Effect of the nitrogen-fixing bacterium Pseudomonas protegens CHA0-ΔretS-nif on garlic growth under different field conditions

Pseudomonas protegens CHA0 is a well-characterized plant-growth promoting rhizobacterium commonly used as biofertilizer or biocontrol agent for plant growth promotion and disease control. Genetically engineered strain CHA0-Delta retS-nif with introduced nitrogen-fixing ability and enhanced bactericidal activity has the potential to stimulate plant growth and suppress phytopathogens. Field experiments was conducted to evaluate the effects of CHA0-Delta retS-nif inoculation on garlic growth, disease prevention and soil microbial diversity. Results revealed that CHA0-Delta retS-nif inoculation largely promoted garlic growth and yields. The total production of garlic in the CHA0-Delta retS-nif treated fields reached up to 34.25 T/ha, with an increase of 12.03% when compared to the untreated control (30.58 T/ha). When nitrogen application was reduced by 25%, CHAO-AretS-nif inoculation had a similar beneficial effects on garlic production with an increase of 10.62% than the uninoculated control. Moreover, CHA0-Delta retS-nif inoculation increased the bacterial population in the garlic rhizosphere and had significant effects against garlic root rot. Disease index in the CHA0-Delta retS-nif inoculated treatment (2.65%) was lower than the uninoculated control (3.31%). These results indicate that P. protegens CHA0-Delta retS-nif inoculation can help reduce chemical fertilizers and pesticides usage, and may be considered as an eco-friendly, viable alternative technology to increase food production in the future.