The Potential of Streptomyces as Biocontrol Agents against the Rice Blast Fungus, Magnaporthe oryzae (Pyricularia oryzae)

Abstract

Rice is a staple food source for more than three billion people worldwide. However, rice is vulnerable to diseases, the most destructive among them being rice blast, which is caused by the fungus Magnaporthe oryzae (anamorph Pyricularia oryzae). This fungus attacks rice plants at all stages of development, causing annual losses of approximately 10–30% in various rice producing regions. Synthetic fungicides are often able to effectively control plant diseases, but some fungicides result in serious environmental and health problems. Therefore, there is growing interest in discovering and developing new, improved fungicides based on natural products as well as introducing alternative measures such as biocontrol agents to manage plant diseases. Streptomyces bacteria appear to be promising biocontrol agents against a wide range of phytopathogenic fungi, which is not surprising given their ability to produce various bioactive compounds. This review provides insight into the biocontrol potential of Streptomyces against the rice blast fungus, M. oryzae. The ability of various Streptomyces spp. to act as biocontrol agents of rice blast disease has been studied by researchers under both laboratory and greenhouse/growth chamber conditions. Laboratory studies have shown that Streptomyces exhibit inhibitory activity against M. oryzae. In greenhouse studies, infected rice seedlings treated with Streptomyces resulted in up to 88.3% disease reduction of rice blast. Studies clearly show that Streptomyces spp. have the potential to be used as highly effective biocontrol agents against rice blast disease; however, the efficacy of any biocontrol agent may be affected by several factors including environmental conditions and methods of application. In order to fully exploit their potential, further studies on the isolation, formulation and application methods of Streptomyces along with field experiments are required to establish them as effective biocontrol agents.

Characterization of Sarocladium oryzae and its reduction potential of rice leaf blast

“…These morphological changes compromise the M. oryzae infection in plants and increase the activity of some enzymes, such as peroxidase. Law et al (2017) evaluated different species of Streptomyces in a greenhouse and also obtained success, reducing in up to 88.3 % the severity of the disease, a fact linked to the production of bioactive compounds by these strains. Some rhizobacteria, such as the Pseudomonas fluorescens genus, have been described by De Vleesschauwer et al (2008), promoting the induction of systemic resistance due to the production of siderophores of the pseudobactin type.…”

Screening, isolation and evaluation of a nematicidal compound from actinomycetes against the pine wood nematode, Bursaphelenchus xylophilus

“…5,11,12 Actinomycetes are Gram-positive bacteria that produce a variety of secondary metabolites useful as biological control agents. 13,14 More than 60% of the natural antimicrobial drug compounds currently used are produced by different species of actinomycetes. [15][16][17] Some metabolic substances produced demonstrate strong nematicidal activity.…”

Cloning and Expression of the Chitinase Encoded by ChiKJ406136 from Streptomyces Sampsonii (Millard & Burr) Waksman KJ40 and Its Antifungal Effect

“…Streptomyces Waksman & Henrici, the largest genus of the phylum Actinobacteria, consists of a group of Gram-positive, aerobic, non-motile, catalase positive, and non-acid-fastbacteria with a filamentous form that resembles fungi [1][2][3]. The members of Streptomyces are well-known for their ability to produce a variety of bioactive compounds with different bioactivities such as antibacterial [4][5][6][7][8][9], antifungal [10], antiviral [11], immunosuppressive [12], anticancer, and antioxidant properties [13][14][15].…”

“…[20]. Previous studies demonstrated that the bioactive compounds of S. sampsonii have important applications in various fields [3]. For example, crude extracts showed antitumor activity against glioblastoma multiforme (GBM) cells, inhibiting cell growth by 70.04% [25], and the supernatant of a S. sampsonii culture showed biological activity against the root-knot nematode [26].…”