Factors affecting aphid acquisition and transmission of soybean mosaic virus

Myzus persicae transmitted soybean mosaic virus (SMV) most efficiently following 30 or 60 s acquisition probes on infected plants. There were no differences in susceptibility to SMV infection of soybean plants 1 to 12 wk old, but symptoms were more severe in plants inoculated when young than when old. Soybeans inoculated between developmental stages R3 and R6 only showed yellowish-brown blotching on one or more leaves. There were no observable differences in the time of appearance or type of symptoms shown by soybean seedlings inoculated either by sap or by aphids; infected plants became acquisition hosts for aphids 5–6 days after inoculation. There was no change in the efficiency with which M. persicae transmitted SMV from source plants up to 18 wk after inoculation. M. persicae transmitted SMV from leaves of field-grown soybeans when plants were inoculated at developmental stages V6, R2, and R3 and tested as sources 57–74 days after inoculation but not from plants inoculated at R5 and tested as sources 14 to 32 days after inoculation. M. persicae acquired SMV from soybean buds, flowers, green bean pods, and unifoliolate, trifoliolate, and senescent leaves. Middle-aged and deformed leaves were better sources of the virus than buds, unfolding and old symptomless leaves. The results are being incorporated into a computer model of SMV epidemiology.     

SMV种传特性及其田间流行的种子传毒率预测

SMV感染供试品种种子传毒率最高为29.60％,最低1.04％。SMV弱毒株系的传毒率高于其强毒株系。大豆品种营养生长的V_4时期以前感染SMV种子传毒率最高,花期感染种传率显著下降。供试品种中,有初花期感病种子即不传毒;有盛花期感病仍有很低的种传率;亦有结荚初期感病还有很低种传率的品种。SMV流行的收获种子传毒率高低主要取决于大豆营养生长和花期田间病株率的高低。根据品种间早期感染SMV的最高种传率不同、花期感染种传率显著下降的特性,建立了SMV田间流行的种子传毒率预测模型。     

A tissue culture method for the preservation of Soybean mosaic virus strains

The activity and longevity of Soybean mosaic virus (SMV) in soybean callus culture were investigated with 11 SMV strains which are distinguished by differential reactions on soybean cultivars [Glycine max (L.) Merr.]. Dual cultures (soybean callus and SMV) were initiated by direct culture of SMV-infected leaves from susceptible soybean plants on Msoy and MS agar medium. Established SMV-callus cultures were maintained at 25 °C under light, subcultured to fresh MS medium at 2-month intervals or as necessary, and assayed periodically for virus infectivity. The infected calluses on MS medium grew better and stayed active longer than those on Msoy medium. At 10–15 °C, calluses and SMV were viable and active for 13–15 weeks or longer without subculture. The infectivity of SMV from callus cultures was comparable with that of SMV from infected plants, and remained stable for more than a year through five successive subcultures. Callus tissues of dual cultures were uniformly infected by SMV, thus ensuring infectious subcultures by random transfers. Production of in vitro inoculum can be significantly increased by multiple subcultures. Biological integrity of the SMV cultures was maintained with no change of viral virulence and pathotype. The method is of value for preserving a collection of SMV strains in a highly infectious and readily available form and reduces the chance of contamination or loss in viability.     

The Role of Infective Plant Debris, and its Concentration in Soil, in the Ecology of Tomato Mosaic Tobamovirus—a Non-vectored Plant Virus

Only a few plants in a crop are generally thought to become infected by abiotic soil transmission. In glasshouse experiments we have induced almost total infection in tomatoes growing in soil with infective debris, but levels of infection are dependent upon certain conditions. We found that as the inoculum concentration decreased (i) a greater percentage of the infections were either latent (symptomless) or restricted to roots and (ii) infection levels decreased. Thus, apparent infection (based on symptoms) of 0. 10% was in reality 0 60–70% based on enzyme-linked immunosorbent assay and immunoelectron microscopy testing of roots and leaves. This occurred whether seedlings or seed were planted into infected mix. Under conditions in which minimal root damage was caused (planting seed) or roots were mechanically inoculated only once, almost all systemically infected plants were symptomless.     

Dry matter production and boron concentrations of vegetative and reproductive tissues of canola and sunflower plants grown in nutrient solution

Prediction of nitrogen (N) mineralization is important for specifying the optimum rate of N fertilizer for flooded rice at the time of sowing. To develop a predictive test, soils (0–0.1 m) were sampled from 22 farms throughout the rice-growing region of southern Australia over a 4-year period. Near infrared reflectance (NIR) spectra of the soils were compared with sixteen biological and chemical soil tests for the prediction of N-uptake by rice plants from these soils in the field and glasshouse. The aim of the study was to develop a soil-NIR calibration as an accurate, rapid and economical mineralization test. Nitrogen uptake by field-grown and glasshouse-grown plants was poorly correlated (r = 0.30), even though significant NIR calibrations were developed with both. Since N uptake by rice in the field was affected by varying weather and management, the field calibration is probably spurious. The calibration of soil NIR spectra with N uptake by glasshouse plants was satisfactory, with a standard error (SE) of 13 kg ha^–1 over a range of 11 – 95 kg ha^–1, and a correlation between calculated and measured N uptake (r = 0.87, P<0.001). An even better soil-NIR calibration was found with N-mineralization after 21 days of anaerobic incubation (SE 16 mg kg^–1, range 52–175 mg kg^–1). Analysis of the soil spectra showed that similar wavelengths were correlated with both plant-N uptake and mineralization. NIR spectroscopy shows considerable potential to predict soil N mineralization, and may assist future fertiliser decision support.     

SMV对大豆花粉表面的污染及对花粉活力的影响

应用PALLAS将病毒粒体转化为乳胶颗粒通过扫描电镜直接观察,成功地检测到了大豆花粉表面污染的大豆花叶病毒(SMV)。田间春大豆宁镇1号的重花叶、轻花叶及无症状植株花粉所吸附的乳胶颗粒依次递减,而健株花粉上极少观测到乳胶颗粒,花粉数量测定及萌发试验表明,SMV的侵染对大豆花粉形成及活力都有明显的影响。     

Re-evaluation of the near infrared spectra of mitochondrial cytochrome c oxidase: Implications for non invasive in vivo monitoring of tissues

We re-determined the near infrared (NIR) spectral signatures (650–980 nm) of the different cytochrome c oxidase redox centres, in the process separating them into their component species. We confirm that the primary contributor to the oxidase NIR spectrum between 700 and 980 nm is cupric Cu_A, which in the beef heart enzyme has a maximum at 835 nm. The 655 nm band characterises the fully oxidised haem a₃/Cu_B binuclear centre; it is bleached either when one or more electrons are added to the binuclear centre or when the latter is modified by ligands. The resulting ‘perturbed’ binuclear centre is also characterised by a previously unreported broad 715–920 nm band. The NIR spectra of certain stable liganded species (formate and CO), and the unstable oxygen reaction compounds P and F, are similar, suggesting that the latter may resemble the stable species electronically. Oxidoreduction of haem a makes no contribution either to the 835 nm maximum or the 715 nm band. Our results confirm the ability of NIRS to monitor the Cu_A centre of cytochrome oxidase activity in vivo, although noting some difficulties in precise quantitative interpretations in the presence of perturbations of the haem a₃/Cu_B binuclear centre.     

Hop line-pattern virus in relation to the etiology and distribution of nettlehead disease

Hop line-pattern virus (HLPV) was transmissible by mechanical inoculation to hop plants; it induced characteristic severe symptoms in Humulus lupulus L. var. neo-mexicanus Nels. & Cockerell and the commercial derivatives College Cluster and Keyworth's Midseason, but none in the traditional English varieties of H. lupulus (e.g. Fuggle).
Mechanical transmission of hop nettlehead virus (HNV) was facilitated by the presence of HLPV in the test plants; hop seedlings and clonal plants escaped infection by sap inoculum that infected plants of two varieties already infected with HLPV. HNV was also transferred by stem contact and by knife cuts to plants carrying HLPV.
Infection with HLPV was latent in twelve nettlehead-diseased Fuggle plants from different fields, and in diseased and symptomless plants in a nettlehead outbreak in W.G.V., a variety that previously had escaped infection. It is suggested either that HLPV predisposes hop plants to infection with HNV or that nettlehead disease is caused by dual infection with both viruses.
Localized and scattered patterns of nettlehead spread were observed in hop plantations; these two types are usually attributed to different modes of spread which would be compatible with a complex etiology of the disease.     

Location of Soybean Mosaic Virus in Seed-Parts of Individual Dormant and Germinating Mottled and Non-mottled Soybean Seeds

Soybean mosaic virus (SMV) was detected in individual embryos of both dormant mottled (50%) and non-mottled (50%) seeds of certified soybean cvs Davis. Essex. Hutchinson, Ransom, Stonewall, and Young by using the double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). SMV was not detected in individual strained seed coats of mottled or non-stained seed coats of non-mottled dormant seeds and endosperms of either type of seed. SMV was not detected m individual stained and nonstained seed coats, epicotyls, and endosperms of mottled and non-mottled seeds at 72 h post-germination. However, the virus was detected in individual hypocotyls at an average level of 31% in post-germinated seeds (mottled and non-mottled) of all cultivars. Symptomless glasshouse-grown 6–8-week-old seedlings from mottled and non-mottled seeds of certified soybean cultivars occurred twice as often as those showing early symptoms. However, almost half of these symptomless plants were found to be SMV-infected by DASELISA. Virus-free soybean plants grown to maturity from non-mottled seeds also produced mottled seeds.     

Application of vibrational spectroscopy in the quality assessment of Buchu oil obtained from two commercially important Agathosma species (Rutaceae)

Quality assessment of natural raw materials and derived consumer products is often done using conventional analytical techniques such as liquid and gas chromatography which are expensive and time consuming. This paper reports on the use of vibrational spectroscopy techniques as possible alternatives for the rapid and inexpensive assessment of the quality of ‘buchu oil’ obtained from two South African species; Agathosma betulina and Agathosma crenulata belonging to the Rutaceae family. Samples of A. betulina (55) and A. crenulata (16) were collected from different natural localities and cultivation sites in South Africa. The essential oil was obtained by hydrodistillation and scanned on Near infrared (NIR), mid infrared (MIR) and Raman spectrometers. The spectral data obtained was processed using chemometric techniques and orthogonal partial least squares discriminant analysis (OPLS-DA) was used to clearly differentiate between A. betulina and A. crenulata. The OPLS-DA technique also proved to be a useful tool to identify wave regions that contain biomarkers (peaks) that contributed to the separation of the two species. The three spectroscopy techniques were also evaluated for their ability to accurately predict the percentage composition of seven major compounds that occur in A. betulina ‘buchu’ oil. Using GC–MS reference data, calibration models were developed for the MIR, NIR and Raman spectral data to predict/profile the major compounds in ‘buchu oil’. A comparison of the three spectroscopy techniques showed that MIR together with PLS algorithms produced the best model (R²X = 0.96; R²Y = 0.88 and Q²Ycum = 0.85) for the quantification of six of the seven major oil constituents. The MIR model showed high predictive power for pseudo-diosphenol (R² = 0.97), isomenthone (R² = 0.97), menthone (R² = 0.90), limonene (R² = 0.91), pulegone (R² = 0.96) and diosphenol (R² = 0.85). These results illustrate the potential of MIR spectroscopy as a rapid and inexpensive alternative to predict the major compounds in buchu oil.     

Design of Experiments-Based Monitoring of Critical Quality Attributes for the Spray-Drying Process of Insulin by NIR Spectroscopy

Moisture content and aerodynamic particle size are critical quality attributes for spray-dried protein formulations. In this study, spray-dried insulin powders intended for pulmonary delivery were produced applying design of experiments methodology. Near infrared spectroscopy (NIR) in combination with preprocessing and multivariate analysis in the form of partial least squares projections to latent structures (PLS) were used to correlate the spectral data with moisture content and aerodynamic particle size measured by a time of flight principle. PLS models predicting the moisture content were based on the chemical information of the water molecules in the NIR spectrum. Models yielded prediction errors (RMSEP) between 0.39% and 0.48% with thermal gravimetric analysis used as reference method. The PLS models predicting the aerodynamic particle size were based on baseline offset in the NIR spectra and yielded prediction errors between 0.27 and 0.48 μm. The morphology of the spray-dried particles had a significant impact on the predictive ability of the models. Good predictive models could be obtained for spherical particles with a calibration error (RMSECV) of 0.22 μm, whereas wrinkled particles resulted in much less robust models with a Q² of 0.69. Based on the results in this study, NIR is a suitable tool for process analysis of the spray-drying process and for control of moisture content and particle size, in particular for smooth and spherical particles.KEY WORDS: moisture content, multivariate analysis, NIR, particle size, spray-drying     

Sources of crown rot (Phytophthora cactorum) infection in strawberry and the effect of cold storage on susceptibility to the disease

Cold-stored plants of strawberry cultivars Tamella, Cambridge Favourite and Redgauntlet were more susceptible to pathogenic isolates of Phytophthora cactorum than similar plants which had not been cold-stored. Indigenous nonpathogenic isolates of P. cactorum did not cause crown rot in cold-stored plants, although a small number of symptomless latent infections occurred. The majority of P. cactorum isolates causing crown rot symptoms were taken from infected strawberry crowns, although two isolates from gooseberry plants, but of uncertain origin, were also pathogenic. Outbreaks of crown rot in areas with no previous history of the disease therefore probably result from the importation of non-indigenous inoculum with planting material. Assessments of the timing of infection in relation to cold storage revealed that a high incidence of death in the cold store and chronic wilt symptoms on planting from the store resulted from initiating symptomless infections prior to cold storage. However, infection during the period immediately after cold storage resulted in rapid wilt symptoms of Phytophthora crown rot. When plated in sterile distilled water for 24 h, pieces of tissue from infected plants which had died during cold storage produced large numbers of sporangia and zoospores. This indicates that such plant material could provide a potent source of inoculum for infections in the post storage thawing environment. It is proposed that a combination of heightened host susceptibility resulting from cold storage and the presence of scatted latent infections or infected debris among the plants could result in a sudden, large scale appearance of crown rot, as sometimes is seen with cold-stored plantings of strawberries.     

Symptom Severity, Yield, Seed Mottling and Seed Transmission of Soybean Mosaic Virus in Susceptible and Resistant Soybean: The Influence of Infection Stage and Growth Temperature

The effect of soybean mosaic virus (SMV) infection on symptom severity, yield, seed mottling and seed transmission in soybean in relation to the growth stage at infection and subsequent temperature was investigated using a susceptible (Harosoy), a moderately resistant (Evans) and a highly resistant (Merit) cultivar. Disease symptoms were more severe with early infection. A greater reduction in plant growth and seed yield, and higher percentages of mottled seeds and seed transmission of SMV also occurred with early infection. Virus titer was higher in younger plants than in older ones and also higher in plants infected at the ealier stage than at the later stage of growth. Merit (a highly resistant cultivar previously reported to be immune to seed mottling) inoculated at the early stage of plant growth resulted in infection and production of some mottled seeds. Temperature affected all parameters investigated. The effect of temperature was greater in the susceptible cultivar than in the resistant one. The optimal temperature for symptom severity, yield, seed mottling and seed transmission was 20 °C. Virus titer was highest at 30 °C in all three cultivars. Maturity of susceptible cultivar was delayed by infection.     

Differentiation between carcasses from suckling lambs reared with ewe milk or milk replacers by near infrared reflectance spectroscopy of perirenal fat

Near infrared reflectance spectroscopy (NIRS) was used to discriminate between carcasses from Churra breed suckling lambs reared with ewe milk or milk replacers. Samples were scanned over the NIR spectral range (1100–2500 nm). The results showed that NIRS could be used successfully to discriminate the suckling lambs depending on milk source, with a 100% of correctly classified samples. NIRS technology would be a good method, since it is a rapid, economical and little complex method.     

Strong light-induced reorganization of pigment-protein complexes of thylakoid membranes in rye (spectroscopic study)

The supramolecular reorganization of LHCII complexes within the thylakoid membrane in Secale cereale leaves under low and high light condition was examined. Rye seedlings were germinated hydroponically in a climate chamber with a 16 h daylight photoperiod, photosynthetic photon flux density (PPFD) of 150 μmol m⁻² s⁻¹ and 24/16 °C day/night temperature. The influence of pre-illumination of the plants with high light intensity on the PSII antenna complexes was studied by comparison of the structure and function of the LHCII complexes and organization of thylakoid membranes isolated from 10-day-old plants illuminated with low (150 μmol m⁻² s⁻¹) or high (1200 μmol m⁻² s⁻¹) light intensity. Aggregated and trimeric with monomeric forms of LHCII complexes were separated from the whole thylakoid membranes using non-denaturing electrophoresis. Analyses of fluorescence emission spectra of these different LHCII forms showed that the monomer was the most effective aggregating antenna form. Moreover, photoprotection connected with LHCII aggregation was more effective upon LHCII monomers in comparison to trimer aggregation. Light stress induced specific organization of neighboring LHCII complexes, causing an increase in fluorescence yield of the long-wavelength bands (centered at 701 and 734 nm). The changes in the organization of the thylakoid membrane under light stress, observed by analysis of absorbance spectra obtained by Fourier transform infrared spectroscopy, also indicated light-induced LHCII aggregation.     

Characterization of SMV resistance of soybean produced by genetic transformation of SMV-CP gene in RNAi

Soybean mosaic virus (SMV), a species of the Potyvirus genus in the Potyviridae family, is one of the most typical viral diseases and results in yield and quality loss of cultivated soybean. Due to the depletion of genetic resources for resistance breeding, a trial of genetic transformation to improve disease resistance has been performed by introducing the SMV-CP gene by the RNA interference (RNAi) method via Agrobacterium-mediated transformation. Among 30 transgenic plants produced, 7 lines with enough seeds were infected with SMV and two lines (3 and 4) showed viral resistance to SMV infection. In genomic Southern blot analysis, all the lines tested contained at least one T-DNA insertion. Subsequent investigation confirmed that no viral CP gene expression was detected in two SMV-resistant lines after artificial inoculation of SMV, while non-transgenic control and other transgenic lines expressed substantial amounts of the viral gene. Viral symptoms affected seed morphology, and clean seeds were harvested from the resistant lines. Also, strong viral gene expression was detected from the seeds of susceptible lines. In further generations, the same phenotypic appearance was maintained among non-transgenic and transgenic plants. Finally, the presence of helper component-proteinase (HC-Pro), known as a suppressor of gene silencing apparatus, was checked among transgenic lines. No expression of HC-Pro in resistant lines indicated that the viral CP-RNAi transformation into soybean somehow created a functional gene silencing system and resulted in a viral-resistant phenotype.     

Green synthesis of silver nanoparticles using cellulose extracted from an aquatic weed; water hyacinth

As part of the desire to save the environment through “green” chemistry practices, we herein report an environmentally benign synthesis of silver nanoparticles (Ag-NPs) using cellulose extracted from an environmentally problematic aquatic weed, water hyacinth (WH), as both reducing and capping agent in an aqueous medium. By varying the pH of the solution and reaction time, the temporal evolutions of the optical and morphological properties of the as-synthesised Ag-NPs were investigated. The as-synthesised cellulose capped silver nanoparticles (C–Ag-NPs) were characterised using Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The maximum surface plasmon resonance (SPR) peak decreased as the pH increased indicating that an increase in the pH of the solution favoured the formation of smaller particles. In addition, instantaneous change in the colour of the solution from colourless to brown within 5 min at pH 11 showed that the rate of reduction is faster at this pH compared to those at lower pH. The TEM micrographs showed that the materials are small, highly monodispersed and spherical in shape. The average particle mean diameters were calculated to be 5.69 ± 5.89 nm, 4.53 ± 1.36 nm and 2.68 ± 0.69 nm nm at pH 4, 8 and 11 respectively. The HRTEM confirmed the crystallinity of the material while the FTIR spectra confirmed the capping of the as-synthesised Ag-NPs by the cellulose. It has been shown therefore that based on this synthetic method, this aquatic plant can be used to the advantage of mankind.     

Rapid Differentiation of Soybean Mosaic Virus Isolates by Antigenic Signature Analysis

Antigenic differences among 14 soybean mosaic virus (SMV) isolates were shown by signature analysis employing a panel of nine well-characterized monoclonal antibodies. Sets of binding curves were generated by reacting aliquots of serial dilutions of leaf extracts from soybean plants infected with each strain of SMV simultaneously with each antibody in the panel. An iterative alignment procedure allowed comparison of binding profiles from different assays in which the starting concentrations of SMV antigen were unknown. Desiccation of infected soybean leaf tissue altered antigenic signatures by inducing changes in reactivity of epitopes recognized by certain antibodies. The method was useful for the elucidation of subtle antigenic differences amongSMV strains. The procedure requires a minimum amount of tissue processing, the analysis is rapid and sensitive, and it requires neither purification nor knowledge of concentration of virus in ground leaf tissue from infected plants.     

Interactive effects of aphid feeding and virus infection on host gene expression and volatile compounds in salt-stressed soybean, <Emphasis Type="Italic">Glycine max</Emphasis> (L.) Merr.

Saline soils are becoming an important limiting factor in production agriculture. Soybean cultivars [Glycine max (L.) Merr.] differ in their ability to tolerate salt stress with those that cannot limit ion uptake into leaves being salt sensitive. Those that can partially limit ion uptake into leaves are generally more salt tolerant. Soybean mosaic virus (SMV) is an important viral pathogen of soybean worldwide and is commonly transmitted by the soybean aphid, Aphis glycines Matsumura. In this study, we investigate the interaction of salt stress in soybean with SMV infection and infestation by the soybean aphid by measuring aphid populations in a no-choice assay, gene expression levels, and the induction of volatile organic compounds using static headspace GC–MS analysis. Salt stress and SMV infection both reduced total aphid populations, though SMV did not reduce the total number of aphids per gram of fresh weight. Aphid suppression of a calcium EF hand gene and OPR1 was lost when salt-sensitive soybean plants were salt stressed and when salt-tolerant plants were subjected to all three stressors. The relative levels of SMV in aphid-infested soybeans were increased by salt stress in the salt-sensitive cultivar, whereas SMV levels decreased in the salt-tolerant cultivar. Static headspace collection of volatile organic compounds revealed that salt stress and SMV infection had suppressive activities on aphid-induced terpenes. These results suggest that although salt stress has a negative impact on aphid population size, the changes in volatiles and SMV levels could alter the incidence of SMV in salt-stressed fields.