Synergy between endophytic Bacillus amyloliquefaciens GGA and arbuscular mycorrhizal fungi induces plant defense responses against white rot of garlic and improves host plant growth

Abstract

White rot, caused by Sclerotium cepivorum, is a serious and economically important disease of garlic, which leads to losses in the garlic production in most of the tropical, subtropical and temperate areas. Biocontrol potential of an endophytic Bacillus amyloliquefaciens GGA and/or arbuscular mycorrhizal fungi (AMF) against this disease was investigated. The B. amyloliquefaciens GGA exhibited antagonistic activity against S. cepivorum in vitro. Scanning electron microscopy revealed alterations in the morphology of the pathogen in response to the exposure to the bacterial metabolites. Results from a pot experiment demonstrated that application of the dual treatment of the B. amyloliquefaciens GGA and AMF reduced disease incidence and severity more than the single treatments, and led to the greatest increases in total phenol content, activities of the defense-related enzymes phenylalanine ammonia-lyase, polyphenoloxidase and peroxidase, and transcriptional expression levels of the defensin and chitinase genes. Growth and yield parameters of garlic plants were enhanced after this treatment. This study showed good efficacy on the tested biocontrol agents for control white rot of garlic plants grown in pots. Future research should evaluate these biocontrol strategies under field conditions.

Synergism between Streptomyces viridosporus HH1 and Rhizophagus irregularis Effectively Induces Defense Responses to Fusarium Wilt of Pea and Improves Plant Growth and Yield

“…In addition, triggering plant immunity was also confirmed. Resistance priming in various crops using arbuscular mycorrhizal fungi has also been extensively studied against different pathogenic fungi [ 28 , 29 ]. Numerous plant defense responses have been reported to be triggered due to mycorrhizal colonization, including the lignification (thickening) of cell walls, the production of fungitoxic polyphenolic substances, induction of pathogenesis-related proteins, and overexpression of many defense-related genes [ 27 ].…”

“…In this symbiotic relationship, the fungus partner benefits from the carbohydrates formed by the host via photosynthesis. Additionally, the host plant receives multiple benefits from the fungus partner, including the promotion of the plant’s growth [ 25 ], water and nutrient acquisition [ 26 ], the induction of the plant’s resistance against many abiotic stresses, such as salinity and drought [ 27 ], and by triggering plant immunity against various plant diseases [ 28 ]. Rashad et al [ 29 ] reported a significant overexpression in many polyphenol biosynthetic pathway genes in mycorrhizal sunflower plants colonized with Rhizophagus irregularis and infected with Rhizoctonia root rot.…”

Ascophyllum nodosum Extract and Mycorrhizal Colonization Synergistically Trigger Immune Responses in Pea Plants against Rhizoctonia Root Rot, and Enhance Plant Growth and Productivity

“…These results are in agreement with the findings of EL-Sharkawy et al [ 16 ], who found that the colonization of wheat plants with AMF induced the defense responses against stem rust disease. The application of AMF as biocontrol agents against different fungal, bacterial, and viral plant diseases has been extensively studied by many researchers [ 13 , 18 ]. The mycorrhization of the plant root leads to extensive genetic reprogramming in the plant cell, resulting in a set of physiological modulations that regulate the plant responses to different biotic and abiotic stresses [ 49 ].…”

“…The activation of the hypersensitivity responses such as cytoplasmic granulation and programmed cell death was also reported in mycorrhizal common bean roots infected with R. solani [ 20 ]. The accumulation of the antioxidant enzymes and defense-related proteins represents another defensive mechanism, which has been reported in different plants in response to mycorrhizal colonization [ 13 ]. Increments in the activity of POD and PPO enzymes reported in this study are in accordance with this information.…”

“…Arbuscular mycorrhizal fungi (AMF) are obligate biotrophs (subphylum Glomeromycotina) that live in a mutualistic relationship with roots of the majority of terrestrial plants [ 12 ]. Multiple benefits are received by the plant partner due to association with AMF, such as improving the plant growth [ 13 ], enhancing nutrients uptake, inducing plant tolerance to salinity and drought stresses [ 14 ], and triggering plant resistance against different plant diseases [ 15 ]. The application of AMF as a biocontrol agent against different plant diseases including Rhizoctonia root rot has been widely studied by many researchers all over the world [ 16 , 17 , 18 , 19 ].…”