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Authors: Hussain, Muhammad Iqbal
Keywords: Applied Sciences
Agriculture & related technologies
Field & plantation crops
Garden crops(Horticulture)
Insect culture
Soil Sciences
Issue Date: 2013
Abstract: Low availability of phosphorus is a major constraint on agricultural productivity in all kinds of soils. Although soils are rich in total phosphorus, yet it is unavailable to plants and is considered as a limiting factor of plant growth. Application of phosphatic fertilizers is essentially required to maximize crop yields. Generally P use efficiency of applied fertilizer is low because of the formation of insoluble complexes with soil colloids. Phosphorus is sequestered mainly through the mechanisms of precipitation and adsorption on Ca, Fe, and Al etc. Although a large amount of the total P in soils is present as organic form; however, the sole form of P assimilated by micro-organisms and plants is mineral orthophosphate ions. One of the major sources of orthophosphate ions is the mineralization of organic phosphorus (Po). Soil organic phosphorus plays an imperative role in P nutrition of crops. Phosphatase enzymes hydrolyze soil organic phosphorus to release inorganic P before it can be utilized and taken up by plant roots from the soil solution. Soil microorganisms are the major source of such enzymes. Besides the conventional methods of mineral phosphate fertilization, microbial P-solubilization may help to improve the availability of phosphates in P deficient soils. Use of phosphate solubilizing bacteria as inoculants directly increases P uptake by releasing organic acids and phosphatases while with their 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and auxin production, these microbes could enhance P acquisition by plant indirectly through increased root growth. Present study was planned to isolate bacteria from the rhizosphere of maize with plant growth promoting traits which included phosphatase activity, auxin production as well as ACC-deaminase activity for increasing the growth and yield of maize with the hypothesis that the inoculation with phosphatase producing bacteria would help in promoting growth of maize in the presence of organic matter in order to manage soils deficient in available P. A series of studies to evaluate the response of rhizobacteria having phosphatase activity, auxin producing and ACC-deaminase activity on growth and yield of maize were conducted. During preliminary screening approach under axenic conditions, inoculation caused up to 40 % increase in shoot length and 59 % increase in root length compared to uninoculated control (jar trial). In pot trial, in combination with farmyard manure (FYM), inoculation with selected bacterial isolates caused up to 16, 11, 33 and 42 % increases in shoot length, root length, grain yield and straw yield of maize compared with uninoculated control, respectively. Moreover, inoculation also significantly increased the phosphatase activity in the rhizosphere, dissolved P and available P in soil compared with control. Correlation analysis revealed that positive and significant correlations existed between the PGPR showing efficient plant growth and their in vitro traits, i.e. phosphatase activity, auxin production and ACC-deaminase activity. Similarly, in field trials, inoculation with phosphatase producing bacterial isolates resulted in significant increase in plant height; cob yield; plant biomass and grain yield of maize (up to 25, 31, 44 and 31 %, respectively) as compared to uninoculated control in the presence of FYM. Regarding physiological parameters, inoculation with phosphatase producing bacterial isolates also resulted in enhanced photosynthetic rate, transpiration rate and water use efficiency which were 62, 28 and 30 % higher than uninoculated control, respectively. Study also demonstrated that multifaceted bacteria could be more effective PGPR than single trait to improve crop growth and yield.
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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