Evaluation of Plant Probiotics on Phosphorus Nutrition in Rice

Objectives of the project

This proposed project is the continuation and part of my large research project on ‘discovery of bio-functional bacteria’ in the Department of Biotechnology. A good number of previously isolated PSB will be used as reference strains. Therefore, the objectives of the research are to –

  1. discover novel PSB from seeds and plants of different varieties of rice using standard laboratory screening methods
  2. quantitatively estimate phosphate solubilization activity in broth culture conditions.
  3. characterize potential bacterial isolates using molecular techniques including 16S rRNA gene sequencing.
  4. evaluate performances of selected PSB in growth and P nutrition in rice.

Rice is a staple food for about 70% of world population. The demand of rice increases because of the fast increase in world population (Brittoet al. 2004). Production of rice requires huge chemical inputs (pesticides and fertilizers), which is not only very expensive but also detrimental to the environment. Plant-associated bacteria (plant probiotic) have high potentials to improve nutrition and protection of plants. Therefore, isolation of those bio-functional bacteria from the native plants andutilize them as bio-fertilizer and/or biopesticides is a new trend of research in sustainable agriculture (Vessy, 2003). Bio-fertilizers promote plant growth by directly or indirectly supplying necessary nutrients to the plant. “Plant probiotics” has been used to describe plant-associated microorganisms, which enhance the growth of the host plants when applied in adequate amounts (Maheshwari et al. 2012). Plant probiotics, which enhance the solubilization of fixed soil P and applied phosphate fertilizer, resulting in better P nutrition in crop plants, are known as phosphate-solubilizing bacteria (Abd-Alla, 1994; Yahya and Al-Azawi, 1989; Mehta andNautiyal, 2001; Islam et al. 2007; Islam and Hossain 2012).1.      2

Phosphorus (P) is the second most important and most frequently limiting macronutrient for plant growth. P makes up about 0.2% of a plant’s dry weight (Schachtmanet al. 1998).P is one of the important players in the process of photosynthesis, nutrient transport, and energy transfer. It is also involved in key enzymatic reactions in major metabolic and signaling pathways (Theodorou and Plaxton, 1993). Therefore, adequate P nutrition is essential for proper growth and yield of any crops.

To solubilize P in P-deficient soils, plants have evolved diverse array of strategies to uptake adequate P under P-limiting conditions, including modifications to root morphology, carbon metabolism, membrane structure; exudation of organic acids, protons, and enzymes; and association with mycorrhizal fungi, and harboring phosphate-solubilizing microorganisms including bacteria (Fig. 1) (Begum and Islam, 2005; Islam et al. 2007). However, rice is very poor in association of mycorrhizal fungi in flooding conditions and also secretion of organic acids (Lipton et al. 1987;Begum et al., 2005). Therefore, inoculation of growth-promoting bacteria such as phosphate-solubilizing bacteria (PSB) seems to be an alternative approach for P nutrition in rice under P-deficient tropical and sub-tropical soilslike Bangladesh (Thakuriaet al., 2004;Islam et al., 2007; Islam and Hossain 2012).

 

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Fig. 1:  A simplified schematic representation of the role of phosphate-solubilizing bacteria (PSB) to P availability in soil and uptake by plants (adapted from the scheme of Richardson and Simpson, 2011)

Expected outcome of research

  1. Discovery of a good number of phosphate-solubilizing bacteria (identified at molecular level) are discovered, which will be an asset of the university as well as for Bangladesh.
  2. Understanding of underlying molecular mechanisms of selected PSB, which will be fundamental for generation of novel bio-rational management of P nutrition in rice plants through further biotechnological approaches.
  3. One trained graduate (MS level).
  4. Publications in international journal having high impact factor.

Duration of the project:  One year (2013-2014)

 Approved grant: Taka 1, 00,000 (One lakh ) only

Funding Agency: RMC

Principle investigator (PI): Dr. Md. Tofazzal Islam, Professor, Department of   Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricultural University

Research associate: Musrat Zahan Surovy, MS student, Department of Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricultural University