USE OF RHIZOSPHERIC MICROORGANISMS TO PROMOTE SUNFLOWER PLANT AGAINST HAZARDOUS EFFECT OF DROUGHT AND SALINITY

Abstract

The characterization and ability of halotolerant microbes to improve sunflower tolerance against salinity and drought were studied. A total of 56 bacteria, 10 actinomycetes and 12 fungi were isolated from rhizosphere of halophyte and xerophyte plants and screened for their ability to tolerate salt and water stress. Isolates with high salt tolerance were screened for their ability to produce salicylic acid, exopolysaccharide, proline and indoles and tested for their capacity to alleviate harmful effect of salt stress on sunflower seed germination in vitro. Halotolerant isolates namely 25Ag, 45Nr, A2, A6, F3 and F4 were found to be the best isolates and were identified as Exiguobacterium acetylicum, Halomonas elongate, Streptomyces mutabilis, Sterptomyces tuirus, Eurotium cristatum and Aspergillus terreus respectively. Pot experiment was conducted to investigate the ability of these isolates to promote sunflower growth under water and salt stress. Results showed that the selected isolates improved the growth parameters of sunflower in addition they maintaned the relative water content and relative membrane permeability of leaves and resulted in higher accumulation in K+ and Ca++ levels in root and shoot. They also caused an increase in total carbohydrates, total protein percentages and proline content in shoot. A field experiment was conducted in salt affected soil and results showed that inoculation with selected isolates positively influenced the growth parameters of sunflower plants subjected to salt stress and enhanced sunflower seed yield and yield components. Maximum increments were obtained from plant inoculated with fungal strain E. cristatum. Treatment of salty soils with these halotolerant isolates can ameliorate the deleterious effects of salt stress on nutrition and growth parameters of sunflower plants under salinity conditions.