拟南芥的抗病信号传导途径

 拟南芥是研究植物与病原物相互作用的模式植物。植物感病和抗病取决于病原物无毒基因产物和寄主抗病基因产物的识别,以及随后的相关防卫反应的激活。在拟南芥的抗病过程中,水杨酸、茉莉酸、乙烯等信号分子都不同程度地参与着抗病过程中的不同环节,起着非常重要的作用。由于这些信号分子在对不同病原菌的抗性中的作用存在差异,因而将抗病信号传导分为依赖于水杨酸和依赖于茉莉酸/乙烯的途径。本文将着重讨论这些信号分子在植物系统获得抗性以及诱导系统抗性中的作用。     

两种化合物联合诱导黄瓜的抗性效应及田间防治试验

用草酸钾和硫酸亚铁两种化合物联合诱导,可使黄瓜同时产生对霜霉病和白粉病的抗性效应.但不同组合方式的诱导所产生的抗性效应明显不同.其中两种化合物分别诱导的抗性效应最低;混合诱导的抗性效应较高;相继诱导的抗性效应最高.田间试验表明,先喷有效浓度60 mmol/L的草酸钾诱导物,间隔3 d再喷有效浓度20 mmol/L的硫酸亚铁诱导物,10 d后以同样顺序进行第2轮相继诱导,对霜霉病的防治效果达82.73%,显著高于70%代森锰锌WP 800倍液的防治效果;对白粉病的防治效果达78.64%,接近50%多菌灵WP 800倍液的防治效果.     

杂交竹抗梢枯病诱导因子筛选及其持续期研究

本文利用病原毒素同源异质的特点诱导杂交竹抗病潜力,筛选出抗梢枯病的最佳诱导因子并排除其对病原菌的直接作用,经琼脂玻片萌发法测定3种诱导因子(温度灭活毒素、蛋白酶降解毒素和细胞壁成分)对杂交竹梢枯病病原菌暗孢节菱孢菌孢子萌发的抑制作用,结果显示经过60℃灭活毒素浓度为40μg/mL处理的孢子萌发效果最为理想。通过最佳诱导因子对杂交竹不同品种诱导持续期进行测定,采用针刺法先接种诱导因子后挑战接种病原菌,1～40 d内观察抗感品种对诱导因子响应的差异,症状上杂交竹8#的感病程度重于3#和6#,40 d时叶片和枝干变黄干枯,病情指数结果表明,3个杂交竹品种接种诱导因子后感病程度降低,诱抗效果显示杂交竹6#的诱抗指数高于3#和8#。以上结果证明诱导因子使不同杂交竹品种均产生了一定的抗性且抗性越强的品种诱导抗性越好。     

赤星菌弱毒株孢子制剂PCF1对烟草赤星病的控制作用

本文研究了赤星菌(Alternaria alternata)弱毒株TBA16的灭活孢子制剂PCF1对烟草抗赤星病的诱导作用,及在田间控制赤星病的效果和对烟叶产量、品质等性状的影响。在温室内幼苗上,PCF1可明显诱导烟草对赤星病的系统抗性,抗性诱导效应为57％—89％。在山东5个主要产烟县进行的田间试验表明,PCF1有3种作用:①可以明显控制赤星病的发生程度,效果与用作对比的化学农药菌核净相当或略低,在烟草生长后期防治效果可达76％;②增强烟株生长和叶片扩展能力,使烟叶(烘烤后)产量提高7％—38％;③明显改善烟叶内在品质、增加上中等烟叶的比例,使产值提高17％。     

化学诱抗剂诱导金银花抗白粉病效果研究

用壳聚糖、草酸、水杨酸、葡聚糖、硅酸钠、硫酸亚铁、氟乐灵、磷酸氢二钾等8种药剂在不同株龄金银花上进行了对白粉病的诱导抗性试验。结果表明壳聚糖、草酸对金银花白粉病有良好的诱导抗性,在1年生、2年生和4年生金银花上对白粉病的平均防治效果分别达82.3%、59.9%和72.1%,54.9%、58.4%和74.1%。水杨酸、硅酸钠、硫酸亚铁有一定的诱导效果,但不稳定。葡聚糖和磷酸氢二钾无明显诱导抗病作用,氟乐灵则有促进发病的作用。     

新化合物吡唑并嘧啶衍生物(BDO-1)和哒嗪酮衍生物(PDZ-1)的诱导抗病性研究

吡唑并嘧啶衍生物 ((E)-N-(2-氟-4-三氟甲基苯乙烯基)-1-甲基-1H-吡唑并[3,4-d]嘧啶-4-胺,简称BDO-1) 和哒嗪酮衍生物 (4-羟基-1-(4-甲氧基苯基)-6-氧代-1,6-二氢吡嗪-3-甲酸甲酯,简称PDZ-1) 是由华东理工大学创制并合成的新化合物,本研究分别测定了其离体抑菌活性及其诱导抗病活性,并对田间应用技术进行了研究。结果表明:离体抑菌试验结果显示,BDO-1和PDZ-1对供试黄瓜的尖孢镰孢菌和多主棒孢菌并无杀菌活性;温室盆栽试验发现,2个化合物对7种蔬菜病害具有明显的诱导抗病活性,其中:BDO-1在10 mg/L下对黄瓜细菌性角斑病、黄瓜棒孢叶斑病、黄瓜枯萎病、黄瓜霜霉病、番茄早疫病、番茄灰叶斑和辣椒疫病的防治效果分别为58.81%、61.79%、69.88%、64.14%,54.42%、54.85%和63.59%;PDZ-1在10 mg/L下对黄瓜细菌性角斑病和黄瓜棒孢叶斑病的防治效果分别为62.33%和59.15%。田间防治效果验证结果表明,BDO-1和PDZ-1对黄瓜枯萎病的防治效果分别为62.95 %和48.45%。研究发现,BDO-1和PDZ-1在质量浓度为10 mg/L、诱导5次、每次间隔5d的条件下施用,对黄瓜枯萎病和棒孢叶斑病可发挥最佳防治效果。     

两种化合物联合诱导黄瓜对炭疽病的抗病性研究初报

通过用草酸钾和硫酸亚铁2种化合物的8种组合方式,诱导黄瓜对炭疽病的抗病性,证明用两种化合物分别独立诱导和联合诱导均有一定的诱导效应,但联合诱导比独立诱导所获得的诱导效应明显增强.其中,首次用草酸钾诱导,间隔3 d后再用硫酸亚铁进行第2次诱导,所获得的诱导效应最高.田间试验达较好的防治效果.     

水稻和稻瘟病菌互作中的信号传导及防御反应基因诱导表达的研究

 水稻和稻瘟病菌互作是研究植物与病原菌互作的模式体系。本文利用3个水稻抗稻瘟病近等基因品系(CO39、C101LAC和C101A51)和2个特异性菌株(M209和M210)构成不同亲和程度的互作关系,研究了稻瘟病菌对3个水稻信号传导途径关键酶合成基因、5个防御反应病程相关蛋白基因和1个防御反应转录因子调控基因诱导表达的作用。结果表明:稻瘟病菌诱导了各种互作关系中水稻OsLOX、OsAOS和OsPAL酶合成基因的表达,水稻启动了茉莉酸和水杨酸防御反应信号传导途径。在不亲和的互作反应中,稻瘟病菌能不同程度地诱导水稻OsPR1a、OsPR2、OsPR3-1、OsPR3-2和OsPR4基因的表达,从而有效激活了防御反应系统,使水稻植株表现为抗病;而在亲和的互作反应中,多数OsPR基因的表达水平低、时间短或没有表达,水稻植株表现为感病。OsMyb基因在各种互作关系中有不同的诱导表达。说明这些防御相关基因的诱导表达可能与水稻抗稻瘟病性相关。     

草酸青霉菌果胶酶诱导黄瓜抗黑星病研究

 本文就草酸青霉菌(Penicillium oxalicum)的固态发酵提取产物--果胶酶粗酶液诱导黄瓜对黑星病(Cladosporium cucumerinum)的抗性进行了研究。以果胶酶粗酶液喷雾处理4个感黑星病黄瓜品种的黄化苗,48 h后挑战接种黑星病菌孢子悬液,其中"中农5号"黄瓜品种表现的诱导抗病效果最好,诱抗效果达62.51%。不同浓度果胶酶诱导处理黄瓜,发现果胶酶浓度在20 U/mL时,可导致黄瓜发病略高于对照;在40~200 U/mL浓度范围内,诱导效果较为明显。通过研究果胶酶诱导抗病的时效性,表明诱导处理前接种病菌或诱导处理后0、6 h接种的各处理病情指数与对照间没有差别,而诱导处理12~72 h后接种病菌的,果胶酶的诱导抗病效果均很明显,诱抗效果达29.64%~60.02%。实验还表明,随着挑战接种压力的增大,果胶酶的诱导抗病效果降低。果胶酶不能抑制黑星病菌孢子萌发,相反可以促进孢子萌发和芽管生长。     

电压依赖性阴离子通道VDAC3参与拟南芥先天免疫

 线粒体外膜蛋白电压依赖性阴离子通道(VDAC)是动物细胞凋亡调控系统中的关键组分,但其在植物中的功能还不明确。拟南芥VDAC家族有4个成员,它们都能被病原菌诱导,VDAC1在由病原菌所引起的超敏性细胞死亡中发挥作用已有报道,但VDAC家族其他成员是否参与植物免疫反应还未见报道。本研究以拟南芥相关T-DNA插入突变体为材料,研究了VDAC3基因在植物抗病反应中的功能。病原相关分子模式flg22诱导的活性氧产生和胼胝质沉积在VDAC3突变体中都显著增强,表明VDAC3参与了病原相关分子模式触发的免疫反应。此外,效应因子激发的超敏性细胞死亡在vdac3突变体中也更明显,显示VDAC3也参与了效应子触发的免疫反应。以上结果说明,VDAC3在多个层面参与植物的抗病反应。     

桑树不同品种和冬伐形式对花叶病抗性的影响

研究桑树不同品种和冬伐形式与桑树对花叶病抗性的关系。结果表明,桑树不同品种间对花叶病的抗性有极显著的差异;母本的抗病性对杂交组合的抗病性有较大的作用;不同冬伐处理对桑树花叶病的抗性有极显著的影响;采用冬留长枝的冬伐形式,可使花叶病株发病率降低55.17%、病情指数降低73.99%、病害对桑叶产量的综合损失率降低86.45%。     

葡萄抗霜霉病机制研究进展

葡萄霜霉病是危害葡萄的重要病害之一,该病害发生时会给葡萄生产造成严重的经济损失。本文综合分析了国内外对葡萄抗霜霉病机制研究的结果,认为葡萄对霜霉病抗性受多种因素影响,主要表现为生理生化物质、叶片形态结构及抗病遗传基因三个方面。由于各种因素对霜霉病病原菌作用关系复杂,目前对于葡萄抗霜霉病的决定性因子还没有明确结论。     

外源化学物质对玉米抗弯孢菌叶斑病的诱导作用

测定了9种外源化学物质对玉米抗弯孢菌叶斑病的诱导作用,它们的诱导效果为9.8%～49.6%。其中,水杨酸的诱导效果最好为49.6%,核黄素、草酸、维生素K3和磷酸氢二钾也表现出较强的诱导能力,诱导效果分别为38.8%、41.5%、27.2%、37.8%;比较了玉米品种间和不同生育期的诱导效果,品种间的诱导效果有一定的差异,但差异不显著。不同玉米生育期的诱导效果以苗期最好,拔节期其次,最差的是成株期。对两种化学物质组合使用研究发现,有些具有协同作用,有些则有抑制作用。     

稻瘟病菌孢子萌发液中诱导侵染活性物质初探

作者报道了稻瘟病菌ZA_(51)、ZA_(49)和ZE_3的孢子萌发液对供试水稻品种秀水04和苏御糯秧苗没有致病性与其它明显毒性,但对它们的亲和性组合如ZA_(49) 秀水04和非亲和性组合如ZE_3 秀水04都有诱导侵染作用。且强致病性稻瘟菌ZA_(49)或ZA_(51)的孢子萌发液的诱导侵染活性高于弱致病性菌株ZE_3的孢子萌发液,孢子萌发液水层部分的诱导侵染活性高于脂层部分。这一事实说明,稻瘟病菌孢子萌发液中存在稻瘟病菌致病因子及有关物质,它将为补充解释水稻抗性品种的“抗性丧失”的原因,为进一步说明稻瘟病菌不同致病菌间的互作及稻瘟病菌致病机制等提供可能性。     

Chitosan enhances disease resistance in pearl millet against downy mildew caused by Sclerospora graminicola and defence-related enzyme activation

BACKGROUND: The present study investigated the effect of chitosan seed priming on the induction of disease resistance in pearl millet against downy mildew disease caused by Sclerospora graminicola (Sacc.) Schroet. RESULTS: Pearl millet seeds were primed with chitosan at different concentrations: 0.5, 1.5, 2.5 and 3 g kg^?1 seed. Of the different concentrations, 2.5 g kg^?1 was found to be optimum, with enhanced seed germination of 99% and seedling vigour of 1782, whereas the untreated control recorded values of 87% and 1465 respectively. At optimum concentration, chitosan did not inhibit sporulation and release of zoospores from sporangia. Furthermore, pearl millet seedlings raised after seed treatment with chitosan showed an increased level of the defence‐related enzymes chitosanase and peroxidase as compared with the untreated pearl millet seedlings on downy mildew pathogen inoculation. The effect of chitosan in reducing downy mildew incidence was evaluated in both greenhouse and field conditions, in which respectively 79.08 and 75.8% disease protection was obtained. CONCLUSION: Chitosan was effective in protecting pearl millet plants against downy mildew under both greenhouse and field conditions by inducing resistance against the pathogen. Thus, chitosan formulation can be recommended for seed treatment in the management of downy mildew disease. Copyright © 2008 Society of Chemical Industry     

马铃薯糖苷生物碱对枸杞镰孢菌果腐病的诱导抗性及相关防御酶活性的影响

为探索马铃薯糖苷生物碱诱导采后枸杞鲜果抗病性的效应,采用菌丝生长速率法测定了离体条件下马铃薯糖苷生物碱对枸杞鲜果采后主要致腐病原菌镰孢菌Fusarium sp.的抑菌活性;采用浸泡处理法测定了马铃薯糖苷生物碱对采后枸杞鲜果发病病情指数及对果实多酚氧化酶(PPO)、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)和超氧化物歧化酶(SOD)等相关防御酶活性的影响。结果表明:不同浓度马铃薯糖苷生物碱对镰孢菌均具有一定的抑制作用,EC50为0.11 g/mL;0.05～0.25 g/mL(提取原料)的马铃薯糖苷生物碱能显著降低采后枸杞鲜果病情指数,较对照降低了10.18%～38.51%;以0.15 g/mL(提取原料)的马铃薯糖苷生物碱处理后对枸杞鲜果抗果腐病的诱导效果最好,达45.81%;马铃薯糖苷生物碱处理枸杞鲜果后,果实中4种防御酶PPO、POD、PAL、SOD的活性均较对照有不同程度提高,分别于处理后第4、5、2、2天与对照差异达到最大,较对照提高了30.76%、21.34%、31.35%和21.91%。表明马铃薯糖苷生物碱能够诱导枸杞鲜果对采后病害的抗性效应,且采后抗病性可能与枸杞相关防御酶活性的增加有关。     

Plant responses to plant growth-promoting rhizobacteria

Non-pathogenic soilborne microorganisms can promote plant growth, as well as suppress diseases. Plant growth promotion is taken to result from improved nutrient acquisition or hormonal stimulation. Disease suppression can occur through microbial antagonism or induction of resistance in the plant. Several rhizobacterial strains have been shown to act as plant growth-promoting bacteria through both stimulation of growth and induced systemic resistance (ISR), but it is not clear in how far both mechanisms are connected. Induced resistance is manifested as a reduction of the number of diseased plants or in disease severity upon subsequent infection by a pathogen. Such reduced disease susceptibility can be local or systemic, result from developmental or environmental factors and depend on multiple mechanisms. The spectrum of diseases to which PGPR-elicited ISR confers enhanced resistance overlaps partly with that of pathogen-induced systemic acquired resistance (SAR). Both ISR and SAR represent a state of enhanced basal resistance of the plant that depends on the signalling compounds jasmonic acid and salicylic acid, respectively, and pathogens are differentially sensitive to the resistances activated by each of these signalling pathways. Root-colonizing Pseudomonas bacteria have been shown to alter plant gene expression in roots and leaves to different extents, indicative of recognition of one or more bacterial determinants by specific plant receptors. Conversely, plants can alter root exudation and secrete compounds that interfere with quorum sensing (QS) regulation in the bacteria. Such two-way signalling resembles the interaction of root-nodulating Rhizobia with legumes and between mycorrhizal fungi and roots of the majority of plant species. Although ISR-eliciting rhizobacteria can induce typical early defence-related responses in cell suspensions, in plants they do not necessarily activate defence-related gene expression. Instead, they appear to act through priming of effective resistance mechanisms, as reflected by earlier and stronger defence reactions once infection occurs.     

Epidemiology in mixed host populations

ABSTRACT Although plant disease epidemiology has focused on populations in which all host plants have the same genotype, mixtures of host genotypes are more typical of natural populations and offer promising options for deployment of resistance genes in agriculture. In this review, we discuss Leonard's classic model of the effects of host genotype diversity on disease and its predictions of disease level based on the proportion of susceptible host tissue. As a refinement to Leonard's model, the spatial structure of host and pathogen population can be taken into account by considering factors such as autoinfection, interaction between host size and pathogen dispersal gradients, lesion expansion, and host carrying capacity for disease. The genetic composition of the host population also can be taken into account by considering differences in race-specific resistance among host genotypes, compensation, plant competition, and competitive interactions among pathogen genotypes. The magnitude of host-diversity effects for particular host-pathogen systems can be predicted by considering how the inherent characteristics of a system causes it to differ from the assumptions of the classic model. Because of the limited number of studies comparing host-diversity effects in different systems, it is difficult at this point to make more than qualitative predictions. Environmental conditions and management decisions also influence host-diversity effects on disease through their effect on factors such as host density and epidemic length and intensity.     

Joint action of disease control measures: a case study of alternaria leaf blight of carrot

ABSTRACT The efficacy of chemical (i.e., foliar fungicide sprays), genetic (i.e., moderately resistant cultivars), and cultural (i.e., drip-irrigation system) control measures was quantified individually and in combination in the management of Alternaria dauci, the causal agent of Alternaria leaf blight of carrot. Whereas host resistance and drip irrigation affected both the time of disease onset and the rate of disease progression, chemical control affected only the latter. In all cases, a single control measure did not provide an acceptable level of disease suppression. Control efficacy values (based on the relative area under the disease progress curve) for chemical, genetic, and cultural control were 58 +/- 11, 39 +/- 20, and 60 +/- 22%, respectively (values are means +/- standard error). By contrast, implementing two control measures concurrently always improved disease suppression significantly compared with the individual measures. Control efficacy values were 91 +/- 8% for the integration of chemical and genetic measures and 82 +/- 23% for the integration of chemical and cultural measures. Moreover, yields in plots protected by two control measures simultaneously were higher by 10.1 to 28.6 t/ha than those in the respective plots protected by single measures. The joint effect of chemical control and host resistance was additive, whereas that of chemical control and drip irrigation was synergistic in most cases. A literature review was performed to determine if these findings represent a general relationship between chemical and genetic, and chemical and cultural measures. Based on 19 reviewed cases, it was concluded that additive effects are the rule and synergistic or antagonistic effects are the exception. Synergistic effects of two control measures were observed when one control measure improved the efficacy of the other directly or when one control measure induced host resistance or predisposed the pathogen to increased susceptibility. These results may enable a more effective selection of candidate control measures for integration in the future.