Role of Salicylic Acid in Systemic Resistance Induced by Pseudomonas spp. Against Pythium aphanidermatum in Cucumber Roots

Pseudomonas corrugata strain 13 and P. aureofaciens strain 63-28, applied to roots, induced systemic resistance against Pythium aphanidermatum in cucumber roots. Salicylic acid (SA) from bacterial culture or plant tissues was quantified by high performance liquid chromatography. Both strains produced SA in King's B broth and also induced cucumber root to accumulate endogenous SA one day after bacterial inoculation. Using a split root system, more SA accumulated in roots treated with bacteria than in distant roots on the opposite side of the root system in the first two days, but this difference disappeared after 3–4 days. SA levels were significantly higher in plants treated with bacteria compared to the split control, from one to five days after bacterization. SA did not inhibit mycelial growth of Pythium aphanidermatum at 100–200µgml^–1 in vitro, but higher levels inhibited mycelial growth. Zoospore germination increased at concentrations of 10–500µgml^–1, but decreased at 1000µgml^–1 compared to lower concentrations. Exogenously applied SA failed to induce local or systemic resistance against a challenge infection by the pathogen in planta. The results of this study show that exogenous applied SA does not induce systemic resistance to cucumber root rot caused by P. aphanidermatum, but endogenous SA accumulation in cucumber roots may be involved in induced systemic resistance.     

Salicylic Acid Induced Insensitivity to Culture Filtrate of Fusarium oxysporum f.sp. zingiberi in the Calli of Zingiber officinale Roscoe

Salicylic acid (SA) was used to induce insensitivity in the callus cultures of Zingiber officinale against culture filtrate (CF) of Fusarium oxysporum f.sp. zingiberi. The treatment of callus cultures with SA (10⁴M) prior to selection with CF of the pathogen-increased callus survival. Exogenous application of SA resulted in increased activity of peroxidase and -1,3-glucanase enzymes in the callus cultures. No increase in the activity of phenylalanine ammonia lyase was obtained. Two new protein bands of 97 and 38kDa molecular weights were obtained by SDS-PAGE analysis of soluble proteins extracted from SA-treated calli. The PR-1 monoclonal antibody used for immunodetection of induced proteins cross-reacted with the 38kDa protein band. In vitro antifungal activity of protein extract of calli treated with SA tested against the spores of F. oxysporum f.sp. zingiberi showed significant reduction in spore germination and germ tube elongation. It is concluded that in ginger, SA may result in the induction of resistance to F. oxysporum f.sp. zingiberi by inducing increased activity of peroxidase, -1,3-glucanase and antifungal PR-proteins.     

二氢茉莉酸丙酯诱导烟草抗黑胫病作用研究

研究了二氢茉莉酸丙酯(PDJ)对烟草黑胫病的控制作用,结果表明:离体条件下,PDJ对烟草黑胫病Phytophthora parasitica Var. nicotianae的菌丝生长、孢子囊产生、游动孢子释放及萌发均无明显的抑制作用;PDJ处理后显著减轻了烟草幼苗黑胫病的病情,其最佳处理浓度为100 mg/L,最佳处理时间是接种前3 d,持效期在15 d以上;并且PDJ 100 mg/L处理烟苗下部第3片叶后,可使上部未处理叶片病情显著减轻。表明PDJ诱导了烟草幼苗对黑胫病的抗性。     

葡聚六糖诱导黄瓜抗霜霉病的研究

黄瓜经喷施人工合成的植物抗病性诱导剂葡聚六糖诱导后 ,黄瓜霜霉病的发病程度显著降低。葡聚六糖诱导黄瓜抗霜霉病的效果以质量浓度为10μg/L ,诱导间隔期为7d ,连续诱导 3次效果较好 ,其诱导持续期可达 7d。结果还表明葡聚六糖的诱导抗性表达不仅与它本身的作用机制有关 ,还与它的使用方法有关     

小麦条锈病菌非亲和性小种诱发小麦抗锈性研究

 在水源11、洛夫林10等7个品种上分别选择小麦条锈菌CY17、CY28等9个生理小种中非亲和小种进行诱发接种,亲和小种为挑战小种。观察发病后的病情指数并与单独接种诱发小种和单独接种挑战小种处理的病情指数进行比较。证明诱发抗病现象是比较普遍的,但表现程度因小麦品种、诱发小种和挑战小种而不同。诱发抗病性的表达时间可持续8 d,以诱发接种后1~2 d表达最强。诱发接种量与诱发抗病性表达呈指数函数关系,也间接证明这种诱发抗性是局部的。作者认为:诱发抗病性在品种、诱发和挑战小种不同组合之间的差异在小种动态中会起一定的作用。     

Altered Phenotypic Response to Peronospora parasitica in Brassica juncea Seedlings Following Prior Inoculation with an Avirulent or Virulent Isolate of Albugo candida

A study was made of the biological interactions between an isolate of Peronospora parasitica compatible with Brassica juncea and two isolates of Albugo candida either incompatible or compatible with the host species. Prior inoculation with the incompatible isolate of A. candida induced resistance to subsequently inoculated P. parasitica. The degree of resistance was proportional to the zoosporangia concentration of the incompatible isolate and induced resistance was more marked in the cotyledon receiving the inducing inoculum compared to the opposite cotyledon and subsequently emerging true leaves that had not been pre-inoculated. Induction of resistance was also observed if the incompatible isolate of A. candida and P. parasitica were co-inoculated simultaneously. However, the effect was greater the longer the interval between inoculations, up to a period of 4 days. When the incompatible isolate of A. candida was inoculated 4h after P. parasitica, there was no marked effect on resistance to the latter. In contrast, prior inoculation with the compatible isolate of A. candida increased susceptibility to P. parasitica inoculated subsequently. However, pre- or co-inoculation with P. parasitica suppressed the development of the compatible isolate of A. candida. A spectrum of responses was observed when one cotyledon was inoculated simultaneously with both the incompatible and compatible isolates of A. candida and followed subsequently with P. parasitica after different time intervals. In such combinations, a transition was observed in the host response to P. parasitica from induced resistance/reduced susceptibility, which increased up to 24h following a simultaneous inoculation with incompatible + compatible isolates of A. candida to an almost neutral reaction after 72h to induced susceptibility after 96h. This range of altered responses appeared to reflect the outcome of the differing kinetics and counter-effects of resistance and susceptibility induction.     

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。     

葡聚六糖诱导烟草抗花叶病毒病的研究

分别采用酶联免疫吸附技术(Fab’)2-ELISA和温室盆栽试验测定了葡聚六糖诱导烟草对花叶病毒病的抗性,结果表明,葡聚六糖诱导烟草抗花叶病毒病的最佳有效浓度为10 μg/mL,最佳诱导间隔期为7 d,持效期约为28 d,诱导抗病的防病效果与诱导次数呈正比。     

番茄青枯病抑病土壤作用机制研究

研究表明,宜春市番茄青枯病抑病土壤(白泥土)作用的主导因素是该类土壤碳酸钙含量高和土壤pH值偏碱,同时,与该类土壤粘腻以及对番茄青枯病的田间蔓延的阻抑作用也有密切的关系,而与土壤中其他微生物无关。研究还表明,白泥土和碳酸钙能抑制番茄青枯病菌及诱导番茄抗青枯病。     

赤星菌弱毒株TBA16对烟草抗赤星病诱导作用条件的研究

用病菌弱毒株TBA16的孢子按4种方法对烟苗进行诱导处理时,叶面喷洒和叶面悬滴诱导处理法可以明显地诱导烟草对赤星病的系统抗性。在叶面悬滴诱导中,诱导抗性在第6天开始表现,第12天达到最高并持续到第21天。重复诱导可使诱导抗性持续期延长,并使抗性程度提高,经3次重复诱导后抗性诱导效应可以由36%-83%提高到100%,4次重复诱导使抗性持续期由21天延长到42天以上。诱导抗性表现程度还与挑战按种后的保湿时间有关,并明显地受温度影响,在24℃左右抗性诱导效应最高,在30℃和16-20℃下效应减弱51.3%-56.4%。病菌毒素诱导比孢子诱导的效果高35%-77%,用叶面悬滴法诱导时,毒素的抗性诱导效应最高可达到100%。