继代培养对水稻纹枯病菌菌丝生长和致病力的影响

用水稻纹枯病菌3株菌株为材料,采取马铃薯蔗糖培养基试管斜面培养的方式进行菌丝继代培养,以离体接种法分析这些病菌菌株的致病力。结果表明,经过60次的继代培养,该病菌的菌丝生长和致病力2个性状均没有出现明显的变异,但菌株间的菌丝生长和致病力存在明显的差异。初步发现,该病菌的菌丝生长情况与致病力相关。     

寄主植物对玫烟色拟青霉致病力的影响

通过比较茄子、黄瓜和节瓜三种寄主植物上烟粉虱的LC_(50)和LT_(50)值,评价了寄主植物对玫烟色拟青霉致病力的影响。烟粉虱的累计校正死亡率回归分析结果表明:在处理后的第8～14天,不同寄主植物上玫烟色拟青霉对烟粉虱的LC_(50)值差异显著;茄子、黄瓜和节瓜上烟粉虱的LC_(50)最小值出现的时间不同,分别在处理后的第14、10、12天。当玫烟色拟青霉的浓度为1．0×10~5和5．0×10~5分生孢子/mL时,黄瓜与茄子、节瓜上烟粉虱的LT_(50)值差异显著;当浓度为5．0×10~6～1．0×10~8分生孢子/mL时,三种寄主植物上烟粉虱的LT_(50)值差异不显著。     

农药对虫生真菌粉虱座壳孢孢子萌发和菌丝生长的影响

虫生真菌粉虱座壳孢Aschersonia aleyrodis是大有前途的粉虱和介壳虫杀虫剂。用6种大田常用农药在推荐浓度下,研究其在25℃下对座壳孢菌孢子萌发和菌丝生长的影响,发现甲氰菊酯和克螨特抑制其孢子萌发和菌丝生长,表明二者与本菌极不相容。吡虫啉、水胺硫磷和双甲脒能促进孢子萌发且后两者亦可加速菌丝生长,多菌灵对其孢子萌发起暂时促进作用然而抑制其菌丝生长。     

UeRbf1调控菰黑粉菌丝状生长和致病力的作用研究

 基于菰黑粉菌的全基因组序列,克隆得到了UeRbf1(GenBank登录号:MW375682),该基因的开放阅读框为1 281 bp,无内含子,编码426 个氨基酸,经预测具有3个C₂H₂锌指结构域,提示其具有转录调控功能。进一步在菰黑粉菌中敲除UeRbf1后进行体外生长及侵染试验,发现:在体外培养时,UeRbf1的缺失没有改变菌株的生长速率及单倍体形态,也未改变两个性亲和UeRbf1缺失突变体的融合及菌丝形成能力,但是融合菌丝的丝状生长能力显著减弱,而且在侵染时UeRbf1缺失突变体丧失了菌丝形成及丝状生长能力,人工接种野茭后也无法使其茎部膨大。以上结果表明,UeRbf1是调控菰黑粉菌丝状生长和侵染能力的一个重要因子。另外, UeRbf1缺失突变后,在体外融合及侵染时相关丝状生长和致病力的调控因子Biz1、Clp1、Hdp1和UeKpp6呈下调表达,其中Biz1的下调表达最为显著,在突变体中几乎不表达,说明UeRbf1对菰黑粉菌丝状生长和致病力的影响,可能是通过调控Biz1来实现的。     

江苏玉米纹枯菌的菌丝融合群及致病力

 玉米纹枯病是江苏省春、夏玉米上近年来发生普遍、危害日重的一种病害。该病是由丝核属(Rhizoctonia DC.ex Fr.)真菌侵染引起的,丝核菌可分为不同的菌丝融合群,不同融合群的致病力存在明显差异,在麦类纹枯病菌的研究中已得到证实。     

三种杀菌剂对牡丹黑斑病菌菌丝生长及分生孢子萌发的影响

为筛选防治牡丹黑斑病的化学药剂,采用菌丝生长速率法和涂布平板法分别测定了多菌灵、苯醚甲环唑和嘧菌酯对牡丹黑斑病菌菌丝生长的抑制活性及对分生孢子萌发和形成的影响。结果表明：苯醚甲环唑对菌丝生长的抑制作用最强,有效中浓度EC₅₀仅为0.30 μg/mL,其次为嘧菌酯6.34 μg/mL和多菌灵92.18 μg/mL;多菌灵可显著降低分生孢子的萌发速率,而苯醚甲环唑和嘧菌酯对孢子萌发的抑制作用较弱,可使分生孢子及芽管发生畸形,并改变分生孢子的萌发方式;3种药剂均可显著抑制芽管的伸长生长,推迟病菌分生孢子梗的形成时间,但对分生孢子的产生数量无显著影响。多菌灵可作为保护剂在病害发生前期使用,苯醚甲环唑和嘧菌酯可在病害发生期轮换使用。     

六种杀菌剂对烟草赤星病菌菌丝生长和分生孢子萌发的抑制作用

采用菌丝生长速率法和孢子萌发法测定了烟草赤星病菌Alternaria alternata对6种杀菌剂(氟硅唑、异菌脲、菌核净、嘧菌酯、醚菌酯及多菌灵)的敏感性。结果表明:6种杀菌剂对烟草赤星病菌菌丝生长和分生孢子萌发均表现出了不同程度的抑制活性。其中,对菌丝生长抑制活性最强的是氟硅唑,EC50平均值为(0.34±0.11)mg/L,其次为菌核净[(1.13±0.68)mg/L]和异菌脲[(2.08±0.24)mg/L];对分生孢子萌发抑制活性最强的是嘧菌酯协同100 mg/L水杨肟酸,EC50平均值为(0.28±0.09)mg/L,其次分别为单独处理的嘧菌酯[(5.79±2.76)mg/L]、醚菌酯[(11.93±3.93)mg/L]、菌核净[(19.95±15.94)mg/L]和异菌脲[(23.33±11.33)mg/L]。多菌灵对烟草赤星病菌菌丝生长和分生孢子萌发的抑制活性均最差,不宜用于烟草赤星病的防治,而异菌脲、氟硅唑、嘧菌酯和醚菌酯均有必要进一步针对烟草赤星病进行田间防效试验。     

五种杀虫剂对爪哇拟青霉生长的影响及其对斜纹夜蛾的联合毒力

研究了锐劲特、美满、除尽、卡死克和高效氯氰菊酯5种杀虫剂对爪哇拟青霉Px04菌株的菌丝生长、孢子产量与萌发率的影响,以及这5种杀虫剂与Px04菌株对斜纹夜蛾的联合毒力。在高于推荐田间用量10倍以上浓度时,锐劲特(500mg/L)、美满(2400mg/L)和除尽(1000mg/L)对Px04菌株的菌丝生长、孢子产量与萌发率没有影响,但卡死克(500、50mg/L)能抑制菌丝生长、孢子产生和萌发;高效氯氰菊酯(100、10mg/L)也表现出较高程度的抑制作用。与Px04菌株混合使用时,卡死克和高效氯氰菊酯表现出拮抗(或减效)作用,锐劲特、美满和除尽表现出相加作用。在亚致死量下,锐劲特(30mg/L)和美满(40mg/L)能使Px04菌株的防治效果显著提高并提前见效,除尽(20mg/L)和高效氯氰菊酯(10mg/L)影响不明显,但卡死克(70mg/L)对防治效果有不良影响。     

玫烟色拟青霉分离株的生物学特性及其对烟粉虱的致病力

对广州地区玫烟色拟青霉16个分离株的菌落生长速率、产孢量、分生孢子萌发率,及其对烟粉虱2龄若虫的致病性进行了比较研究。结果表明:不同分离株的菌落生长速率差异不显著,但产孢量、孢子萌发率和对烟粉虱2龄的致病力差异显著。经过综合比较,筛选出PF01 N4和PF01 N8两个优良分离株,它们具有产孢量大(2 8×109和2 95×109个孢子/ml)、孢子萌发率高(89 06%和87 7%)、致病力强(7d后对烟粉虱2龄若虫的致病力分别为99 22%和97 79%)等特点。     

内蒙古自治区向日葵小核盘菌的菌丝亲和组类型及其菌株的生物学特性、致病力和交配型

为明确内蒙古自治区阴山北麓地区向日葵小核盘菌Sclerotinia minor的遗传变异,对自内蒙古自治区乌兰察布市、包头市和呼和浩特市向日葵上分离纯化的110株向日葵小核盘菌菌株进行菌丝亲和组(mycelium compatibility group,MCG)划分,并对5个主要MCG组间和组内各菌株的生物学特性、致病力和交配型进行测定。结果表明,供试的110株菌株被划分为14个亲合组,其中MCG1为主要类型,包含32株菌株,占总菌株的29.1%;MCG2包含来自7个地点的25株菌株;5个MCG仅包含1株菌株;在这14个MCG中,MCG1～MCG5包含92株菌株,占总菌株数的83.6%。MCG1～MCG5组间各菌株在菌落直径和草酸分泌量上存在差异,但在菌核形成量、多聚半乳糖醛酸酶活性和致病力上无显著差异;而MCG1～MCG5组内各菌株在菌落直径、草酸分泌量、菌核形成量、多聚半乳糖醛酸酶活性和致病力上均有一定差异。在MCG1～MCG5各菌株的交配型中,除MCG2中菌株的负反转型与正反转型比例接近1∶1外,其它4个MCG中菌株的负反转型与正反转型比例均偏离1∶1,表明内蒙古自治区向日葵小核盘菌具有较高的遗传变异程度。     

Antifungal vapour-phase activity of allyl-isothiocyanate against Penicillium expansum on pears

The fungitoxicity of allyl-isothiocyanate (AITC) vapour against Penicillium expansum , the causal agent of blue mould on pears (cvs Conference and Kaiser), was evaluated. The best control of blue mould was obtained by exposing fruits for 24 h in a 5 mg L⁻¹ AITC-enriched atmosphere, the extent of control depending on the inoculum density. Lesion diameter was inversely related to AITC concentration. In treated fruits the percentage of infected wounds increased with conidial concentration, with fewer than 20% affected at 1 × 10³ conidia mL⁻¹ to almost 80% at 1 × 10⁶ conidia mL⁻¹. In comparison, >98% of wounds were infected in untreated fruits irrespective of conidial concentration. AITC treatments were effective up to 24 h after inoculation for Conference and 48 h for Kaiser. AITC treatments also controlled a thiabendazole-resistant strain of P. expansum , reducing the incidence of blue mould by 90% in both cultivars. The use of AITC produced from pure sinigrin or from Brassica juncea defatted meal may be an economically viable alternative to synthetic fungicides against P. expansum .     

Monitoring system for the biocontrol agent Pichia anomala strain K using quantitative competitive PCR-ELOSA

A quantitative-competitive PCR (QC-PCR) method with enzyme-linked oligosorbent assay (ELOSA) was developed to monitor Pichia anomala strain K, a biocontrol agent against postharvest diseases on apples. The procedure involved: (i) extraction of strain K DNA; (ii) coamplification of a constant amount of the extracted DNA (containing a strain K DNA marker of 262 base pairs (bp) specifically amplified with SCAR primers K1 and K2) with an internal standard (IS) titration; and (iii) differential hybridization with two specific biotinylated probes either for the target or for the IS sequence on microplate. The IS sequence differed from the target by only a short internal region of 35 bp providing the differential detection between both sequences. Both target and IS sequences proved to be competitive in PCR as well as in sandwich hybridization. Two copies of the target sequence were detected in the strain K genome by means of enzymatic restriction and Southern blot analysis. Varying amounts of strain K cell suspension were quantified in the phosphate buffer used for recovering cells from the apple surface. An accurate estimate of the strain K population was obtained from 10³ to 10⁶ yeast cells per apple. The threshold of the method was found to be at 1000 colony-forming units per apple, which was around 100 times more sensitive than the plating method for monitoring strain K.     

UV protectants for Candida oleophila (strain O), a biocontrol agent of postharvest fruit diseases

This study investigated the influence of UV‐B radiation (280–320 nm) on survival of Candida oleophila strain O, an antagonist yeast that prevents postharvest diseases caused by Botrytis cinerea and Penicillium expansum on apple and pear fruits. Lethal doses (LD₅₀ and LD₉₀) were, respectively, 0·89 and 1·45 Kj m^?2 for in vitro exposure and 3·06 and 5·5 Kj m^?2 for in vivo exposure. A screening test of UV‐B protectants for strain O was also evaluated under in vitro and in vivo conditions. The in vitro results showed that sodium ascorbate (0·1% and 0·01%), riboflavin (0·1%) and uric acid (0·1% and 0·01%) were the most effective and most suitable protectants. However, only riboflavin (0·1%) and uric acid (0·1%) were effective under in vivo conditions. The efficacy obtained with strain O against P. expansum, when subjected to UV‐B radiation, was 75·0% and 49·2% for pathogen concentrations of 10⁵ and 10⁶ spores mL^?1, respectively. Adding riboflavin to strain O gave a similar efficacy (64·2%). Applying strain O together with uric acid (0·1%) was less active (47·7%). Nonetheless, its efficacy when applied with the antioxidants sodium ascorbate (71·1%) or ascorbic acid (82·5%) was the greatest. Riboflavin and uric acid were the most cost‐effective protectants, and could be included in the final formulation of strain O when applied preharvest.     

Efficacy ofCandida oleophila strain 182 in preventingPenicillium expansum infection of nectarine fruits

The potential of the yeastCandida oleophila for postharvest control ofPenicillium expansum infection on nectarines was assessed on wound-inoculated fruits held at 20°C, or at 0°C in either air or controlled atmosphere storage. In addition, the efficacy of a prestorage dip with a yeast suspension, the fungicide dicloran, or a combination of the two, for controlling natural infections following storage was examined.C. oleophila reduced the level of infection caused byP. expansum in harvested nectarines. The yeast’s effectiveness was not reduced by controlled atmosphere storage or by application together with the commercial fungicide dicloran.     

中国薯蓣干腐病的病原鉴定

在薯蓣发病块茎组织中分离到真菌菌株HSQM2005,经柯赫氏法则验证该菌为薯蓣致病菌。对菌株HSQM2005核糖体DNA内转录间隔区(internal transcribed spacer,ITS)进行序列分析,并结合其形态特征、培养性状将该菌鉴定为Penicillium sclerotigenum Yamamoto。该菌生长温度范围10～31℃,最适温度22～28℃;在pH 2～12均能生长,最适pH为5～8。     

The Effect of Nitrogen on Disease Development and Gene Expression in Bacterial and Fungal Plant Pathogens

Successful colonisation of plants by pathogens requires efficient utilisation of nutrient resources available in host tissues. Several bacterial and fungal genes are specifically induced during pathogenesis and under nitrogen-limiting conditions in vitro. This suggests that a nitrogen-limiting environment may be one of the cues for disease symptom development during growth of the pathogens in planta. Here we review recent literature on the effect of nitrogen and nitrogen-regulated genes on disease development, caused by phytopathogenic bacteria and fungi. Furthermore, the potential influence of nitrogen-limitation or general nutrient limitation on several in planta-induced bacterial and fungal pathogenicity, virulence and avirulence genes will be discussed.