Tuesday, 10 February 2015

Fish, plants, phytohormones, beneficial bacteria, aquaculture and hydroponics. This project has it all!

John Allwright Fellow, Jonathan Mangmang, is completing his PhD at the University of Sydney under the supervision of Dr Gordon Rogers and Rosalind Deaker. Jonathan is on secondment from Visayas State University, Philippines where he worked on an ACIAR-funded protected vegetable cropping project. He is interested in more efficient and sustainable food production system, particularly in the integration of beneficial microbes in aquaponics vegetable production.

Source: Jonathan Mangmang



Increasing population growth exerts pressure on the food supply, land for housing, water and other resources required for food production. Therefore, new ways must be developed to enahnce food production while at the same time conserving the diminishing natural resources and deteriorating environmental quality to meet the growing demand for food.

Fish farming (aquaculture) and hydroponics are two promising ways that have become increasingly popular as alternative methods to conventional agriculture. The combination of these two sustainable technologies is termed “Aquaponics” and offers a great opportunity to enhance food production with greater water and nutrient efficiencies through recycling of waste water and organic materials. Previous studies on aquaponics have focused on the optimisation of the system design including plant-fish and water/nutrient stabilities within the system. Aquaponics has gained considerable attention to both researchers and growers worldwide due to its practical applications and resources benefits. However, this system  is faced with a sustainability question relating to nutrient use efficiency to maximise plant production without chemical fertiliser supplementation.

Source: Jonathan Mangmang

Jonathan is exploring the role of plant growth promoting rhizobacteria, or PGPR. These bacteria can colonise plant roots and enhance plant productivity by increasing mineral nutrient solubility, fixing atmospheric nitrogen, producing phytohormones, suppressing disease and improving stress tolerance. One prominent genus of PGPR is Azospirillum that can produce phytohormones particularly indole-3-acetic acid (IAA), which alters root morphology leading to improved mineral and water uptake. Azospirillum lessens pathogen attack and damage to plants by competing with pathogens for suitable environment and eventual displacement, enhancing general plant vigor to resist pathogen infection, and possible inhibition of fungal growth through the production of microbial toxic substances and activation of plant defence systems. Thus far, the use of PGPR as bioinoculant has gained worldwide importance and acceptance due to its promising potential for sustainable food production and environmental protection.

Initial results of Jonathan’s work show that strains of Azospirillum brasilense produced an amount of IAA sufficient to alter the morphological, physiological and other plant metabolic activities that led to growth enhancement. For instance, they enhanced chlorophyll and phosphorous content, endogenous plant IAA and peroxidase activity. In addition, PGPR Azospirillum showed substantial colonisation activity and caused little or no disturbance to the existing bacterial community.

The basics of aquaponics and integration of PGPR Azospirillum

It is hoped that this research can assist in a better understanding of the role of PGPR as an agent to further maximise the usefulness of fish effluent for plant production using aquaponic systems and produce quality horticulture products.

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