University of Khartoum

Plant Growth Promoting Rhizobacteria From Acacia senegal (L.)Willd Growing Under Field Conditions

Plant Growth Promoting Rhizobacteria From Acacia senegal (L.)Willd Growing Under Field Conditions

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Title: Plant Growth Promoting Rhizobacteria From Acacia senegal (L.)Willd Growing Under Field Conditions
Author: Elmardi, Eiman Ahmed ELtigani
Abstract: The study aimed to isolate , characterize and screen the multiple plant growth promoting traits of rhizopheric bacteria (Rhizobium, Bacillus , Pseudomonas , Azospirillum , PSB )from Acacia senegal (L.) Willd. rhizosphere. In addition , to select the most potential isolates that can be used as bioinoculant. The study was conducted on the rhizospheric soil of A.senegal trees in 3 sites in Kordofan State (Khortagat , Damokya , Gandil) and 3sites in El Gedarif State (El Gedarif Town , Galalnahal , Feel Forest), during dry and rainy seasons. Cultural , morphological and biochemical tests were conducted for rhizobacterial isolates using standard procedures. Cluster analysis was carried out to group the isolates according to similarities into perspective categories. Selected isolates for each group were subjected to physiological analysis. Measurements of plant hormones (auxin, gibberellin, and cytokinins), siderophore production and phosphorus solubilization were conducted qualitatively and quantitatively using TLC, UV spectrophotometry and HPLC techniques. Statistical analysis (ANOVA) at 5% level of significance (randomized design) was used to evaluate the most effective isolates in the growth experiments. Five different genera of bacteria, 197 isolates had been isolated using selective medium for each type: 60 Rhizobium isolates, 60 Bacillus isolates, 31 Pseudomonas isolates , 39 PSB isolates and 7 Azospirillum isolates..Most of samples gave positive results.For Rhizobium ,Pseudomonas and PSB the maximum population in Kordofan and El Gedarif States were in Gandil (7.5×107 cfu),(10.2×105),(0.5×107)and Galalnahal (17×105 cfu),(6.7×105),(13×107) respectively. Bacillus maximum population were in Gandil (1.9×104 cfu), and in Feel forest (11.5×107 cfu). Maximum population of Azospirillum in Kordofan were in Gandil (4×106 cfu), and in El Gedarif (5.3×106 cfu). Enumeration of population density revealed that Bacillus species were the most abundant isolates of bacteria (95%) followed by Rhizobium (4.1 %), PSB (0.12 %), Azospirillum (0.2%) and Pseudomonas (0.01%). Separation of the bacterial extract by TLC revealed the presence of plant hormones in some isolates. The maximum auxin production was recorded by Rhizobium isolate KRR3 with concentration 7.8mg /L. Gibberellin detection gave negative results in most isolates but highest gibberellin production was recorded for Rhizobium isolate LRR2 (8.3 mg/L). Cytokinin showed positive results in some isolates with uneven rates and the maximum production was given by DRR3(0.137 mg/ml). PSB revealed uneven rates of solubilization of phosphorus and the maximum production was given by NSR2 up to 3 mg/ml. The maximum siderophore production was recorded by PSB isolate KSR2(18.6%). Inoculation of A.senegal seedlings by 10 Rhizobium isolates were studied, and shoot and root growth, and nitrogen content were determined. The results revealed that dry weight of root system showed high significant difference for treated plants with Rhizobium strains KRR3and LRR2 when compared to control plants. The number of leaves and dry weight of shoot system showed significant variance when compared to control for Rhizobium isolates LRR2, KRR3, LRR3 and NRR1. There was a significant variance in nitrogen content for all treated plants when compared with the control. The study concluded that 4 Rhizobium isolates (LRR2,KRR3,LRR3 and NRR1)are the most effective plant growth promoting rhizobacteria for A. senegal trees,which can be used in the future for the production of bioinoculants for this economically important forest tree species
URI: http://khartoumspace.uofk.edu/123456789/26597


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