Root Tissue Samples Research Articles

Risk prediction tools and the interaction of soybean sudden death syndrome and soybean cyst nematode

A test for the soybean sudden death syndrome (SDS) pathogen was recently developed using root tissue or soil samples to determine the quantity of the pathogen's DNA that is present. This was used to predict where the SDS hot spots were going to develop in the field. Soybean cyst nematode numbers were also found to be risk factors in predicting where the SDS hot spots and yield loss were going to occur. Earn 0.5 CEUs in Integrated Pest Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/701.

Transfer of Copper and Zinc from Soil to Grapevine-Derived Products in Young and Centenarian Vineyards

Application of fungicides on grapevines is the main source of soil contamination by copper and zinc. Studies on this issue in relatively young grapevines are common; however, studies that elucidate the metal transfer in a soil-plant-food production system in a centenarian vineyard are scarce. The present work was aimed at tracing the copper and zinc accumulation in three different compartments—soil, plant, and vine products—in young and centenarian vineyards. Soil samples were collected in the middle plant row and rhizosphere positions of the vineyards; samples of root and leaf tissue and of grape juice and wine from these vineyards were also collected. In the centenarian vineyard, the soil available copper, regardless of vineyard position, reached 1100 mg kg−1. Copper in root and leaf tissues reached 12,300 mg kg−1 and 6800 mg kg−1, respectively. In grape juice and wine, copper was 9.08 mg L−1 and 0.78 mg L−1, respectively. The roots retained most part of the metals reducing their transfer through the system. However, Cu levels in the grape juice from the centenarian vineyard exceeded by 908% the limit established by Brazilian and international norms. Zinc concentrations in soil and vine products were within the permitted level. Finally, the magnitude of metal transfer and accumulation is due to decades of cupric fungicide application and varies according to the compartment evaluated. The findings will provide information to rethink the vineyard agricultural practices in order to avoid environmental contamination by metals and compromising the whole food chain.

The abundance of arbuscular mycorrhizal fungal species in symbiosis with okra plants is affected by induced drought conditions in a calcareous substrate

Here we examined the effect of soil drought conditions on the community and abundance of arbuscular mycorrhizal fungi (AMF) in symbiosis with okra (Abelmoschus esculentus), where the inoculated AMF community was originally obtained from the rhizosphere of an okra crop grown in the Sudan. Okra seedlings were cultivated in a calcareous pot substrate, where the water content was either maintained at 20% for the well-watered (W) or reduced to 10% for the drought treatment (D). At harvest, in both irrigation treatments the root length was highly AMF colonised and compared with treatment W, the drought condition (D) significantly limited the uptake of phosphorus but not that of nitrogen, potassium, iron or zinc. The AMF DNA sequences recovered from the initial field soil, substrate and root samples identified twelve AMF taxa in total belonging to the two Glomeromycotina families Glomeraceae (91%) and Claroideoglomeraceae (9%). The number of operational taxonomic units (OTUs) in root tissue and pot substrate samples was unaffected by the stress treatment D. However, while certain AMF taxa (notably Glomus hoi) were likewise present in samples recovered from both the water treatments, there was a shift of abundance for other taxa. The abundance of Rhizophagus aff. arabicus was significantly higher in D than in W, mainly at the expense of Dominikia sp. The results suggested that, within a few weeks of root colonisation, soil drought together with low P availability imposes a major shift in the relative abundance of some AMF taxa. Moreover, under the given dry substrate conditions, R. aff. arabicus appeared to comprise a high competitiveness within the Glomeraceae - dominated AMF community.

Patterns of storage tissue and starch distribution in the young taproot of obligate seeders and resprouters of Australian Proteaceae (Juss.): Possible evidence of homoplastic evolution

The ancient Gondwanan family Proteaceae has its greatest speciation in fire-prone environments of Australia. Fire response is either by seedling recruitment from parent plants that succumb to fire (obligate seeders), or survival and resprouting from protected buds (resprouters). Starch is the main source of energy for resprouting and in roots is restricted to parenchyma tissue. This study compared the size and distribution of storage parenchyma and the magnitude of starch reserves in roots of several proteaceous species from different genera in relation to their fire response and taxonomy. Cross-sections (2 μm) of roots of 51 resprouter and 42 seeder species from 12 genera were stained for starch. Areas of cortex and ray parenchyma along with starch grain density were measured using image analysis software (Assess 2.0) and comparable samples of root tissue were assayed chemically for starch. Starch, where present, predominated in ray and cortex tissue with a greater percentage in resprouters (13.4 ± 1.03) than seeders (1.8 ± 0.26); these results correlated significantly with the chemical assay for starch (r = 0.93, P < 0.0001). Resprouters also had more storage parenchyma (56.9 ± 1.72%) than seeders (41.9 ± 1.91%) mostly due to broader rays (17.5 ± 1.22%) compared with seeders (8.2 ± 0.16%). Percentage of cortex tissue was similar for seeders and resprouters (39.4 ± 2.24 and 33.7 ± 2.04 respectively). Anatomical preferences for storage site were consistent within genera and broad suprageneric groupings. This study shows that histological analysis of root starch is a reliable predictor of resprouting capacity in Proteaceae and that patterns of storage tissue within genera, together with the persistence of parenchyma devoid of starch in seeders, are consistent with response to fire and suggests homoplastic evolution of this response within the family.

Endurance assessment of Eichhornia crassipes (Mart.) Solms, in heavy metal contaminated site–A case study

AbstractIn this study, the ability to hyper accumulate heavy metals from contaminated site by water hyacinth (Eichhornia crassipes) was monitored. The heavy metal-contaminated habitat was validated by X-ray diffraction and energy dispersive X-ray elemental spectrometry analysis of the soil samples. Heavy metal contamination in soil and water; accumulation in foliar, root and bulb tissue samples were determined by atomic absorption spectroscopy and were monitored as a function of accumulation in different tissues. Significant differences were recorded in the bioaccumulation capability of heavy metals by different tissue. Discrete variation in protein profile of leaves and high expression of alcohol dehydrogenase (ADH), peroxidase (POX) and altered regulation of esterase (EST) in root tissue was observed in contaminated site grown Eichhornia. The high metal accumulation efficiency of water hyacinth due to the biomass production suggests this species as reliable organic biomarker for heavy metal contamination.

Effect of Postharvest Defoliation on Carbon and Nitrogen Resources of High-Yielding Sauvignon blanc Grapevines

We quantified the importance of postharvest carbohydrate assimilation and nitrogen availability to replenish vine reserves, over and above maintaining optimal growth, productivity, and fruit quality of high-yielding, vigorous Sauvignon blanc grapevines. To create different carbohydrate (CHO) and nitrogen (N) reserve concentrations, our factorial-design trial consisted of a postharvest defoliation treatment overlaid with a pruning treatment in which 48 or 72 nodes were retained on four- or six-cane vertical shoot positioned vines, respectively. In defoliation (Defol) vines, all leaves were removed immediately after fruit harvest, while foliated vines (Fol) went through normal senescence. From just after ectodormancy in 2008, samples of root and trunk tissue were taken throughout the years for CHO and N analyses and results were compared with annual yield data. Both defoliation and node number treatments reduced vine growth and yield. Additionally, differences in CHO and N of the permanent structure were found. Depleted winter reserves in trunk and root were replenished during the next growth cycle, suggesting that grapevine N and CHO partitioning favor survival of the permanent structure over increasing vine size and yield. However, after two consecutive years of defoliation, the cumulative effects of smaller, less fruitful canes from year one and reduced carbohydrates from the subsequent year reduced both yield and vegetative growth in the third growing season. Therefore, even the short-lived postharvest canopy in cool climates contributes to the vine CHO economy. Defoliation or excessive crop loads affected carbohydrate reserves in vines, but only after several consecutive years of low recharge; this manifested iteself in lower yields and poorer vegetative growth.

Effect of Biochar Amendments on Peach Replant Disease

The use of biochar as a soil amendment has generated interest all over the world, and it has been advocated as a means to improve soil fertility and sequester carbon. The objective of this study was to test if the use of pinewood biochar could reduce the detrimental effects of replant disease (RD) on peach tree growth and biomass production. An RD-susceptible peach rootstock, Lovell, was grown in soil from a peach replant site (control), sterilized soil (sterilized), and biochar-amended soil at 10% and 20% (v/v) [low biochar (LB) and high biochar (HB), respectively], all from the same site. Trunk diameter increase was measured weekly; total aboveground and belowground biomass was determined by harvesting a subsample of plants at 11, 22, and 33 weeks after planting. Soil samples, and foliar and root tissue samples were collected before each harvesting date and analyzed for nutrient content. Total aboveground and belowground biomass production was significantly higher in the biochar and sterilized soil treatment (S) compared with the control. Root carbon (C*) content was significantly greater in the HB treatment compared with the control. Soil nitrate-N was significantly greater in the HB treatment by the third harvesting date, and foliar magnesium (Mg) concentrations were significantly higher in both biochar treatments for all harvesting dates. The results from this study provide evidence that biochar may alleviate RD in peach trees.

Transcriptome Analysis of Drought Induced Stress in &amp;lt;i&amp;gt;Chenopodium quinoa&amp;lt;/i&amp;gt;

Quinoa (Chenopodium quinoa Willd.) is a halophytic, allotetraploid grain crop of the Amaranthaceae family with impressive drought tolerance, nutritional content and an increasing worldwide market. Here we report the results of an RNA-seq transcriptome analysis of Chenopodium quinoa using four water treatments (field capacity to drought) on the varieties “Ingapirca” (representing valley ecotypes) and “Ollague” (representing Altiplano Salares ecotypes). Physiological results, including growth rate, photosynthetic rate, stomatal conductance, and stem water potential, support the earlier findings that the Altiplano Salares ecotypes display greater tolerance to drought-like stress conditions than the valley ecotypes. cDNA libraries from root tissue samples for each variety × treatment combination were sequenced using Illumina Hi-Seq technology in an RNA-seq experiment. De novo assembly of the transcriptome generated 20,337 unique transcripts. Gene expression analysis of the RNA-seq data identified 462 putative gene products that showed differential expression based on treatment, and 27 putative gene products differentially expressed based on variety × treatment, including significant expression differences in root tissue in response to increasing water stress. BLAST searches and gene ontology analysis show an overlap between drought tolerance stress and other abiotic stress mechanisms.

Relationships between Microsclerotia Content and Hyperspectral Reflectance Data in Soybean Tissue Infected by Macrophomina phaseolina

Alternative methods are needed to assess the severity of charcoal rot disease [Macrophomina phaseolina (Tassi) Goid] in soybean [Glycine max (L.)] plant tissue. The objective of this study was to define the relationship between light reflectance properties and microsclerotia content of soybean stem and root tissue. Understanding that relationship could lead to using spectral reflectance data as a tool to assess the severity of charcoal rot disease in soybean plants, thus reducing human bias associated with qualitative analysis of soybean plant tissue and cost and time issues connected with quantitative analysis. Hyperspectral reflectance measurements (400-2490 nm) were obtained with a non-imaging spectroradiometer of non-diseased and charcoal rot diseased ground stem and root tissue samples of six soybean genotypes (“Clark”, “LD00-3309”, “LG03- 4561-14”, “LG03-4561-19”, “Saline”, and “Y227-1”). Relationships between the reflectance measurements and tissue microsclerotia content were evaluated with Spearman correlation (rs) analysis (p < 0.05). Moderate (rs = ±0.40 to ±0.59), strong (rs = ±0.60 to ±0.79), and very strong (rs = ±0.80 to ±1.00) negative and positive statistically significant (p < 0.05) monotonic relationships were observed between tissue spectral reflectance values and tissue microsclerotia content. Near-infrared and shortwave-infrared wavelengths had the best relationships with microsclerotia content in the ground tissue samples, with consistent results obtained with near-infrared wavelengths in that decreases in near-infrared spectral reflectance values were associated with increases in microsclerotia content in the stem and root tissue of the soybean plants. The findings of this study provided evidence that relationships exist between tissue spectral reflectance and tissue microsclerotia content of soybean plants, supporting spectral reflectance data as a means for assessing variation of microsclerotia content in soybean plants. Future research should focus on the modelling capabilities of the selected wavelengths and on the feasibility of using these wavelengths in machine learning algorithms to differentiate non-diseased from charcoal rot diseased tissue.

Boron accumulation and tolerance of hybrid poplars grown on a B-laden mixed paper mill waste landfill

Paper mill wastes are a mixture of by-products from pulp production and on-site energy production, consisting of paper mill sludge, ash and cinders. Landfilling of these highly boron (B) and heavy metal laden waste products carries environmental risks. Poplars have been successfully employed in the phytomanagement and hydraulic control of B contaminated sites. Here, we assess the performance of hybrid poplars on a paper-mill waste landfill, investigate the accumulation of B by the trees and explore the relationship between local-scale root growth and substrate properties. Leaf and root tissue samples were collected on three plots and analyzed for their chemical properties and root traits. Additionally, we sampled four soil cores in the vicinity of each of the trees and determined chemical and physical properties. Using a principal component analysis followed by a cluster analysis, we identified three substrate types. This method delineated the soil effects on tree survival and growth, although correlations with individual soil element concentrations were weak. Despite signs of B toxicity in some leaves, B was not the key limiting factor for poplar growth. Instead, Ca deficiency caused by a Mg:Ca imbalance was the primary reason for the poor performance of some trees. Root growth was not limited by toxicity effects of soil contaminants. Our results show that hybrid poplars perform well under the harsh growing conditions on a multi-contaminated, B-laden substrate in a hemiboreal climate. Exploiting the differences in the performance of the four clones in relation to the soil types, could increase the success of revegetation on this and other landfills.

Ice-Cap: A Method for Growing &lt;em&gt;Arabidopsis&lt;/em&gt; and Tomato Plants in 96-well Plates for High-Throughput Genotyping

It is becoming common for plant scientists to develop projects that require the genotyping of large numbers of plants. The first step in any genotyping project is to collect a tissue sample from each individual plant. The traditional approach to this task is to sample plants one-at-a-time. If one wishes to genotype hundreds or thousands of individuals, however, using this strategy results in a significant bottleneck in the genotyping pipeline. The Ice-Cap method that we describe here provides a high-throughput solution to this challenge by allowing one scientist to collect tissue from several thousand seedlings in a single day 1,2. This level of throughput is made possible by the fact that tissue is harvested from plants 96-at-a-time, rather than one-at-a-time. The Ice-Cap method provides an integrated platform for performing seedling growth, tissue harvest, and DNA extraction. The basis for Ice-Cap is the growth of seedlings in a stacked pair of 96-well plates. The wells of the upper plate contain plugs of agar growth media on which individual seedlings germinate. The roots grow down through the agar media, exit the upper plate through a hole, and pass into a lower plate containing water. To harvest tissue for DNA extraction, the water in the lower plate containing root tissue is rapidly frozen while the seedlings in the upper plate remain at room temperature. The upper plate is then peeled away from the lower plate, yielding one plate with 96 root tissue samples frozen in ice and one plate with 96 viable seedlings. The technique is named "Ice-Cap" because it uses ice to capture the root tissue. The 96-well plate containing the seedlings can then wrapped in foil and transferred to low temperature. This process suspends further growth of the seedlings, but does not affect their viability. Once genotype analysis has been completed, seedlings with the desired genotype can be transferred from the 96-well plate to soil for further propagation. We have demonstrated the utility of the Ice-Cap method using Arabidopsis thaliana, tomato, and rice seedlings. We expect that the method should also be applicable to other species of plants with seeds small enough to fit into the wells of 96-well plates.

Ice-Cap: A Method for Growing &lt;em&gt;Arabidopsis&lt;/em&gt; and Tomato Plants in 96-well Plates for High-Throughput Genotyping

It is becoming common for plant scientists to develop projects that require the genotyping of large numbers of plants. The first step in any genotyping project is to collect a tissue sample from each individual plant. The traditional approach to this task is to sample plants one-at-a-time. If one wishes to genotype hundreds or thousands of individuals, however, using this strategy results in a significant bottleneck in the genotyping pipeline. The Ice-Cap method that we describe here provides a high-throughput solution to this challenge by allowing one scientist to collect tissue from several thousand seedlings in a single day 1,2. This level of throughput is made possible by the fact that tissue is harvested from plants 96-at-a-time, rather than one-at-a-time.The Ice-Cap method provides an integrated platform for performing seedling growth, tissue harvest, and DNA extraction. The basis for Ice-Cap is the growth of seedlings in a stacked pair of 96-well plates. The wells of the upper plate contain plugs of agar growth media on which individual seedlings germinate. The roots grow down through the agar media, exit the upper plate through a hole, and pass into a lower plate containing water. To harvest tissue for DNA extraction, the water in the lower plate containing root tissue is rapidly frozen while the seedlings in the upper plate remain at room temperature. The upper plate is then peeled away from the lower plate, yielding one plate with 96 root tissue samples frozen in ice and one plate with 96 viable seedlings. The technique is named "Ice-Cap" because it uses ice to capture the root tissue. The 96-well plate containing the seedlings can then wrapped in foil and transferred to low temperature. This process suspends further growth of the seedlings, but does not affect their viability. Once genotype analysis has been completed, seedlings with the desired genotype can be transferred from the 96-well plate to soil for further propagation. We have demonstrated the utility of the Ice-Cap method using Arabidopsis thaliana, tomato, and rice seedlings. We expect that the method should also be applicable to other species of plants with seeds small enough to fit into the wells of 96-well plates.

Selenium Regulates Gene Expression for Glucosinolate and Carotenoid Biosynthesis in Arabidopsis

Glucosinolates (GSs) and carotenoids are important plant secondary metabolites present in several plant species, including arabidopsis (Arabidopsis thaliana). Although genotypic and environmental regulation of GSs and carotenoid compounds has been reported, few studies present data on their regulation at the molecular level. Therefore, the objective of this study was to explore differential expression of genes associated with GSs and carotenoids in arabidopsis in response to selenium fertilization, shown previously to impact accumulations of both classes of metabolites in Brassica species. Arabidopsis was grown under 0.0 or 10.0 μM Na2SeO4 in hydroponic culture. Shoot and root tissue samples were collected before anthesis to measure GSs and carotenoid compounds and conduct gene expression analysis. Gene expression was determined using arabidopsis oligonucleotide chips containing more than 31,000 genes. There were 1274 differentially expressed genes in response to selenium (Se), of which 516 genes were upregulated. Ontology analysis partitioned differentially expressed genes into 20 classes. Biosynthesis pathway analysis using AraCyc revealed that four GSs, one carotenoid, and one chlorophyll biosynthesis pathways were invoked by the differentially expressed genes. Involvement of the same gene in more than one biosynthesis pathway indicated that the same enzyme may be involved in multiple GS biosynthesis pathways. The decrease in carotenoid biosynthesis under Se treatment occurred through the downregulation of phytoene synthase at the beginning of the carotenoid biosynthesis pathway. These findings may be useful to modify the GS and carotenoid levels in arabidopsis and may lead to modification in agriculturally important plant species.

Bacterial Leaf Scorch, a New Blueberry Disease Caused by Xylella fastidiosa

Since 2004, growers and scientists have observed a disorder described as “yellow twig” or “yellow stem” affecting a major selection of southern highbush blueberry, FL 86-19, in the south Georgia blueberry production region. The initial symptom observed was leaf marginal chlorosis and subsequent necrosis, which eventually progressed throughout the whole leaf resulting in early leaf fall. Thin, yellow twigs or yellow stems became evident on some cultivars. The described symptoms on blueberry were similar to those exhibited on grapes with Pierce's disease and on plum with leaf scald disease. This prompted the enzyme-linked immunosorbent assay (ELISA) tests and isolations of Xylella fastidiosa, which is the causal agent of the previously mentioned grape and plum diseases. Two leaf and two root tissue samples were collected from a diseased FL 86-19 plant for isolation and ELISA testing on 2 Mar. 2006. ELISA results indicated all four tissues tested positive for the bacterial pathogen, X. fastidiosa, whereas only the two root tissues provided positive isolations. One leaf and one root tissue sample were later collected from each of five additional diseased plants for isolation and ELISA testing. Both isolation and ELISA testing methods obtained positive results. Cultures were multiplied to inoculate seedlings of three cultivars: ‘Southern Belle’ (eight plants), ‘Premier’ (six), and ‘Powderblue’ (six) on 23 May 2006 and one selection, FL 86-19 (eight), on 31 May 2006. Two FL 86-19 plants started to show symptoms of marginal necrosis 54 days postinoculation, whereas one plant each of ‘Southern Belle’ and ‘Powderblue’ started to show symptoms of marginal necrosis 63 days postinoculation and ‘Premier’ stayed symptomless. All eight culture-inoculated FL 86-19 plants (100%) showed symptoms 72 days postinoculation, but no symptoms were observed on the control plants. One hundred twenty-six days postinoculation, two ‘Powderblue’ and four ‘Southern Belle’ plants showed mild symptoms, whereas all ‘Premier’ plants were asymptomatic. Positive reisolations of the bacteria from the inoculated symptomatic plants, not from asymptomatic plants, fulfilled Koch's postulates, which confirmed X. fastidiosa was the causal bacterium of the new blueberry disorder, the bacterial leaf scorch of blueberry.

Sanitizing long-term micropropagated grapes from covert and endophytic bacteria and preliminary field testing of plants after 8 years in vitro

Micropropagated grape (Vitis vinifera L.) cv. Arka Neelamani cultures showed a decline in root and shoot growth performance after 6–7 yr of continuous in vitro culture. Indexing the culture medium using nutrient agar or 523 bacteriological medium (Viss et al., 1991) revealed covert bacteria in 75–100% cultures. Testing the tissue from different parts of in vitro plantlets on nutrient agar showed bacteria comprising of six or more morphotypes in 100% of root and collar tissue samples but less frequently in stem segments. The shoot tips had the lowest incidence of bacterial association. The whole shoots treated with NaOCl (4% chlorine) or HgCl2 (0.1%) showed endophytic bacterial survival. Culturing the HgCl2-treated (5 min) shoot tips on antibiotic overlaid medium (1 ml of 50 mg l−1 gentamycin and/or cefazolin) in culture tubes (150×25 mm) for 1 mo. facilitated the cleansing of cultures with 75% recovery of contaminant-free shoots as monitored through indexing for the next 2 yr. Repeated indexing of medium and tissue from various plant parts during the first two to four subculture cycles following antibiotic treatment was instrumental in reliably identifying clean cultures and preventing bacterial re-emergence. Antibiotic incorporation in the medium was detrimental to grape microcuttings. Bacteria-freed cultures showed 80–100% rooting and a high number of plantlets that could be acclimatized. The plants put in the field after 8 yr of active micropropagation showed some juvenile characteristics initially, which disappeared in 6–8 mo., and the pruned shoots showed flowering and bunch development within 1 yr of field planting. This indicated the feasibility of keeping grape plants in vitro for long periods if covert microbes were eliminated.

Root and Foot Rot on Tomato Caused by Phytophthora infestans Detected in Belgium.

In January 2003, a severe root and foot rot was observed on 2-month-old wilted tomato (Lycopersicon esculentum Mill.) plants in a large-scale (2.5 ha) commercial greenhouse setting in Belgium. Tomato plants (10%) produced from healthy nursery-grown seedlings and planted to new, clean rockwool and drip irrigation with UV-disinfected water developed symptoms. Symptom development was restricted to lower plant parts with severe rotting of the entire root system and dark lesions girdling the stem base. No symptoms of disease were observed on the foliage or upper stems. Cross sections of the stem base revealed brown discoloration of internal tissue, including the vascular tissue and pith. Dark brown lesions also occurred on the roots. Sections of the stem base, the upper roots (sampled near to the stem base), and the lower roots (sampled on roots deeper in the rockwool) were plated separately on corn meal agar. The oomycete pathogen Phytophthora infestans (Mont.) de Bary was identified in each sample on the basis of morphological characteristics observed directly with light microscopy. Branched sporangiophores with slight swellings and characteristic lemon-shaped sporangia (35 × 20 μm and ratio length/width of 1.75 μm) at their tips were obvious after incubation in darkness at 24°C. Oospores and chlamydospores were not observed. After multiple soil treatment with oomycete-specific fungicides, the plants recovered. Since the occurrence of P. infestans on roots is unusual, the identity of the pathogen on the diseased plant tissues was confirmed with three techniques, DNA array identification, internal transcribed spacer (ITS) sequencing, and a polymerase chain reaction (PCR) amplification using P. infestans-specific primers. DNA was directly processed from separate samples of upper and lower root and stem base tissue. The DNA array used was originally developed to detect and identify the key fungal pathogens of tomato (2). Among detector probes for other tomato pathogens, this array contains oligonucleotide detector probes for P. infestans (PIN1: 5'-GGT TGT GGA CGC TGC TAT T and PIN2: 5'-AAT GGA GAA ATG CTC GAT TC). These probes are based on ITS sequences (ITS I and ITS II). Using conserved ribosomal primers OOMUP18Sc (5'-TGC GGA AGG ATC ATT ACC ACA C) and ITS4, oomycete DNA was amplified by PCR and simultaneously labeled with alkaline-labile digoxigenin (2). All generated amplicons strongly hybridized to the oligonucleotide detector probes for P. infestans and not to any other pathogen-specific detector probe present on the array. The pathogen could not be detected in roots and stem bases of symptomless plants. In addition, the ITS-region was sequenced and showed 100% homology with multiple GenBank accessions of P. infestans sequences. As a third confirmatory test, a PCR was performed on DNA extracts from infected root and stem base tissues using a primer set specific to P. infestans (O8-3/O8-4 [1]). A band of the expected size was produced for the infected stem base and root samples. Until now, this pathogen was known worldwide to cause late blight on potatoes and tomatoes. To our knowledge, this is the first report of root and foot rot of tomato caused by P. infestans.

Glucosinolate content and isothiocyanate evolution--two measures of the biofumigation potential of plants.

A total of 570 lyophilised Brassica root and shoot tissue samples were hydrolyzed, and the liberated isothiocyanates (ITCs) were analyzed by gas chromatography-flame photometric detection (GC-FPD). Glucosinolates (GSLs) were extracted from samples of the same tissues and analyzed by high-performance liquid chromatography (HPLC). The concentrations of six GSLs/ITCs (2-propenyl, 3-butyl, 4-pentenyl, benzyl, 4-methylthiobutyl, and 2-phenylethyl) as determined by the two techniques were compared. In 79% of the samples, the concentration of GSLs in the tissues was greater than that of the ITCs released on hydrolysis. Several possible reasons for the difference are proposed, including the effect of tissue storage time, hydrolysis of GSLs may be less efficient than the GSL extraction procedure, or some of the ITCs formed reacted with plant proteins and amino acids in the sample and were therefore not detected in the extract. GSL concentration in plant tissues is used to estimate the biofumigation potential of the plant tissue, whereas the actual biofumigation effect is thought to be due to the ITCs formed by hydrolysis of the plant-based GSLs. The variation between ITC and GSL values therefore has implications for the assessment of the biofumigation potential of the plant tissue.

Release of phytoalexins and related isoflavonoids from intact chickpea seedlings elicited with reduced glutathione at root level

Induction of phytoalexin formation in roots of chickpea ( Cicer arietinum L.) seedlings treated with the reduced form of glutathione (GSH) was investigated. Accumulation of phytoalexins and constitutive isoflavonoids upon GSH treatment was assessed by high performance liquid chromatography analysis of extracts from roots and liquid incubating media of seedlings, whereas the requirement for concurrent de novo synthesis of induced compounds was assessed in elicitation studies conducted in the presence of key enzyme inhibitors of the phenylpropanoid pathway and/or 〚U- 14C〛-L-phenylalanine. The results indicate that: (a) GSH elicits the formation not only of the pterocarpan phytoalexins medicarpin and maackiain, but also that of the constitutive isoflavones biochanin A and formononetin and, in seedlings older than 4 d, that of the isoflavanones homoferreirin and cicerin. (b) GSH-induced secondary metabolites do not accumulate in plant root tissue; rather, they are released into the surrounding external medium. (c) Phytoalexins and isoflavonoids induced by GSH are de novo synthesized from early phenylpropanoid pathway precursors rather than derived from pre-existing conjugate forms or immediate precursors. (d) Because of metabolic competence and/or proximity, only a small proportion of root cells is responsive to GSH elicitation, hence the very small amounts or absence of induced compounds detected in root tissue samples.

Determination of Heavy Metals in Soil Extracts and Plant Tissues at Around of a Zinc Smelter

Extractable contents of heavy metals such as Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Bi in soil and plant tissue samples (fruit, leaf, twig and root) collected, along a distance of 1100 m to the West, from the surroundings of a metallurgical factory producing mainly zinc, cadmium and lead were determined by flame atomic absorption spectrometry (FAAS). In addition, the determinations of Ca and Mg, macro nutrient elements for plants, were also performed. Three extractant solutions were used for dissolution of soil samples, namely aqua regia (1 HNO3+ 3 HCl) for total metal analysis, 1 mol L−1 ammonium acetate for exchangeable metal contents, and a dilute acid mixture (0.1 M HCl in 0.025 M H2SO4) for acid soluble metal contents. A mixture of HNO3 and HClO4 was used to analyze the fruit samples. The analyses of the leaf, the twig, and the root tissue samples were made by dry ashing method. The detection limits of the metals were in the range of 0.04 to 0.45 μg/mL for all soil extracts and 0.01 to 1.50 μg/mL for the fruit samples. The recovery values for all the determinations were higher than 95%. The results obtained from the analyses of plant tissue and soil samples were evaluated using linear correlation analysis and concentration factors to identify the effect of the factory near the grape-vine area.

Seasonal Concentrations of Non-structural Carbohydrates of Five Actinidia Species in Fruit, Leaf and Fine Root Tissue

To characterize seasonal patterns of carbohydrate concentrations in Actinidia species from different natural habitats, leaf, fruit and fine root tissue samples from five species (A. arguta, A. deliciosa, A. chinensis, A. polygama and A. eriantha) were collected over one season, and analysed for fructose, glucose, sucrose, myo -inositol and starch concentrations. Sucrose and starch peaked in leaf tissue around flowering time. In fruit, hexose sugars and/or myo -inositol transiently increased early in development. Starch accumulated in fruit of all species, beginning sooner after anthesis in A. arguta and A. polygama than in the other species. Sucrose accumulation coincided with onset of net starch degradation in A. arguta but was delayed in the other species. At final fruit sampling, concentrations of glucose and fructose were greater than sucrose in all species exceptA. arguta . myo -Inositol concentrations constituted >10% of total sugars for most of the season in leaf and fruit tissues of all species except A. polygama. Fine roots of A. arguta and A. polygama contained significantly more starch and sucrose for most of the year than those of the other species. Observed differences in seasonal carbohydrate patterns may reflect different natural habitats, with A. arguta and A. polygama growing naturally in colder climates than the other species. Transient accumulation of sugars in fruit during early stages of development has been considered to act as primary osmoticum for cell expansion. However, the presence of only low sugar concentrations in A. eriantha questions this hypothesis.