Biofortification of Iron in Plants by Plant Growth Promoting Rhizobacteria (PGPR)
Authors: PRIYANKA CHANDRA & POONAM JASROTIA
Micronutrient malnutrition is a serious problem to human health throughout the world, primarily in resource limited countries. There are several methods for coping with this problem but this malnutrition can be reduced through a natural process called biofortification: a process to produce micronutrient enriched staple food. Plant growth promoting rhizobacteria (PGPR) can fortify iron content in tissues of plant by increasing its availability through various mechanisms.
According to the study of World Health Organization (WHO), around two billion people are suffering from malnutrition of vitamin A, iron and iodine. Iron deficiency is most common nutritional disorder affecting 2.5 to 5 billion people around the world where poor households and children are mostly affected.
Iron acts as co-factor for several enzymes involved in basic functions in human body. Inadequate supply of iron contributes to disability, anemia and stunted mental growth. Its malnutrition may be reduced by enhancing the bio-available iron content through iron supplementation and food fortification. These are very costly and difficult on daily basis particularly in developed countries suffering more with malnutritrion. Therefore, crop fortification is essential with iron with cost effective approach to overcome the malnutrition.
Biofortification can be done through mineral fertilizer, conventional breeding and transgenic approaches but their success have not always been consistent. Plant growth promoting rhizobacteria are known to fortify the iron contents in food crops besides improving the soil fertility and crop yield through siderophore production. Siderophores are low molecular weight organic compound having high affinity for iron. Typically, there are four major groups of siderophore namely catecholates, hydroxamates, hydroxypyridonates, or aminocarboxylates. Siderophores form very stable iron complexes and enhance the dissolution of iron bearing minerals by chelation of iron atom. Plant growth promoting rhizobacteria produces siderophores, and chelate iron complex and translocate to the plant through roots. These iron siderophores complexes are taken up by plant through transporter proteins that are located on plasma membrane of root. Furthermore, these rhizobacteria enhance plant growth by conferring several beneficial effects such as increased nitrogen fixation, phosphorus solubilization, synthesis of phytohormones, and production of organic acid and reduce susceptibility to disease. Therefore, biofortification of plant through PGPR is considered as safe measure to improve iron content in different edible plant parts and to alleviate its malnutrition.
Biofortification of iron in plants by PGPR:
Various results showed that inoculation with PGPR significantly enhanced the plant height, root length, root fresh and dry weights, shoot fresh and dry weights and iron content compared to un-inoculated control plants. The studies suggested that PGPR can help plants to uptake extra Fe from soil, if soil is supplemented with additional Fe. These findings supports that microbial assisted biofortification in grain can alleviate micronutrient deficiency in humans especially in resource limited countries.
Inoculation with PGPR along with Fe increased the iron uptake and overall growth and yield of crops. Therefore, it can be concluded that application of Fe with rhizobacteria could be the most promising and cost effective strategy for improving the iron contents of several crops. However, more work is still needed to reveal the exact mechanism of biofortification of micronutrients by rhizobacteria.
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About Author / Additional Info:
I am working as Scientist in ICAR-Indian Institute of Wheat and Barley Research . My specialization is in Agricultural Microbiology. The Co-author of the article is Poonam Jasrotia is agricultural entomologist in the same institute.