Pathogenicity for onion and genetic diversity of isolates of the pathogenic fungus Colletotrichum gloeosporioides (Phyllachoraceae) from the State of Pernambuco, Brazil

Onion anthracnose, caused by Colletotrichum gloeosporioides, is one of the main diseases of onions in the State of Pernambuco. We examined the pathogenicity of 15 C. gloeosporioides strains and analyzed their genetic variability using RAPDs and internal transcribed spacers (ITS) of the rDNA region. Ten of the strains were obtained from substrates and hosts other than onion, including chayote (Sechium edule), guava (Psidium guajava), pomegranate (Punica granatum), water from the Capibaribe River, maracock (Passiflora sp), coconut (Cocus nucifera), surinam cherry (Eugenia uniflora), and marine soil; five isolates came from onions collected from four different regions of the State of Pernambuco and one region of the State of Amazonas. Pathogenicity tests were carried out using onion leaves and bulbs. All strains were capable of causing disease in leaves, causing a variable degree of lesions on the leaves; four strains caused the most severe damage. In the onion bulb tests, only three of the above strains caused lesions. Seven primers of arbitrary sequences were used in the RAPD analysis, generating polymorphic bands that allowed the separation of the strains into three distinct groups. The amplification products generated with the primers ITS1 and ITS4 also showed polymorphism when digested with three restriction enzymes, DraI, HaeIII and MspI. Only the latter two demonstrated genetic variations among the strains. These two types of molecular markers were able to differentiate the strain from the State of Amazonas from those of the State of Pernambuco. However, there was no relationship between groups of strains, based on molecular markers, and degree of pathogenicity for onion leaves and bulbs.     

Control of stem nematode, Ditylenchus dipsaci, in onions, by granular nematicides applied to the soil

Aldicarb at 1.4–5.6 kg a.i. ha^-l or oxamyl at 1.3–5.2 kg a.i. ha^-1 applied over the seed furrows during sowing prevented much of the damage resulting from stem nematode attack in spring-sown onions. Rotting of bulbs in store due to stem nematode infestation was sometimes lessened by these treatments. Neither sowing onion seeds on soil ridges, nor applying aldicarb in two equal doses, one over the seed furrows during sowing, the other over the plants mid-season, controlled the nematode better or increased onion yields more than a single equivalent dose over the seed furrows. Applied as two doses in this way, aldicarb was sometimes more effective against the nematode in summer-sown onions than was an equivalent amount applied over the seed furrows during sowing. Only 2.5 kg or less aldicarb ha^-1 can be applied to onions without leaving unacceptable residues (>0.15 μg g^-1) in the harvested bulbs.     

Exogenous ethylene inhibits sprout growth in onion bulbs

Background and Aims

Exogenous ethylene has recently gained commercial interest as a sprouting inhibitor of onion bulbs. The role of ethylene in dormancy and sprouting of onions, however, is not known.

Methods

A cultivar (Allium cepa ‘Copra’) with a true period of dormancy was used. Dormant and sprouting states of onion bulbs were treated with supposedly saturating doses of ethylene or with the ethylene-action inhibitor 1-methylcyclopropene (1-MCP). Initial sprouting was determined during storage at 18 °C by monitoring leaf blade elongation in a specific size class of leaf sheaths. Changes in ATP content and sucrose synthase activity in the sprout leaves, indicators of the sprouting state, were determined. CO₂ and ethylene production of onion bulbs during storage were recorded.

Key results

Exogenous ethylene suppressed sprout growth of both dormant and already sprouting onion bulbs by inhibiting leaf blade elongation. In contrast to this growth-inhibiting effect, ethylene stimulated CO₂ production by the bulbs about 2-fold. The duration of dormancy was not significantly affected by exogenous ethylene. However, treatment of dormant bulbs with 1-MCP caused premature sprouting.

Conclusions

Exogenous ethylene proved to be a powerful inhibitor of sprout growth in onion bulbs. The dormancy breaking effect of 1-MCP indicates a regulatory role of endogenous ethylene in onion bulb dormancy.Key words: Bulb dormancy, Allium cepa, onion, sprout growth, ethylene, CO₂ production, respiration, 1-methylcyclopropene     

Mutagenicity monitoring of airborne particulate matter (PM10) in the Czech Republic.

The mutagenic activities associated with inhalable airborne particulate matter (PM10) collected over a year in four towns (Czech Republic) have been determined. The dichloromethane extracts were tested for mutagenicity using the Ames plate incorporation test and the Kado microsuspension test both with Salmonella typhimurium TA98 and its derivative YG1041 tester strains in the presence and absence of S9 mixture. The aim of this study was to assess the suitability of both bacterial mutagenicity tests and to choose the appropriate indicator strain for monitoring purposes. To elucidate the correlation between mutagenicity and polycyclic aromatic hydrocarbons (PAHs), the concentration of PAHs in the air samples were determined by GC/MS. In general, the significant mutagenicity was obtained in organic extracts of all samples, but differences according to the method and tester strain used were observed. In both mutagenicity tests, the extractable organic mass (EOM) exhibited higher mutagenicity in the YG1041 strain (up to 97 rev/microg in the plate incorporation and 568 rev/microg in the microsuspension tests) than those in TA98 (up to 2.2 rev/microg in the plate incorporation and 14.5 rev/microg in the microsuspension tests). In the plate incorporation test, the direct mutagenic activity in YG1041 was on average 60-fold higher and in microsuspension assay 45-fold higher with respect to strain TA98. In the presence of S9 mix, the mutagenic potency in YG1041 declined (P<0.001) in summer, but increased in TA98 (P<0.05) in samples collected during the winter season. The microsuspension assay provided higher mutagenic responses in both tester strains, but in both strains a significant decrease of mutagenic potency was observed in the presence of S9 mix (P<0.001 for YG1041, P<0.05 for TA98 in winter). The mutagenic potencies detected with both indicator strains correlated well (r=0.54 to 0.87) within each mutagenicity test used but not (for TA98) or moderately (r=0.44 to 0. 66 for YG1041) between both of the tests. The mutagenic activity (in rev/m(3)) likewise the concentration of benzo[a]pyrene and sum of carcinogenic PAHs showed seasonal variation with distinctly higher values during winter season. A correlation between the PAH concentrations and the mutagenicity results for the plate incorporation, but not for the microsuspension tests was found. In samples from higher industrial areas, the higher mutagenicity values were obtained in plate incorporation test with TA98 and in both tests with YG1041 in summer season (P<0.05). According to our results, plate incorporation test seems to be more informative than microsuspension assay. For routine ambient air mutagenicity monitoring, the use of YG1041 tester strain without metabolic activation and the plate incorporation test are to be recommended.     

Mutagenic activity of dichloroethylamino derivatives of nitronaphthofuran and some nitrobenzofurans in the Salmonella/microsome assay.

The mutagenic activity of five dichloroethylamino 2-nitrobenzofuran derivatives and one dichloroethylamino 2-nitronaphthofuran derivative was analysed in the Salmonella/microsome assay. We investigated the influence of the position of the dichloroethylamino and/or the methoxy groups on the mutagenic activity of these nitro arenofurans in S. typhimurium strain TA100 and its variant TA100NR, deficient in nitroreductase. Without metabolic activation 7-[bis(2-chloroethyl)amino]-2-nitronaphtho[2,1-b]furan (1), 4-[bis(2-chloroethyl)amino]-7-methoxy-2-nitrobenzofuran (2), 7-[bis(2-chloroethyl)amino]-4-methoxy-2-nitrobenzofuran (5) and 6-[bis(2-chloroethyl)amino]-2-nitrobenzofuran (6) are mutagenic in TA100, while 4-[bis(2-chloroethyl)amino]-5-methoxy-2-nitrobenzofuran (4) is weakly mutagenic and 5-[bis(2-chloroethyl)-amino]-2-nitrobenzofuran (3) toxic. In the NR deficient strain compounds 1, 3 and 6 are strong mutagens and 4 is weakly positive. The two isomers 2 and 5 are negative in that strain. The naphthofuran derivative 1 is highly mutagenic in the absence of S9 mix in both strains considered, but less than R7000 (7). A decrease in the electronic polarity of compound 1 versus compound 7 according to the hypothesis developed by Royer et al. is a possible explanation. After exogenous metabolic activation by S9 mix all the compounds tested are highly mutagenic in both Salmonella strains. The position of the dichloroethylamino group and/or the presence of a methoxyl on the alpha-nitroarenofuran derivatives seem to modify the activity of bacterial as well as exogenous nitroreductases or other activating enzymes.     

Distribution of Burkholderia cepacia phenotypes by niche, method of isolaiton and pathogenicity of onion

Several proposals have been made for the subdivision of the bacterial species Burkholderia cepacia. Data applying these schemes to a collection of 188 strains of B. cepacia, isolated using a variety of methods, from soils, decayed onions, and nosocomial sources are presented. None of the schemes could be shown to be associated with the method of isolation, niche from which a strain was isolated, pectolytic activity, or pathogenicity to onion. Strains isolated by serial dilution on onion slices were much more uniform than were strains isolated using semiselective media. The nutritionally stringent medium of Lumsden and Sasser (US Patent No. 4 588 584) was judged better for the collection of a phenotypically broad sample of B. cepacia than those of Hagedorn, Gould, Bardinelli & Gustavson (1987) and Wu & Thompson (1984), which are based on antibiotic insensitivity. Pectolytic activity and pathogenicity to onion were shown to be highly correlated characters. None of the strains of clinical origin was capable of macerating onion tissue.     

Overwintering locations and hosts for onion thrips (Thysanoptera: Thripidae) in the onion cropping ecosystem in New York

Identifying locations where onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), overwinter and subsequently disperse is important for designing control strategies. In upstate New York from 2003 through 2006, potential overwintering sites in the commercial onion, Allium cepa L., cropping system were investigated early in the spring before onion seedling emergence and again late in the season after onions were harvested. Onion thrips adults were sampled directly from the soil and indirectly from the soil by using emergence cages. Sampling locations included onion field interiors and edges and areas outside of these fields, including woods. Host material sampled included onion culls; volunteer onions, which sprout from cull onions left behind after harvest; and weeds. Onion thrips adults were found in all sections of onion fields and in locations outside of onion fields, with the fewest emerging from woods. Emergence began in early May and extended into June. Peak emergence occurred during the last half of May, at which time 50-75% of the population had emerged. Adults colonized volunteer onions as early as late March and as late as mid-November. No adults were found overwintering in onion cull piles. Adults also colonized several weed species, especially pigweed, Amaranthus hybridis L., and lambsquarters, Chenopodium album L., late in the fall. Our results indicate that onion thrips adults overwinter in the soil within and near onion fields and that they probably colonize volunteer onion plants before subsequent generations infest the onion crop in the spring. Volunteer onions and weeds also provide onion thrips with a host after onions are harvested. Consequently, onion thrips management strategies should include tactics that reduce volunteer onion and weed abundance.     

Antioxidant and xanthine oxidase inhibitory activities of total polyphenols from onion

Onions (Allium cepa L.) comprise a valuable vegetable crop in many countries. Modern scientific research has shown that onions possess many biological activities, including antibacterial, anticancer, hypoglycemic, hypolipidemic, antiplatelet aggregation, and antioxidant activities. The goal of this study was to investigate the impact of total onion polyphenols on antioxidant and xanthine oxidase (XO) inhibitory activities. Total onion polyphenols showed significant antioxidant activity in DPPH, FRAP, and OH-assays (IC₅₀ [µg/mL]), 43.24, 560.61, and 12.97, respectively). In a X/XO system, antioxidant properties of these polyphenols significantly inhibited XO activity (IC₅₀ [µg/mL], 17.36). These results indicated that total onion polyphenols showed promising antioxidant and anti-gout properties and might be used as potential, natural drugs against oxidative diseases after successful studies in vivo as well as clinical trials.     

Mutagenic activity of 4 active-principle forms of pharmaceutical drugs. Comparative study in the Salmonella typhimurium microsome test, and the HGPRT and Na+/K+ ATPase systems in cultured mammalian cells

The nitroimidazole derivatives used in human therapy have shown a strong mutagenic activity in bacterial tests using Ames strains of Salmonella typhimurium. Our study compared the response of 4 products of this family on bacterial target cells as well as on mammalian target cells (Chinese hamster V79 cells). The strong positive response on TA100 was greatly reduced on the nitroreductase-deficient strain TA100 Frl. Furthermore, no mutagenic activity was found in V79 mammalian cells that we examined for ouabain and 6-thioguanine resistance.     

The effect of temperature on the rate of sprout growth and development within stored onion bulbs

In order to understand better the effects of storage temperature on the time to visible sprouting in stored onions, sprout growth was measured by regularly dissecting samples from bulbs stored at 1, 10, 15 or 25°C for 243 days. The dry-weight of the shoot or sprout within stored onion bulbs increased exponentially with time. The rate of increase of sprout dry weight, as well as the rate of leaf initiation by the shoot apex was faster at 17° than at 10 or 25°C, and almost zero at 1°C. The rate of loss of dry weight from storage tissue was similar at 17°C and 25°C but slower at 10°C and slower still at 1°C.     

Non-enzymic activation of polycyclic aromatic hydrocarbons as mutagens.

Samples of 22 polycyclic aromatic hydrocarbons and related derivatives were subjected to ⁶⁰Co gamma radiation in air, and the irradiated samples were tested for mutagenicity with the Salmonella typhimurium strains TA 98, TA 1535, TA 1537, and TA 1538. Testing was conducted with the bacterial strains alone, thus not fortified with liver-microsomal enzymes or other metabolizing systems. Marked mutagen responses were obtained for several irradiated samples with the TA 98, TA 1537, and TA 1538 strains but not with the TA 1535 strain. Irradiated samples of benzo[a]anthracene, benzanthrone, benozo[g,h,i]perylene, benzo[a]pyrene, chrysene, fluorene, 9-methylanthracene, 1-methylphenanthrene, 2-methylphenanthrene, and pyrene gave positive mutagenic tests and dose-responses, whereas unirradiated control samples of these were inactive. Acenaphthene, phenanthrene, and phenanthrenequinone exhibited toxicity which interfered with interpretation of mutagenicity testing. Samples of 2-methylanthracene and tetracene were mutagenic with or without irradiation. Alizarin, anthracene, anthraquinone, anthrone, dobenzo[a,h]anthracene, picene, and triphenylene negative results. Samples of benzo[a]pyrene adsorbed on silica gel irradiated in air by ⁶⁰Co gamma radiation or by 254 nm ultraviolet light and samples adsorbed on filter paper irradiated by visible light yielded preparations mutagenic towards the TA 98, TA 1537, and TA 1538 strains. These results suggest that parent polycyclic aromatic hydrocarbons not themselves mutagenic towards S. typhimurium may be oxidized in air by radiation-induced processes to products whose mutagenicity resembles that of liver-microsomal metabolites of the parent polycyclic aromatic hydrocarbon.     

Similarities and relationships among populations of the bulb onion as estimated by nuclear RFLPs

Random nuclear restriction fragment length polymorphisms (RFLPs) were used to assess similarities and relationships among open-pollinated (OP) populations of the cultivated bulb onion (Allium cepa). Seventeen OP populations and 2 inbreds of contrasting daylength response [termed by convention as long (LD) and short (SD) day], 1 shallot (A. cepa var. ascalonicum), and one cultivar of bunching onion (Allium fistulosum) were examined with 104 cDNA clones and two to four restriction enzymes. Sixty (58%) clones detected at least 1 polymorphic fragment scorable among the OP populations and were used for analyses. The average number of polymorphic fragments per polymorphic probe-enzyme combination was 1.9, reflecting that numerous monomorphic fragments were usually present. Similarities were estimated as the proportion of polymorphic fragments shared by 2 populations. Average similarity values among LD, among SD, and between LD and SD OP populations were 0.79, 0.67, and 0.68, respectively. Relationships among the OP populations were estimated by parsimony, cluster analysis of similarities using the unweighted-pair-group method (UPGMA), and multivariate analysis using principle components. Parsimony analysis generated a strict consensus tree that grouped all but 1 LD onion with unresolved relationships to the SD OP populations. The UPGMA analysis placed together the LD storage OP populations. Principal component analysis grouped all but 2 LD onions; the other OP populations were dispersed. The results suggest that LD and SD onions do not represent distinct germ plasm, but that LD storage onions represent a derived group selected for production at higher latitudes. If it is assumed that the sampled populations are representative of all onion OP populations, the lower similarities among SD OP populations indicate that their collection and maintenance in germ plasm collections is important for the preservation of genetic diversity.     

Cyromazine seed treatments to control onion maggot, Delia antiqua, on green onions

Cyromazine seed treatments were evaluated for onion maggot control in green onion crops. The more tolerant to organophosphates of two populations of onion maggots was chosen for further research, based on the results of adult assays in a Potter spray tower. In the laboratory, first-instar mortality was compared between film-coated seed treatment and soil drench treatment. The LC50 for the film-coated seed treatment was approximately one fourth that of the soil drench treatment. In choice assays, no significant difference was observed between the number of eggs deposited on seedlings grown from film-coated seeds with cyromazine and film-coated seeds without cyromazine. Field studies demonstrated that all rates of cyromazine seed treatment resulted in protection of onion plants from onion maggot damage. Green onions may not require as high a rate of cyromazine for control of onion maggots as the rate established for use in dry onions for two reasons: the seeding rate is much higher for green onions resulting in more AI/ha for a given amount of AI/kg of seed, and a given percentage of stand loss is more difficult to detect in green onions than in dry onions.     

Comprehensive metabolite profiling of onion bulbs (<Emphasis Type="Italic">Allium cepa</Emphasis>) using liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

Introduction

Onion (Allium cepa) represents one of the most important horticultural crops and is used as food, spice and medicinal plant almost worldwide. Onion bulbs accumulate a broad range of primary and secondary metabolites which impact nutritional, sensory and technological properties.

Objectives

To complement existing analytical methods targeting individual compound classes this work aimed at the development and validation of an analytical workflow for comprehensive metabolite profiling of onion bulbs.

Method

Metabolite profiling was performed by liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-QTOFMS). For annotation of metabolites accurate mass tandem mass spectrometry experiments were carried out.

Results

On the basis of LC/ESI-QTOFMS and two chromatographic methods an analytical workflow was developed which facilitates profiling of polar and semi-polar onion metabolites including fructooligosaccharides, proteinogenic amino acids, peptides, S-substituted cysteine conjugates, flavonoids and saponins. To minimize enzymatic conversion of S-alk(en)ylcysteine sulfoxides, a sample preparation and extraction protocol for fresh onions was developed comprising cryohomogenization and a low-temperature quenching step. A total of 123 metabolites were annotated and characterized by chromatographic and tandem mass spectral data. For validation, recovery rates and matrix effects were determined for 15 model compounds. Repeatability and linearity were assessed for more than 80 endogenous metabolites.

Conclusion

As exemplarily demonstrated by comparative metabolic analysis of six onion cultivars the established analytical workflow in combination with targeted and non-targeted data analysis strategies can be successfully applied for comprehensive metabolite profiling of onion bulbs.

     

Stimulation of sclerotial germination ofSclerotium cepivorum by host-plant extract

Summary Extract from onion bulbs and diffusate from roots of onion seedlings were fractionated by column chromatography. The stimulatory effects of the different fractions of onion extract on sclerotial germination ofSclerotium cepivorum were studied. The sugar fraction was the most stimulatory, whereas, the amino acid fraction was not effective. Paper chromatographic analysis revealed the presence of glucose, fructose and no amino acids in the root diffusate. These two sugars and 13 amino acids were identified in the onion extract. When various sugars and amino acids were supplied individually to autoclaved soil, only glucose, fructose, mannose and maltose effectively induced sclerotial germination. Partial stimulation occured in nonsterile soil amended with high glucose concentrations. Studies on the antibiotic effect of the different fractions against some soil fungi by the spore germination method showed that, the sugar fraction inhibits completely the spore germination of all the fungi, tested, whereas, the amino acid fraction was non-inhibitory. Both fractions did not show antibiotic activity when tested by the filter paper disc method. Attempts to extract inhibitory substances from soil which inhibit sclerotial germination were unsuccessful. It was suggested that onion extract plays a twofold role in stimulating sclerotial germination in natural soil: (a) a direct nutritional influence; (b) an antibiotic effect on soil mycoflora which reduces competition for nutrients.     

The "pro-drug" RibCys decreases the mutagenicity of high-LET radiation in cultured mammalian cells

We are carrying out studies aimed at reducing the mutagenic effects of high-LET 56Fe ions and 12C ions (56Fe ions, 143 keV/microm; 12C ions, 100 keV/microm) with certain drugs, including RibCys [2-(R,S)-D-ribo-(1',2',3',4'-tetrahydroxybutyl)-thiazolidine-4(R)-carboxylic acid]. RibCys, formed by condensation of L-cysteine with D-ribose, is designed so that the sulfhydryl amino acid L-cysteine is released intracellularly through nonenzymatic ring opening and hydrolysis leading to increased levels of glutathione (GSH). RibCys (4 or 10 mM), which was present during irradiation and for a few hours after, significantly decreased the yield of CD59- mutants induced by radiation in AL human-hamster hybrid cells. RibCys did not affect the clonogenic survival of irradiated cells, nor was it mutagenic itself. These results, together with the minimal side effects reported in mice and pigs, indicate that RibCys may be useful, perhaps even when used prophylactically, in reducing the mutation load created by high-LET radiation in astronauts or other exposed individuals.     

The response of growth rate to temperature in seedlings of several Allium crop species

Relative growth rates (R_w), leaf area ratios (LAR), net assimilation rates (NAR), and leaf weight ratios (LWR) were estimated for seedlings of onion, leek, Japanese bunching onion and chives grown at constant temperatures of 10, 12, 15, 19, 23, 27 and 31 C. R_w was greatest at 19 C in Japanese bunching onion and chives, and at 27 C in onions and leeks. R_w increased approximately linearly between 10 and 19 C in all species; between 19 and 27 C it either increased further, decreased or remained constant depending on species but at 31 C R_w was lower than the maximum in all cases. LAR's were greatest at 27 C in onions and leeks and at 23 C in the other two species. Between 10 and 19 C both LAR and NAR increased in all species. Between 19 and 27 C increases in LAR were compensated for by decreases in NAR with the result that R_w showed little change with temperature. Averaging over all temperatures the species were ranked in order of decreasing R_w, NAR and LWR as onion, leek, Japanese bunching onion and chives. For LAR this ordering was reversed with respect to onions and leeks. Plant to plant variability increased in the order onion, leek, Japanese bunching onion then chives. Although onions were the fastest growing of the Alliums tested their R_w was lower than that of several other vegetable species for which R_w was similarly measured.     

Delaying onion planting to control onion maggot (Diptera: Anthomyiidae): efficacy and underlying mechanisms

Onion maggot, Delia antiqua (Meigen) (Diptera: Anthomyiidae), is an important pest of onion, Allium cepa L., in northern temperate areas, especially in the Great Lakes region of North America Management of D. antiqua relies on insecticide use at planting, but insecticide resistance can cause control failures that threaten the long-term viability of this strategy. Delaying the time onions are planted was investigated as an alternative management approach for D. antiqua and the ecological and behavioral mechanisms underlying host age and insect relationships were examined in laboratory and field experiments. Delaying onion planting by two to four weeks reduced damage to onions by 35 and 90%, respectively. Onions planted later emerged later and this reduced the period overwintered flies had to oviposit on the plants. Moreover, flies tended to lay few to no eggs on these young, late-planted onions. As anticipated, D. antiqua laid 4-8 times more eggs on older onions than on young onions, and older onions were more resilient to injury caused by D. antiqua neonates compared with younger onions. However, the resiliency to maggot attack lessened as the density of D. antiqua increased from 2 to 10 eggs per plant, which probably explains why greater levels of maggot damage are typically observed in early onion plantings compared with later plantings. Delaying onion planting until mid-May reduced D. antiqua damage without jeopardizing the period required to produce marketable yield, but this cultural tactic must be combined with other management strategies to prevent economic loss.     

OEM—A new medium for rapid isolation of onion-pathogenic and onion-associated bacteria

Onions (Allium cepa L.) are plagued by a number of bacterial pathogens including Pantoea ananatis, P. agglomerans, Burkholderia cepacia, Enterobacter cloacae, Pectobacterium carotovorum subsp. carotovorum, Xanthomonas axonopodis pv. axonopodis and several Pseudomonas spp. We developed a semi-selective medium, termed onion extract medium (OEM), to selectively and rapidly isolate bacteria pathogenic to and associated with onions and onion-related samples including bulbs, seeds, sets, transplant seedlings, soil and water. Most strains of interest grow sufficiently on OEM in 24 h at 28 °C for tentative identification based on colony morphology, facilitating further characterization by microbiological and/or molecular means.     

Cytotoxic effect of chlorophenols on cells of the root meristem of welsh onion (Allium fistulosum L.) seeds

Chlorophenols are precursors to more dangerous environmental toxicants, which are characterized by mutagenic and carcinogenic properties. The methods of bioassay on plant test objects to study the influence of different pollutants allow one to connect the mutagenicity and cytotoxicity of investigated substances. The genotoxic and cytotoxic effects of pentachlorophenol and trichlorophenol solutions on root meristem cells of the Welsh onion Allium fistulosum L. shoots have been studied. Doze-dependent inhibition of seed germination of Welsh onions as a consequence of the influence of pentachlorophenol and trichlorophenol solutions with different concentrations shows a significantly greater toxic effect of pentachlorophenol, dependending on the doze, on seed germination than trichlorophenol.