Transgenic resistance confers effective field level control of bacterial spot disease in tomato

We investigated whether lines of transgenic tomato (Solanum lycopersicum) expressing the Bs2 resistance gene from pepper, a close relative of tomato, demonstrate improved resistance to bacterial spot disease caused by Xanthomonas species in replicated multi-year field trials under commercial type growing conditions. We report that the presence of the Bs2 gene in the highly susceptible VF 36 background reduced disease to extremely low levels, and VF 36-Bs2 plants displayed the lowest disease severity amongst all tomato varieties tested, including commercial and breeding lines with host resistance. Yields of marketable fruit from transgenic lines were typically 2.5 times that of the non-transformed parent line, but varied between 1.5 and 11.5 fold depending on weather conditions and disease pressure. Trials were conducted without application of any copper-based bactericides, presently in wide use despite negative impacts on the environment. This is the first demonstration of effective field resistance in a transgenic genotype based on a plant R gene and provides an opportunity for control of a devastating pathogen while eliminating ineffective copper pesticides.     

An antagonistic actinomycete for suppression of tobacco brown spot

We have identified a promising antagonistic micro-organism for suppressing brown spot disease. This isolate (strain 182-2) was found belonging to Streptomyces cacaoi. Strain 182-2 and its bacteria-free culture broth filtrate showed inhibitory effects both in vitro and in vivo, and is highly stable. Strain 182-2 has great potential to be developed as a commercial agent.     

Effect of selected fungicides and Bio-Pesticides on the mycelial colony growth of the Helminthosporium oryzae. brown spot of rice

Helminthosporium oryzae, a fungal pathogen causing Brown Spot of Rice is one of the disastrous biotic factors responsible for 16–43% yield in rice. To control in vitro fungal growth of this pathogen, four fungicides viz. Mencozeb, Thiophanate Methyl, Iprovalicarb + Propineb and Propineb were used with four different concentrations: 50, 100, 150 and 200 ppm. Plant extracts of five species as Azadirachta indica, Calotropisprocera, Allium sativum, Datura stramonium and Zingiber officinale were also tested with three doses (5, 10 and 15 ml). While, 24 isolates of Bacterial isolates were investigated for their antagonistic effect. The in vitro results of the four fungicides contributed that Mancozeb and Thiophanate Methyl inhibited the colony growth at the higher doses (150 and 200 ppm) with no linear colony growth. However, Propineb was found moderately effective at (5.00 mm) and Iprovalicarb + Propineb was less effective (7.25 mm). Similarly, the in-vitro efficacy of the five plant extracts against H. oryzae at different doses revealed that Zingiber officinale and Allium sativum were more effective at high doses (00.00 mm, 2. mm). Also, Datura stramonium (4.62 mm) Azadirachta indica (18.00 mm) and Calotropisprocera (12.00 mm) performed better as compared to the control (40.00 mm). The results revealed that out of 24 isolates, 4 isolates of bacteria Agrobacterium spp, Xanthomonas, Erwinia, Streptomyces has inhibited the linear colony growth of H. oryzae up to 1-2 mm. This study can be useful for controlling the fungal disease as the two fungicides Mancozeb and Thiophanate Methyl were more effective and the Zingiber officinale and Allium sativum plant extracts were highly effective against the brown spot of rice. Biocontrol also reduced leaner colony Helminthosporium oryzae.     

In vitro screening of rice germplasm for resistance to brown spot disease using phytotoxin

Summary Two R₁ IR₈ plants derived from somatic cells cultured in 25% Helminthosporium oryzae toxin-medium, and one IR₅₄ plant derived from a control (toxin free medium) were found to have mutated resistance to brown spot disease of rice. In the second generation (R₂, the offspring of the R₁ generation) of the three resistant populations, the segregation of resistance and susceptibility to the disease was observed. This is the first report about a disease resistant mutation obtained successfully in rice by tissue culture and in vitro screening with phytotoxin.This research was conducted at the IRRI, Manila     

Identification and fine-mapping of a bacterial brown spot disease resistance gene in maize

Bacterial brown spot (BBS) in maize (Zea mays L.) is caused by Pseudomonas syringae pv. syringae Van Holl (Pss). In China, this disease is not prevalent in maize at present. Here, we report the identification and fine mapping of the gene, referred to as Psy1, which confers resistance to BBS. An F₂ population, derived from the cross P25/F349, was used for linkage analysis and mapping of the resistance gene Psy1. Analysis of a BC₈F₂ population, derived from the same parents, confirmed that Psy1 was located on chromosome 10L and inherited as a single dominant gene. For fine mapping of Psy1, two introgression lines, X41 and X44, homozygous at the resistant gene locus, were introduced to hybridize with the susceptible parent P25 respectively, and developed a mixed BC₁ population. We found the closest markers to Psy1 are EST1 and FG29-3, which located on two adjacent BACs respectively, based on the B73 BAC sequence. Sequence analysis of these two BAC sequences (~300 kb) revealed the presence of a homologous sequence of receptor-like kinase. Also a co-segregation marker was developed based on this homologous sequence. These results will be useful for cloning of Psy1 and for transferring or pyramiding Psy1 through MAS in maize breeding programs.     

A rapid colony screening method for the detection of arsenate-reducing bacteria

A rapid and simple method has been developed for the detection of arsenate reducing bacteria based on the presence of arsenite [As (III)], the end product of anaerobic arsenate [As (V)] respiration. Confirmation of As (III) product is made by the reduction of starch-iodine complex. The method can be used over a large pH range (5.5–9.0) and can easily be determined at arsenite concentration as low as 0.025 mM. Major advantages of this technique are that a large number of samples can be analyzed easily at a time.     

Effectiveness of acibenzolar-S-methyl, fungicides and antibiotics for the control of brown eye spot, bacterial blight, brown leaf spot and coffee rust in coffee

This study was carried out to evaluate the potential of acibenzolar‐S‐methyl (ASM), combined or not combined with fungicides and antibiotics for the control of brown eye spot (Cercospora coffeicola) and bacterial blight (Pseudomonas syringae pv. garcae) in coffee seedlings, and ASM combined with conventional fungicide application schedules for the control of coffee rust (Hemileia vastatrix) and brown leaf spot (Phoma costarricencis) under field conditions in two coffee crops in the State of São Paulo, Brazil. ASM protected coffee seedlings against C. coffeicola when applied at the rates of 2.5 and 5 g of active ingredient per hectolitre of water (g a.i. hL^?1), providing 34–55% of disease control, and against bacterial blight, when applied at the rates of 2.5, 10 and 20 g a.i. hL^?1, with 38–57% of disease control. Tebuconazole (100 g a.i. hL^?1) and azoxystrobin (10 g a.i. hL^?1) showed the best results for brown eye spot control. Oxytetracycline + streptomycin, kasugamycin hydrochloride, oxytetracycline + metallic copper, copper oxychloride and mancozeb + copper oxychloride also controlled bacterial blight in levels similar to those shown by ASM. In the field experiments, all fungicide application schedules tested, cyproconazole (December, February, April), epoxiconazole (December, March), tetraconazole (December, February, April), cyproconazole (December, February) and azoxystrobin (January, March) were effective for coffee rust control and provided partial control of brown leaf spot. The results also showed that for all experiments, there was no synergistic effect of the combination of ASM with azoxystrobin, cyproconazole or cupric fungicides.     

Enhancement of the citrus immune system provides effective resistance against Alternaria brown spot disease

In addition to basal defense mechanisms, plants are able to develop enhanced defense mechanisms such as induced resistance (IR) upon appropriate stimulation. We recently described the means by which several carboxylic acids protect Arabidopsis and tomato plants against fungi. In this work, we demonstrate the effectiveness of hexanoic acid (Hx) in the control of Alternaria brown spot (ABS) disease via enhancement of the immune system of Fortune mandarin.     

The expression of a baculovirus-derived chitinase gene increased resistance of tobacco cultivars to brown spot (Alternaria alternata)

The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) chitinase gene coding region was amplified using the polymerase chain reaction, inserted into a plasmid (pROK‐2) and replicated in Escherichia coli XL1–blue. The recombinant plasmid was mobilised into Agrobacterium tumefaciens LBA 4404 and inoculated into tobacco leaf discs. The presence of the expressed chitinase in foliar tissue of kanamycin‐resistant plantlets of three Nicotiana tabacum cultivars (CF80, K326 and Xanthi‐nc) was inferred using immunoblotting, and enzyme activity was confirmed using a fluorometric assay. Confocal laser scanning microscopy with immunofluorescent staining of foliar sections from N. tabacum Xanthi‐nc expressing the viral chitinase indicated that the enzyme was restricted to the vascular tissue. Heliothis virescens larvae fed on leaf tissue expressing chitinase were not impaired either in their development to pupation or in their feeding behaviour, in comparision with their counterparts that had consumed similar amounts of untransformed tobacco leaf tissue. By contrast, when tobacco leaves were mechanically inoculated with Alternaria alternata, very few brown spots were observed at inoculation sites in chitinase‐expressing tissue, whereas large and spreading lesions formed in untransformed tobacco tissue. Of all lines that were transformed, as determined by kanamycin resistance, 59% had fewer symptoms of disease (smaller disease indices) than those for untransformed controls.     

A rapid method for assessing the resistance of polyurethanes to biodeterioration

A rapid soil burial method for assessing the susceptibility of polyurethanes to biodeterioration was developed. The time of the test was reduced by prestressing the polyurethanes. The degree of deterioration was measured by following changes in the appearance of the polyurethanes and in selected physical properties. It was found that pre-stressing produced significant reductions in the tensile strength of a known susceptible polyurethane after burial in soil for 2 weeks. The reduction was greater than that found with unstressed polyurethanes buried for 26 weeks in active soil. Changes in tensile strength were less after burial for 4 weeks in sterile soil than after burial in active soil for the same period. The results suggest that deterioration of polyurethane during soil burial is a result of both chemical and microbial action.     

褐飞虱对吡虫啉抗性监测方法的研究

从结果的稳定性、准确性和操作方便等角度出发 ,建立了适合于监测褐飞虱 (NilaparvatalugensSt l)对吡虫啉抗性的稻苗浸根法。与其他方法相比 ,该方法除具有简单易行的特点外 ,还表现出很好的监测准确性。通过建立不同虫态和不同若虫龄期敏感基线以及对桂林、安庆、东台 3个地区的抗性监测 ,发现 3地褐飞虱对吡虫啉都处于敏感性下降阶段 ,安庆和东台地区的敏感性弱低于桂林     

A rapid method to screen fungi for resistance to toxic chemicals

Although many species of fungi are able to degrade highly toxic chemicals, only a few species have been evaluated for resistance to toxic effects of these chemicals. In this paper we demonstrate the successful application of a method to rapidly screen several species of fungi for toxicity to chemicals or mixtures of chemicals using pentachlorophenol (PCP) as a model toxic compound. Cellulose antibiotic assay disks were soaked in solutions containing different concentrations of PCP (5, 10, 25, 50, and 80 mg l^–1) and then placed in a triangular pattern outside the growing edge of the mycelia of eighteen species of white rot fungi. The plates were incubated and observed for development of inhibition zones (non-growth areas) around the disks. The short-term (24 h) growth of all eighteen species of fungi was inhibited by 5–10 mg-PCP l^–1, a range similar to that observed using previously reported techniques. Long-term growth studies using this screening method were not useful since PCP diffused from the disk into the agar, decreasing the applied dose.     

A rapid method for the evaluation of nerve conduction blocking compounds

A simple and easily accessible cockroach nerve preparation is described. Afferent potentials elicited by electric stimulation of the cercus showed remarkable stability, providing a fairly adequate background for pharmacological experimentation. Type I and type II pyrethroids were tested on the nerve preparation, and the results were compared with toxicity data obtained on the same species. Blockade of nerve conduction showed positive correlation (r = 0.804) with lethal effects. The preparation would be useful for determining neuronal point of attack of test compounds and the study of pyrethroids.     

A rapid method for detecting mitochondrial DNA variation in the brown trout, Salmo trutta

A method is described for the amplification and restriction digestion of two variable regions of mitochondrial DNA (mtDNA) in the brown trout ( Salmo trutta ) as a non-invasive sampling and rapid screening technique for measuring genetic variation in populations.     

Screening of chilli germplasm for resistance to Alternaria leaf spot disease

Chilli is one of the spices used to enhance the flavour and taste of cooked food. Fungal diseases are the main biological constraints in chilli production, and Alternaria leaf spot disease caused by Alternaria alternata is one of the most devastating diseases of chilli. One of the effective and environmentally friendly ways to control this disease is introgress resistance from wild relative/varieties to the cultivated one. The first step towards introgression of resistance genes is to screen the chill germplasm for leaf spot resistance. In the current study, we screened the chilly germplasm and identified the sources of leaf spot resistance, which can be harnessed in resistance breeding programmes.     

A rapid method to test for chloroplast DNA involvement in atrazine resistance

A point mutation in the chloroplast psbA gene at codon 264 resulting in an animo acid substitution (ser-gly) manifests itself as atrazine resistance in all recognized weed species studied to date. The single base substitution overlaps a highly conserved Mae1 restriction site which is present in susceptible but not in resistant plants. This restriction enzyme, recently commercialized, has been used to show that it is now possible to discriminate rapidly between the two biotypes without the need for DNA sequencing.     

A rapid method for evaluation of analgesic and anti-inflammatory activity in rats

Carrageenin (2%) was used to produce edema and hyperalgesia; indomethacin, phenylbutazone, aspirin, ibuprofen, analgin, paracetamol and phenacetin were tested at different doses for anti-inflammatory and analgesic activity in the same rats as the peak for the edema reached at the end of 3rd hr and for the hyperalgesia at the end of 4th hr. Indomethacin, phenylbutazone and ibuprofen reduced edema and increased the pain threshold. Analgin and aspirin increased the pain threshold relatively at a low dose. Paracetamol and phenacetin were inactive in the doses tested. Carrageenin (2%) was observed to possess both phlogistic and allogenic properties.     

An automated method for rapid determination of diffusion coefficients via measurements of boundary spreading

The use of a simple device by which a layer of solvent may be deposited onto a solution of an optically absorbing solute in a cylindrical quartz tube, without substantial mixing of solution and solvent, is described. The spreading of the boundary thus formed may be monitored as a function of time using an automated absorbance scanning device previously described [A. K. Attri and A. P. Minton (1983) Anal. Biochem. 133, 142-152]. A semiautomatic procedure for determining the diffusion coefficient from the time dependence of the shape of the boundary is described and is particularly well-suited for real-time data analysis with a laboratory microcomputer. The diffusion coefficients of several proteins have been measured using the technique reported, and the results are generally in good agreement with values reported in the literature. The feasibility of using this technique in combination with a previously described method for measuring the sedimentation coefficient [A. K. Attri and A. P. Minton (1984) Anal. Biochem. 136, 407-415] to rapidly determine the molecular weight of a protein is established.     

Use of cell culture to screen sunflower germplasm for resistance to Phomopsis brown/gray stem spot

Resistance to Phomopsis sp. (Diaporthe sp.) brown/gray stem spot was confirmed by screening sunflower calli on shoot induction media amended with fungal filtrate. Calli of sunflower genotypes OCMS 74 and NS-H-45, which show resistance to the disease in field trials, remained viable on media with 15% (v/v) fungal filtrate, while calli of field susceptible genotypes RHA 273 and PAG/SF 103 were killed on media with as little as 7.5% fungal filtrate. Fresh weight of calli of all genotypes was significantly reduced by 2.5% fungal filtrate, and calli of all genotypes were killed by filtrate concentrations of 20%. These in vitro results corroborate prior field observations for disease reaction of these genotypes.