Combining proteolytic and phloroglucinol‐producing bacteria for improved biocontrol of Pythium‐mediated damping‐off of sugar beet

Abstract

Pseudomonas fluorescens F113 and Stenotrophomonas maltophilia W81 protect sugar beet from Pythium-mediated damping-off through production of the antifungal secondary metabolite 2,4-diacetylphloroglucinol and extracellular proteolytic activity, respectively. In this study, the two biocontrol strains were combined in a consortium, with the objective of improving upon the level of protection achieved when using each strain singly. Growth and in vitro production of 2,4-diacetylphloroglucinol by F113 and extracellular lytic enzymes by W81 were not affected when inoculated in combination. The abilities of W81 and F113 to colonize the rhizosphere of sugar beet were essentially similar when the two strains were applied singly or coinoculated onto seeds in a 1 : 1 ratio, both in natural soil microcosms and under field conditions. Concomitantly, single inoculation with W81 or F113 effectively prevented colonization of sugar beet seeds by Pythium spp. in soil microcosms, without the necessity for combining both strains. However, this parity was not reflected in seed emergence where the combination of W81 and F113 significantly enhanced final sugar beet stands (to the level achieved with chemical pesticides) under microcosm conditions at 28 days after sowing. In a field experiment, the only inoculation treatment capable of conferring effective protection of sugar beet was that in which W81 and F113 were coinoculated, and this treatment proved equivalent to the use of chemical fungicides. In conclusion, when compared with single inoculations of either biocontrol strain, the combined use of a phloroglucinol-producing P. fluorescens and a proteolytic S. maltophilia improved protection of sugar beet against Pythium-mediated damping-off.

Rapid detection of Ganoderma disease of coconut and assessment of inhibition effect of various control measures by immunoassay and PCR

“…In our study, the mixture of two antagonists (P. fluorescens + T. viride) suppressed Ganoderma disease development. Numerous modes of action have been postulated and demonstrated for the antagonistic effects of P. fluorescens in controlling diseases; they include synergistic effects observed on fungal pathogens with a combination of antifungal compounds (DOWLING & O'GARA 1994;DUNNE et al 1998), competition for nutrients (O'SULLIVAN &d O'GARA 1992), production of cell wall lytic enzymes (SINGH et al 1999) and induced systemic resistance (DALISAY & KUC 1995;NANDAKUMAR et al 2001). Several antibiotics have been reported to be produced by bacteria (RAAJIMAKERS & WELLER 2001).…”

Colonization of the developing rhizosphere of sugar beet seedlings by potential biocontrol agents applied as seed treatments

“…Previous investigations by other workers have shown that co-inoculation with two BCAs can either suppress the rhizosphere activity of one of the isolates or that the activity of both isolates remains unaffected. For example, Dunne et al (1998) demonstrated that the rhizosphere competence of Pseudomonas fluorescens F113 and Stenotrophomonas maltophilia W81 were essentially similar when the two strains were applied to sugar beet seed as single seed treatments or co-inoculated. In contrast, Chiarini et al (1998) reported that rhizosphere populations of a strain of Burkholderia cepacia on sorghum were suppressed by a species of Enterobacter but not by Ps.…”

Screening of bacterial strains for developing effective pesticide-tolerant plant growth-promoting microbial consortia from rhizosphere soils of vegetable fields of eastern Uttar Pradesh, India

“…Strains IESDV5, IESDV10, IESDV13, IESDV14, IESDV23, IESDV26, IESDV27 and IESDV28 showed higher zone of solubilization on cellulose Congo red agar media as compared to strains IESDV1, IESD2, IESD3, IESD4, IESD11 and IESD12. Dunne et al (1998) reported that the chitinase, protease, gluconase or cellulase enzymes have ability to degrade the structural matrix of fungal cell (Table 4). The enzyme catalase present in some microorganisms breaks down hydrogen peroxide to water and oxygen and helps them in their survival (McCord et al 1971;Aneja 2003).…”