Detection,distribution and long-term persistence of potato spindle tuber viroid in true potato seed from heilongjiang,China

Return-polyacrylamide gel electrophoresis (R-PAGE) and tomato bioassay followed by R-PAGE were compared for the detection of potato spindle tuber viroid (PSTVd) from individual true potato seed (TPS). Both methods detected PSTVd from single TPS. TPS extract formulated as sap or nucleic acids in two different buffers did not affect the percentage of viroid detection on tomato plants. There was some evidence of viroid inhibitor in TPS extracts but not in nucleic acid extracts of TPS. Because R-PAGE is more rapid than the tomato bioassay followed by R-PAGE, the former was used to determine the extent of PSTVd in TPS of China’s Keshan Potato Research Institute breeding material. Over 1700 individual TPS were tested. Twenty-four of the 46 seedlots tested (inbred and outcrossed) contained PSTVd. The viroid was detected in 70% of lots from inbred lines compared to 38% of lots from outcrosses. TPS (20 lots) stored in paper bags at room temperature as far back as 1965 were also tested, and PSTVd was detected in TPS stored for 21 years.     

Seed transmission of potato spindle tuber virus

Seed transmission of potato spindle tuber virus (PSTV) has special significance for potato breeding programs. Transmission of PSTV has been reported to occur via true seed. Test families in the Frito-Lay breeding program were obtained from self- and cross-pollinations to determine the incidence of infected seedlings from healthy and diseased parents. Diseased seedlings from PSTV-infected Katahdin selfed were scored by visual and tomato index procedures as 100% and 87% infected, respectively. A similar result was obtained among seedlings from the cross of PSTV-infected Sebago x PSTV-infected Katahdin. Symptoms of PSTV infection were not detected by either method among seedlings from healthy Katahdin, selfed. The Frito-Lay, Inc., potato breeding program employs a number of phyto-sanitary procedures to exclude or reduce the possibility of PSTV contamination and spread.     

Additional indicator plants for potato spindle tuber virus

Thirteen hybrids ofLycopersicon esculentum Mill. (tomato) and threeLycopersicon species proved susceptible to sap inoculation with the potato spindle tuber virus (PSTV). These hosts showed the characteristic symptoms of epinasty and rugosity of the leaves, vein necrosis of leaves and petioles, and some stem necrosis. No local lesions were observed. These hybrids and species can possibly then be used as additional hosts showing systemic symptoms of the virus in addition to the most commonly used indicator, tomato cultivar Rutgers.     

Efficacy of five disinfectants against Potato spindle tuber viroid

Viroids are RNA molecules which are harmful to numerous cultivated plant species and considered, for some of them, as quarantine organisms. Because these pathogens are readily transmitted by contact, effective disinfection measures to clean the cultivating tools, machineries or facilities have to be found and approved. To this end, five disinfectants: Virkon^®, Hyprelva™ SL, Jet 5 ^®, MENNO^® clean and Virocid™, were evaluated for their effectiveness against Potato spindle tuber viroid (PSTVd). The virucids were assessed on dried droplets and in aqueous solutions of PSTVd infected tomato sap. For both experimental setups, the infectiousness of the sap and disinfectant mixtures was checked by inoculation on tomato seedlings followed by RT-PCRs. The experiments involving aqueous solutions, which allowed a discrimination of tested virucids, were carried out in 5 laboratories. In these experiments, MENNO^® clean, the only approved product for PSTVd in several European countries, was not found to be effective at the minimum manufacturer's recommended contact time or at an intermediate contact time for the minimum manufacturer's recommended concentration. Conversely, the four other commercial disinfectants: Virocid™; Hyprelva™ SL; Virkon^® and Jet 5^®, were not found to be significantly different from the bleach control. However, in the experiments performed on dried sap droplets, the effectiveness of the five commercial disinfectants decreased substantially.     

Purple top roll disease of potato

A graft transmissible disease of potato termed purple top roll is prevalent in several potato varieties grown in the hilly tracts of India. The common symptoms are rolling of the basal parts of younger leaves, sometimes accompanied by pink or purple pigmentation. The plants are stunted with profuse growth of axillary branches and aerial tubers. The losses in yield varied from 40 to 70%. Five to 20% of the tubers from diseased plants developed hairy sprouts. Tuber transmission of the pathogen varied from 6 to 33%, depending on the variety.Datura, tomato and white clover are among susceptible plants.N. rustica was tolerant or a symptomless carrier. Sunnhemp, Petunia andSesamum were immune to the pathogen, which was transmitted by the leaf hopper,O. albicinctus Distant but not byCuscuta spp. or by sap inoculation. Application of Chloramphenicol, Tetracycline and Antiamoebin resulted in remission of symptoms and increased tuber yields, indicating possible association of a mycoplasma-like organism.     

Sap extraction device for sampling potato leaves and tubers

An adaptation of a metal shop crimping machine with knurled rollers and driven with a foot-switch activated, geared-down electric motor was used to express sap from potato foliage or tuber pieces placed in triangular polythylene envelopes. Approximately 150–180 leaf samples/hour were processed by one operator. This sap extraction system eliminated the need for washing the rollers between samples and prevented contamination between samples. It worked equally well with oat or sorghum foliage.     

A detached-leaf method to evaluate late blight resistance in potato and tomato

We developed a detached leaf method for evaluating potato (Solanum tuberosum L.) and tomato (Lycopersicon esculentum Mill.) germplasm for reactions toPhytophthora infestans, the causal organism of late blight. Primary leaves from the third to the sixth node of potato plants, and the fourth to sixth node of tomato plants were excised at the stem. Their petioles were inserted into 14 mm × 100 mm floral aqua tubes containing 9 ml of sterilized distilled water. The leaves in the aqua tubes were placed with abaxial sides down on galvanized metal hardware cloth (12.5 × 12.5 mm mesh). A 12.5 mm sensi-disc containing 50μl of 2 × 10⁴ zoospores was placed in the centers of the terminal leaflet and the second leaflet pair of the potato leaf. A single disc was placed on the center of the tomato leaf. The supporting hardware cloth was placed 2.5 cm above distilled water (2.5 cm deep) in 31 cm × 17 cm × 8 cm clear plastic boxes with tight fitting lids. Leaves on intact tomato and potato plants were inoculated in a similar manner and placed in a mist chamber. Lesion growth was determined 4, 5, and 6 days following inoculation. There were no significant differences in reactions to isolates ofP. infestans on detached and intact leaves of potato cultivars Green Mountain and Kennebec and the tomato cultivar Bonnie Best.     

Integration of Pseudomonas fluorescens and acibenzolar-S-methyl to control bacterial spot disease of tomato

Xanthomonas axonopodis pv. vesicatoria was isolated from infected tomato seedlings grown in an open field in Egypt. All the tested isolates infected tomato plants but with different degrees of disease severity. In an attempt to manage this disease, tomato seeds and/or seedlings were treated with an antagonistic local isolate of Pseudomonas fluorescens as a suspension or its formulation or acibenzolar-S-methyl (BTH). When the above three treatments were applied to tomato seeds under laboratory conditions, they improved seed germination and seedlings vigour relative to control seeds treated with sterile distilled water and pathogen but P. fluorescens culture was the most effective. Under greenhouse and field conditions, combinations of the above treatments were used. All treatments significantly reduced disease severity of bacterial spot in tomato relative to the infected control. The biggest disease reduction compared to seedlings inoculated with the pathogen alone resulted from a foliar application of P. fluorescens. Combined application of P. fluorescens or its formulation with BTH reduced the pathogen population and increased seedling biomass and tomato yield relative to control seedlings.     

An assay to quantify vascular colonization of potato byVerticillium dahliae

A procedure was developed and tested to evaluate potato germ plasm for relative rates of vascular colonization byVerticillium dahliae. The number of colony forming units (CFU) per ml of plant sap, extracted from stems and plated on a medium, was used to assess vascular colonization from plants grown for 100 days in a field plot infested withV. dahliae. Sap extracted from main stem tissue at the ground line gave more CFU ofV. dahliae than tissue at the mid and apical region of the main stem. Aliquots of 0.05, 0.1 and 0.2 ml of plant sap were equally efficient in measuring vascular colonization. Thirty-three clones were evaluated for amount of vascular colonization in field and greenhouse tests with the former giving the best results. Cultivars and clones resistant to Verticillium wilt in Idaho, Maine, Minnesota, North Dakota and New York each had a low index of wilt and a low number of CFU/ml ofV. dahliae in plant sap in these tests. Clones intermediate in both wilt index and vascular colonization as well as selections with a high wilt index and extensive vascular colonization were found using the fresh sap assay method. Correlation values of, r = 0.92, r = 0.91 and r = 0.86 were observed between CFU/ml and percentage of foliar wilt for 11 clones/cultivars in 1986, 1987 and 1988, respectively. The correlation between CFU/ml and both moisture and temperature for the cultivars Kennebec and Russet Burbank, during a 6-yr period was r = 0.83.     

Detection of potato leaf roll virus and potato viruses M,S, X and Y by dot immunobinding on plain paper

Summary Potato leafroll virus and potato viruses M, S, X and Y in green leaves were detected by dot immunobinding (DIB) on plain paper and on nitrocellulose membranes. On both materials, DIB could detect the presence of very small amounts of virus, e.g. 30 pg of purified PVX. The sensitivity of the DIB test on plain paper and on nitrocellulose was compared to Double Antibody Sandwich ELISA (DAS-ELISA) by serial dilutions of infected plant sap made in healthy plant sap. Detection of potato viruses by DIB on plain paper and nitrocellulose was found to be equally sensitive whereas DAS-ELISA was 2 to 8 times more sensitive. Possible simplifications of the DIB procedure to suit the requirements of a routine method were examined. The use of the DIB method for routine testing of potato viruses is discussed.     

茶多酚-壳聚糖复合膜的制备及保鲜效果研究

本研究以聚乙烯醇（PVA）和壳聚糖（CTS）为基材,甘油作为增塑剂,以茶多酚（TP）为功能性添加剂制备无污染、可降解且具有抗氧化功能的活性包装材料TP-CTS/PVA复合膜,分析TP浓度对复合膜机械性能、抗氧化能力、抑菌能力等理化性质的影响,研究复合膜与包装相关性能的影响,以期提高复合膜的综合性能。将其应用于圣女果的保鲜,测定其在贮存期间理化指标及微生物指标,进一步将不同TP浓度的复合膜涂抹于新鲜圣女果表面,分析圣女果在贮存期间的感官品质、腐烂率、失重率、可溶性糖、可滴定酸等指标的变化,系统研究复合膜对圣女果的保鲜效果。结果表明：以TP为功能性添加剂共混CTS和PVA制备的复合膜兼具抗氧化和抑菌效果;随着TP浓度增加,复合膜的颜色逐渐变深,TP浓度为1.5%时,复合膜的水溶性最低(19.85±0.64)%,此时复合膜的抗张强度呈最大值(13.19±0.77)MPa;当TP浓度增大,其对Escherichia coli和Staphylococcus aureus的抑菌能力也不断增强,能有效抑制细菌生长; TP浓度为2.0%时,复合膜对DPPH自由基清除率达到最大值(38.53±0.91)%;采用复合膜涂覆对圣女果能减少水分蒸腾、延缓果蔬机体衰老从而起到良好的保鲜效果,涂膜能有效延缓圣女果的腐烂和失水变质的现象,表明TP-CTS/PVA复合膜能改善果蔬的保鲜货架期和商品价值;在相同贮存时间内,当用TP浓度为1.50%复合膜涂抹圣女果时,圣女果的感官评价得分、失重率、腐烂率、可滴定酸含量、可溶性糖含量等各项指标较其他TP浓度试验组效果更好。研究表明,当TP浓度为1.5%~2.0%时制备的TP-CTS/PVA复合膜其抑菌性、耐水性、抗氧化性、以及保鲜性能等各项指标较为均衡,将其实际应用于生产中可根据需求调整TP浓度。本研究目的为探索开发抗菌抗氧化功能型复合膜和功能型包装材料替代塑料包装材料的可能性,为同时解决食品保鲜与环境污染问题提供依据。     

Characterisation of genes isolated from a potato swellingstolon cDNA library

Summary In screening to isolate a full-length copy of a previously isolated cDNA clone, a further three cDNAs were also isolated from a library prepared from sub-apical swelling-stolon tissue of potato (Solanum tuberosum L.). Sequence analysis showed these clones to be similar to extensin-like protein genes, acyl carrier protein thioesterase genes and high mobility group protein genes, respectively. A further cDNA, isolated by subtractive hybridisation, was similar to a tomato cDNA previously isolated on the basis of its down-regulation following nematode infection. While all the newly isolated genes were expressed in swelling stolons, for most, maximal expression was seen to be in stem tissue. Possible roles for these genes in the development of potato plants are discussed, as is the significance of gene expression in stems and stolons to the process of tuberisation.     

Albinism of potato spindle tuber viroid-infected Rutgers tomato in continuous light

Potato spindle tuber viroid (PSTV) caused albinism in the new growth of Rutgers tomato under continuous light. The albinism response was obtained with 4 isolates causing severe symptoms in tomato and with 1 mild isolate which is normally symptomless. Rutgers tomato inoculated with the 4 severe strains of PSTV developed typical ‘bunchy top’ symptoms in 12 to 16-hr day lengths. Symptoms developed slower and much less distinctly on plants incubated in 6-hr days. New growth in PSTV-infected plants was green in short days (12-hr illumination) and chlorotic to white in continuous light. Infectivities of extracts from white portions of plants were from 3 to 10 times greater than those from green portions of infected plants. Albino symptoms also developed in other tomato varieties when inoculated with PSTV and kept under continuous light. Albinism was most pronounced under continuous light at 30°C, somewhat less intense at 24°, and at 16°, new growth of infected leaves and stems remained green. Albinism did not develop in otherSolanum species which are symptomless hosts of PSTV nor in seedling potato plants grown in continuous light.     

矮壮素和乙烯利对樱桃番茄幼苗生长的影响

选用矮壮素和乙烯利对樱桃番茄幼苗进行处理,分析不同浓度的矮壮素和乙烯利对樱桃番茄幼苗生长的影响。结果表明,400 mg/L 50％矮壮素水剂或800 mg/L 40％乙烯利是适宜的喷施浓度,能显著抑制樱桃番茄幼苗株高,增加茎粗、根冠比,提高叶片中SOD和POD酶活性,符合培育壮苗的要求。     

不同促根处理对番茄幼苗的影响

[目的]研究不同促根处理对番茄幼苗的影响。[方法]番茄集约化育苗采用不同促根处理,测定幼苗生长指标并计算壮苗指数。[结果]光合剂500倍液处理、壮根1号200倍处理、50 mg/L赤霉素处理有利于根的生长发育,有利于壮苗,其中光合剂500倍液处理最好;多孔(9孔/边)处理比正常穴盘浇水处理盘根好,生长快,增加了生物量,特别是大大促进了根的生长发育。[结论]为番茄集约化育苗促根处理培育壮苗提供理论依据。     

Two Bacillus amyloliquefaciens strains isolated using the competitive tomato root enrichment method and their effects on suppressing Ralstonia solanacearum and promoting tomato plant growth

Two tomato root colonizing strains, Bacillus amyloliquefacien CM-2 and T-5, were isolated after the enrichment procedure on the roots of tomato seedlings, and evaluated for their antagonistic activities against pathogenic Ralstonia solanacearum (RS) in vitro. Three inoculation methods were used to test their biocontrol efficacy and growth promotion effects in greenhouse based on their colonization ability in rhizosphere soil. Both CM-2 and T-5 strains showed strong biocontrol and growth promotion effects on tomato seedlings. The best biocontrol efficacy was obtained by treating both seedlings and soils with the biocontrol agents. In comparison to the control, the disease incidence was reduced by 70.1 and 79.4% for CM-2 and T-5, respectively. The numbers of colony-forming units of RS in rhizosphere soil were significantly (P < 0.05) decreased as compared to the control. The density of both strains in the rhizosphere soils remained at a high level (≥10⁷ CFU/g) during a five-week period. Both strains were recovered from the interior of the stems and roots of plants. They showed positive reactions for ammoina, indole acetic acid and siderophores production, and phosphate solubilizing activity. Our data proved the potential of isolated strains for the biocontrol of tomato bacterial wilt.     

Retention of infectious potato virus X on common surfaces

Potato virus X in sap from potato leaves was applied by atomizer to surfaces commonly contacted during potato planting, growth, harvesting, grading and storage. The virus retained its infectivity toGomphrena globosa L. or Netted Gem potato for 10 seconds on leather, 3 hours on unpainted wood, iron, rubber and human skin, 6 hours on painted wood, jute and cotton, and 24 hours on soil.     

Preparation,characterization of antibacterial PLA/TP nanofibers

Polylactic acid (PLA)/Tea polyphenol (TP) composite nanofilms were prepared using an electrospinning process. The mixed dichloromethane (DCM) and N,N-dinethylformamide (DMF) (70:30, v/v) was found to be the most suitable solvent for electrospinning. Various blends of PLA/TP solutions were formed. The morphology of the electrospun nano-scale fibers was investigated by scanning electron microscope (SEM), and the antibacterial performance was tested using shake flask method. The average diameter of the fibers is between 380 and 850 nm. It was found that the fiber diameter decreases as TP content increases, however the fibers may become brittle when the blend ratio of PLA and TP reached 50/50 (w/w). The antibacterial performance can be improved at the beginning when TP content increased. But it gradually gets impaired when TP content surpasses a certain value. The highest inhibitory rate against Escherichia coli and Staphylococcus aureus are 96.9 and 97.6 % respectively.     

A rapid technique for assessing the resistance of families of potato seedlings to potato leaf roll virus

Summary A technique is described by which families of potato seedlings can be rapidly screened for resistance to potato leaf roll virus (PLRV) in the greenhouse with a minimum expenditure of labour and bench space. Seed of different families was sown in rows in four replicated blocks and the seedlings produced were exposed to viruliferousMyzus persicae when very young. Symptoms resembling those typical of secondary infection with PLRV developed within a few weks and families with few affected seedlings compared with the susceptible control were classed as resistant. Tests done at different times with similar sets of families gave similar results. Applying infectiveM. persicae by shaking heavily colonised potato shoots above the seedlings was more effective and far less time consuming than transferring them individually by hand using a fine paint brush.     

Differential diagnosis ofVerticillium dahliae in potato with antisera to partially purified pathogen-produced extracellular antigens

Summary An extracellular protein-lipopolysaccaride antigen (PLP) was purified from culture fluids ofVerticillium dahliae. Antiserum produced in rabbits to the PLP detected the antigen in homogenates of tubers, stems and leaves ofV. dahliae-infected potato plants but not in extracts of healthy potato tissue or extracts of potato plants infected by other fungal pathogens. The antigen was not detectable in extracts of potato isolates ofV. tricorpus, V. nigrescens andV. nubilum or various other fungi. The antigen was shown to be different from cross-reactive antigens detected by antisera to mycelial antigens. When used as a tool for specific diagnosis ofV. dahliae infection in potato, antiserum to PLP was more reliable than that prepared against fungal body antigens. Publication of the Agricultural Research Organization No 245-E.