biofilm formation by fluorescent pseudomonads and its role in biological control of take-all disease of wheat by gaeumannomyces graminis var.tritici

abstract the role of fluorescent pseudomonads in biocontrol of take-all disease caused by gaeumannomyces graminis var.tritici (ggt) has been the subject of many researchs in the recent years. biofilm formation in fluorescent pseudomonads play an important role in biocontrol disease. for this purpose,130 strains of fluorescent pseudomonads isolated from wheat rhizosphere in different regions of khorasan province were chosen for different experiments. among them, 21 strains with higher inhibitory effect in dual culture test against ggt colony were selected for more investigations. the ability of selected strains for forming biofilm, and for their adhesion power to the glass plates were determined in 492 nm wave length . this results indicated that 6 strains( f1, f3, f4, f141, p4 and 2-79) were able to forming the biofilm and demonstrated the higher level of adhesion to the glass plates. the same strains also shown better biocontrol potential on take-all disease in greenhouse experiments. the decrease rate of take-all disease in treatments using f1, f3, f4, f141, p4 and 2-79 strains was noted %79, %80, %77, %79, %77 and %80 respectively. whereas for treatments using strains which were not able to forming biofilm, the biocontrol potential was very less important, among them f140 strain reduced only 10% of disease severity . the good and significative correlation (0/84) was found between biocontrol potential of strains and their ability to forming biofilm. these results showed the important role of fluorescent pseudomonads strains which are able to forming biofilm in biocontrol of take-all disease of wheat. this ability can probably be attributed to the better colonization and more longer persistence of strains on the roots and in rhizospheric zone of wheat.