转基因抗虫棉根系分泌物对棉花黄萎病菌生长的影响

转基因抗虫棉的抗病性下降已成为制约我国棉花生产的重要因素之一.以转基因抗虫棉及其亲本非转基因棉花对照为材料,研究转基因抗虫棉根系分泌物对棉花黄萎病菌孢子萌发和菌丝生长的影响,并对其根系分泌物中氨基酸及糖类的组成和含量进行了测定.结果表明：与亲本非转基因棉相比,2种转基因抗虫棉对棉花黄萎病菌的抗性下降,转基因抗虫棉的根系分泌物对黄萎病菌孢子萌发和菌丝生长均具有促进作用.与亲本常规棉中23相比,转基因双价抗虫棉中41根系分泌物中多了甲硫氨酸和赖氨酸,并且天冬氨酸、谷氨酸、丝氨酸、丙氨酸、缬氨酸、亮氨酸、酪氨酸的含量显著升高.泗棉三号与单价抗虫棉GK12的根系分泌物中虽然含有相同的氨基酸组分,但GK12的根系分泌物中酪氨酸、缬氨酸、亮氨酸的含量显著下降.中41根系分泌物中检测出4种糖类,而中23中仅检测出葡萄糖.抗虫棉GK12和泗棉三号根系分泌物中都检测出4种糖类,但其含量差异明显.     

Proteomic analysis of the sea-island cotton roots infected by wilt pathogen Verticillium dahliae

Verticillium wilt of cotton is a vascular disease mainly caused by the soil-born filamentous fungus Verticillium dahliae. To study the mechanisms associated with defense responses in wilt-resistant sea-island cotton (Gossypium barbadense) upon V. dahliae infection, a comparative proteomic analysis between infected and mock-inoculated roots of G. barbadense var. Hai 7124 (a cultivar showing resistance against V. dahliae) was performed by 2-DE combined with local EST database-assisted PMF and MS/MS analysis. A total of 51 upregulated and 17 downregulated proteins were identified, and these proteins are mainly involved in defense and stress responses, primary and secondary metabolisms, lipid transport, and cytoskeleton organization. Three novel clues regarding wilt resistance of G. barbadense are gained from this study. First, ethylene signaling was significantly activated in the cotton roots attacked by V. dahliae as shown by the elevated expression of ethylene biosynthesis and signaling components. Second, the Bet v 1 family proteins may play an important role in the defense reaction against Verticillium wilt. Third, wilt resistance may implicate the redirection of carbohydrate flux from glycolysis to pentose phosphate pathway (PPP). To our knowledge, this study is the first root proteomic analysis on cotton wilt resistance and provides important insights for establishing strategies to control this disease.     

Multiple forms of pectin trans-eliminase from Verticillium dahliae Klebahn -- cotton wilt agent

From the culture liquid filtrate of Verticillium dahliae--cotton wilt agent--pectin trans-eliminase (EC) was isolated. The enzyme was isolated and examined, using ultrafiltration, gel filtration, ion exchange chromatography, isoelectrofocusing, and electrophoresis. The fungus was found capable to produce several forms of pectin trans-eliminase that differed in their molecular weight, charge, synthesis and release regulation, substrate action (position of bonding breakdowns in the pectin polymer molecule). Pectin trans-eliminase activity was also detected in cell walls of the fungal mycelium. Possible origin of multiple forms of the enzyme is discussed.     

The fine structure of developing microsclerotia of Verticillium dahliae Kleb.

Summary Electron micrographs of the early stages in microsclerotial development in v. dahliae Kleb. showed that hyphae became swollen and vacuolate and extruded melanizing particles into the interhyphal spaces of the microsclerotium. Peripheral microsclerotial cells were killed either by a process of autoparasitisation from adjacent hyphae or by autolysis. Variations in the thickness of the melanized material surrounding cells gave the superficial appearance of variations in cell wall thickness between individual cells though actual changes in cell wall thickness were not observed.     

大丽轮枝菌微丝荧光标记载体构建及应用

微丝在真菌生长发育、胞质分裂等生命过程中具有重要功能。通过农杆菌介导遗传转化方法,将荧光mCherry标记微丝的表达载体pSULPH-Lifeact-mCherry转入大丽轮枝菌(Verticillium dahliae Kleb.)野生型V592,获得稳定的微丝荧光标记菌株V592/Lifeact-mCherry,并检测了其生物学表型和孢子萌发、菌丝生长等过程中的微丝荧光动态变化。结果表明:微丝荧光标记菌株的菌落形态、生长速率、产孢量、萌发率等表型与野生型没有显著差异;且可以观察到微丝荧光信号在分生孢子和菌丝的顶端及隔膜都有清晰定位,同时对该菌株隔膜形成过程微丝动态观察发现,微丝参与胞质分裂进程中肌动球蛋白收缩环CAR (Contractile actomyosin ring)的形成。微丝荧光标记菌株可用于微丝在真菌发育中的动力学研究,这为深入研究微丝在真菌发育及致病过程中的作用机制提供理论与实践支撑。     

棉花内生细菌数量动态及其对棉花黄、枯萎病菌的拮抗作用

摘要：【目的】了解棉花内生细菌数量动态,从棉花中获得拮抗黄、枯萎病菌的内生细菌资源【方法】对棉花根、茎、叶表面灭菌,采用稀释平板法分离棉花内生细菌;通过对峙培养法体外鉴定分离的棉花内生细菌对棉花黄、枯萎病菌的拮抗作用,并对拮抗棉花黄、枯萎病菌的内生细菌16S rDNA序列进行了分析【结果】棉花根中内生细菌的数量显著高于茎、叶;根的苗期总体内生细菌数量低于开花期、吐絮期,茎、叶中的内生细菌数量在不同生育期呈现一定的波动性,但趋势性不明显;6个棉花品种根中内生细菌平均数量差异并不显著,但茎、叶中内生细菌数量不同品种间呈现一定程度差异。平板对峙鉴定显示:棉花根中具有较高比例的拮抗棉花黄、枯萎病菌的内生细菌,拮抗强致病落叶型黄萎病菌（V107）的内生细菌比例不仅低于枯萎病菌（F108）,而且低于非落叶型黄萎病菌（V396）。同时拮抗棉花黄、枯萎病菌的内生细菌有44株,16S rDNA分子序列分析表明：这些拮抗内生细菌的类群包括了两个门(变形杆菌门、拟杆菌门)8个属,其中10个菌株与已报道菌株相似性<97%,可能是新的种（属）,优势种群为肠杆菌属（18株）、泛菌属（15株）。【结论】棉花的品种、生育期与器官影响棉花内生细菌数量;棉花拮抗黄、枯萎病菌的内生细菌具有优势种群,且具多样性。     

Evaluation of potential biocontrol rhizobacteria from different host plants of Verticillium dahliae Kleb

AIMS: A screening approach was developed to assess the potential of rhizobacterial strains to control Verticillium wilt caused by Verticillium dahliae Kleb. METHODS AND RESULTS: Sixty randomly chosen antagonistic bacterial strains originally isolated from rhizosphere of three different host plants of V. dahliae--strawberry, potato and oilseed rape--were evaluated for biocontrol and plant growth promotion by analysing in vitro antagonism towards V. dahliae and other plant pathogenic fungi, production of fungal cell wall-degrading enzymes and plant growth-promoting effects on strawberry seedlings. To test the plant growth-promoting effect, a microplate assay with strawberry seedlings was developed. Although the rhizobacterial strains were isolated from different plants they showed effects on the growth of strawberry seedlings. According to the in vitro biocontrol and plant growth-promoting activity, the three best candidates Pseudomonas putida B E2 (strawberry rhizosphere), Ps. chlororaphis K15 (potato rhizosphere) and Serratia plymuthica R12 (oilseed rape rhizosphere) were selected for greenhouse experiments to verify the in vitro screening results. Under greenhouse conditions the isolates selected according to this strategy were as effective, or more effective than commercial biocontrol agents and may therefore possibly be valuable as antagonists of V. dahliae. CONCLUSIONS: In this study, the screening strategy resulted in a selection of three interesting biocontrol candidates against Verticillium: Ps. putida B E2 (strawberry rhizosphere), Ps. chlororaphis K15 (potato rhizosphere) and Ser. plymuthica R12 (oilseed rape rhizosphere). SIGNIFICANCE AND IMPACT OF THE STUDY: A new combination of in vitro screening methods including a microplate assay with strawberry seedlings to test the plant growth promoting effect which allow to more efficiently select potential biological control agents was developed successfully.     

Paramural bodies in hyphae of Verticillium dahliae Kleb. revealed by freeze etching

Summary Freeze etched replicas of hyphae of Verticillium dahliae revealed the presence of paramural bodies and elaborations of the plasmalemma. It is suggested that the presence of these structures in freeze etched preparations is indicative of their presence in living cells rather than as post-mortem artifacts following fixation.     

Physiological cotton wilt in the Sudan Gezira

Cotton wilt of physiological origin appears to have been present in the Gezira area of the Anglo-Egyptian Sudan since 1924 if not previously. The present investigations showed that between mid-October and mid-December three factors occur which cause water stress in the crop. At some time during this period there is marked reduction in the size of the absorbing system of the plant, correlated with maximum boll development. Greatly increased day temperatures and higher evaporation prevail, while during the whole period available water in the soil declines. The hypothesis is put forward that when all three factors occur at the same time at their maximum intensity, permanent wilting and death of the plants result; at lesser intensities, wilting is followed by recovery, but with reduction of yield. Experiments are described, the results of which appear to confirm this view. In the author's opinion a return to the earlier sowing date formerly favoured locally would lead to considerably increased losses.     

Systemic fungicides in the control of strawberry wilt (Verticillium dahliae)

In a series of experiments between 1970 and 1973 the application of benomyl or thiophanate methyl to field-grown strawberries, planted on Verticillium-mtested land, gave control of wilt for up to 5 months, the duration of control being related to the amount of fungicide applied in the spring. Treatment of inoculated plants grown on in chloropicrin-fumigated soil was effective for at least two seasons. An autumn-planted multi-factorial experiment in heavily-infested soil showed that, to achieve maximum wilt control, it was advantageous to grow cv. Gorella rather than cv. Cambridge Vigour; to drench the runners at planting rather than to dip them in the fungicide suspension; and to use a high concentration (0–075 % a-i-) and large volume (600 ml per plant) for a supplementary treatment in May rather than a lower concentration (0.025 %) ^or smaller volume (400 ml). There were small but significant advantages in applying benomyl rather than thiophanate methyl, and in using 0–2% a.i. suspension at planting rather than 0–05%. No advantage was gained by dividing the spring application into two equal doses applied 2 wk apart. Extrapolation from the logarithmic relation between wilt index and total dose of fungicide applied in the spring suggested that I.I g/plant would have given almost complete control until October; such control had been achieved in an earlier experiment in which 1–2 g/plant was applied. Crop yield in the second year was determined by the treatment applied in the first year, but although these treatments had given significantly better control of wilt in Gorella than in Cambridge Vigour, the greater growth and yield potentials of the latter cultivar had an over-riding effect on crop production; Cambridge Vigour yielded more than Gorella under all chemical treatments, but in the absence of treatment Gorella gave a larger crop than Cambridge Vigour. A proposed regime, entailing spring and autumn applications, is aimed at minimizing the colonization of the plant throughout the year, thus reducing the production of new inoculum and, by limiting the quantity of the pathogen in contact with the systemic chemicals, minimizing the probability of selecting fungicide-resistant variants of V. dahliae.     

Electrophoretic karyotype and gene mapping of the vascular wilt fungus Verticillium dahliae

The karyotype profile of Verticillium dahliae was resolved by pulse-field gel electrophoresis. It revealed 6 chromosomal bands that corresponded to 7 chromosomes as shown by RFLP analysis using as probe the telomeric consensus sequence (AACCCT)(5). The number of chromosomes was further verified by the sensitivity of the hybridization signals to Bal31 digestion and the exclusion of interfering mitochondrial DNA signals. The corresponding sizes of the seven separated chromosomes were 6.7, 5.6, 4.1, 3.4, 3.1, 3.1 and 2.4Mb, raising the total genomic size of the fungus to approximately 28.4Mb. Twenty five homologous V. dahliae genes obtained either from randomly sequenced clones or PCR amplification were used as hybridization probes and were located onto the seven chromosomes.     

Influence of inoculum density of Verticillium dahliae, temperature and relative humidity on epidemics of verticillium wilt of cotton in northern Iran

During 1992--2003, frequency of Verticillium dahliae propagules, disease incidence and severity of verticillium wilt of cotton were determined in several cotton growing fields in Golestan province, northeastern Iran. Inoculum density varied among fields and different years ranging between 2-47 propagules/g of air-dried soil with an average of 18.96+/-0.73. In addition, the pattern of diseased plants varied with type of field and year. Simple regression analysis showed a linear relationship between inoculum density of V. dahliae at planting time on one hand, disease incidence and severity for all years on the other. The straight line model described the increase in disease intensity index over the accumulated physiological time from sowing. The number of days above 28 degrees C (T) and the area under relative humidity (RH) had significant effects on inoculum density in soil (MS) and final disease development (Y) and fitted the Y = 65.840 - 0.0034 RH + 0.57 MS - 1.7T model with R2 = 0.859 and significant F-function (p<0.0001).     

Dynamic infection of Verticillium dahliae in upland cotton

• Verticillium wilt, an infection caused by the soilborne fungus Verticillium dahliae, is one of the most serious diseases in cotton. No effective control method against V. dahliae has been established, and the infection mechanism of V. dahliae in upland cotton remains unknown.
• GFP‐tagged V. dahliae isolates with different pathogenic abilities were used to analyse the colonisation and infection of V. dahliae in the roots and leaves of different upland cotton cultivars, the relationships among infection processes, the immune responses and the resistance ability of different cultivars against V. dahliae.
• Here, we report a new infection model for V. dahliae in upland cotton plants. V. dahliae can colonise and infect any organ of upland cotton plants and then spread to the entire plant from the infected organ through the surface and interior of the organ.
• Vascular tissue was found to not be the sole transmission route of V. dahliae in cotton plants. In addition, the rate of infection of a V. dahliae isolate with strong pathogenicity was notably faster than that of an isolate with weak pathogenicity. The resistance of upland cotton to Verticillium wilt was related to the degree of the immune response induced in plants infected with V. dahliae. These results provide a theoretical basis for studying the mechanism underlying the interaction between V. dahliae and upland cotton. These results provide a theoretical basis for studying the mechanism underlying the interaction between V. dahliae and upland cotton.