Development of the teleomorph of non-self-anastomosing isolates of Rhizoctonia solani by a buried-slide method

A buried-slide method of inducing teleomorph development was compared with a soil method for isolates of Rhizoctonia solani in anastomosis group 2. The teleomorph ( Thanatephorus cucumeris ) developed frequently in the buried-slide method. For non-self-anastomosing isolates, which cannot grow through soil, the teleomorph was observed only in the buried-slide method. One of the five soils tested was particularly favourable. The buried-slide method allows easy examination of the teleomorph with minimum disturbance to the hymenium. It has demonstrated the identity of non-self-anastomosing isolates with T. cucumeris.     

Sites of Persistence of Lumpy Skin Disease Virus in the Genital Tract of Experimentally Infected Bulls

The objectives of this work were to determine the site of persistence of lumpy skin disease virus (LSDV) in bulls shedding the virus in semen for a period longer than 28 days, to determine if the virus is present in all fractions of semen and to study lesions that developed in the genital tract. Six serologically negative postpubertal bulls were experimentally infected with a virulent field isolate of LSDV. The polymerase chain reaction (PCR) was performed on sheath washes, vesicular fluid, supernatant and cell‐rich fractions of semen from day 10 to day 26 postinfection (p.i.). Bulls that were positive by PCR on the whole semen sample collected on day 28 p.i. were slaughtered and tissue samples from their genital tracts submitted for histopathological evaluation, immunoperoxidase staining, virus isolation and PCR. Two of the bulls developed severe lumpy skin disease (LSD) and were found to be shedding viral DNA in their semen on day 28 p.i. Viral DNA was identified in all semen fractions from all bulls, but mostly from the cell‐rich fraction and from the severely affected bulls. The PCR assay was positive on postmortem samples of testes and epididymides from the two severely affected bulls. Virus could be recovered from the testes of these two bulls and from the epididymis of one of them. Immunoperoxidase staining was positive for LSDV staining in sections of testes and epididymides exhibiting necrosis. This study suggests that the testis and epididymis are sites of persistence of LSDV in bulls shedding virus in semen for prolonged periods and revealed that viral DNA is present in all fractions of the ejaculate.     

大田遮阴对夏玉米光合特性和叶黄素循环的影响

以郑单958和振杰2号为试验材料,大田条件下设置花粒期遮阴(S1)、穗期遮阴(S2)、全生育期遮阴(S3) 3个处理,遮光度为60%,以自然光照为对照,研究遮阴对夏玉米光合特性和叶黄素循环的影响。结果表明,遮阴后夏玉米产量显著降低,且遮阴时期对产量的影响表现为S3>S1>S2,郑单958和振杰2号的S3分别减产96.87%和90.78%。遮阴后叶片的光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、叶绿体色素含量显著降低,胞间CO₂浓度(C_i)较同期对照先降低后升高,即叶片光合作用的降低受到气孔与非气孔因素双重影响,2个供试品种变化一致。遮阴期间光合电子传递量子效率(Ф_PSII)降低,原初光能转换效率(F_v/F_m)和非光化学猝灭(NPQ)显著升高,叶黄素循环库(A+Z+V)和脱环化状态(A+Z)/(A+Z+V)升高,即在长期遮阴条件下叶片捕获的光能分配发生了变化,光合电子传递的能量占吸收光能的比例降低,叶黄素循环的启动辅助过剩光能的热耗散。遮阴结束初期(A+Z)/(A+Z+V)和NPQ迅速升高,说明光恢复初期叶片对弱光适应后的自然光照比较敏感,叶黄素循环增强抑制强光对光合机构的破坏。     

3种紫金牛属植物光合光响应特性的研究

利用LI-6400便携式光合测定系统对人工遮阳栽培的东南紫金牛、朱砂根、红凉伞3种紫金牛属植物叶片进行光模拟试验,结果表明在低光照下,随着光合有效辐射强度(PARi)的增强,3种植物的净光合速率(Pn)增大,蒸腾速率(Tr)加大,叶温(Tf)均升高,气孔导度(GS)迅速增大,胞间CO2浓度(Cj)值下降,水分利用效率(WUE)增加.当PARi达到400lanol·m-2·s-1时,出现了明显的光抑制现象;当PARi达到800μmol·m-2·s-1时,Gs下降,气孔运动受到影响.3种植物的光合饱和点(LSP)在199.251 8～281.5106μmol·m-2·s-1,光补偿点(LCP)在11.934 0～51.678 9μmol·m-2·s-1,最大WUE为2.27～7.56μmolCO2·mmol-1H2O,说明3种植物耐阴喜湿的特性,可以适应室内的生态环境.对3种植物进行对比分析表明,东南紫金牛的LSP及LCP相对较高,Tr比较大,Tf变幅小,Gs大,说明东南紫金牛与朱砂根及其变种红凉伞相比.有较好的适应强光的能力,生长势强.     

Elimination of toxicity and enhanced detection of lumpy skin disease virus on cell culture from experimentally infected bovine semen samples

Lumpy skin disease virus (LSDV), a poxvirus of the genus Capripoxvirus, is shed in the semen of infected bulls. The screening of semen for infectious virus requires a sensitive diagnostic method. The isolation of the virus on cell cultures and/or the polymerase chain reaction (PCR) are sensitive diagnostic tests which may be used to screen semen for LSD viral DNA prior to artificial insemination. Although cell culture detects infectious virus and is a sensitive method, there are major difficulties in using this method due to the toxic effect of semen on the cells. The aim of this study was to find a method that decreases the toxic effect of semen and enhances the isolation of LSDV on cell culture. Semen samples from LSDV sero-negative bulls were collected and infected with a field isolate of LSDV, strain V248/93, with a titre of 6.5 log TCID50. The semen samples were treated with one of four different methods: centrifugation, serial dilution, filtration and chemical treatment with kaolin. The samples subjected to centrifugation, serial dilution and filtration were supplemented with gentamycin. Semen toxicity on cell cultures was eliminated when supernatants of semen samples centrifuged at 2000 rpm for 1, 3 and 5 min and serially diluted were used to inoculate confluent monolayer bovine dermis cells. The toxicity recorded when the pellet fractions of semen samples centrifuged for 5 min at 2000 rpm was comparable to results obtained from serially diluted samples supplemented with gentamycin. Filtration and kaolin treatment of semen samples did not remove the toxic effect.