Microencapsulation: Toward the Reduction of the Salinity Stress Effect on Wheat Plants Using NPK Rhizobacteria
Maged M. Saad *
Department of Agriculture Genetic Engineering Research, Institute Agriculture Research Center (ARC), Giza, Egypt.
Hanaa A. Abo-Koura
Department Agricultural Microbiological Research, Soils, Water and Environment Research Institute (SWERI), Agricultural Research Center (ARC), Giza, Egypt.
Mounira M. Bishara
Department of Environment and Bio-agriculture, Faculty of Agriculture, Al-Azhar University, Cairo, Egypt.
Ibrahim M. Gomaa
Department of Environment and Bio-agriculture, Faculty of Agriculture, Al-Azhar University, Cairo, Egypt.
*Author to whom correspondence should be addressed.
Abstract
Salinity is one of the most vicious environmental factors controlling the productivity of crop plants as most of the crop plants are sensitive to salinity affected by high concentrations of salts in the soil. The objective of this study was to evaluate the influence of the inoculation with the encapsulated and liquid culture of three halo-tolerant plants growth-promoting rhizobacteria (PGPR) strains of Paenibacillus polymyxa MSRH5, Bacillus nakamurai MSRH1 and Bacillus pacificus MSR H3 on the growth and yield of wheat (Triticum aestivum L.). The three strains MSRH1, MSRH3 and MSR H5 were characterized as salt-tolerant bacteria. P. polymyxa MSRH5 had nitrogen fixation ability while B. nakamurai MSRH1 and B. pacificus MSRH3 were able to solubilize phosphate and K respectively. All strains can produce indole acidic acid (IAA) and exopolysaccharides (EPS) under saline conditions. Encapsulated beads were observed under Scanning Electron Microscope (SEM). Colonization of encapsulated bacteria on the root of the wheat plant was studied by Transmission Electron Microscopy (TEM). Under soil salinity conditions in two consecutive field tries, results cleared that strains in two forms succeed to colonize the plant root, the reduction in shoot proline was 35.8% with capsules inoculation as well as improved relative water content (%) to 60.57% and improved the electrolyte leakage recorded 18.1% respectively compared to control. Generally, halo-tolerant PGPR inoculation increased DHA (?), acidic and alkaline phosphatase activities compared to control, inoculation with capsules exhibited a reduction in catalase enzymes 46.00%, 37.5% in ascorbate peroxidase and 40% in superoxide dismutase respectively in shoots of the wheat plant. There is a significant increase in all yield parameters, the highest plant height 115.8 cm, spike length 21 cm and 1000 grains 71.3 g respectively recorded with capsules inoculation, it had considerable effects on the content of N, P, K and Na in shoots of wheat plants and reduced the value of Na/K ratio in all treatments inoculated compared to un-inoculated wheat plant.
Keywords: Halo-tolerant bacteria, PGPR, alginate beads, wheat, colonization.