Plant Growth-Promoting Bacteria as an Emerging Tool to Manage Bacterial Rice Pathogens

Abstract

As a major food crop, rice (Oryza sativa) is produced and consumed by nearly 90% of the population in Asia with less than 9% produced outside Asia. Hence, reports on large scale grain losses were alarming and resulted in a heightened awareness on the importance of rice plants' health and increased interest against phytopathogens in rice. To serve this interest, this review will provide a summary on bacterial rice pathogens, which can potentially be controlled by plant growth-promoting bacteria (PGPB). Additionally, this review highlights PGPB-mediated functional traits, including biocontrol of bacterial rice pathogens and enhancement of rice plant's growth. Currently, a plethora of recent studies address the use of PGPB to combat bacterial rice pathogens in an attempt to replace existing methods of chemical fertilizers and pesticides that often lead to environmental pollutions. As a tool to combat bacterial rice pathogens, PGPB presented itself as a promising alternative in improving rice plants' health and simultaneously controlling bacterial rice pathogens in vitro and in the field/greenhouse studies. PGPB, such as Bacillus, Pseudomonas, Enterobacter, Streptomyces, are now very well-known. Applications of PGPB as bioformulations are found to be effective in improving rice productivity and provide an eco-friendly alternative to agroecosystems.

Keywords: Oryza sativa; bacterial rice pathogens; biocontrol agents; bioformulations; plant growth-promoting bacteria.

Figure 1

Biological control interactions exerted by the plant growth-promoting bacteria (PGPB). This illustration depicts the interactions between PGPB, phytopathogens, and plants. PGPB promote plant growth either by direct and or indirect mechanisms. PGPB colonize plant’s rhizosphere and produce antimicrobial metabolites. In the plant’s rhizosphere, antibiosis and nutrient competition interaction suppresses the growth of phytopathogens. Elicitors of induced systemic resistance (ISR) production by PGPB and in the simultaneous presence of phytopathogens enhanced the plant ISR. Thus, this mediated defense response of plants towards phytopathogens and consequently enhanced plant growth and health.