Infection process of Rhizoctonia solani on Solanum tuberosum and effects of granular nematicides     

T. W. Hofman  P. H. J. Jongebloed 《European journal of plant pathology / European Foundation for Plant Pathology》1988,94(5):243-252

The infection process ofRhizoctonia solani AG-3 was studied on potato sprouts, cv. Bintje, in growth chamber trials at 15 °C. Initially hyphae ofR. solani grew predominantly in the longitudinal direction of the sprouts (runner hyphae). They tended to follow the junctions between epidermis cells as was observed by SEM. The hyphae formed side-branches mainly half-way of the subterranean parts of the sprouts. They branched several times with short swollen cells to form infection cushions. Lesions developed only underneath the infection cushions and were first observed five days after inoculation. The necrotic area was proportional to the area covered with infection cushions on the sprouts. Depth of the lesions could extend up to the vascular bundle. Sprouts were colonized only in healthy tissue in the epidermal layer underneath the infection cushion and in necrotic tissue. A few days after appearance of the lesions,R. solani formed brown, uninfective mycelium on and in the circumference of these lesions.Aldicarb did not influence any part of the infection process. Ethoprophos delayed the emergence of sprouts, but increased the number of sprouts per tuber. As soon as sprouts had emerged, growth was considerably promoted by ethoprophos. Ethoprophos delayed the appearance of lesions and reduced their size. Oxamyl showed the same effects to a smaller extent.As the size of lesions appears to be proportional to the size of the infection cushions, any agents that change the size of the infection cushions, such as pesticides or antagonists, may alter the severity of the disease.Samenvatting Het infectieproces vanRhizoctonia solani AG-3 werd bestudeerd op aardappelspruiten, cv. Bintje, in een klimaatcel bij 15C. Aanvankelijk groeide de schimmel met runnerhyfen voornamelijk in de lengterichting van de spruit. Via SEM kon waargenomen worden, dat de hyfen hierbij vooral over de begrenzingen van de epidermiscellen groeiden. Het mycelium vormde veel zijvertakkingen, bestaande uit iets gezwollen korte cellen, welke voornamelijk halverwege op het ondergrondse deel van de spruit gevormd werden. Een dichte massa van deze cellen vormde een infectiekussentje. Lesies, welke vanaf vijf dagen na inoculatie werden waargenomen, bevonden zich slechts onder spruitoppervlak bezet met infectiekussentjes. De lesiegrootte was recht evenredig met het spruitoppervlak dat bezet was met infectiekussentjes. De diepte van de lesies reikte tot aan de vaatbundels. De spruit werd alleen door de schimmel gekoloniseerd in gezond epidermisweefsel onder het infectiekussentje en in necrotisch weefsel. Enkele dagen na verschijning van lesies vormde R.solani bruin, niet infectieus, mycelium op en rondom de lesies.Aldicarb had geen effect op het infectieproces. Ethoprophos vertraagde de opkomst en verhoogde het aantal tot ontwikkeling gekomen spruiten per knol in gestoomd zand. Direct na opkomst had ethoprophos echter een sterk groeistimulerend effect. Ethoprophos vertraagde de lesievorming en reduceerde de lesiegrootte, vergeleken met onbehandelde planten. Oxamyl vertoonde deze effecten in geringere mate.Daar de lesiegrootte direct gecorreleerd blijkt met de grootte van het infectiekussentje, mag verwacht worden dat elke beïnvloeding van de ontwikkeling van het mycelium van R.solani, bijvoorbeeld door pesticiden of antagonisten, een verandering van de lesiegrootte ten gevolge heeft.  相似文献   

Strawberry Production in Central Europe     

《International Journal of Fruit Science》2013,13(1):91-105

Abstract

This paper focuses on the cropping systems in central European countries such as Belgium, The Netherlands, UK, Ireland, Germany, Switzerland and the northern part of France and Italy. During the last decade there has been a consistent increase in programmed “out-of-season” strawberry production in several central European countries. This is being achieved in part, by using cultivars with different cropping seasons, but mainly by sequential planting of cold-stored plants and by growing strawberries in greenhouses and plastic tunnels. These methods have made it possible to extend the strawberry production for 11 months, from the end of February until mid January in central European countries with moderate climates.  相似文献   

高含沙水流水轮机转轮的改型与抗磨蚀研究   总被引：1，自引：2，他引：1  

梁武科  罗兴琦  郭鹏程  王得意 《中国农村水利水电》2004,(2):78-80

进行高含沙水流水轮机转轮的改型研究，关键是要从正确确定转轮设计参数和轴面流道型式入手，根据三维水力设计理论，考虑导叶与转轮匹配关系进行叶型设计，针对不同破坏机理选择强磨蚀区采用金属喷涂或非金属保护等综合措施，使水轮机在高舍沙水流中运行时出力增加、抗磨蚀能力提高。  相似文献   

CFD技术在水轮机转轮抗空蚀改造中的应用   总被引：3，自引：1，他引：3  

宋海辉  匡和碧 《中国农村水利水电》2004,(10):100-102

CFD是用计算机来模拟流体的流场，建立流体机械最佳流道的流体动态分析软件，是当今先进的流体动力学模拟分析工具。介绍了CFD技术的理论基础，并且将其成功应用于锦江电站水轮机转轮的抗空蚀改造中，取得了良好的效果。  相似文献   

Relative abundance and activity of melanized hyphae in different soil ecosystems     

Annemieke van der Wal  Jaap Bloem  Wietse de Boer 《Soil biology & biochemistry》2009,41(2):417-419

Here we report on the frequency of melanized fungal hyphae in 323 soils, covering different land use types. The proportion of total hyphae that was melanized averaged 61%. Arable fields with loamy sand, heathlands and city parks on sandy soils had the highest percentage of melanized hyphae. In addition to the frequency determinations, a microcosm study was performed on the role of melanized hyphae in two different ecosystems: an ex-arable field and a forest. Melanized hyphae appeared to be part of the active hyphae in the forest soil but not in the ex-arable soil. In conclusion, our results indicate that (1) melanized hyphae represent a large proportion of the total fungal biomass in soils and that (2) their function might differ between ecosystems.  相似文献   

Effects of nitrogen feeding for extraradical mycelium of Rhizophagus irregularis maize symbiosis incorporated with phosphorus availability     

Zhifang Li  Benard Ngwene  Ting Hong  Eckhard George 《植物养料与土壤学杂志》2019,182(4):647-655

In terrestrial ecosystems, plants are frequently in symbiosis with arbuscular mycorrhizal fungi (AMF) with mineral nutrients and photosynthesis carbon exchanges in between. This research sought to identify the effects of phosphorus (P) levels on the nitrogen (N) uptake via extraradical mycelium (ERM) and the mycorrhizal growth response (MGR) of maize plants within the AMF symbiosis. Pots were separated into root compartments and hyphae compartments (HCs) with two layers of a 30‐μm mesh membrane and an air gap in between, where only hyphae could pass through, to avoid both N diffusion and root growth effects. Maize plants were inoculated with Rhizophagus irregularis with different N fertilization in HCs under two different P fertilization levels. Our results indicated that a strong increase in MGR with low‐P fertilization. The same tendency was not observed with high‐P fertilization, although both had a large increase in P concentration as a potential source of growth in shoot tissue of mycorrhizal plants. Substantial effects (10.5% more N) were observed in the case of high‐P availability for the host plants from ERM fed with N, whereas under low‐P conditions ERM may prioritize P uptake rather than N uptake. The AM fungi increase the uptake of N and P, which are most limiting in the soil with fewer forces from soil resources. In addition, there was still more P accumulated than N due to the high N for ERM with high‐P supply. Low N in HCs corresponded with a lower colonization rate in roots but with high hyphae density in HCs; this result suggest that N and P availability might change the ratio of extraradical to intraradical hyphae length.  相似文献   

类黄酮对AM真菌侵染菌丝生长及酶活性的影响          下载免费PDF全文

董昌金  姚发兴  赵斌 《土壤学报》2006,43(3):473-477

类黄酮（hesperitin）能显著促进AM真菌[Glomus intraradices（G.i）、Acaulospora laevis（A.l）、G.i＋A.l]对宿主植物（玉米、棉花）根段的侵染,提高菌丝琥珀酸脱氢酶（Succinate dehydrogenase,SDH）和碱性磷酸酶（Alkaline phosphatase,ALP）的活性.当用15 nmol L^-1、150 nmol L^-1、1.5 μmol L^-1类黄酮处理时,第6周取样,G.i对玉米根段的侵染率分别为76.2%、84.5%、75.8%（对照为45.9%）,菌丝SDH酶活性分别为68.4%、75.9%、67.4%（对照为40.7%）,菌丝ALP酶活性分别为45.8%、51.4%、45.1%（对照为27.1%）;G.i对棉花根段的侵染率分别为85.2%、88.9%、83.8%（对照为59.8%）,菌丝SDH酶活性分别为76.8%、81.2%、75.0%（对照为53.1%）,菌丝ALP酶活性分别为51.2%、53.7%、49.4%（对照为35.2%）.同时,类黄酮能显著增加土壤中AM真菌菌丝的总量,对宿主植物（玉米、棉花）的生物量也有一定的影响.  相似文献   

Microscopic analysis of the effect of azoxystrobin treatments on Mycosphaerella graminicola infection using green fluorescent protein (GFP)‐expressing transformants     

Eric A Rohel  Nadine Cavelier  Derek W Hollomon 《Pest management science》2001,57(11):1017-1022

Green fluorescent protein (GFP)‐expressing transformants were used to investigate the effects of strobilurin fungicide azoxystrobin on Mycosphaerella graminicola infection. Azoxystrobin treatments (125 or 250 g AI ha^?1) were applied at various stages of the infection process under controlled conditions. GFP transformants showed conserved in vitro sensitivity to azoxystrobin and pathogenicity. Azoxystrobin controlled over 90% of M graminicola infections when applied before or during penetration of the pathogen (15% of the incubation phase). Azoxystrobin also impaired the growth of intercellular hyphae in M graminicola post‐penetration infection stages when applied at up to 50% of the incubation phase. Incubating infections observed in treated leaves were viable, but their growth was impaired and they did not induce necrosis under controlled conditions. Reduction by half of azoxystrobin dosage had little or no effect on azoxystrobin efficiency in controlling M graminicola. The contribution of post‐penetration fungistatic effect to azoxystrobin curative properties toward M graminicola in a field situation is discussed. © 2001 Society of Chemical Industry  相似文献   

烟色离褶伞基内菌丝生长规律及生产中的应用     

李晓  李玉 《中国食用菌》2009,28(4):18-19

烟色离褶伞基内菌丝自接种点向PDA培养基内延伸的生长距离最长为1.5 cm,但足以布满18 mm×180 mm PDA斜面试管基内各个角落.基内菌丝继代转接的原种菌丝较气生菌丝继代转接的原种生长快、菌丝茁壮,但在产量上没有显著差异.通过对基内菌丝生长规律的观察,发现了食用菌母种再生千倍转接技术,使其扩展应用到食用菌生产中,为进一步改进食用菌生产程序、缩短生产时间提供理论基础.  相似文献   

Gamna‐Gandy bodies: a case of mistaken identity in the spleen of a cat     

Julia K. Ryseff  Colleen Duncan  Gabriella Sfiligoi  Paul R. Avery 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2014,43(1):94-100

A 4‐year‐old, female spayed Domestic Shorthair cat was presented for a 2‐day history of lethargy, anorexia, and vomiting. Diagnostic assessments revealed a severe, regenerative anemia and the presence of a solitary, 3 × 4 cm splenic mass. Cytologic examination of fine‐needle aspirates of the splenic mass showed sheets of pleomorphic histiocytic cells with numerous intracellular and extracellular, negatively staining to deeply basophilic, branching structures. These structures were typically of thin uniform thickness with random angled branching that formed geometrical shapes and fragments, occasionally with sharpened ends and a crystalline appearance. Septal‐like divisions were irregularly spaced along some of the linear branches. The cytology was interpreted as a probable histiocytic inflammatory response to the unidentified foreign material with histiocytic sarcoma as a differential diagnosis. Histopathologic evaluation of the splenic mass resulted in a diagnosis of histiocytic sarcoma. The branching material stained positively for both iron and calcium, indicating that the material was compatible with Gamna‐Gandy bodies present secondary to tumor‐associated hemorrhage and the formation of calcium–iron complexes.  相似文献