Non-destructive methods of detecting Curtobacterium flaccumfaciens pv. flaccumfaciens in mungbean seeds

An indirect immunofluorescent assay (IF) with specific monoclonal antibodies (MAbs) and a semi-selective agar medium for Curtobacterium flaccumfaciens pv. flaccumfaciens , developed in this study, were compared with foliar symptoms and microscopic bacterial ooze for detection of this pathogen in mungbean seed 6 d and 28 d after germination. The IF method detected more infected seedlings than the other three methods at both samplings. Symptomless carriers of C. flaccumfaciens pv. flaccumfaciens in mungbean were detectable only by the IF method and, less frequently, by plating out on media. Poor agreement between the IF and other methods was found. The IF method gave the best agreement in the detection of the pathogen between early and late samplings of individual germinated seed. Currently, the IF technique with a specific MAb is being used for selecting clean seedlings for production of disease-free seed.     

Evaluation of the efficacy of immunomagnetic separation for the detection of Clavibacter michiganensis subsp. michiganensis in tomato seeds

Aims: To evaluate the effectiveness of the optimized immunomagnetic separation (IMS)‐plating protocol in relation to other culture, serological and molecular techniques currently used for Clavibacter michiganensis subsp. michiganensis in seed‐testing laboratories. Methods and results: Bacterial suspensions, tomato seed extracts spiked with the pathogen and naturally infected seeds were IMS‐plated for the detection of C. m. subsp. michiganensis. These results were compared with plating on general (YPGA) and semiselective (mSCM) media, double‐antibody sandwich enzyme‐linked immunosorbent assay (DAS‐ELISA), immunofluorescent assay (IF) or polymerase chain reaction (PCR). Different seed lots and pathogen strains were also tested. IMS‐plating allowed the detection of less than 10 CFU ml^?1 of pathogen in all assayed samples. The mSCM medium provided positive results for 10 CFU ml^?1 in naturally infected seeds, but up to 14 days was necessary for the typical colonies of the target to be come visible. By serological techniques, 10³ and up to 10⁴ CFU ml^?1 were detected by IF and ELISA, respectively. DNA extraction was required to obtain positive results by PCR in seed extracts containing 10³ CFU ml^?1 or more. Conclusions: Among the evaluated methods, IMS‐plating provided the best results regarding sensitivity and specificity for C. m. subsp. michiganensis detection, allowing the recovery of viable bacteria from seed extracts. Significance and impact of the study: IMS‐plating increases isolation rates of C. m. subsp. michiganensis and could improve standard protocols currently used for routine analysis.     

A serological test for detecting Botrytis allii, the cause of neck rot of onion bulbs

Polyclonal antisera for the immunological detection of Botrytis allii, the cause of onion neck rot, were raised from cell wall and cytoplasmic fractions of the fungus, and from surface plate washings of two isolates of the pathogen. These antisera were used to develop an indirect ELISA for the detection of latent B. allii infection in stored onion bulbs. The antisera did not react with healthy onion tissue and showed only minimal recognition of fungi from other genera. Some cross-reactivity was observed with B. cinerea but not with other Botrytis spp. tested. In many instances following infection, fungal antigen could be detected earlier by ELISA than by direct culture. In tests on bulbs from a commercial store, the level of B. allii infection was found to be 3.3% by both ELISA and direct plating, but this result was achieved 7 days sooner by ELISA. In field tests, the indirect ELISA gave a good indication at harvest of the probable incidence during storage of neck rot in untreated and artificially inoculated plants, whilst culturing gave results consistently lower than the ELISA until bulbs had been in store for several months, when results for ELISA and culturing were the same. Spores applied to growing plants during the growing season led to greater levels of neck rot than did infested seed, indicating that field debris and waste from cold stores may be more important sources of inoculum in some years than seed contamination.     

Occurrence of <Emphasis Type="Italic">Xanthomonas axonopodis</Emphasis> pv. <Emphasis Type="Italic">phaseoli</Emphasis>, the causal agent of common bacterial blight disease,on seeds of common bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) in upper Egypt

Common bean seed lots collected from different seed dealers and Malawii agriculture station were screened for the presence of Xanthomonas axonopodis pv. phaseoli. In the laboratory the pathogen was isolated following the routine laboratory assay method, i.e. direct plating method using yeast extract-dextrose-calcium carbonate agar medium (YDC). Yellow, convex, mucoid colonies of Xanthomonas were consistently isolated on YDC from seed samples. The presumptive pathogen was confirmed by isolation on semiselective medium, such as mTBM and MD5A. Further, the pathogen was confirmed by biochemical, physiological and, finally, the pathogenicity tests. Five samples out of seven were positive for Xanthomonas. The isolates were found to cause common blight of 3-week-old common bean plants by 7 d after inoculation. Bacteria with the same characteristics as those inoculated were re-isolated from the infected plants.     

Serological and conductimetric assays for the detection of Pseudomonas syringae pathovar pisi in pea seeds

Test protocols for detecting Pseudomonas syringae pv. pisi , the causal agent of bacterial blight, in pea seeds are generally based on dilution-plating assays. These assays are usually very specific and reliable, but are time-consuming and laborious. Tests suited for large scale screening of seed lots are therefore needed. Conductimetric assays, immunofluorescence microscopy (IF) and an enzyme-linked immunosorbent assay (ELISA) for detecting Ps. syr. pv. pisi in pea seed extracts were compared with dilution-plating by two extraction methods, viz. 6 h soaking of seeds and 2 h soaking of flour of ground pea seeds in water. In general, the detection of Ps. syr. pv. pisi with conductimetric, IF and dilution-plating assays in the suspension water of the ground and 2 h-soaked pea samples was less sensitive than detection in suspension water of the 6 h-soaked pea seeds. The detection threshold of these assays varied per seed lot between 0 and 4.08 log cfu ml^-1 for the 6 h soaking procedure. The detection threshold of ELISA varied for both extraction methods generally between 4.08 and 6.08 log cfu ml^-1. Detection times recorded in conductimetric assays correlated well (— 0.89 < r < —0.98) with the log colony-forming units of Ps. syr. pv. pisi added to seed extracts at 27 as well as 17°. However, confirmation of results by isolation on semi-selective media after conductimetry was more successful at 17° than at 27°, because of the relatively lower activity of saprophytic Pseudomonas spp. at this temperature.     

Strobilurins Seed Treatment Enhances Resistance of Common Bean Against Bean common mosaic virus

Commercial formulations of strobilurins (azoxystrobin, kresoxim‐methyl, trifloxystrobin and pyraclostrobin) were evaluated for their efficacy against Bean common mosaic virus (BCMV) in screenhouse and field conditions. Highest seed germination and seedling vigour were recorded with 20 μg/ml pyraclostrobin seed treatment in comparison with the control. In screenhouse studies, 76% protection against BCMV was recorded with pyraclostrobin seed treatment at 10 μg/ml. Under field conditions with natural BCMV inoculum, pyraclostrobin seed treatment resulted in 65% protection against BCMV. The protection offered by strobilurins against BCMV was evaluated by ELISA, with lowest immunoreactive values recorded in common bean seedlings raised from seeds treated with pyraclostrobin and kresoxim‐methyl. Strobilurins in addition to exerting a direct positive physiological effect on common bean plants also protect bean plants against BCMV infection in screen house and field conditions. Thus, it is proposed that these reduced‐risk pesticides are potential inducers against BCMV and growth enhancers and could be a beneficial component of integrated disease management of common bean.     

A Cocktail ELISA Semi‐nested RT‐PCR Assay to Detect Bean pod mottle virus in Soya bean Seeds

Bean pod mottle virus (BPMV) has been identified as an important pathogen for plant quarantine in China because large quantities of soya bean seeds (approximately 7 × 10⁷ tons) are imported annually. To develop a practical detection programme for BPMV, a cocktail enzyme‐linked immunosorbent assay (ELISA) nested RT‐PCR using a combination of serological and molecular methods was designed for soya bean seeds. The single‐vessel detection assay was performed in a 96‐well ELISA plate, which served as a carrier for the subsequent nested RT‐PCR assay. Assay specificity was demonstrated by the production of the expected 330‐ and 296‐bp bands using the external and internal primers, respectively. This method was 10⁴‐fold more sensitive than immunocapture‐RT‐PCR (IC‐RT‐PCR). In particular, it is important to note that this assay resulted in successful micro‐extraction from soya bean seeds and combined the advantages of each individual technique. The cocktail ELISA nested RT‐PCR is a specific, sensitive, rapid and economical procedure to rapidly identify and characterize BPMV and could be suitable for both primary‐level platforms and laboratories.     

The potency determination of human varicella-zoster immunoglobulin by enzyme-linked immunosorbent assay, complement-fixation test and indirect fluorescent antibody tests

Traditionally, plasma for the production of the human varicella-zoster immunoglobulin (VZIG) has been selected on the basis of the complement-fixing antibody (CFA) titre. Since immune individuals may lack CFA to varicella-zoster virus (VZV), non-CFA may be of importance in protection. In a search for a simple and reliable method for potency determination, 24 VZIG preparations were quantified by enzyme-linked immunosorbent assay (ELISA), the complement-fixation test (CFT), the indirect fluorescent antibody test to acetone-fixed (IF) and viable (FAMA) VZV-infected cells, respectively. The antibody titres obtained by the various methods were compared. Arranged in order of decreasing agreement, the correlation coefficients (r) of the regression equations between the variables were 0.62 for CFT and FAMA, 0.50 for CFT and ELISA and 0.26 for CFT and IF in a log2 plot. There was complete agreement between the titres obtained by the commercially available Enzygnost Varicella/Zoster kits (Behring Institute, Marburg, F.R. Germany) and the ELISA microtitre plates produced at our institute (r = 1). The regression equation lines for ELISA/CFT and FAMA/CFT titres tended to be parallel to each other, while the line for IF/CFT titres had a less steep slope. Similar titration curves were obtained for VZIGs fractionated by two different methods. Furthermore, the titration curves of serum pools from varicella and zoster convalescents, respectively, had a similar shape below delta OD = 0.4. Generally, a steeper slope was observed above delta OD = 0.4. As antibody detectable by ELISA seems to correlate with protection and the method is sensitive, specific, reproduceable, simple to carry out and easily automated, it may be suitable for the potency determination of VZIGs.     

Resistance of Common Bean (Phaseolus vulgaris) to Bacterial Wilt Caused by Curtobacterium flaccumfaciens pv. flaccumfaciens

Bacterial wilt caused by Curtobacterium flaccumfaciens pv. flaccumfaciens is an important new disease of common bean (Phaseolus vulgaris) in western Canada. Both yellow and orange variants of the pathogen were found in the region. A controlled environment study was conducted to assess 124 common bean cultivars and lines from eight market classes for resistance to the yellow and orange variants of the pathogen, using the hilum injury/seed inoculation method. Results of the screening tests showed significant (P < 0.05) differences in resistance to bacterial wilt among the cultivars or lines. The great northern line L02E317, the great northern cultivar Resolute and pinto lines L02B662 and 999S‐2A, were highly resistant to both variants of the pathogen, with disease severity indices of 0 on a rating scale of 0 (no wilt symptoms) to 5 (dead seedling). Resistant cultivars or lines were found among black, great northern, pink, pinto, small red and Flor de Mayo bean market classes. The study concludes that new bacterial wilt‐resistant germplasm exists among Canadian bean cultivars and lines, and constitutes a valuable resource for breeding common beans for resistance to both yellow and orange variants of C. flaccumfaciens pv. flaccumfaciens.     

Immunological detection of bean common mosaic virus in French bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) leaves

Bean common mosaic potyvirus (BCMV) is an important seed borne pathogen of French bean. Differential inoculation with bean common mosaic virus at cotylodonary trifoliate leaf stage and pre-flowering stage of crop growth revealed that cotyledonary leaf infection favored maximum disease expression. Under immunosorbent electron microscopy (ISEM) the virus particles of filamentous structure having a diameter of 750 nm (l) and 15 nm (w) were observed. These particles gave positive precipitin tests with polyclonal antiserum of Potato virus Y.     

中华鳖病毒的血清学检测

中华鳖病毒（ＴＳＶ）是从病鳖中分离到的一种病毒病原。经细胞培养和差异离心制备ＴＳＶ抗原,肌注家兔获ＴＳＶ抗体（ＴＳＶ－Ａｂ）,中和效价为１：２０,用ＴＳＶ－Ａｂ进行双向免疫扩散和间接ＥＬＩＳＡ检测,被检样品有健康和病鳖组织匀浆液、ＴＳＶ细胞培养液、提纯的ＴＳＶ,以及鱼传染性胰脏坏死病毒（ＩＰＮＶ）、草鱼呼肠孤病毒（ＧＣＶ）、鱼病毒性出血败血症病毒（ＶＨＳＶ）、鲁痘疮病毒（Ｃａｒｐ ｐｏｘ ｖｉｒｕ     

Early detection and rapid identification of Streptococcus pneumoniae and Haemophilus influenzae in acute pneumonias

The comparative study of the diagnostic value of the enzyme immunoassay (EIA), indirect immunofluorescence (IF) and countercurrent immunoelectrophoresis (CIE) was made. The serological identification of the isolated and reference pneumococci (19) and H. influenzae (38) strains revealed the possibility of using all three microanalytical methods for this purpose. The study of pneumococcal and H. influenzae antigens in native sputum obtained from 74 patients with acute pneumonia showed that EIA and indirect IF were highly sensitive, their sensitivity considerably exceeding that of the bacteriological analysis. Pneumococcal antigens were detected in 66.2% of patients by EIA and in 54.0% of patients by indirect IF, while H. influenzae antigens were detected in 58.1% of patients by EIA and in 67.6% of patients by indirect IF. The sensitivity of CIE proved to be considerably lower; in the detection of pneumococcal antigens it was level with the sensitivity of the bacteriological analysis (23.0%) and H. influenzae antigens could be detected only in 27.0% of patients.     

Diagnosis of murine infections in relation to test methods employed

Comparative investigations of Sendai virus, pneumonia virus of mice (PVM), mouse encephalomyelitis virus (mouse polio), minute virus of mice (MVM), and reovirus type 3 (Reo 3) infected murine colonies revealed a 30% higher incidence of positive sera when enzyme-linked immunosorbent assay (ELISA) was employed instead of hemagglutination inhibition (HI) tests. Equivalent sensitivity as in the ELISA was obtained when the same sera were investigated by indirect immunofluorescence (IF) tests. The virus purification techniques described resulted in highly suitable antigens for all indirect ELISA established. Since IIF requires no purified antigens, this test is recommended as an alternative to ELISA as well as to HI and complement fixation (CF) tests for laboratories lacking the necessary equipment for high speed centrifugation. A high incidence of false positive HI reactions was found particularly in Reo 3 routine serology. An updated survey of seromonitoring showed that European murine colonies appeared to be infected far less with Reo 3 if ELISA or IIF tests were employed. During 1982-1984, only 13% of the mouse colonies screened possessed Reo 3 positive sera whereas no natural Reo 3 infection was found in rat colonies. Mouse hepatitis virus (MHV) and the coronaviruses of rats exhibited the highest incidence in murine colonies. A total of 60% of mouse and 41% of rat colonies were found to be infected by these viruses. In comparison with earlier serological surveys, the relative incidence of other murine infections was similar. Antibodies against Bacillus piliformis (Tyzzer's disease) were detected by the IIF test in 41% of the rat colonies screened.     

黄曲霉毒素B_1抗独特型抗体的制备和应用研究II.抗独特型抗体应用

以抗独特型抗体(anti-idiotypeantibody,Ab2)的酶切片段Fab2替代黄曲霉毒素B1(AFB1)建立一种不需要使用AFB1的无毒酶联免疫吸附(Enzyme-LinkedImmunosorbentAssay,ELISA)试剂盒,研究该试剂盒特异性、稳定性和AFB1的加标回收,并将该试剂盒用于农产品和饲料中AFB1的检测。结果表明,该试剂盒具有和常规ELISA试剂盒一样的特异性和加标回收能力,无毒试剂盒和常规试剂盒一样都可以用于农产品和饲料中AFB1的检测,并且两种试剂盒的检测结果并无显著差异,无毒ELISA试剂盒在适当处理后,40C放置3个月和-200C放置5个月,以间接非竞争ELISA测定的吸光值分别是起始时的85%和87%。     

Repair of UV-damaged DNA in mammalian skin followed by the immunohistochemical method

DNA repair in murine and guinea pig skin has been studied by the immunohistochemical method. For the detection of DNA photolesions in situ by the indirect immunofluorescence (IF) method two antisera directed against DNA-pyrimidine-dimers and DNA-psoralen-photoadducts have been applied. The IF assay enabled to detect the DNA photodamage induced by high UV-doses, exceeding more than fivefold minimal phototoxic response of the skin. It was found that IF staining gradually disappeared due to DNA repair, and at 48 h after UV-exposure both types of the DNA photolesions were no more detectable. Importantly, the IF method revealed that the persistence of DNA-pyrimidine-dimers could be traced for a longer time than that detectable by UV-endonuclease incision method.     

Improving nutritional quality and fungal tolerance in soya bean and grass pea by expressing an oxalate decarboxylase

Soya bean (Glycine max) and grass pea (Lathyrus sativus) seeds are important sources of dietary proteins; however, they also contain antinutritional metabolite oxalic acid (OA). Excess dietary intake of OA leads to nephrolithiasis due to the formation of calcium oxalate crystals in kidneys. Besides, OA is also a known precursor of β‐N‐oxalyl‐L ‐α,β‐diaminopropionic acid (β‐ODAP), a neurotoxin found in grass pea. Here, we report the reduction in OA level in soya bean (up to 73%) and grass pea (up to 75%) seeds by constitutive and/or seed‐specific expression of an oxalate‐degrading enzyme, oxalate decarboxylase (FvOXDC) of Flammulina velutipes. In addition, β‐ODAP level of grass pea seeds was also reduced up to 73%. Reduced OA content was interrelated with the associated increase in seeds micronutrients such as calcium, iron and zinc. Moreover, constitutive expression of FvOXDC led to improved tolerance to the fungal pathogen Sclerotinia sclerotiorum that requires OA during host colonization. Importantly, FvOXDC‐expressing soya bean and grass pea plants were similar to the wild type with respect to the morphology and photosynthetic rates, and seed protein pool remained unaltered as revealed by the comparative proteomic analysis. Taken together, these results demonstrated improved seed quality and tolerance to the fungal pathogen in two important legume crops, by the expression of an oxalate‐degrading enzyme.     

An approach to obtain specific polyclonal antisera to Xanthomonas campestris pv. cyamopsidis and its potential application in indexing of infected seeds of guar

Clusterbean seed health testing is warranted since the pathogen (Xanthomonas campestris pv. cyamopsidis (Xccy)) is seed-borne and seed-transmitted. A polyclonal antibody was developed in rabbit via subcutaneous and intramuscular injections and characterized for sensitivity, specificity and its applicability to ELISA which: (i) was sensitive in detecting as few as 102 cells ml - 1 at a titre of 1: 4000; (ii) was specific, since it reacted only with Xccy and not with other xanthomonads; (iii) reacted both with Xccy cells and culture filtrate, indicating that the antigenic determinant is a secretory component; (iv) was applicable and reliable in seed health testing since it reacted only with infected seeds and plant materials and not with healthy seeds and (v) a purified fraction of antibody was virulent-specific since heat-denatured and avirulent isolates were not detected. The ELISA thus developed is highly reproducible and therefore suitable for the evaluation of the potential disease status of seeds and plant health, which is appropriate for routine seed health testing.     

基于TbpA蛋白的副猪嗜血杆菌抗体间接酶联免疫吸附试验检测方法的建立及应用

[背景]副猪嗜血杆菌(Haemophilusparasuis,HPS)是猪革拉瑟氏病(Glasser's Disease)的病原体,抗生素治疗和疫苗接种对于防控该病效果不明显,建立快速、准确的抗体检测方法尤为重要.[目的]利用表达纯化的HPS转铁结合蛋白A(TbpA)建立检测HPS抗体的间接酶联免疫吸附试验(ELISA...     

Purification and characterisation of a novel papain inhibitor from common bean (Phaseolus vulgaris) seed

A proteinaceous inhibitor of papain was purified to apparent homogeneity from mature seeds of common bean ( Phaseolus vulgaris L.). After four chromatographic steps, the papain inhibitor was purified 219‐fold with 12% recovery. On the basis of papain inhibitory activity, cystatins have been estimated to account for about 0.1% of the total protein content of mature common bean seeds. The purified protein, as other plant cystatins, is an acidic protein, heat stable and insensitive to reducing agents. Its molecular mass is about 37 kDa as judged by size exclusion chromatography and SDS‐PAGE. Moreover it is immunologically related to oryzacystatins, since it is recognised by a specific oryzacystatin I antiserum. Based on its biochemical properties the papain inhibitor described here belongs to the phytocystatin family. Papain inhibitory assays carried out during seed development showed that bean cystatin is active since early maturation stages. Our results suggest that, in common bean seed, cysteine proteinase inhibitors are important during seed development with a putative role in the control and regulation of endogenous thiol protease activity.