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1.
The infection and survival of sclerotia of Sclerotinia minor and the production ofmacroconidia of the mycoparasite, Sporidesmium sclerotivorum, were studied in vitro when each fungus was added to soil at various initial inoculum densities. The rate at which S. sclerotivorum invaded host sclerotia and caused their decay varied with the amount of the mycoparasite added to soil. The results suggest that approximately 5 macroconidia of the mycoparasite g?1 of soil are needed to successfully infect sclerotia and bring about their decay, when soils are sampled and mixed every 2 weeks. The rate at which S. sclerotivorum infects sclerotia of S. minor and causes their decay is also dependent on the initial inoculum density of the host. Each infected sclerotium supports the production of about 15,000 new macroconidia in soil regardless of the initial inoculum density of the host. It is concluded that successful biological control by S. sclerotivorum is dependent on the soil population of both the host and the mycoparasite.  相似文献   

2.
Ascospores of Sclerotinia sclerotiorum produced from apothecia are the primary source of inoculum for causing diseases such as white mold of common bean, pod rot of pea, stem blight of canola and head rot of sunflower and safflower in the Canadian prairies. A field study was conducted for 4 years to determine efficacy of control of production of apothecia from carpogenically germinated sclerotia of S. sclerotiorum by soil amendment with Perlka® (calcium cyanamide) and S-H mixture (a formulated compound). Results of the 4-year experiments showed that amendment of soil with Perlka® at low (30 g/m2) or high (60 g/m2) rate was effective in reducing carpogenic germination of sclerotia and production of apothecia under the canopy of host crops (common bean and canola) and a non-host crop (wheat). In the experiments of 1988, for example, the numbers of apothecia produced in the treatments of Perlka®-low rate (30 g/m2), Perlka®-high rate (60 g/m2) and untreated control were 42, 46, and 182 apothecia/plot (m2), respectively, for bean; 89, 42, and 318 apothecia/plot (m2), respectively, for canola; and 146, 143, and 412 apothecia/plot (m2), respectively, for wheat. However, soil amendment of S-H mixture at low (30 g/m2) or high (60 g/m2) rate was ineffective in reducing carpogenic germination of sclerotia and production of apothecia for all the 4 years of testing in all three crops. The ineffectiveness of S-H mixture and the practicality of Perlka® for control of Sclerotinia diseases of crops grown under Canadian prairie conditions are discussed.  相似文献   

3.
For taxonomic purposes and because many wild relatives of Allium crops are endangered in their native habitat (Sancir et al., 1989), a collection of Allium species was built up in the IPK at Gatersleben. At present it consists of more than 3000 accessions representing about 330 species. In this context it was necessary to study the seed germination behaviour and dormancy of certain wild Allium species. Therefore, seeds of 91 wild and three cultivated Allium species were tested at germination temperatures of 5°, 11°, 16° and 26°C. The purpose of this study was to develop routine germination tests for the genebank work with wild alliums.  相似文献   

4.
Rhizoctonia solani causes worldwide losses in numerous crops. Sclerotia of R. solani remain viable for several years in soil and are an important source of primary infection. In this study the effect of soil incorporation of Kraft pine lignin, a side product of the paper industry, on viability of R. solani AG1-1B sclerotia was investigated. The efficacy of lignin was assessed in a sandy loam (Oppuurs) and a silt loam soil (Leest) collected from commercial fields in Belgium. Evaluating sclerotial viability after 4 weeks incubation in the two soils amended with 1% (w/w) Kraft pine lignin demonstrated a soil-dependent effect. In Leest soil the addition of lignin resulted in a significantly reduced sclerotial viability, together with an increased mycoparasitism by Trichoderma spp.; in Oppuurs soil, on the other hand, only a slight and insignificant reduction in sclerotial viability was observed. Based on phospholipid fatty acid analysis, different changes in microbial community structure upon lignin amendment were detected in the two soils. Both amended soils showed a significant increase in Gram negative bacteria. In Leest soil this increase was accompanied with a significantly higher increase in fungi and actinomycetes compared with Oppuurs soil. In addition, Kraft pine lignin resulted in both soils in a small but significant increase in manganese peroxidase activity and this increase tended to be higher in Leest soil. Manganese peroxidase produced by lignin-degrading basidiomycetes has previously been shown to degrade melanin, which protects the sclerotia against biotic and abiotic stress. We hypothesize that lignin-degrading fungi increased the susceptibility of the sclerotia to sclerotial antagonists such as Trichoderma, Gram negative bacteria and actinomycetes. Clearly, the effect observed here did not rely on the stimulation of one microbial group, but is the result of an interaction of different groups.  相似文献   

5.
The colonization of Macrophomina phaseolina sclerotia by microbial parasites was evaluated in unsterilized field soil at different levels of soil moisture (0,-5, and-10 kPa) and temperature (20, 30, and 40°C). The maximum colonization of sclerotia was recorded in soil held at-5 or-10 kPa at 30–40°C. Trichoderma harzianum isolate 25–92 and Pseudomonas fluorescens isolate 4–92 were recorded as potential sclerotial parasites, and they significantly (P=0.05) reduced the germination of sclerotia by 60–63%. Cells of P. fluorescens and buffer-washed conidia of T. harzianum were completely agglutinated at 28°C with crude agglutinin of M. phaseolina. The ability of different antagonists to parasitize the sclerotia were correlated with the agglutination ability of the antagonists.  相似文献   

6.
The population and distribution of sclerotia of Rhizoctonia solani Kühn in two sugar beet field soils was determined at harvest by a sieving-flotation method. In rhizosphere soil (RS) and non-rhizosphere soil (NRS) from the most heavily infected roots of sugar beets, 1.43–2.5 and 0.83–1.0 sclerotia g?1 dry soil were detected, respectively. In the soil around healthy sugar beet, these values were 0.04–0.12 and 0.03–0.04 sclerotia g?1 dry soil. More sclerotia were always obtained from RS than from NRS. More than 80% of the sclerotia were in the upper 10 cm of soil and within 10 cm of diseased roots. Therefore, there is a non-uniform distribution of sclerotia of R. solani in soil.The sclerotial population in soil increased significantly with disease severity and a good correlation was obtained between the number of sclerotia and the disease severity on infected plants. Most of the sclerotia collected from the field soil ranged in size from 0.5 to 2.0 mm diameter.Viability of sclerotia increased as severity of crown rot increased and as the size of the sclerotia increased. Conversely, there was a progressive decrease in sclerotial germination with increasing depth in soil and increasing distance from the infected root.  相似文献   

7.
采用植物化感作用与诱捕作物消除列当土壤种子库   总被引：4，自引：1，他引：3  
研究证明化感作用需要满足如下4个方面:1)供体植物释放化感物质使得受体植物受到连续和定量的影响;2)能从供体植物中分离、鉴定得到化感物质,而且这些化感物质无论是在室内还是在田间,都能对在自然生态系统中邻近的伴生植物产生效应;3)供体植物产生和释放的化感物质在自然条件下能以足够的浓度到达邻近受体植物;4)以足够生物活性到达受体植物的化感物质能够被吸收并能够影响受体植物的生理生化过程,而且这种影响必须排除受体植物的生长发育不是由于竞争、动物侵害、病菌感染以及物理环境等非化感因素产生的影响。列当是列当科(Orobanchaceae)列当属(Orobanche)的根寄生植物,是一种寄生于其他植物根部的全寄生植物。全世界已发现100种列当属根寄生植物,在我国危害较为严重的是向日葵列当(O.cumana)和瓜列当(O.aegyptiace)。向日葵列当主要分布在陕西北部、河北、新疆、山西、内蒙古及东北三省,主要危害向日葵。瓜列当主要分布在新疆,危害瓜类、番茄、马铃薯。列当杂草的种子体积小、重量轻(3~6μg),而且每株植物可以生产大量种子。这些种子数量巨大且在土壤中可以保持生存力长达15~20年以上。成熟后的列当种子需要经过一段时间的后熟过程,完成后熟的列当种子在发芽之前需要1~2周时间在一定的温度和湿度条件下进行预培养,预培养后的列当种子还必须从寄主那里获得一个化学物质才能发芽,在自然条件下这种发芽刺激物质是由寄主或非寄主植物的幼根分泌提供的。获得该物质后,列当种子的"发芽管"可在数日内长出种皮,之后在吸器诱导物质的作用下很快形成吸器,与寄主根吸附并穿入根内后与寄主根的木质部形成联结,从寄主植物那里竞争性地夺取水分、养分及生长激素。由于列当属植物是根寄生杂草,在没有长出地面之前,它已经给作物造成严重的伤害,所以不易控制,有效的途径是尽量减少土壤中的列当种子含量。诱捕作物是指该作物的根系能够分泌列当属植物种子发芽的刺激物质,但是又不会被列当正常寄生,诱捕作物本身可以进行正常收获。由于列当属植物种子的生命只有一次,发芽后不能寄生就会死亡,这种发芽又称之为"自杀发芽",如此可以在列当找不到寄主之前死亡,从而大大降低土壤中列当的种子库。本文介绍了作者项目组从事采用化感作用与诱捕作物(小麦、玉米、棉花、大豆等)消除列当土壤种子库最新研究进展。  相似文献   

8.
Summary Only 10% of sclerotia germinated in a tarpcovered plot after 45 days of treatment while 50% of sclerotia germinated in the control plot. However, complete inhibition of sclerotia germination was not achieved. The maximum temperature recorded was 53°C, after 45 days of treatment in a tarped plot at 1 cm depth. The incidence of Acrophialophora fusispora, Aspergillus spp., Spicaria sp., and Trichoderma viride increased in soil after 45 days of the solar treatment.  相似文献   

9.
Aspects of the biology of C. minitans and its potential for control of S. sclerotiorum were investigated.Temperatures below 7°C resulted in comparatively slow rates of germination and infection of sclerotia by C. minitans. The optimum temperature for germination, growth, infection of sclerotia, and destructive parasitism by C. minitans was 20°C. The optimum relative humidity for germination, growth and infection by C. minitans was above 95%.Autumn inoculations with suspensions of conidia, pycnidia and mycelium of C. minitans in the field resulted in negligible numbers of sclerotia remaining viable after 1 month. With culture-grown sclerotia 2 months were required for a similar reduction of sclerotial viability. In the absence of C. minitans mulching had no significant effect on sclerotial viability. In the presence of C. minitans mulching did, however, influence the viability and infection by C. minitans of culture-grown sclerotia. Populations of field sclerotia also differed from culture-grown sclerotia in that they harboured an internal population of microorganisms, which included C. minitans, and had a lower level of viability at the commencement of the treatments.A winter application of C. minitans did not result in significant infection of sclerotia nor in a reduction in viability of sclerotia. This failure is believed to have resulted from low temperatures and dry conditions.  相似文献   

10.
Ten isolates of Trichoderma spp were examined for their ability to antagonize growth and to parasitize mycelium of Sclerotium rolfsii (Sr-1) on agar media, to inhibit germination of sclerotia of S. rolfsii on natural soil plates and to sporulate on the sclerotia, and to protect bean seedlings against the pathogen in the greenhouse. A high negative correlation (r = ?0.844) was observed between plant stand in the greenhouse and sclerotial germination on soil plates but not with antagonism on agar plates. Three isolates of T. harzianum (Th-7, Th-20, WT-6) and one of T. hamatum (TRI-4) were especially effective in reducing sclerotial germination and controlling disease in the greenhouse. Three isolates of Trichoderma spp (WT-6, TMP, and TRI-4), effective in reducing sclerotial germination of isolate Sr-1, also prevented sclerotial germination in four out of five additional S. rolfsii isolates studied.  相似文献   

11.
A single injection of 0.2 ml diallyl disulphide (DADS) at 0.156% (v/v) into soil containing naturally-produced sclerotia of Sclerotium cepivorum and maintained in the laboratory at 15°C stimulated sclerotial germination and reduced sclerotial numbers by 67%; ungerminated sclerotia remained viable. Higher concentrations of DADS had no additional effect except that at 20% (v/v), germination was slightly inhibited. A similar reduction in sclerotial numbers was obtained when the mixture of soil and sclerotia was exposed to DADS vapour. Four, monthly applications of DADS at 0.2 ml 0.15% (v/v) per application did not give a further reduction.The effect of DADS was temperature dependant, with a reduction in sclerotial numbers of 65 and 9% at 15 and 5°C respectively.  相似文献   

12.
土壤学不应忽视对作物土传病原微生物的研究   总被引：14，自引：1，他引：13  
蔡祖聪  黄新琦 《土壤学报》2016,53(2):305-310
随着集约化种植程度的提高,管理不善、单一作物连续种植、秸秆还田等因素导致的土传病害日益严重,使作物高产对农药的依赖程度不断提高,对我国农业可持续发展、环境和农产品安全构成了很大的威胁。但是,我国当前土壤学几乎忽视了这一土壤学范畴的研究领域。土传植物病原微生物功能明确,是研究土壤微生物区系和生物多样性与功能、土壤微生物与植物生长、土传病原微生物与拮抗微生物等关系的理想研究对象。土壤学在揭示土传病原微生物的生长规律、控制土传病原微生物数量、发挥拮抗微生物的作用、防治作物土传病害等方面具有独特的优势。深入认识土传病原微生物适宜生长的土壤环境是防控作物土传病原微生物生长,实现农药使用量零增长的基础。解决当前严重的作物土传病害不仅是土壤学的责任和义务,而且可以极大地推动土壤学的发展。  相似文献   

13.
This study was undertaken to investigate the feasibility of using Paecilomyces lilacinus NRRL 13 866, chitin, and cellulose amendments, in order to reduce survival and prevent germination of sclerotia from Aspergillus flavus NRRL 6556, NRRL 13 048, and A. parasiticus NRRL 13 005, NRRL 13 539 buried in sandy soil in Georgia and Illinois (April–October, 1990). The number of sclerotia that germinated sporogenically in moist chambers following burial in Illinois was twice that of sclerotia buried in Georgia and varied among the four sclerotium-producing Aspergillus spp. strains. Sclerotium viability, as measured by Aspergillus spp. colony formation on potato dextrose agar, was high (>84%) for all strains and treatments (e.g. amendment, location). Even so, A. parasiticus NRRL 13 539 sclerotia were apparently more susceptible to P. lilacinus colonization than sclerotia from other strains. Treatment with Paecilomyces sp. caused a small but significant reduction in germination among sclerotia buried in Georgia.  相似文献   

14.
A study dealing with ecological sustainability of plantation based land use initiated in 1991 in a 19 yr old coconut plantation consists of growing certain leguminous crops like Atylosia, Pueraria, Centrosema and Calopogonium as soil cover in separate plots with lemon grass as live bounds. These cover crops are grown during the rainy season and incorporated into the soil towards the end of the monsoon every year. The effect of such cover crops on soil microbial counts (total counts, fungi, actinomycetes and bacteria), biomass C, organic C, total N and on the activity of enzymes like urease, amidase, L-glutaminase, aryl sulphatase and dehydrogenase was determined in soils (Ap horizon) collected from these plots after 5 years. Soils with cover crops registered significantly higher microbial biomass, biomass C, organic C and total N compared to control. Consequently, all the enzymes were activated to different degrees in soils with cover crops. Significant and positive relationships of enzyme activities with organic C, mineral N and total N suggested that growing cover crops, increased C turnover and N availability and therefore, provided a conducive environment for microbial proliferation, enzyme synthesis and accumulation in the soil matrix.  相似文献   

15.
Bacteria, isolated from canola and soybean plants, produced antifungal organic volatile compounds. These compounds inhibited sclerotia and ascospore germination, and mycelial growth of Sclerotinia sclerotiorum, in vitro and in soil tests. Ascospore germination in cavity slides was inhibited 54-90% by the volatile producers. When mycelial plugs or the sclerotia, exposed to these volatiles, were transferred to fresh agar plates, the pathogen could not grow, indicating the fungicidal nature of the volatiles. Head space volatiles, produced by bacteria, were trapped with activated charcoal, by passing nitrogen continuously over shake cultures for 48 h. The compounds were eluted from the charcoal with methylene chloride and identified using Gas Chromatography-Mass Spectrometry (GC-MS). The volatile compounds included aldehydes, alcohols, ketones and sulfides. Of the 23 compounds assayed for antifungal activity in divided Petri plates, with filter-disks soaked with these compounds (100 and 150 μl), only six compounds completely inhibited mycelial growth or sclerotia formation, suggesting their potential role in biological control. The compounds are benzothiazole, cyclohexanol, n-decanal, dimethyl trisulfide, 2-ethyl 1-hexanol, and nonanal. Volatiles may play an important role in the inhibition of sclerotial activity, limiting ascospore production, and reducing disease levels. Studies are under way to understand this phenomenon under field conditions. This is the first report on the identification and use of bacterial antifungal organic volatiles in biocontrol.  相似文献   

16.
ABSTRACT

The neutral monosaccharide composition of forest soils differs from that of non-forest soils suggesting there is an accumulation of microbial saccharides. Ectomycorrhizal (ECM) fungi can be responsible as the fungi are typical in forest soils. We investigated neutral saccharides of ECM fungal sclerotia to determine what part it might play in the origin of forest soil polysaccarides. Sclerotial grain (SG) was collected from the O, A1 and A2 horizons of a soil of subalpine forest of Mt. Ontake, central Japan. Neutral saccharides in soil and SG were analyzed by two step hydrolysis with sulfuric acid and gas-chromatography of alditol acetate derivatives. Saccharides accounted for 6.0?16% of the SG by carbon content. The SG contained predominantly easily hydrolysable (EH)-glucose, which accounted for 75–85% of the composition depending on grain size and the soil horizon, followed by mannose (7.7?15%), galactose (2.2?4.8%) and non-easily hydrolysable (NEH)-glucose (1.7?6.1%). The SG contained all of these sugars irrespective of its size. The SG collected from the A1 and A2 horizons contained all sugar components found in that from the O horizon, except for fucose in that from A2 horizon. The monosaccharide composition of SG indicates that accumulation of ECM fungal sclerotial polysaccharides might have been responsible for enlarging the molar ratios of (galactose + mannose) /(arabinose + xylose) and EH-glucose/NEH-glucose of forest soils. The proportions of SG saccharides relative to soil saccharides were 3.6, 1.2, and 0.83% for the O, A1 and A2 horizons, respectively. These levels of the proportion are considerable as ECM fugal sclerotia are the products of a limited species among hundreds and thousands of microbial species inhabiting forest soils. The sclerotia forming ECM fungal species such as Cenococcum geophilum may be key sources of forest soil polysaccharides.  相似文献   

17.
冬季作物对水稻生育期土壤微生物量碳、氮的影响   总被引：3，自引：1，他引：2  
选取我国南方4种冬季作物黑麦草、紫云英、油菜、马铃薯,以冬闲田作对照,对水稻生育期土壤微生物量碳（SMBC）和土壤微生物量氮（SMBN）的短期内动态变化进行了研究。结果表明,早稻田翻耕前,冬季作物处理土壤SMBC和SMBN与冬闲田存在显著差异(P0.05),黑麦草处理SMBC为398.5 mg/kg,显著高于其他作物;紫云英处理SMBN最高,为97.8 mg/kg。在早稻整个生育期,黑麦草处理SMBC显著高于其他处理,晚稻生长过程中各处理无显著差异。冬季作物对稻田土壤微生物商(MQ)的影响,随着水稻生长发育进程有不同程度的变化,黑麦草处理在早稻整个生育期高于冬闲田。  相似文献   

18.
The effects of three Coniothyrium minitans isolates (Conio, IVT1 and Contans®), applied to soil as conidial suspensions or as maizemeal-perlite (MP) inocula (Conio), on apothecial production and infection of Sclerotinia sclerotiorum sclerotia were assessed in two soil pot bioassays and two novel box bioassays in the glasshouse at different times of the year. C. minitans isolate Conio applied as either MP or ground MP at full rate (106-107 cfu cm−3 soil) consistently decreased the carpogenic germination, recovery and viability of sclerotia and increased C. minitans infection of the sclerotia of S. sclerotiorum by in comparison with either MP or conidial suspension treatments applied at lower rates (103-104 cfu cm−3 soil). Additionally, when applied at the same rate, MP inoculum of C. minitans was consistently more effective at reducing carpogenic germination than a conidial suspension. The effect of MP and ground MP at full rate on carpogenic germination was expressed relatively early as those sclerotia recovered before apothecia appeared on the soil surface already had reduced numbers of apothecial initials. In general, there were few differences between the isolates of C. minitans applied as conidial suspensions. Box bioassays carried out at different times of the year indicated that temperature and soil moisture influenced both apothecial production and mycoparasitism. Inoculum concentration of C. minitans and time of application appear to be important factors in reducting apothecial production by S. sclerotiorum.  相似文献   

19.
Leek (Allium porrum) plants from organic farming were harvested at 15, 59, and 210 days after seed germination. Organochlorine pesticide (OCP) levels were quantified by GC-ECD in vegetative tissues (roots and aerial), bulk soil and rhizosphere. Leek plant bioaccumulate OCPs efficiently in their aerial and root tissues and alter the concentration of the soil where they are grown. OCPs distribution pattern of bulk soil was endosulfans > DDTs > dieldrin, while it was endosulfans > HCHs > DDTs in leek tissues. There were statistically significant declines in DDTs, chlordane, dieldrin, and heptachlor in the rhizosphere, indicating that recalcitrant residues of OCPs may be removed from contaminated soil using leek crops under normal growing conditions. The DDE/DDT and alpha-/gamma-HCH ratios of < 1 would indicate recent inputs of DDT and lindane in the environment. The occurrence of OCPs in this farm could be the result of atmospheric deposition and/or surface runoff of these pesticides.  相似文献   

20.
Soil management practices, including the use of cover crops, affect soil and plant health through varied mechanisms. Impacts on microbial communities are known to be important, but are not well understood. Various techniques are used to measure the effect of treatments on microbial communities, but rarely are the results of more than one technique compared. This field study examined the impacts of a single-season application of cover crops on detection of pathogen species in the tomato crop rhizosphere. The study took place in Maryland, New York and Ohio (MD, NY and OH) in the summers of 2010 and 2011, with a total of 260 plots tested using both macroarray and T-RFLP analyses. The macroarray used in this study was specifically designed to detect thirty-one pathogens of solanaceous crops and had not previously been used for such a field study. The results of T-RFLP analysis, which is a common tool for examining microbial communities, were compared to the macroarray results and the limitations and benefits of each are presented. While not a quantitative measure, the macroarray was able to detect certain fungi with much greater sensitivity than T-RFLP. Our findings suggest that the results of PCR-based techniques used for microbial community studies should be compared to other methods to verify sensitivity.  相似文献   

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