Isolation of Rhizobacteria and Micro Algae from Saline Soil and Production of Plant Growth Promoters

Abstract

Twenty-six bacterial and four algal isolates were isolated from rhizosphere of rice and sugar beet
plants, grown in saline soil in Sahl El-Hussinian Station, El-Sharkia Governorate, Egypt and in vitro
screening was done for different plant growth promotion activities i. e. indole acetic acid (IAA),
gibberellic acid (GA) and carbohydrate production. Bio-control ability of bacterial isolates was screened
by antagonistic activity against certain fungal pathogens. Results revealed that bacterial isolates No. 7
and 26 produced high amount of IAA (78.63 µg ml-1 and 78.73 µg ml-1 , respectively), while isolate No. 5
was most potent isolate for GA (173.91 µg ml-1 ) and carbohydrate (187.18 µg ml-1 ) production. The
active bacterial isolates (No. 5, 7, 26) in plant growth promoting substances production showed high
antagonistic activity against certain pathogenic fungi (Fusarium sp. and Rhizoctonia sp.). Additionally,
algal isolate No. 3 was active in production IAA (29.26 µg ml-1 ), while isolates No. 2 and 1 were efficient
in GA (83.91 µg ml-1 ) and carbohydrate (178.81 µg ml-1 ) production, respectively. The most efficient
rhizobacterial isolates (No. 5, 7 and 26) were selected and identified using Bio-log technique and 16S
rRNA as Bacillus subtilis and Pseudomonas aeruginosa, respectively. Based on 16S rRNA sequence
analysis both bacterial isolates (No. 7 and 26) identified as Pseudomonas aeruginosa. The most potent
algal isolates (No. 1, 2 and 3) for plant growth promoting substances production were chosen and
identified according to classical morphological characters as Anabaena sp., Nostoc muscorum and
Anabaena variabilis, respectively. The optimum incubation period for highest production of IAA and GA
by efficient bacterial and algal isolates was three and twenty days, respectively, while highest
carbohydrate production was obtained after four and twenty five days, respectively.
.