Elhalag K M, Messiha N A S, Emara H M, Abdallah S A
Bacterial Diseases Research Department, Plant Pathology Research Institute, Agricultural Research Center (ARC), Giza, Egypt.
Faculty of Science, Botany Department, Benha University, Benha, Qalubia, Egypt.
J Appl Microbiol. 2016 Jun;120(6):1629-45. doi: 10.1111/jam.13097. Epub 2016 Apr 9.
The aim of this study was the monitoring of different mechanisms involved in the antibacterial activity of the biocontrol agent, Stenotrophomonas maltophilia (PD4560), against Ralstonia solanacearum in vitro and in vivo. Optimization of conditions that favour these mechanisms was the second target of this study.
Proteolytic activity of Sten. maltophilia (PD 4560), was tested on skimmed milk medium. The biocontrol agent was able to produce an alkaline serine protease enzyme with a molecular weight of 40 KDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses. Spraying of salicylic acid (SA) led to an increase in the efficacy of Sten. maltophilia in controlling the Ralstonia potato wilt while spraying of ammonium sulphate (AmS) did not affect the biocontrol efficacy. The efficacy was correlated with the expression of protease enzyme genes; Prt genes (mainly PrtP and Prt4) and PR genes (mainly PR-1 and PRQ) as evaluated using real-time polymerase chain reaction analysis.
The biocontrol activity of Sten. maltophilia can be attributed to the direct mechanism alkaline serine proteolytic enzyme production and through induction of host systemic acquired resistance as indirect mechanism. Tuber bulking was the most suitable physiological growth stage to apply either SA or the biocontrol agent.
Both SA and peat-moss as an organic carrier enhanced the antibacterial efficiency of the biocontrol agent. Application of Sten. maltophilia is more suitable under alkaline soil conditions.
本研究旨在监测生防菌嗜麦芽窄食单胞菌（PD4560）对青枯雷尔氏菌的体外和体内抗菌活性所涉及的不同机制。优化有利于这些机制的条件是本研究的第二个目标。
在脱脂牛奶培养基上测试了嗜麦芽窄食单胞菌（PD 4560）的蛋白水解活性。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析确定，该生防菌能够产生一种分子量为40 kDa的碱性丝氨酸蛋白酶。喷洒水杨酸（SA）可提高嗜麦芽窄食单胞菌对马铃薯青枯病的防治效果，而喷洒硫酸铵（AmS）对生物防治效果没有影响。使用实时聚合酶链反应分析评估，该效果与蛋白酶基因（Prt基因，主要是PrtP和Prt4）和病程相关基因（PR基因，主要是PR-1和PRQ）的表达相关。
嗜麦芽窄食单胞菌的生物防治活性可归因于直接机制，即产生碱性丝氨酸蛋白酶，以及通过诱导宿主系统获得性抗性作为间接机制。块茎膨大期是施用SA或生防菌的最合适生理生长阶段。
SA和作为有机载体的泥炭藓均提高了生防菌的抗菌效率。嗜麦芽窄食单胞菌在碱性土壤条件下施用更合适。
