Department of Biotechnology, Barkatullah University, Bhopal, 462 026 India.
Indian J Microbiol. 2007 Dec;47(4):289-97. doi: 10.1007/s12088-007-0054-2. Epub 2008 Jan 11.
Plants possess a range of active defense apparatuses that can be actively expressed in response to biotic stresses (pathogens and parasites) of various scales (ranging from microscopic viruses to phytophagous insect). The timing of this defense response is critical and reflects on the difference between coping and succumbing to such biotic challenge of necrotizing pathogens/parasites. If defense mechanisms are triggered by a stimulus prior to infection by a plant pathogen, disease can be reduced. Induced resistance is a state of enhanced defensive capacity developed by a plant when appropriately stimulated. Systemic acquired resistance (SAR) and induced systemic resistance (ISR) are two forms of induced resistance wherein plant defenses are preconditioned by prior infection or treatment that results in resistance against subsequent challenge by a pathogen or parasite. Selected strains of plant growth-promoting rhizobacteria (PGPR) suppress diseases by antagonism between the bacteria and soil-borne pathogens as well as by inducing a systemic resistance in plant against both root and foliar pathogens. Rhizobacteria mediated ISR resembles that of pathogen induced SAR in that both types of induced resistance render uninfected plant parts more resistant towards a broad spectrum of plant pathogens. Several rhizobacteria trigger the salicylic acid (SA)-dependent SAR pathway by producing SA at the root surface whereas other rhizobacteria trigger different signaling pathway independent of SA. The existence of SA-independent ISR pathway has been studied in Arabidopsis thaliana, which is dependent on jasmonic acid (JA) and ethylene signaling. Specific Pseudomonas strains induce systemic resistance in viz., carnation, cucumber, radish, tobacco, and Arabidopsis, as evidenced by an enhanced defensive capacity upon challenge inoculation. Combination of ISR and SAR can increase protection against pathogens that are resisted through both pathways besides extended protection to a broader spectrum of pathogens than ISR/SAR alone. Beside Pseudomonas strains, ISR is conducted by Bacillus spp. wherein published results show that several specific strains of species B. amyloliquifaciens, B. subtilis, B. pasteurii, B. cereus, B. pumilus, B. mycoides, and B.sphaericus elicit significant reduction in the incidence or severity of various diseases on a diversity of hosts.
植物拥有一系列主动防御机制，可以对各种规模的生物胁迫（从微观病毒到植食性昆虫）做出主动响应。防御反应的时机至关重要，反映了植物应对坏死性病原体/寄生虫等生物挑战的方式。如果在植物病原体感染之前，防御机制被刺激触发，则可以减少疾病。诱导抗性是植物在受到适当刺激时增强防御能力的状态。系统性获得抗性（SAR）和诱导系统抗性（ISR）是两种诱导抗性形式，其中植物防御机制通过先前的感染或处理预先调节，从而对随后的病原体或寄生虫挑战产生抗性。一些植物生长促进根际细菌（PGPR）菌株通过细菌与土壤传播病原体之间的拮抗作用以及在植物根部和叶片病原体方面诱导系统抗性来抑制疾病。根际细菌介导的 ISR 类似于病原体诱导的 SAR，因为这两种类型的诱导抗性使未感染的植物部分对广谱植物病原体更具抗性。一些根际细菌通过在根表面产生水杨酸（SA）来触发依赖 SA 的 SAR 途径，而其他根际细菌则通过独立于 SA 的不同信号途径触发。在拟南芥中已经研究了 SA 独立的 ISR 途径，该途径依赖于茉莉酸（JA）和乙烯信号。特定的 Pseudomonas 菌株在康乃馨、黄瓜、萝卜、烟草和拟南芥中诱导系统抗性，表现在挑战接种时增强防御能力。ISR 和 SAR 的组合可以增加对通过这两种途径抵抗的病原体的保护，并且比单独的 ISR/SAR 对更广泛的病原体提供更长的保护。除了 Pseudomonas 菌株外，ISR 还由 Bacillus spp. 进行，其中已发表的结果表明，几种特定的芽孢杆菌属物种 B. amyloliquifaciens、B. subtilis、B. pasteurii、B. cereus、B. pumilus、B. mycoides 和 B.sphaericus 菌株可以显著降低各种宿主上各种疾病的发病率或严重程度。
