9株猪瘟分离毒株的致病特性

采用9株临床表现强、中、低致病特点的猪瘟野毒分离株第3代细胞毒作为种毒,按3mL/头剂量分别注射猪瘟抗原及抗体阴性猪,再用上一代传代猪发病后的血毒作为下一代接毒用种毒接种试验猪1头或2头,或上一代传代猪发病后,同圈放入1头或2头试验猪进行同居感染.如此进行,GDGZ1/95、BJCY1/96和JL1/94传至8代;FJFQ1/99传至7代;HeBHH1/95、HeNBY1/96、BJTX3/96、GXBH1/98和HeNXH2/98传至3代.结果显示:上述分离株传至3～5代过程中均表现出毒力增强的趋势,从3～5代传代到8(7)代的过程中毒力进一步增强并保持稳定,且均超过了标准石门强毒株的发病特点.所有试验猪均出现较典型的猪瘟临床症状,解剖后均表现出不同程度的病理变化,死后或解剖后的各种脏器经HCFA检查均为强阳性,这种现象进一步证实了猪是猪瘟病毒的敏感动物,各毒株之间毒力没有明显差异.对其中7株分离株传代血毒部分代次E2基因主要区域进行序列分析,结果仅GDGZ1/95株从F1～F8代中的F6代有2个核苷酸的差异,引起1个相应氨基酸的变异,其余毒株的不同代次没有碱基发生变异,初步说明猪瘟病毒基因型表现相对的稳定性.     

斯氏艾美耳球虫的致病性及病理学研究

用纯种斯氏艾美耳球虫孢子化卵囊人工感染25只断奶幼兔,进行致病性和病理学研究。试验兔分为1个不感染对照组和4个感染组,各感染组每只幼兔分别口服感染2.0×103、1.0×104、5.0×104、2.5×105个孢子化卵囊。与对照组相比,接种2.0×103个和1.0×104个孢子化卵囊的两个感染组的平均病变记分、肝重指数、血清转氨酶活性有显著差异(P<0.05);接种5.0×104个和2.5×105个孢子化卵囊的两个感染组上述指标有极显著差异(P<0.01)。表明斯氏艾美耳球虫对幼兔具有很强的致病性,能导致严重的肝球虫病。     

不同菌株绿僵菌和白僵菌对刚竹毒蛾幼虫致病力及林间防治试验

刚竹毒蛾(Pantana phyllostachysae Chao)是福建省毛竹林的一种主要害虫,本研究应用5种金龟子绿僵菌(Metarhizium anisopliae)菌株和1种白僵菌(Beauveria bassiana)菌株,对3龄初幼虫进行感染力测定,旨在筛选出感染该虫的高致病力菌株。结果表明:应用1.45×10 7孢子/mL孢悬液感染12 d后,3龄初幼虫的校正死亡率均达到63.16%以上;其中MaFzzL-01和Ma1291-2两个绿僵菌株对该幼虫的致病力分别为90.93%和84.21%,其LT50值分别为5.97 d和6.67 d,LC50值分别为1.727×10 4孢子/mL和2.029×10 4孢子/mL。结果说明:绿僵菌MaFzzL-01和Ma1291-2两个菌株对该幼虫的致病力强,且致死速度快。应用1.45×10 8孢子/mL孢悬液进行林间防治可以取得良好效果。     

莱氏野村菌CQNr01对斜纹夜蛾幼虫的侵染研究

以莱氏野村菌Nomuraea riley CQNr01菌株接种斜纹夜蛾Spodoptera litura 2龄和4龄幼虫,观察感病率,并利用荧光染色观察菌株在幼虫离体表皮上的孢子萌发和附着胞产生情况。结果显示,菌株CQNr01孢子悬液浓度为1×10^8、1×10^9孢子·mL^-1时斜纹夜蛾2龄幼虫的累计死亡率分别为86.58%和89.91%,而4龄则只有13.33%和16.67%。菌株CQNr01的孢子能够成功附着在斜纹夜蛾幼虫的离体表皮上,但孢子在2龄幼虫表皮的粘附能力优于4龄幼虫;接种24 h起两个龄期的离体表皮上均开始有孢子萌发现象并有附着胞和芽管产生,并随着接种时间的增长芽管不断伸长,但相同接种时间下孢子在2龄幼虫表皮上的萌发率和附着胞产生数量明显多于4龄幼虫表皮。研究证明菌株CQNr01对斜纹夜蛾高龄和低龄幼虫的致病力差异显著,其差异主要源于斜纹夜蛾幼虫体壁的屏障作用。     

Phaeosphaeria sp.HD-06菌株对马唐的致病性分析及初步鉴定

为了得到能够有效抑制马唐Digitaria sanguinalis生长的生防微生物,在农田采集马唐种子,进行萌发试验,观察种子的萌发状况,从发病的种子和马唐幼苗基部分离致病菌,通过形态学观察以及ITS序列分析对致病菌进行鉴定。结果从罹病的马唐幼苗基部分离得到一株致病菌HD-06,该菌株的发酵液用水稀释至60%浓度时,对马唐种子的萌发抑制率和幼苗发病率均达到100%,这说明菌株HD-06对马唐有较好的生物防治作用。根据其形态学特点及ITS序列分析结果,鉴定菌株HD-06为暗球腔菌属Phaeosphaeria的真菌。这些结果为深入研究其对马唐的防治作用奠定了基础。     

洋葱伯克氏菌群不同基因型菌株对几种重要植物病原真菌的抑制作用及其潜在致病性

从玉米和水稻根围分离到70株不同基因型的洋葱伯克氏菌,对这些菌株进行了拮抗植物病原菌的筛选,并对高拮抗菌株进行了潜在致病性和安全性分析。结果表明,有46株洋葱伯克氏菌对一种或多种病菌有较高的拮抗活性。在不同的洋葱伯克氏菌基因型内,以基因型Ⅴ内拮抗菌株占的比例最高,对所测5种病原真菌的平均拮抗菌株比率为80．0％,其中部分菌株表现出很强的拮抗活性。筛选出的4株高拮抗菌株对洋葱不具有致病性,同时也未检测到与人体致病相关的BCESM毒力基因。     

A faster inoculation assay for Armillaria using herbaceous plants

Armillaria (honey fungus) is a virulent necrotrophic pathogen that causes Armillaria root disease. Conventional Armillaria inoculation assays use young saplings as hosts and consequently are cumbersome, frequently conducted outdoors, and take many years from establishment to analysis of infection. We have developed and evaluated a faster inoculation assay for Armillaria that uses herbaceous plants as hosts, is carried out in controlled conditions, and reduces experimental durations to 3 months. Plant species of known susceptibility to Armillaria and comparisons between virulent A. mellea and opportunistic A. gallica were used to validate the assay. Mortality and diagnostic symptoms of Armillaria root disease such as epiphytic rhizomorphs and mycelial fans were used to assess levels of infection. We also attempted to reduce assay preparation time by substituting woody inocula with agar inocula, but typical symptoms of Armillaria root disease were only observed on plants infected with woody inocula. Through our assay, we identified five new potential herbaceous hosts of Armillaria: Kniphofia hirsuta, Hordeum vulgare, Lobelia cardinalis, Nicotiana tabacum and Helenium hoopesii – further expanding the extensive list of plants with susceptibility to Armillaria and suggesting infection of herbaceous species may be more widespread than currently acknowledged.     

Incomplete systemic movement of Xanthomonas campestris pv. musacearum and the occurrence of latent infections in xanthomonas wilt‐infected banana mats

Management of banana xanthomonas wilt (XW) (caused by Xanthomonas campestris pv. musacearum, Xcm) has been impeded by poor adoption of control options that are complex, cumbersome and costly. To improve XW management, this study investigated Xcm survival and latent infections in subsequent generations, survival of latently infected planting materials (suckers), incidence of latent infections in symptomless plants in mats having diseased plants, and XW status across farms and markets in districts previously devastated but currently endemic. On‐station experiments were protected from new infections. Latent bacteria at low levels were detected in up to 20% of the third generation suckers, with a significant (P < 0·05) reduction (43–20%) in subsequent generations. Only 3–6% of latently infected suckers succumbed to XW. Incidence of Xcm in symptomless suckers from farmers' fields (with up to 70% incidence) was low (3%) while it increased (8–25%) with disease severity in mats in controlled experiments. In the surveyed districts, incidence had significantly declined with yields observed to have recovered relative to earlier reports, although latent infections remained high. This study provides evidence that if new infections are prevented, fields with high XW incidence can be rejuvenated. It showed incomplete systemic movement of Xcm in mats coupled to a gradual decline of bacterial load in subsequent generations to levels that cannot initiate disease. These studies explain the current successes in farms practising single diseased plant removal instead of whole mat rouging, and gives hope to farmers lacking access to clean planting material.     

Secretion of Natural and Synthetic Toxic Compounds from Filamentous Fungi by Membrane Transporters of the ATP-binding Cassette and Major Facilitator Superfamily

This review provides an overview of members of the ATP-binding cassette (ABC) and major facilitator superfamily (MFS) of transporters identified in filamentous fungi. The most common function of these membrane proteins is to provide protection against natural toxic compounds present in the environment of fungi, such as antibiotics produced by other microorganisms. In plant pathogenic fungi, these transporters can also be an important determinant of virulence on host plants by providing protection against plant defence compounds or mediating the secretion of host-specific toxins. Furthermore, they play a critical role in determining base-line sensitivity to fungicides and other antimycotic agents. Overexpression of some of these transporters can lead to the development of resistance to chemically-unrelated compounds, a phenomenon described as multidrug resistance (MDR). This has been observed in a variety of organisms and can impose a serious threat to the effective control of pathogenic fungi.     

环境因子对球孢白僵菌侵染桔小实蝇致病力的影响

本文测定了温湿度、紫外线及常见杀虫剂等环境因子对球孢白僵菌B6菌株侵染桔小实蝇致病力的影响。结果表明,在19℃~31℃的温度范围内,B6菌株对桔小实蝇成虫、蛹与老熟幼虫均有致病力。在19℃~25℃条件下,桔小实蝇上述三种虫态的死亡率均随着温度的升高而增加,但在28℃和31℃温度条件下,桔小实蝇的死亡率则随着温度升高而降低。在1.8×108孢子/ml浓度条件下,成虫在25℃温度条件下的致死中时LT50为6.6d,在31℃的LT50为30.2d。在不同温度条件下,B6菌株对桔小实蝇成虫的致死中时差异较大。湿度越大,球孢白僵菌致病力越强,桔小实蝇的死亡速率越快。球孢白僵菌孢子萌发率随着紫外线照射时间增加而逐步降低。测定了7种常见的杀虫剂对球孢白僵菌菌落的生长影响,其中25%高效氯氟氰菊酯、2.0%阿维菌素、40%辛硫磷和10%除尽对菌落生长有促进作用。