Pyrenophora graminea on Winter Barley Seed: Effect on Disease Incidence and Yield Losses

Field experiments were carried out in 1982–83 and 1983–84 in Northern and Central Italy (3 locations) in order to investigate the effect of different levels of seed infection of Pyrenophora graminea on disease incidence and yield losses in ‘Perga’ winter barley. Six levels of natural seed infection, assessed by the deep-freezing blotter method have been compared in 8 row-plots, 7.5 m long, arranged in randomized blocks with 4 replications. The percentage of infected plants and tillers has been recorded in all locations and the yield in two of them. A highly significant correlation was found between seed infection, plant infection, tiller infection and yield reduction. Major ratios found were: infected seeds/infected seedlings 1: 0.4, infected tillers/yield loss 1: 0.9, infected seeds/yield loss 1: 0.3. The threshold of seed infection at which production was not significantly different from the healthy control was 14%. Therefore seed treatment is advisable, under the conditions of Northern and Central Italy, when the percentage of seed infection in commercial seed lots is above this level. A tolerance near zero is recommended in prebasic and basic seeds.     

Detection of infection by Pseudomonas phaseolicola (Burkh.) Dowson in white-seeded dwarf bean seed stocks

Seeds of white-seeded varieties of dwarf beans infected with Pseudomonas phaseolicola may show fluorescent areas in the testa under ultra-violet light. Fluorescence is not visible in seed with dark-coloured testas and is masked by coloured seed dressings. Bacterial infection is not the only cause of fluorescence in testas and the type and colour of the fluorescence cannot be used to diagnose infection. Of 542 fluorescing seeds examined 112 were infected by the pathogen, and only six infected seeds were found in 495 non-fluorescing seeds from the same samples. It is estimated that in two seed stocks used for these experiments 64 and 68 % of infected seeds were of the fluorescent type. A 34 lb sample of seedstock has to be taken for examination to detect, with 95 % confidence, ten infected seeds in 1 cwt. The selection of all fluorescing seeds from such large samples effectively concentrates the infected seed into a sample small enough to be tested by bacteriological methods. Test seeds are examined bacteriologically by enrichment-culture in nutrient broth. Ps. phaseolicola is identified in these cultures from the diagnostic symptoms of halo-blight disease induced in bean seedlings inoculated with aliquots of the cultures.     

大豆花叶病毒种子传毒率测定方法的比较

用苗期症状观察和酶联免疫吸附试验(ELISA)两种方法检查了大豆种子内的大豆花叶病毒(sMV)的传毒率及带毒率,并对两种方法所得的结果进行了比较。带毒大豆种子产生的病苗,其症状主要有花叶、卷叶、叶脉束状、叶脉坏死、凸斑和单叶扭曲等类型。苗期症状观察得到的种子传毒率,与用ELISA法检查去种皮大豆种子的带毒率高度吻合,相关系数r=0.92(n=31),说明此两种方法检查种子传(带)毒率具有相同的生物学和病理学意义。 本文提出了种子“群体病毒浓度”的概念。“群体病毒浓度”=群体内病毒总量/群体内种子总数。38个处理组合和3,591粒种子逐粒用ELISA法检查表明,“群体病毒浓度”与该群体的种子传毒率呈正相关,r=0.93(n=38)。将种子群体作为一个整体用ELISA法检查的结果也证明,“群体病毒浓度”与种子传毒率呈直线相关。因此认为可以用ELISA法对种子群体直接进行测定来估计种子的传毒率。     

Verticillium dahliae (Kleb.) Infecting Pumpkin Seed

This study investigated the natural occurrence of Verticillium dahliae (Kleb.) infection in pumpkin (Cucurbita pepo L.) seed. The mean incidence of infection was found to be 21.0%. Isolates recovered from seeds were pathogenic to pumpkin (cultivar ‘Jamaican squash’). Surface sterilization by immersion in 0.6% sodium hypochlorite for 20 min eradicated V. dahliae from infected pumpkin seeds without affecting germinability. Plating of seed components revealed that the fungus was present in the seed coat but not in the embryo or cotyledons. In a growing‐on test, 25% of 6‐week‐old plants grown from untreated seeds were infected. Germination and production of normal seedlings were unaffected by V. dahliae infection of seeds. Verticillium dahliae in pumpkin seed was found to be external and transmissible to plants. The findings of this study are important in devising disease control strategies.     

Methods for inoculating field crops with mycorrhizal fungi

Four methods were compared for inoculating red clover with selected mycorrhizal fungi when sown in a field containing an indigenous mycorrhizal population. The largest amount of mycorrhizal infection (around 65% of root length infected) was obtained by placing inoculum with the seeds in furrows. The inoculum used was standard soil inoculum from stock plant cultures spread by hand or the same inoculum concentrated to about one seventh by wet-sieving, and then fluid-drilled. The effectiveness of multiseeded pellets (seeds stuck onto pellets of soil inoculum) applied broadcast was more variable, infection ranging widely around an average of 30%. Applying both soil inoculum and seeds broadcast produced just under 10% infection, similar to that in the controls given autoclaved inoculum. Seedling establishment, in contrast, was-better where seeds were applied broadcast than in furrows. It seemed therefore that multiseeded pellets might be the best compromise for achieving reasonable infection in most plants, but fluid drilling had the advantages of greatly reducing the amount of inoculum needed and of readily combining seeds and inoculum in a single carrier.     

A gene coding for a basic pathogenesis-related (PR-like) protein from Zea mays. Molecular cloning and induction by a fungus (Fusarium moniliforme) in germinating maize seeds

Pathogenesis-related proteins (PRs) are plant proteins produced in leaves in response to infection by pathogens including viruses, viroids, fungi and bacteria. Information on the presence and/or expression of PRs in monocotyledonous plants is scarce. Here we report the identification of cDNA and genomic clones coding for a basic form of a protein from germinating maize seeds having a high homology with the group of PR-1 from tobacco.A cDNA library enriched in aleurone-specific sequences was prepared from maize seeds two days after germination. One clone was found to contain an open reading frame encoding a protein homologous to PR proteins from tomato (p14) and tobacco (PR-1 group). Sequence analysis of the corresponding genomic clone revealed that it was encoded by a single exon. Besides, DNA blot hybridization indicates that this PR-like protein is encoded by a single-copy gene in maize. The accumulation of its mRNA increases after rehydration of desiccated seeds. Furthermore, a relationship was found between its expression and infection by a natural pathogen of maize, the fungus Fusarium moniliforme. The possible role of this protein as a response mechanism following fungal infection in cereal seeds is discussed.     

转基因棉籽检测中DNA模板提取方法研究

在转基因棉籽的检测中,需要得到合适的DNA模板,以进行PCR扩增。应用CTAB1,CTAB2,KIT,KIT1,SDS等五种DNA模板提取方法提取转基因棉籽中的DNA模板,根据模板DNA的OD260/OD380值,波长扫描,琼脂糖凝胶电泳,3个基因的PCR扩增结果,评价五种DNA模板提取方法的提取效果,发现以KIT1方法提取棉籽中DNA模板效果为好,可用于实际检测中。     

The quantitative estimation of the infection of bean seed with Pseudomonas phaseolicola (Burkh.) Dowson

A routine laboratory method for the detection of Pseudomonas phaseolicola in bean seed is described. The method will detect low levels of seed-borne infection and has been used in a statistical procedure (the most probable number method) to give an estimate of percentage infection. Infection in seeds harvested from heavily infected crops varied from 10 to 1%, compared with from 1% to less than 0.1% in commercial seed stocks. A high proportion of infected seeds failed to produce infected plants and this may account for the very low levels of primary infection reported in the field. Removal of seeds showing possible ‘symptoms’ of disease reduced, but did not eliminate, infection from seed stocks.     

The Possible Involvement of Lipoxygenase in Downy Mildew Resistance in Pearl Millet

The downy mildew disease, incited by Sclerospora graminicola,is a major biotic constraint for pearl millet production inthe semi-arid tropics. Sources of resistance to this diseasehave been identified. However, the mechanism of host resistancestill remains obscure. The enzyme lipoxygenase (LOX) is knownto play a role in disease resistance in many host-pathosystems.In the present study, LOX activity was tested in seeds of differentgenotypes of pearl millet with different susceptibility to downymildew. The LOX assay of the seeds indicated a good correlationbetween enzyme activity and their downy mildew reaction in thefield. Maximum activity was recorded in seeds of highly resistantgenotypes and minimum activity was found in the highly susceptiblegenotypes. Seeds obtained from plants recovered from the downymildew disease had more LOX activity than that of the originalparent seeds. Thus, in seeds, the LOX activity can be used asa biochemical marker for screening different genotypes of pearlmillet for downy mildew. The study, carried out in the susceptiblegenotype of pearl millet seedlings, showed that LOX activitydecreased after inoculating with S. graminicola zoospores whencompared with uninoculated controls. However, a significantincrease in the enzyme activity was observed on the second andthird days after inoculation in resistant seedlings. The possiblerole of LOX in conferring resistance to downy mildew infectionof pearl millet is discussed. Key words: Lipoxygenase, pearl millet, downy mildew     

Over‐expression of fHbp in Arabdopsis for development of meningococcal serogroup B subunit vaccine

Due to lack of commercial vaccine against the serogroup B (MenB) of Neisseria meningitides, the incidence of meningococcal disease remains high. To solve the issue, transgenic plants are used as bioreactors to produce a plant‐derived fHbp subunit vaccine. In this study, the fHbp gene was optimized according to the codon usage bias of Arabidopsis thaliana, synthesized artificially, cloned into an expression vector, driven by a seed‐specific promoter, and introduced into A. thaliana by Agrobacterium‐mediated floral‐dip transformation. Transgenic plants were identified by glufosinate selection, quickstix strips for PAT/bar tests and PCR analysis. The five plants showing higher expression of recombinant fHbp were screened through indirect ELISA. Southern blot analysis showed that the transgenic line rHF‐22 had a single‐copy integration and the highest expression of fHbp. Recombinant fHbp was purified from seeds of rHF‐22 by nitrilotriacetic acid‐mediated affinity chromatography, and the purity was 82.5%. BALB/c mice were tested for fHbp vaccine protection from lethal MenB infection, and the relative percent survival was found to be 80%. This study indicates that the recombinant fHbp produced from seeds of rHF‐22 is a potential candidate for commercial MenB vaccine. It also provides a reference for safe, cheap and large‐scale production of other plant‐made vaccines.     

Reduction of protease inhibitor activity by expression of a mutant Bowman-Birk gene in soybean seed

A mutant Bowman-Birk gene was created that encoded an inactive high-sulfur product. It was used to transform soybean line Asgrow 3237. Transformants bearing the mutant gene were identified by GUS expression, PCR analysis, and Southern analysis. The amount of steady state mRNA from the mutant gene in the transformed plants showed that the gene was highly expressed, but the amount of message from the unmodified Bowman-Birk gene did not change detectably. Proteins synthesized at the direction of the mutant Bowman-Birk gene accumulated in seeds of the transformed plants, and there was a marked decrease in the ability of extracts prepared from these seeds to inhibit trypsin and chymotrypsin despite the presence of Kunitz trypsin inhibitor. The more prevalent mRNA from the mutant gene was considered to out-compete message from the native genes to decrease the amount of active Bowman-Birk inhibitor.     

Toxoplasmosis: stages of the protozoan life cycle and risk assessment in humans and animals for an enhanced awareness and an improved socio-economic status

Toxoplasma gondii is a protozoan parasite distributed globally. It causes toxoplasmosis, which is prevalent in animals, birds, and soil. T. gondii infection leads to severe pathological impacts in immunodeficient patients and congenital cases. This review indicated that high prevalence groups had close contact with cats, dogs, consumed uncooked raw fruits, meat, or vegetables and the socio-economic level noted to be one of the crucial factors that influence toxoplasmosis. Toxoplasmosis infection is high in low-income countries and low in developed European countries. Immunosuppressed groups and pregnant women were the highly vulnerable groups. The epidemiology of the parasite enumerated various routes of infections; but consumption of T. gondii contaminated food was the major route of disease transmission. However, the role of meat and meat-producing animals on disease transmission remained unclear. Unfiltered water acts as the primary reservoir of toxoplasmosis transmission. The diagnostic methods for determining T. gondii infection are not the gold standard, and different approaches have been prescribed to analyze the infected populations based on the organs affected. Although toxoplasmosis was reported before 70 years, no appropriate solution noted to be recommended to treat this disease. Based on the present analyses, it concluded that the eradication of toxoplasmosis would be challenging from the world until people''s socio-economic level is improved. The main aim of the present study was to analyze and update the disease transmission, epidemiology, and possible clinical interventions of toxoplasmosis.     

Resistance in rice to Rice yellow mottle virus and evidence of non-seed transmission

Nine rice cultivars were evaluated under screenhouse conditions for resistance to Rice yellow mottle virus (RYMV) and possible seed transmission. Completely randomised design with three replications was used. In Experiment 1, the seedlings were inoculated with the virus at two weeks after planting. In Experiment 2, the seeds collected from Experiment 1 were dried for four weeks before planting. For each genotype, the seeds from healthy plants were planted as a control. Disease incidence and severity (scales 1–9), yield and yield components were recorded. Statistical analyses included Area Under the Disease Progress Curve (AUDPC) and independent t test. The cultivars FARO 37, FARO 52 and Gigante were highly resistant, whereas WAB189-B38HB was resistant. Paddy yield was highest (3.6 g) in FARO 37. There were no symptoms of virus disease in all the plants originating from the seeds of RYMV-infected plants. The differences between the seeds from infected and healthy plants for all the measured traits were not significant (p > 0.05). The number of days to seedling emergence was uniform (5.5 days) in all the cultivars. Plant height, number of tillers per plant, number of days to heading and paddy yield from the seeds of virus-infected plants varied from 54.8 to 68.4 cm, 17 to 21, 85.3 to 96 days and 2.7 to 4 g, respectively. Conversely, a range of 54.9–68.7 cm, 17–22, 83–95 days and 2.8–4.1 g was found in the seeds of healthy plants. Selection and cultivation of high-yielding, resistant and healthy seeds would enhance food security.     

The Possible Role of Cyanobacterial Filaments in Coral Black Band Disease Pathology

Black band disease (BBD), characterized by a black mat or line that migrates across a coral colony leaving behind it a bare skeleton, is a persistent disease affecting massive corals worldwide. Previous microscopic and molecular examination of this disease in faviid corals from the Gulf of Eilat revealed a number of possible pathogens with the most prominent being a cyanobacterium identified as Pseudoscillatoria coralii. We examined diseased coral colonies using histopathological and molecular methods in order to further assess the possible role of this cyanobacterium, its mode of entry, and pathological effects on the coral host tissues. Affected areas of colonies with BBD were sampled for examination using both light and transmission electron microscopies. Results showed that this dominant cyanobacterium was found on the coral surface, at the coral–skeletal interface, and invading the polyp tissues and gastrovascular cavity. Although tissues surrounding the invasive cyanobacterial filaments did not show gross morphological alterations, microscopic examination revealed that the coral cells surrounding the lesion were dissociated, necrotic, and highly vacuolated. No amoebocytes were evident in the mesoglea of affected tissues suggesting a possible repression of the coral immune response. Morphological and molecular similarity of the previously isolated BBD-associated cyanobacterium P. coralii to the current samples strengthens the premise that this species is involved in the disease in this coral. These results indicate that the cyanobacteria may play a pivotal role in this disease and that the mode of entry may be via ingestion, penetrating the coral via the gastrodermis, as well as through the skeletal–tissue interface.     

抗病高干特异资源材料徐781的特性鉴定和亲本利用评价

通过对引自国际马铃薯中心的甘薯实生种子、高代品系进行生产力、抗病性、品质分析等性状的全面鉴定,筛选出抗病高干特异资源材料徐781,并对其不孕群别、砧木适合性、遗传特点等进一步评价,结果表明徐781具有与国内常用亲本亲缘关系远、高干率、高抗茎线虫病、易开花、结实率高、后代入选率高等特点,是国内现有育种材料中罕见的很有利用价值的优异育种材料。     

Rapid biochemical test for seed germinability.

Sugar and aminoacids were investigated in sterile distilled water after Pinus pinea seeds had been soaked in it during 24 hours at 37 degrees C. Germination viability decreased with the ageing of the seeds and was accompanied by sugar and aminoacids increase in the exudate. The sugar content from seeds with loss of germinability was about 50 to 80 times greater than that from seeds with good germinability. Paper chromatography showed that there was an increase in mono, di, oligosaccharides and amino-acids in seeds without germinability, but these substances were only found as trace quantities in viable seeds. The methods already described by TKAYANAGI and MURAKAMI to determine germinability could be applied with some modifications to Pinus pinea seeds. The presence of sugar in the exudate could be detected by urine sugar test after 24 hours at 37 degrees C. It was necessary to concentrate the exudate till a final volume of 2 ml.     

水稻双链RNA结合蛋白同源基因OsRBP的克隆及其表达的分析

在基因数据库中发现两个水稻EST片段与大白菜BcpLH基因的双链RNA结合结构域 (dsRBD)有同源的区域 ,根据同源片段的位置特征设计引物 ,用RT-RCR扩增粳稻 (Oryzasativasubsp .japonica)愈伤组织的cDNA ,得到大小为 1.8kb的DNA片段。该cDNA片段含完整的编码区 ,有两个典型的dsRBD ,分别与BcpLH的dsRBD在氨基酸水平上同源性为 75 %左右 ,故将其命名为OsRBP。RT -PCR表达分析显示该基因在未成熟的种子和愈伤组织中表达 ,在根、茎、叶、穗、成熟种子及胚芽鞘中没有表达信号 ,由此推测该基因的表达可能与种子和胚的早期发育相关。该研究首次从水稻中分离到双链RNA结合蛋白基因 ,并初步研究了其表达方式 ,为进一步探讨水稻重要器官的发育和植物中双链RNA结合蛋白的调节作用奠定了基础     

A comparison of methods for delivering DNA to wheat: the application of wheat dwarf virus DNA to seeds with exposed apical meristems

The apical meristems in dry wheat seeds were exposed (dissected seeds) to provide a target for DNA uptake. Using wheat, dwarf virus as the marker DNA, various methods of delivery were compared. Dry dissected seeds imbided in wheat dwarf virus DNA solution gave infection in 16% of the seedlings growing from them. A wheat dwarf virus dimer placed between the T-DNA borders of a vector plasmid inAgrobacterium tumefaciens (disarmed C58) andA. rhizogenes (LBA 9402) gave high levels of infection (79%) when dissected seeds were soaked in theAgrobacterium inoculum (agroinfection). Bombardment of dry dissected seeds with tungsten particles coated in wheat dwarf virus DNA did not give infection, but when softened by presoaking in water for 14 h, infection was observed at a low level (3%). The exposure of the apical meristem in all three methods gave a higher frequency of infection compared with treating intact seeds and in some cases the difference was substantial. The significance of the approach for DNA uptake studies is discussed along with its relevance to achieving stable transformation with non-viral constructs.     

Expression of small RNAs of Mycobacterium tuberculosis in murine models of tuberculosis infection

The determination of the mechanisms contributing to the survival of pathogenic bacteria in the infected organism and the possible ways of their blocking is a promising approach to the development of new methods of affecting these bacteria. Among these mechanisms, the regulation of bacterial metabolism by small RNAs attracts particular interest since it has been found recently to play an important role in the bacterial pathogenesis. We have studied the expression of three most highly expressed small RNAs of Mycobacterium tuberculosis: MTS0997, MTS1338, and MTS2823 during tuberculosis progression in the strains of mice having different genetic resistance to the disease. It has been shown that the maximum expression of these small RNAs occurs at earlier stages of infection.     

Seed predation,pathogen infection and life-history traits in Brassica rapa

Herbivory and disease can shape the evolution of plant populations, but their joint effects are rarely investigated. Families of plants of Brassica rapa (Brassicaceae) were grown from seeds collected in two naturalized populations in an experimental garden. We examined leaf infection by the fungus Alternaria, seed predation by a gall midge (Cecidomyiidae) and plant life-history traits. Plants from one population had heavier seeds, were more likely to flower, had less fungal infection, had more seed predation and were more fecund. Fungal infection score and seed predation rate increased with plant size, but large plants still had the greatest number of undamaged fruits. Spatial heterogeneity in the experimental garden was significant; seed predation rate and fecundity varied among blocks. An apparent tradeoff existed between susceptibility to disease and seed predation: plants with the highest fungal infection score had the lowest seed predation rate. Alternaria infection varied between populations, but the disease had no effect on fecundity. Seed predation did reduce fecundity. Damaged fruits had 31.4% fewer intact seeds. However, evidence for additive genetic variation in resistance to seed predation was weak. Therefore, neither disease nor seed predation was likely to be a strong agent of genetically based fecundity selection.