鸡贫血因子病的血液病理学变化

本实验用鸡贫血病毒感染１日龄健康ＡＡ雏鸡，以未感染雏鸡为对照，在感染后７、１４、２８、３５、４２日龄检测其外周血液各种血细胞数量，血红蛋白含量，红细胞压积，红细胞平均体积，红细胞平均血红蛋白量、红细胞平均血红蛋白浓度；骨髓红系祖细胞、粒单系祖细胞（ＣＵＦ－ＧＭ）、基质成纤维祖细胞（ＣＦＵ－Ｆ）的增殖功能；血清因子和胞腺集落刺激因子（ＣＳＦ）对造血祖细胞增殖功能的影响；骨髓造血细胞分化功能；骨髓造血     

Starved bacteria retain their size but lose culturability - Lessons from a 5000 years old undisturbed A-horizon

The vast majority of soil bacteria are unable to form visible colonies on agar media. One hypothesis is that unculturable soil bacteria are dwarf cells that may either be small starved forms derived from larger species or represent inherently small species. We test the hypotheses that cells of extremely starved soil bacterial communities are smaller and less culturable than cells of bacterial communities from a richer soil, and that culturability is related to cell size by comparing an extremely starved community from a 5200-year-old A-horizon buried under a burial mound with a community from a modern agricultural A-horizon.We serially filtered cell suspensions through filters with successively smaller pore sizes (0.8 μm, 0.6 μm and 0.4 μm) and assessed total cell number and culturability, i.e. the ability to form colonies on two types of agar media, in each size fraction. Cell size distributions were assessed in unfiltered suspensions. Average cell size was only moderately reduced in the starved community, where culturability was low for all size classes. In contrast, culturability was much higher in the modern community, where culturability decreased dramatically with decreasing cell sizes.     

Effect of glyphosate on Macrophomina phaseolina in vitro and its effect on disease severity of soybean in the field

Laboratory and field studies were conducted to assess the effects of glyphosate on Macrophomina phaseolina culture growth in vitro and the disease severity of charcoal rot in soybean fields at Stoneville, MS and Jackson, TN. Glyphosate inhibited M. phaseolina growth in a linear dose dependent manner when technical grade glyphosate acid (GlyCry) was used; however, growth was inhibited in an exponential dose dependent manner when a commercial formulation of glyphosate-potassium salt (Gly-K salt) was used. The glyphosate GR₅₀ values (glyphosate concentration required to cause a 50% reduction) in culture radial growth ranged from 0.25 to 9.94 mM among the M. Phaseolina isolates, temperatures, and formulations. The three isolates differed in response to various concentrations across the three temperature regimes. Among the three isolates, TN 410 was the most sensitive for both GlyCry (GR₅₀ = 7.74 mM) and Gly-K salt (GR₅₀ = 0.25 mM) at 30 °C. This research indicates that glyphosate has the ability to inhibit growth of M. phaseolina in culture in vitro. The preliminary field studies demonstrated that application of glyphosate to glyphosate-resistant soybeans did not enhance or reduce the severity of charcoal rot in a no-till field in TN but had some suppressing effect in a tilled environment in MS when single applications were made at growth stage V3 and V6.     

小白菜表面粪大肠菌群的污染及其耐药性研究

为明确粪大肠菌群对蔬菜的污染及其耐药性,对厦门市集美区主要菜市场及超市的小白菜进行抽样调查。采用平板计数和MPN法对小白菜表面的粪大肠菌群进行计数,并通过对分离的细菌进行药敏试验,揭示粪大肠菌群对常用抗生素的耐药性。结果显示平板计数粪大肠菌群数量平均为631.3 CFU·g-1,合格率达90.9%;MPN计数平均为48.2 MPN·g-1,合格率达87.9%。清洗处理后粪大肠菌群数量从564.7 CFU·g-1降到92.5 CFU·g-1;流水浸泡10 min后,粪大肠菌群数量从564.7 CFU·g-1降到99.2 CFU·g-1。药敏试验结果表明,粪大肠菌对青霉素和四环素的耐药率达到100%,对红霉素的耐药率达到85.0%,但对庆大霉素、阿米卡星和环丙沙星没有耐药性。研究表明清洗处理显著降低粪大肠菌群的数量,粪大肠菌群对常用抗生素具有一定程度的耐药性,其耐药谱较广。     

绿僵菌对小云斑鳃金龟毒力及在土壤中的宿存

室内测定了从棕色金龟子HolotrichiatitanisReitter幼虫体上分离的金龟子绿僵菌MetarhiziumanisopliaeMetschnikoff(Sorokin)KMa0107对危害马铃薯的小云斑鳃金龟PolyphyllalaticollalaticollisLewis幼虫的毒力,并用时间-剂量-死亡率模型进行了分析。结果表明,该绿僵菌菌株对小云斑鳃金龟幼虫具有较强的毒力,剂量效应参数为0.74;在108～106孢子/mL下,接种后第10d小云斑金龟的累积死亡率达100%,在102孢子/mL下的累积死亡率为3.3%。在108孢子/mL下对小云斑金龟的LT50和LT90分别为4.6d和6.4d,在106孢子/mL下的LT50和LT90分别为5.6d和7.9d。绿僵菌菌株对小云斑鳃金龟第7d的LD50和LD90分别为5.5×106和2.3×108孢子/mL,第10dLD50和LD90分别为1.0×106和4.7×107孢子/mL。分生孢子在灭菌和未经灭菌的土壤中的宿存量随接种后时间的延续下降,在未经灭菌的土壤处理中分生孢子活力下降快于灭菌土处理,每g土壤中CFU的对数与处理后的天数x成线性相关关系,在未灭菌土和灭菌土中的半衰期分别为17和23d。     

白僵菌在土壤中宿存的数量、毒力及产孢量变化研究

研究白僵菌在土壤中宿存情况,结果表明,球孢白僵菌在土壤中宿存两个月内,成菌落数呈波动状态,下降较慢,1g、5g、10g区分别下降50%,60%和64%。自第3个月起,成菌落数每月下降85%至95%,最终土壤中的成菌落数维持在10^3-10^4CFU/土样水平。不同处理浓度表明,处理浓度过大不利于白僵菌的长期缩存;而白僵菌在缩存过程中,其毒力和产孢能力的稳定性有利于害虫的持续控制。     

莱氏野村菌云南菌株的宿存时间特征研究*

 室内测定了莱氏野村菌云南菌株NE050913和NE050909在土壤中及在不同温度下的宿存时间特征。结果表明，莱氏野村菌接种于土壤后随时间的延续，活孢率逐渐降低，在土壤中宿存3个月以上活孢率迅速降低，接种119d时孢子全部失活。每g土壤中两菌株CFU的对数与处理后的天数x成线性相关关系，其中菌株NE050913 的时间-CFU对数的关系式为lg y=7.7029-0.1932x,（R=0.89），半衰期为41.4d；菌株NE050909的时间-CFU对数的关系式为lg y=6.8531-0.1475x（R=0.854），半衰期为49.5d，即菌株NE050909分生孢子失活快于菌株NE050913。在4℃和22℃条件下存贮菌株NE050913的分生孢子，随着存贮时间的延续，孢子活性渐降低，22℃条件下孢子活性的下降明显快于在4℃条件下存贮的孢子，22℃存贮的孢子的萌发率在86d时已经失去萌发能力，而4℃存贮的孢子仍有16.3%的萌发率。由此表明，在22℃条件下不利于莱氏野村菌分生孢子的存贮，4℃条件下可作为临时存贮。     

利用红色荧光蛋白标记的轮枝镰孢研究病原菌对玉米根系的系统侵染和定殖

采用农杆菌介导法将红色荧光蛋白基因DsRed转入轮枝镰孢Fv-1菌株,利用荧光显微镜观察轮枝镰孢在玉米自交系B73根部定殖和生长的规律。土壤中的轮枝镰孢首先侵染玉米的须根等组织,并在其中大量增殖,随后沿主根向上侵染,以菌丝的形式扩展到地上组织。有些孢子附着在根表皮的纹理中,萌发形成菌丝而扩展;有的则向内侵染附着的细胞,然后再继续向周边侵染。由根内部向上侵染的菌丝多沿着细胞间隙上行,有些也会穿行在不同细胞之间。分析接种不同时间轮枝镰孢在玉米根和茎基部组织形成的单菌落数量(CFU)发现,轮枝镰孢在根部的CFU值随时间逐渐减小,而茎基部的CFU值则呈逐渐增大的趋势。这说明土壤中的轮枝镰孢能够通过根系侵染途径危害地上部组织。本研究的结果为进一步探明轮枝镰孢和玉米之间的互作关系,以及其他土传真菌与植物之间的互作提供了有益的参考。     

Evaluation of ‘Hamlin’ sweet orange + ‘Montenegrina’ mandarin somatic hybrid for tolerance to Xanthomonas axonopodis pv. citri and Xylella fastidiosa

Asiatic citrus canker (ACC), caused by Xanthomonas axonopodis Starr & Garces pv. citri (Hasse) Vauterin et al., and citrus variegated chlorosis (CVC), caused by Xylella fastidiosa Wells et al., are considered the main diseases affecting sweet orange scion varieties in Brazil. Among commercial varieties, mandarins and tangerines are recognized as tolerant to these pathogens. We report herein the production of ‘Hamlin’ sweet orange (Citrus sinensis L. Osbeck) + ‘Montenegrina’ mandarin (Citrus deliciosa Ten.) allotetraploid somatic hybrid plants by protoplast fusion with improved disease tolerance that could be used as a donor of resistance genes in interploid hybridisation. Somatic hybridisation was confirmed by leaf morphology, flow cytometry and RAPD analyses. The somatic hybrid was propagated by grafting and cultivated in a screenhouse for tolerance assays. For X. axonopodis pv. citri assays, buds were collected from both ‘Hamlin’ sweet orange and the somatic hybrid and grafted onto ‘Cleopatra’ mandarin (Citrus reshni hort. ex Tanaka). As a negative control, buds from ‘Mexerica Tardia’ mandarin (C. deliciosa) were collected and grafted onto ‘Cleopatra’ mandarin. Two-month old plants with at least one young vegetative flush were individually spray-inoculated with a 10⁶ CFU mL⁻¹X. axonopodis pv. citri suspension and incubated in a growth chamber, at 27 °C, under 16-h photoperiod. The somatic hybrid showed a statistically significant reduction in susceptibility to ACC 30 days after inoculation. Compared to ‘Hamlin’ sweet orange, disease severity was reduced by 70%, with similar tolerance to that of the mandarin negative control. For X. fastidiosa assays, buds were collected from the somatic hybrid and its parental plants and grafted onto ‘Rangpur’ lime (Citrus limonia Osbeck). The developed plants were needle-inoculated with a X. fastidiosa suspension (8.7 × 10¹⁰ CFU mL⁻¹) into the new growth flush stem. Bacterial population was quantified both at 4 (at the inoculation point) and 8 months (50 cm above the inoculation point) after inoculation. The first evaluation detected X. fastidiosa in 63% of ‘Hamlin’ sweet orange and ‘Hamlin’ + ‘Montenegrina’ mandarin samples. In the second evaluation, X. fastidiosa was detected in 47.4% of ‘Hamlin’ sweet orange and 10.5% of ‘Hamlin’ + ‘Montenegrina’ somatic hybrid samples, suggesting that bacterial movement was restricted in the somatic hybrid. X. fastidiosa was not detected in both evaluations in samples collected from leaves of ‘Montenegrina’ mandarin. These results indicate that the ‘Hamlin’ sweet orange + ‘Montenegrina’ mandarin somatic hybrid has potential for improved disease tolerance that should enhance its value regarding future use in citrus breeding programs.