ABSTRACT

Sugarcane is a leading biofuel crop besides being a source of crystal sugar and biomaterials worldwide. This study chiefly focuses on the role of diazotrophic bacteria isolated from sugarcane rhizosphere exhibiting different plant growth-promoting traits and biocontrol activities. Several bacterial isolates were obtained from the rhizosphere soil samples of four sugarcane cultivars. Out of these, 23 strains were selected and identified by 16S rRNA gene sequencing which confirmed different PGP-traits, biocontrol, and nitrogenase activities with nifH gene amplification. Two prominent strains, Kosakonia radicincitans-BA1 and Stenotrophomonas maltophilia-COA2 were selected for further analysis. Biolog plate assay was used to establish the utilization of various carbon and nitrogen sources and pH and osmotic stress tolerance for both strains. Colonization of selected strains in the sugarcane plant was observed by scanning electron microscopy and confocal laser scanning microscopy exhibited bacterial cells were frequently located in sugarcane tissues. Inoculation of the strains in GT11 and GXB9 cultivars led to a significant increase in growth parameters, nitrogen content, expression of nifH, and stress-related genes under greenhouse conditions. This is the first study to explore K. radicincitans and S. maltophilia as nitrogen-fixing plant growth-promoting rhizobacteria in sugarcane for disease management and reduce the practice of chemical fertilizers.

摘要

甘蔗除了是全球冰糖和生物材料的来源外，还是主要的生物燃料作物。这项研究主要侧重于从甘蔗根际分离出的重氮营养细菌的作用，这些细菌表现出不同的促进植物生长的特性和生物防治活性。从四个甘蔗品种的根际土壤样品中获得了几种细菌分离株。从这些菌株中，选择了23个菌株，并通过16S rRNA基因测序进行了鉴定，这些菌株通过nifH基因扩增证实了不同的PGP特性，生物防治和固氮酶活性。选择了两个显着菌株，即Radioscitans-Kosakonia radicincitans-BA1和嗜麦芽窄食单胞菌-嗜麦芽窄食单胞菌-COA2。使用Biolog平板测定法确定两种菌株的各种碳源和氮源的利用率以及pH和渗透压耐受性。通过扫描电子显微镜和共聚焦激光扫描显微镜观察到甘蔗植物中选定菌株的定殖，显示细菌细胞经常位于甘蔗组织中。在温室条件下，在GT11和GXB9品种中接种该菌株导致生长参数，氮含量，nifH的表达以及与胁迫相关的基因显着增加。这是第一个探索K. radicincitans和S. Maltophilia作为甘蔗中固氮促进植物生长的根瘤菌的疾病管理方法，并减少了化学肥料的使用。在温室条件下，在GT11和GXB9品种中接种该菌株导致生长参数，氮含量，nifH的表达以及与胁迫相关的基因显着增加。这是第一个探索K. radicincitans和S. Maltophilia作为甘蔗中固氮促进植物生长的根瘤菌的疾病管理方法，并减少了化学肥料的使用。在温室条件下，在GT11和GXB9品种中接种该菌株导致生长参数，氮含量，nifH的表达以及与胁迫相关的基因显着增加。这是第一个探索K. radicincitans和S. Maltophilia作为甘蔗中固氮促进植物生长的根瘤菌的疾病管理方法，并减少了化学肥料的使用。