comparison was made at a confidence level of 99%, and the two methods scored equally in terms of repeatability and accuracy even at the edge of the method specifications. The new method can provide accurate results in very short times once the setup is complete and could be utilized in areas where vast amounts of samples must be analyzed.     

Isolation and identification of 2-methoxy-3,5-dimethylpyrazine, a potent musty compound from wine corks

The compound responsible for a "fungal must" taint evident in industry assessments of wine corks was identified as 2-methoxy-3,5-dimethylpyrazine. The identification was made on the basis of gas chromatography/odor analyses, collection of material using micropreparative techniques, determination of chemical properties of collected material, and comparison by gas chromatography/mass spectrometry with an authentic sample, synthesized from 2-hydroxy-3,5-dimethylpyrazine. 2-Methoxy-3,5-dimethylpyrazine is an extremely potent compound with an unpleasant, musty, moldy aroma and an aroma threshold in a white wine of 2.1 ng/L. While its contribution to the frequency and intensity of cork taint in bottled wine is yet to be established, it has been assessed by some wine industry personnel as second only to 2,4,6-trichloroanisole as a cause of cork taint in Australian wine.     

Genetic inheritance analysis of four enzymes in date-palm (Phoenix dactylifera L.)

The genetic inheritance of four date-palm enzymes hasbeen carried out in 29 Tunisian cultivars. Our data provide evidenceof five polymorphic genes involving 12 alleles. It has been assumedthat either Pgm or Shdh are specified by three different alleles,while Got-1, Got-2 and Pgi-2 loci are biallelicgenes. On the other hand, analysis throughout progenies of twocontrolled crosses support significantly these hypothesis. In thewhole, results are in agreement with reports that describeddate-palm isozymes. Nevertheless, we assume that other alleleare involved in Pgm gene. Also, isozymes controlled by Got-2locus are of a dimeric structure. Opportunely, it can be establishedthat the resultant isoenzymes would constitute polymorphic markerssuitable to analyze the genetic diversity in date-palm.     

Screening for durum wheat (Triticum durum Desf.) cultivar resistance to drought stress using an integrated physiological approach

Journal of Crop Science and Biotechnology - Drought is one of the major abiotic stresses with a detrimental impact on plant growth and development irrespective of the developmental stage. Thus,...