Characterization and identification of compatible bacterial and fungal isolates as biological control agents

Forty  six   bacterial isolates ;including 24 fluorescent pseudomonads and 22 actinomycetes ; 
along with ten fungal  isolates of Trichoderma spp.  were  isolated  from some plant  rhizospheres 
and  evaluated for their relative biocontrol  potential  using dual culture technique against   six  
phytopathogenic fungi which were isolated from diseased plants and identified based on  their 
morphological characters. Some pathogenic fungi were very resistant while others are very 
sensitive to inhibition by all the tested bacterial and Trichoderma isolates. The efficient isolates 
were tested to produce the inhibiting agents siderophore and hydrogen cyanide. Four fluorescent 
pseudomonads isolates (5 Ps; 7 Ps; 12 Ps; 8 Ps) and three Trichoderma isolates exhibited high 
antagonistic effects; high production of   inhibiting agents and high compatibility was detected 
among the tested four bacterial or Trichoderma isolates. These Trichoderma isolates were 
identified using standard identification keys as Trichoderma viride; Trichoderma harzianum and 
Trichoderma hamatum. The mixture of individual or  mixed batch cultures of bacterial strains were 
tested for their relative bio-efficacy against pathogenic fungi in vitro. Results revealed that  the 
mixture batch culture was less efficient  aganist the phytopathogenic fungi compared to single 
culture except with Rhizoctonia solani and  F. moniliforme. Production of  IAA; cytokinins; 
chitinase; siderophores and hydrogen cyanide were determined qualitatively to select the most 
efficient  antagonists.The selected bacterial isolates were genotypically characterised using 16S 
ribosomal DNA (rDNA) sequencing; and random amplified polymorphic DNA (RAPD) validating  
as Pseudomonas alcaligenes ; Pseudomonas sp. Pseudomonas fluorescens and  Pseudomonas 
protegens .