PGPR for enhancing growth and phosphorus availability in rice


Rice is one of the main nutrition sources and feeds approximately 50% of the planet’s population

PGPR for enhancing growth and phosphorus availability in riceIntroduction

Approximately 75% of a billion of the world’s poorest individuals depend upon rice as a staple to survive. The grain has molded the history, culture, eating routine, and economy of people of Asia. Large numbers of them sleep on the rice straw and drink rice liquor. Rice is the second most important cereal after wheat in Pakistan. It is cultivated on an area of 2793 thousand hectares with 6849 thousand tons production and an average yield of 2514 kg ha1 during the year 2016-17.

Rice plays various roles in agrarian’s economy of Pakistan. The rice industry provides employment to the rural population and contributes to the country’s foreign exchange. During year 2016-17, rice added 3% value to agriculture and 0.6% added to GDP of Pakistan. Asia’s food security mainly depends on irrigated rice, a system that is consuming most of the available water resources.

In Asia, irrigated agriculture system consumes 90% of total water diverted, through which 50% is consumed to irrigate rice. About 75% of the world’s rice is. Obtained from 79 m ha of irrigated land in Asia. The major limiting factor the global “water crisis” threatens the irrigated rice production on a sustainable basis. There is an increase in scarcity of available water resources in the rice production system and increasing competition from domestic, industrial and agriculture sectors suggests conserving irrigation water through irrigation use efficiency. The transplanting method is commonly practiced for rice cultivation. This method involves the nursery establishment and then transplanted to the flooded field.

This traditional method requires continuous water applications and labor for doing different operations, an increase in the water and labor costs in and also increases the overall cost of production and affects the sustainable rice production system and food security in Asia. In addition, due to the changing socio-economic environment in Pakistan, farmers require a solution for high water inputs, higher labor costs, and unavailability of labor are major problems.

Hurdles and constraint and their remedies  

There is a shortage of water due to increased water consumption in other non-agricultural sectors increasing labor cost due to shortage of labor. Due to these problems, there is a need to introduce some alternative methods for rice cultivation that consume less water and labor as compared to the traditional transplanting method. So, there is a need for alternative means of rice cultivation which require less water, less labor and produce more with less cost. Direct seeding is a viable alternative. Direct seeding method for rice cultivation, rice cultivation in un-puddle soil without nursery raising without standing water is the most attractive method than the traditional transplanting method.

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Direct seeding has great importance over transplanting, reduces crop duration leading to early flowering and maturity. It is more economical, saves labor required for transplanting and nursery raising saves time and also gives higher yield if managed properly. This method requires 20-40% less water (up to 80% in some cases) than transplanted rice, it has more advantages over transplanted at a critical period of water scarcity. Direct seeded rice cultivation should be the optimal option due to advantages over the traditional methods, labor for transplanting, required less water, timely sowing possible, less input required, reduced cost of production. Direct seeding also resolves the edaphic argument between rice to subsequent non-rice crop, maintain the sustainability of wheat-rice production system and other winter crops which are sown after wheat.


Phosphorus is a major macronutrient that is essential for plant growth and development. It has a significant role in the physiological processes of plants. It is part of various enzymes that are involving in growth and also a structural component of nucleic acid (DNA or RNA). It promotes root growth and also leads to early maturity. It strengthens straws and protects plants against lodging and increases resistance against various diseases and stresses. Plant growth retarded and reduced yield as a result of phosphorus deficiency. Phosphorus management can increase crop yield traits, decrease cost per unit production and also lowers environmental damage.

Early applications of phosphorus significantly increase grain yield and dry matter partitioning at different developmental stages. Phosphorus applications significantly increase plant height, tillering capacity, grains per panicle, grain weight and maximize production. Phosphorus enhances root development, seed quality, seedling vigor, reduce and also reduce the flower shedding. Phosphorus applications significantly increase the number of panicles per m2, reduces kernel sterility, increase grains per panicle, number of spikelets per panicle and increase (1000) grain weight of rice. Phosphorus use efficiency is in the range from 10-25% all over the world and phosphorus concentration becoming low with time.

The major problem is that there is sufficient amount of total P is present in the soils but not uptake by the plants due to its presence in unavailable form and additional P fertilizer applications increase the cost of production due to high price. About 90% of P deficiency in Pakistani soils have been recorded which limit crop production. Phosphorus deficiency is not a big problem, but the problem is less P mobility due to fixation. So, to overcome the above-mentioned problems, there is dire need to find some ways under which phosphorus use efficiency can be enhanced to sustain the crop production.

Plant growth promoting rhizobacteria (PGPR)

Plant growth promoting rhizobacteria (PGPR) are a group of soil rhizobacteria bacteria with potential to stimulate plant growth by increasing availability of nutrients through various mechanisms such as biological nitrogen fixation, phosphorus solubilization, increase root surface and make nutrients available to rhizosphere. Plant growth promoting Rhizobacteria promotes growth through N-fixation, producing phytohormones solubilizing the nutrients and through reducing roots membrane potential. Many microorganisms have the potential to produce hormones including auxins, cytokinins, gibberellins, and ethylene. PGPR applications to soils increase the availability of essential macro and micronutrients including K, Ca, Zn, Fe, Cu, and Mn, and uptake of these nutrients occurs during acidification. Soil microbes are involved directly or indirectly in plant growth through various biological and physiochemical changes to the Soil environment. PGPR strains facilitate the plants to uptake essential nutrients like NPK and other micronutrients through solubilizing and converting to available forms, suppress disease causing pathogens and finally increase crop production.

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Many PGPR species increase resistance against different biotic and Abiotic stresses. Microbial strains also have the potential to increase germination%, seedling vigor as a result of seed treatments with specific bacterial strains. Several inorganic compounds found in soil which are present in abundant quantity but plants cannot use these compounds due to their existence in an unavailable form. Phyton is a major P containing compound which is directly unavailable to plants that must be hydrolyzed. Phosphate solubilizing bacteria (PSB) are present in an abundant form in the soil. Several tested microbial strains have the potential to solubilize four major types of insoluble inorganic phosphate including dicalcium phosphate (DCP), tricalcium phosphate (TCP), rock phosphate (RP) and ferric phosphate (FP).

Several bacterial strains and fungi are isolated from the rhizosphere for their capacity of mobilizing different organic and inorganic forms of phosphorus. Microorganisms are a central part of the soil-phosphorus cycle and mediate phosphorus availability to plants. Pure culture of several microbial strains has the capacity to solubilize precipitated forms of phosphate and improve the phosphorus nutrition of plants (Gerretsen, BM8). This work is taken under consideration over many decades due to the involvement of microorganisms in phosphorus solubilization and finding opportunities to manipulate some specific microbes which can increase phosphorus availability. Several microbial strains are identified which have the potential to solubilize the soil fixed phosphorus and known as phosphate solubilizing bacteria (PSB). Phosphorus mediating microbes are under more interests because now a day’s phosphorus deficiency is worldwide mostly in weathered and B tropical soils higher fertilizer cost and low phosphorus use efficiency unless soils have abundant phosphorus. Microbes make the plants able to acquire phosphorus through enhancing root growth, root hairs and produce hormones which stimulate root growth.

Various species of symbiotic and non-symbiotic organisms are well-known phosphorus solubilizers, can solubilize the precipitated P such as Rhizobium, Bacillus and Pseudomonas spp. Microorganisms initially require phosphorus for their own requirements to carry out mineralization and solubilization to meet crop nutrients. When microbes are inoculated with phyton, phosphorus availability and uptake increase uptake due to the release of different enzymes that decompose the phyton and make phosphorus available to plants. Keeping in view the above-mentioned problems, facts and available solutions the present research was conducted with the following objectives; Check the individual effect of microbial strains and phosphorus levels on the growth and yield of direct-seeded rice. To evaluate the potential of microbial strains to solubilize phosphorus and enhanced uptake of phosphorus in direct-seeded rice verities of MN-17 and MN-54.

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In chemical analysis of soil and plant for major nutrients nitrogen (N) phosphorus (P) and potassium (K) results in higher availability and uptake of major nutrients NPK in the pots under the PGPRs applications. PGPRs applications enhance the nutrient’s availability in the root of the plant due to which plants can uptake more amount of nutrients in abundance of available nutrients. The results of phosphorus parameters show that both the PGPR strains significantly increased the soil available phosphorus, P concentration in shoots and grains. Both strains have the potential to solubilize the soil phosphorus and also increased the P- uptake by plants. The performance of MN-17 was better than MN-54.

The applications of phosphorus also significantly increased soil, shoot, and grain P concentration. The maximum value of soil available phosphorus, shoot P and grain P under the individual effect of phosphorus recorded in the pots under the higher phosphorus application (80 kg ha-1 P) and P concentration, significantly decreased with decreasing order of phosphorus. The PGPR inoculation also increased the soil potassium (K) availability and K nutrition of rice plants. The significantly increased P and K concentration in straw or their uptake by rice plants may be due to higher soil availability of P and K and also due to a higher growth rate of rice. The higher growth of the crop is associated with plant hormone production, availability of essential nutrients by the PGPR strains.

Higher availability of nutrients resulted in more uptakes by plants. The higher available concentration and uptake of other nutrients with increasing phosphorus may be as the result of synergistic effects of nutrients with one and another. Previous researches showed accordingly that the effect of PGPR strains in combination with different phosphorus levels on growth, yield and nutrients uptake of the rice and reported that NPK contents in grains and straws of rice significantly affected with composite treatments of PGPR with different phosphorus levels. The P concentration in grains and straws significantly increased with increasing applications of phosphorus from 0-60 kg ha’1 P2O5 due to the presence of P-availability in soil due to the addition of phosphatic fertilizer. 50% increase in NPK contents and uptake by wheat due to PGPR application

Corresponding authors

1Faran Muhammad

3Nargis Naheed

1Muhammad Ali Tariq

2Hira Hafeez

4Muhammad Raheel Javaid

5Muhammad Asif

1Jamshed Haider

1Hafiz Muhammad Hamza Saleem

1Muhammad Dilawaiz Khan

1Department of Agronomy, University of Agriculture, Faisalabad-38000, Pakistan 2Department of Botany, University of Agriculture, Faisalabad-38000, Pakistan

3Department of Zoology, University of Agriculture, Faisalabad-38000, Pakistan

4Department of Horticulture, University of Agriculture, Faisalabad-38000, Pakistan

5Department of Forestry, University of Agriculture, Faisalabad-38000, Pakistan

Faran Muhammad

Faran Muhammad

An agronomist by profession, deal with scientific data analysis with statistical tools.

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