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1.
旱地垄作膜面胡麻精量播种机设计和仿真   总被引：1，自引：0，他引：1  
针对西北旱区胡麻种植利用谷物条播机代播,人工种植效率低、质量差、出苗率低等问题,设计了一种旱地垄作膜面胡麻精量播种机。为提高播种机转向和运输时穴播轮提升、下降的精确性,采用平行四杆机构和摇杆装置,并确定其各项尺寸参数;为保证穴播轮播种深度,采用四连杆仿形机构,且计算出最大上、下仿形量均为89.87 mm,并验证了仿形机构的可行性;为提高该播种机播种精度,设计了一种新型取种装置;利用Solidworks软件中的插件motion对成穴器成穴过程进行运动仿真分析,研究了不同滑移率δ、机具前进速度v、成穴器入土深度h1对穴孔宽度（固定鸭嘴入出土位移）的影响,并得到最优组合参数：当δ=11%,v=0.5 m·s-1,h1=0.03 m时,该成穴器具有较小的滑移量,且不易产生挑膜、撕膜等现象。  相似文献   

2.
为探求沼液穴灌条件下土壤入渗特征及适宜入渗模型,通过室内试验研究了沼液配比（沼液∶水,体积比,1∶4、1∶6、1∶8及纯水）、穴孔直径（3、5、7 cm）和土壤容重（1.35、1.45 g·cm-3）对土壤入渗特征的影响,利用数理统计方法分析影响沼液穴灌入渗的因素和湿润体变化规律,同时应用Philip入渗模型对沼液穴灌累积入渗量进行了拟合分析。结果表明：沼液穴灌累积入渗量均随沼液配比和土壤容重的增大而降低,随着穴孔直径的增加而增大,当入渗历时180 min时,土壤容重1.35 g·cm-3和1.45 g·cm-3的CK处理累积入渗量分别是沼液配比为1∶4、1∶6、1∶8处理的3.62、3.12、2.77倍和3.47、2.64、2.16倍;湿润体形状随穴孔直径的增加逐渐由水平轴大于垂直轴的椭球体趋向于水平轴小于垂直轴的椭球体,土壤容重1.35 g·cm-3和1.45 g·cm-3对应各穴孔直径（3、5、7 cm）的垂向最大湿润距离（V）与水平最大湿润距离（H）的比值(V/H)分别为0.929、1.081、1.111和0.957、1.048、1.064;幂函数能够准确描述湿润锋最大湿润距离与时间的函数关系;建立的多元线性方程能够较好描述累积入渗量与土壤容重、穴孔直径和沼液配比的关系,偏回归系数检验均达到显著或极显著水平;Philip入渗模型能够准确描述沼液穴灌累积入渗量随时间的变化规律,决定系数（R2）在0.98以上;Philip入渗模型中的土壤吸渗率(S)随穴孔直径的增大而增加,随沼液配比和土壤容重的增加而降低;土壤稳定入渗率（A）为负值与沼液的粘性及所含有的有机悬浮颗粒有关。基于以上分析,在农业生产中建议实施方案为：土壤容重1.35 g·cm-3、穴孔直径5 cm、沼液配比1∶6和土壤容重1.45 g·cm-3、穴孔直径7 cm、沼液配比1∶8。  相似文献   

3.
针对Hydrus-2D软件在红壤区涌泉根灌土壤水分运移模拟的适用性问题,依据非饱和土壤水动力学理论,并结合红壤区涌泉根灌土壤水分运动特征建立了涌泉根灌土壤水分的入渗模型,利用Hydrus-2D软件对模型进行求解,并对湿润锋运移距离以及土壤含水率的模拟值和实测值进行了对比验证。结果表明：在灌水结束时,Hydrus-2D软件对竖直向下方向湿润锋的模拟值和实测值之间相对误差为5.21%,水平方向湿润锋的模拟值和实测值之间相对误差为-7.28%,且湿润锋模拟值和实测值的相关系数(R2)均大于0.980,RMSE均在1.300 cm以内,F检验P值也均大于0.05;在灌水结束时,距离灌水器不同距离处土壤含水率剖面分布的模拟值和实测值基本一致,均表现为随着土层深度的增加而先增大后减小,在距离灌水器不同位置处,Hydrus-2D软件对剖面土壤含水率的模拟值和实测值之间的相对误差均在±10%以内,且土壤含水率的模拟值和实测值相关系数（R2）均大于0.990,RMSE在0.030 cm3·cm-3以内,F检验P值也均大于0.05。说明模拟值和实测值具有较好的一致性,模拟结果可为红壤区涌泉根灌系统的合理设计及运行提供依据。  相似文献   

4.
运用温室葡萄水热平衡观测资料,分析了东北日光温室葡萄的能量平衡和能量分量日变化、生育期变化以及分配规律,同时也分析了潜热通量（λET）对环境因子的响应。结果表明：水热通量各分量在整个生育期日变化总体上呈现为单峰趋势,净辐射（Rn）的峰值最大为618.75 W·m-2,λET峰值最大为242.73 W·m-2,感热通量（H）峰值最大为327.93 W·m-2;在新梢生长期,白天λET较小,为34.55 W·m-2,随着生育期推进,λET逐渐增大,在果实着色成熟期达到最大值（78.49 W·m-2）之后减小;H在各生育期能量中均占了绝大部分;白天潜热通量占净辐射的比例（λET/Rn）在新梢生长期最小,为25.28%,在果实着色成熟期最大,为44.17%;感热通量占净辐射比例（H/Rn）整个生育期几乎都达50%以上,土壤热通量占净辐射比例（G/Rn）相对较小,变化范围为4.46~12.32 W·m-2;在整个生育期能量比率大小依次为H/Rn>λET/Rn>G/Rn。在不同生育阶段瞬时尺度上,Rn是影响潜热变化最主要的气象因子,R2高达0.88。在日尺度上,各气象因子对潜热通量的影响在逐渐变弱,相对湿度（RH）与λET相关系数仅为0.28。但无论从瞬时尺度还是日尺度,Rn都是影响潜热通量最主要的气象因子。各气象因子对潜热通量的影响大小依次为：Rn>VPD>Ta>RH。  相似文献   

5.
为构建适用于干旱区膜下滴灌条件的土壤水盐动态分布和棉花生长模型，基于2020—2021年的田间试验，经过对SWAP模型的土壤、土壤水力功能和作物生长等模块进行率定和验证，对灌溉水矿化度为1、2、3、4、5、6 g·L-1时的土壤水盐分布特征、作物生长过程和干物质累积分配进行数值模拟。结果表明：（1）土壤含水率与土壤含盐量的模拟精度以20～100 cm土层较好，0～20 cm土层模拟精度较差，其中土壤含水量的模拟效果优于土壤含盐量；随着灌溉水源矿化度的增加，土壤含水率和含盐量的模拟误差逐渐变小。（2）不同矿化度水源膜下滴灌棉花叶面积指数模拟效果较好（R2=90.72%，RMSE=0.35 cm2·cm-2，NRMSE=8.73%，IOA=0.98）。（3）不同矿化度水源膜下滴灌棉花茎干物质累积量模拟效果较好（R2=89.08%，RMSE=6.12 g，NRMSE=23.16%，IOA=0.96）。研究结果表明，SWAP模型可以较好地对不同矿化度水源膜下滴灌的土壤水盐动态分布和棉花生长过程进行模拟。  相似文献   

6.
为了准确估算滴灌条件下农田土壤湿润体,利用亮蓝染色剂示踪技术分别在陕西杨凌(粘壤土)、甘肃武威(沙壤土)和宁夏盐池(沙土)3个试验站点开展了农田滴灌试验。试验设不同灌水量和滴头流量,研究不同土壤质地条件下灌水量和滴头流量组合对农田土壤湿润体的影响,进而探求不同土壤质地的土壤湿润体估算模型。结果表明：在相同的土壤条件下灌水后农田土壤形成的湿润体随灌水量的增加而增大,在相同灌水量下增加滴头流量能够显著增加水平方向的湿润距离,相较于小滴头流量(1.38 L·h-1)而言,大滴头流量(3.0 L·h-1)形成宽浅形湿润体。在相同的灌水量和滴头流量下,农田土壤湿润体的垂向湿润距离随土壤饱和导水率(Ks)的增加而增加,随灌水前土壤有效持水能力(Δθ)的增加而减小,而水平方向的湿润距离随土壤饱和导水率(Ks)和有效持水能力(Δθ)的增加而减小。在试验的基础上,利用土壤饱和导水率(Ks)、灌水前土壤有效持水能力(Δθ)、灌水量(v)和滴头流量(q)建立了湿润体垂直和水平方向湿润距离的估算模型(幂函数连乘模型),并结合湿润体形状利用椭圆方程描述湿润体的轮廓形状(湿润体估算模型)。经试验数据验证,农田土壤湿润体估算模型能够很好估算湿润体轮廓,模拟值和试验实测值的决定系数(R2)在0.93~0.99之间,均方根误差(RMSE)在1.3~4.1 cm之间。  相似文献   

7.
配置模式对枣棉间作棉花光合及干物质积累特征的影响   总被引：3，自引：0，他引：3  
在新疆自然生态条件下,研究了不同密度下宽窄行（45 cm+15 cm）和等行距（30 cm）配置模式对枣棉间作棉花光合及干物质积累特征的影响。结果表明：枣棉间作条件下,不同配置模式棉花在盛花期以前LAI、SPAD及Pn差异未达显著水平,盛花期后差异显著。棉花Pn全生育期呈抛物线形态变化,蕾期以低密度等行距较高,随密度增大各处理Pn呈下降趋势,Pn在盛花期达到峰值,中密度宽窄行最高,为34　μmol·m-2·s-1,盛铃期、吐絮期以高密度宽窄行最高,各时期均以冠外区高于冠下区。高密度种植利于降低宽窄行t0,提高Vm,Vm最大值为269.8 kg·d-1,分别比中、低密度高11 %、52.8%,而中、低密度等行距Vm高于宽窄行,高密度反之。△t、t1、t2表现为高密度>中密度>低密度。因此,枣棉间作棉花适宜宽窄行、高密度种植。  相似文献   

8.
采用田间试验对不同灌水处理灌水后玉米地（天津滨海盐碱地）0~60 cm土层土壤K+/Na+、Ca2+/Na+及玉米干物质累积量进行研究,共设计4个处理,分别为LI10（常规滴灌,灌水10 mm）、LI20（常规滴灌,灌水20 mm）、FI10（膜下滴灌,灌水10 mm）和FI20（膜下滴灌,灌水20 mm）。结果表明：灌水后不同灌水方式下灌水量较大的处理0~60 cm各土层K+/Na+均大于灌水量较小的处理,且均表现出0~20 cm土层K+/Na+较大,40~60 cm土层K+/Na+较小;相同灌水量下膜下滴灌处理0~60 cm各土层Ca2+/Na+均较大,灌水后不同灌水处理0~60 cm各土层Ca2+/Na+差异较小,变化范围为0.10~0.22;FI20处理0~20 cm土层K+/Na+和Ca2+/Na+大于其他处理,分别达到0.78和0.22;随着灌水次数的增多,LI20和FI10处理0~20 cm土层K+/Na+和Ca2+/Na+均逐渐增大,LI10处理则均逐渐减小;灌水后各处理之间0~60 cm各土层K+/Na+和Ca2+/Na+差异均达显著水平;全生育期干物质累积量与其对应的0~20 cm土层（K+/Na+）/Ca2+二次拟合相关系数均达0.90以上,相同（K+/Na+）/Ca2+下,FI20处理干物质累积量始终最大,LI10处理始终最小;（K+/Na+）/Ca2+>1.72时,各处理干物质累积量均随（K+/Na+）/Ca2+的增大而增大。  相似文献   

9.
基于HYDRUS模型的暗管排水水盐运移模拟   总被引：4，自引：0，他引：4  
为了探索暗管排水条件下膜下滴灌农田的水盐运移规律,本文设计了埋深1 m,间距4 m的暗管排水模型试验,研究分析灌水淋洗过程中土壤水分和盐分的动态变化规律,并利用HYDRUS模型对暗管排水条件下的水盐运移规律进行数值模拟分析与验证。结果表明：经过3次灌水淋洗后,表层0~20 cm土层内盐分含量下降至2 g·kg-1,达到了非盐化土水平,20~60 cm土体内上层土壤脱盐效果高于下层,总盐分含量下降至8 g·kg-1以下;经过实测值与模拟值的验证,土壤盐分和水分的均方根误差RMSE最大分别为0.632和1.324,决定系数R2最小分别为0.992和0.906,说明模拟结果与实测结果吻合度较好,HYDRUS模型能够较好地模拟暗管排水过程中水盐运移规律。通过模型模拟6次灌水（共90 d）后暗管排水条件下不同土层深度的水盐动态变化特征,模拟结果表明,0~40 cm土层内盐分含量下降至2 g·kg-1,40~80 cm土层内盐分含量下降至4 g·kg-1左右,基本达到轻度盐化水平;距离暗管不同间距处的土壤剖面盐分含量呈波动变化,距离暗管越远,土壤剖面含盐量越大,盐分含量在0~8 g·kg-1范围内变化。  相似文献   

10.
为探索适宜豫西旱地烤烟高质量发展的烟薯产业综合体模式，以烤烟‘LY1306’和鲜食甘薯‘普薯32’为材料，采用田间试验研究“烟垄栽薯”2∶2间作模式下烤烟不同株距（65、60 cm和55 cm）配置对烟株生长及产量质量的影响。结果表明：在烟株移栽后90 d，与烤烟单作相比，烤烟株距为65 cm时，烟薯间作烟叶的最大叶长和最大叶宽分别提高5.09%~5.12%和5.17%~8.17%，叶绿素相对含量（SPAD值）提高4.90%~6.81%，净光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr）分别提高16.39%~21.50%、23.82%~27.72%和36.21%~45.31%，土传根茎病害发病率降低74.38%~78.42%；烤烟株距为60 cm时，烟薯间作烟叶的最大叶长和最大叶宽分别提高3.71%~4.79%和4.69%~7.61%，SPAD值提高3.80%~5.55%，Pn、Gs和Tr分别提高14.03%~19.77%、15.68%~22.49%和29.83%~35.78%，土传根茎病害发病率降低75.30%~78.11%；两种株距下烤后烟叶内在化学成分配比较烤烟单作更为合理。随着烤烟株距的减小，间作处理的土地当量比（LER）、总产值及烤烟感官评吸总分表现为先增加后减小；当烤烟株距为60 cm时，烟薯间作的总产值在2021年和2022年分别达82 855.40 CNY·hm-2和81 654.55 CNY·hm-2，较烤烟单作提高15.85%和22.43%。综上，豫西旱地采用“烟垄栽薯”2∶2间作模式的LER>1，具有间作优势，且烤烟株距调整为60 cm时（烤烟单作株距65 cm），烟株生长较好，产量质量指标最优，综合效益最大。  相似文献   

11.
Fifteen species of dermestid beetles were recorded at ‘Evolution Canyon’ (EC), Lower Nahal Oren, Mt. Carmel, Israel. They represent ~35% of known Israeli dermestid species. The following three species were recorded for the first time in Israel:Trogoderma svriaca Dalla Torre, 1911;Ctesias svriaca Ganglbauer, 1904; andAnthrenus (s.str.) jordaniens Pic, 1934. Adults of 13 species were collected on the more solar radiated, warmer and climatically more fluctuating south-facing slope (SFS); ten species were collected on the opposite, north-facing slope (NFS), which was cooler and climatically more stable. The abundance of adult dermestid beetles was 1.9 times higher on the SFS than on the NFS (86 and 47, respectively). Species richness and abundance distribution at EC (three collecting stations on each slope and one at the valley bottom) were significantly negatively correlated with the plant cover that consisted of trees and bushes (Spearmanr s ,P=0.007 and 0.039, respectively) and perennials (Spearmanr s ,P=0.039 and 0.077, respectively), indicating that non-woody plants were preferred by adult dermestid beetles.  相似文献   

12.
Recent data on the epidemiology of the common mycotoxigenic species of Fusarium, Alternaria, Aspergillus and Penicillium in infected or colonized plants, and in stored or processed plant products from the Mediterranean area are reviewed. Emphasis is placed on the toxigenicity of the causal fungal species and the natural occurrence of well known mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone, patulin, Alternaria-toxins and moniliformin), as well as some more recently described compounds (fusaproliferin, beauvericin) whose toxigenic potential is not yet well understood. Several Fusarium species reported from throughout the Mediterranean area are responsible of the formation of mycotoxins in infected plants and in plant products, including: Fusarium graminearum, F. culmorum, F. cerealis, F. avenaceum, F. sporotrichioides and F. poae, which produce deoxynivalenol, nivalenol, fusarenone, zearalenone, moniliformin, and T-2 toxin derivatives in wheat and other small grains affected by head blight or scab, and in maize affected by red ear rot. Moreover, strains of F. verticillioides, F. proliferatum, and F. subglutinans, that form fumonisins, beauvericin, fusaproliferin, and moniliformin, are commonly associated with maize affected by ear rot. Fumonisins, were also associated with Fusarium crown and root rot of asparagus and Fusarium endosepsis of figs, caused primarily by F. proliferatum. Toxigenic A. alternata strains and associated tenuazonic acid and alternariols were commonly found in black mould of tomato, black rot of olive and citrus, black point of small cereals, and black mould of several vegetables. Toxigenic strains of A. carbonarius and ochratoxin A were often found associated with black rot of grapes, whereas toxigenic strains of A. flavus and/or P. verrucosum, forming aflatoxins and ochratoxin A, respectively, were found in moulded plant products from small cereals, peanuts, figs, pea, oilseed rape, sunflower seeds, sesame seeds, pistachios, and almonds. Finally, toxigenic strains of P. expansum and patulin were frequently found in apple, pear and other fresh fruits affected by blue mould rot, as well as in derived juices and jams.  相似文献   

13.
The genera ofMicrogaster Latreille 1804 andHygroplitis Thomson 1895 from China are presented systematically in this paper. Thirty-two species ofMicrogaster and three species ofHygroplitis are known in China. Diagnosis, character variation, distribution and host of each species among the two genera are presented, including its host and distribution. Keys to the species ofMicrogaster andHygroplitis are given. http://www.phytoparasitica.org posting Dec. 19, 2006.  相似文献   

14.
Plant Viruses Transmitted by Whiteflies   总被引：18，自引：0，他引：18  
One-hundred and fourteen virus species are transmitted by whiteflies (family Aleyrodidae). Bemisia tabaci transmits 111 of these species while Trialeurodes vaporariorum and T. abutilonia transmit three species each. B. tabaci and T. vaporariorum are present in the European–Mediterranean region, though the former is restricted in its distribution. Of the whitefly-transmitted virus species, 90% belong to the Begomovirus genus, 6% to the Crinivirus genus and the remaining 4% are in the Closterovirus, Ipomovirus or Carlavirus genera. Other named, whitefly-transmitted viruses that have not yet been ranked as species are also documented. The names, abbreviations and synonyms of the whitefly-transmitted viruses are presented in tabulated form together with details of their whitefly vectors, natural hosts and distribution. Entries are also annotated with references. Whitefly-transmitted viruses affecting plants in the European–Mediterranean region have been highlighted in the text.  相似文献   

15.
Broad bean mottle virus (BBMV) was transmitted from infected to healthy faba-bean plants by the curculionid weevilsApion radiolus Kirby,Hypera variabilis Herbst,Pachytychius strumarius Gyll,Smicronyx cyaneus Gyll, andSitona lineatus L. The latter appeared to be an efficient vector: acquisition and inoculation occurred at the first bite, the rate of transmission was c. 41%, and virus retention lasted for at least seven days.S. lineatus transmitted the virus from faba bean to lentil and pea, but not to the three genotypes of chickpea tested. This is the first report on the generaHypera, Pachytychius, andSmicronyx as virus vectors, and onA. radiolus, H. variabilis, P. strumarius, andS. cyaneus as vectors of BBMV.Out of 351 samples of food legumes with symptoms suggestive of virus infection, 16, 11, 19, and 17% of the samples of chickpea, lentil, pea, and common bean, respectively, were found infected when tested for BBMV in DAS-ELISA. This is the first report on the natural occurrence of BBMV in chickpea, lentil, pea, and common bean. The virus should be regarded as a food-legume virus rather than a faba-bean virus solely, and is considered an actual threat to food legume improvement programmes.  相似文献   

16.
A collection of 38 PVY isolates from seed potato batches, originating from several Western European countries, was characterized by using current biological, serological and molecular tools differentiating PVY strains and groups. The correlation between the three kinds of tests was good but not absolute. No single serological or PCR method was able to discriminate among the five isolate groups found. Twenty-nine isolates belonged to the PVYN strain and six to the PVYO strain. No PVYC was found. Two other isolates reacted serologically like PVYO, but were unable to elicit a hypersensitive response from the Nytbr gene and probably represent the PVYZ group. At the molecular level, these two isolates showed a combination of both PVYO and PVYN and could be recombinants of these strains. Another isolate reacted serologically like PVYO, but induced vein necrosis in tobacco, like PVYN-Wilga. Some PVYN isolates caused tuber ring necrosis in glasshouse conditions. These might belong to the PVYNTN group. The PVYNTN, PVYN-Wilga and PVYZ groups probably represent pathotypes within strains PVYN and PVYO, respectively. The present study also confirms previous reports showing a high genetic variation at the 5 end within the PVYN strain.  相似文献   

17.
The phenology of the autumn leafroller,Syndemis musculana, a local pest of apple, was studied in order to forecast larval emergence. From 1983–1986, peak flight as determined with sexpheromone traps was always between 13–18 May. The duration of embryonic development was determined at various constant temperatures and used to estimate the periods of egg hatch in these four years. Each year, most eggs should have hatched in the second decade of June.Differences in attack rates between apple cultivars seem to be explained largely by the variation in picking time. Larvae are only half grown at the beginning of harvest (cv. James Grieve), and have gone into hibernation when the latest variety (cv. Golden Delicious) is picked. Moreover, the varieties Cox's Orange Pippin and Belle de Boskoop, picked about half time, are liable to receive additional damage by caterpillars brought with the picked fruits into storage.Various hymenopterous parasites were reared from caterpillars. As the only leafroller in the orchard which hibernates as mature larva,S. musculana may promote winter survival of some parasitoids, like the eulophidColpyclypeus florus.Samenvatting De fenologie van de herfstbladroller (Syndemis musculana Hübner), een incidentele plaag op appel, werd nader bepaald met het doel het uitkomen van de eieren te kunnen voorspellen. In 1983–1986 viel de piekvlucht, bepaald met behulp van feromoonvallen, steeds tussen 13 en 18 mei.De ontwikkelingsduur van de eieren bij verschillende constante temperaturen werd gebruikt om de periode van uitkomen te schatten. De meeste eieren zullen ieder jaar in de eerste helft van juni uitkomen.Geconstateerde verschillen in schade tussen appelrassen blijken goeddeels terug te voeren op verschillen in pluktijdstip. De rupsen van de herfstbladroller zijn pas half-was als de eerste appels eind augustus geplukt worden, terwijl tegen het einde van de oogst begin oktober de meeste al in winterslaap zijn. Met name tussentijdse rassen, als Cox's Orange Pippin and Schone van Boskoop, lopen extra schade op doordat grotere rupsen met de geplukte vruchten in de kist terecht komen.Uit de rupsen werden negen, al van andere boomgaardbladrollers bekende, sluipwespen gekweekt, Omdat deze bladrollersoort, als enige in de boomgaard, als volgroeide rups overwintert, lijkt zij bij uitstek geschikt als winterwaard.This study was carried out at the Experimental Orchard De Schuilenburg, Schuilenburg 3, 4041 BK Kesteren, the Netherlands, to which address correspondence should be addressed.  相似文献   

18.
In the summer of 2004 an epidemic of sclerotinia blight of peanut, a disease caused by Sclerotinia minor, occurred in Texas in fields where the disease was never previously detected. The disease was observed on many plants within one of the fields (>3000 disease foci), although most foci were <1 m. It is hypothesized that these observations were inconsistent with the recent introduction of a monocyclic pathogen, even if disease developed under conducive environmental conditions. The pattern of disease is most suggestive of the presence of foliar (ascospore) infections, although air temperature was above the known limits for apothecia development if the pathogen had arrived in the field in 2004 peanut seed. To further examine this epidemic, 232 isolates were collected, across a variety of spatial scales spanning this field and other Texas peanut fields, and evaluated for aggressiveness, fungicide sensitivity and genotypic diversity. There was wide variation among isolates for the phenotypic characteristics measured, but there was no evidence that a genotypically unique, highly aggressive, and fungicide resistant isolate had been introduced or evolved. The predominant genotype, TX1, which contained 154 isolates, was found in every county and field population.  相似文献   

19.
In 1975 many tumours were observed in plants ofBegonia Schwabenland grown in Aalsmeer. Submersion of the roots ofNicotiana megalosiphon seedlings in a homogenate of tumorous tissue, induced tumours after two weeks. Short periods of submergence yielded results similar to those obtained after longer periods. Tumour homogenates lost their infectivity after ten min at 50°C. Aphids transmitted the infectious agent.Treatment with propylene oxide did not inhibit infectivity completely. Filtration through a 450 nm filter removed the infectious agent.Tobacco tumor virus or a viroid could not be isolated. Cultures ofCorynebacterium fascians, isolated from tumours ofN. megalosiphon were highly infectious and induced tumours in healthyN. megalosiphon andBegonia. Tumorous tissue homogenates ofPelargonium zonale, Dahlia sp.,Gladiolus sp., andLilium sp. also caused tumours inN. megalosiphon, from whichC. fascians was isolated. It was not possible to produce tumours inN. megalosiphon with homogenates from roses with symptoms of bud proliferation.Samenvatting In 1975 werden vele tumoren waargenomen inBegonia Schwabenland op Aalsmeerse bedrijven (Fig. 1). De infectiositeit van tumorweefsel kon goed en snel worden vastgesteld door de wortels van zaailingen vanNicotiana megalosiphon in een homogenaat van tumorweefsel te dompelen. Tumoren ontstonden na twee weken, de eindbeoordeling geschiedde na een maand (Fig. 2). Ook verschillende andereNicotiana spp.,Melilotus officinalis (Fig. 3) enPisum odoratum (Fig. 4) werden aangetast.Bij de infectiositeitstoets gaven zeer korte dompeltijden even goede resultaten als langere (Tabel 1). Infectieus sap verloor zijn infectievermogen na 10 min verhitting bij 50°C. Bladluizen brachten de smetstof over. Propyleenoxide verminderde de infectiositeit wel, doch onderdrukte deze niet totaal. Bij filtratie door een 450 nm filter bleef het infectieuse agens op het filter achter. Het tumor-inducerende agens was ook aanwezig in die delen van planten met tumoren welke gezond leken en het ging voor een gering deel over met zaad (Tabel 2).Uit tumoren konden wij geen tabakstumorvirus of een viroïde isoleren. Culturen vanCorynebacterium fascians, geïsoleerd uit tumoren vanN. megalosiphon bleken zeer infectieus en veroorzaakten tumoren inN. megalosiphon enBegonia. Homogenaten van tumorweefsel vanPelargonium zonale, dahlia (Fig. 5), gladiool (Fig. 6) enLilium Mid Century Hybrid Enchantment (Fig. 7) veroorzaakten ook tumoren opN. megalosiphon, waaruitC. fascians werd geïsoleerd. Met sap van kroeskopzieke rozen konden wijN. megalosiphon niet besmetten.  相似文献   

20.
Four species so far classified in Pseudocercosporella or Ramulispora (hyphomycetes) are associated with eyespot disease symptoms of cereals. Two of these have been linked to teleomorphs that were described in Tapesia. Sequence data derived from the Internal Transcribed Spacer region (ITS1, 5.8S and ITS2) of the rDNA operon showed, however, that the eyespot fungi associated with Tapesia are not congeneric with Ramulispora sorghi, the type of Ramulispora. The genus name Tapesia is now rejected in favour of the conserved name Mollisia, which appears to comprise heterogeneous fungi. Tapesia yallundae is not closely related to the type of Mollisia, M. cinerea, but clusters separately, being more closely allied to species with Cadophora anamorphs. A new holomorph genus, Oculimacula, is therefore proposed for teleomorphs of the eyespot fungi, while the anamorphs are accommodated in Helgardia gen. nov.  相似文献   

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