Project Number: 5348-22000-013-05
Project Type: Reimbursable

Start Date: Sep 30, 2005
End Date: Jun 30, 2009

Objective:
Combining strategically selected genes conferring diverse modes of action against plant pathogens into one organism can improve the efficacy of biological control agents. This strategy eliminates the costly process of screening new strains of uncertain value, simplifies formulation, avoids competition among introduced strains, and enables agents already adapted to a particular agroecosystem to reliably deliver metabolites with known activity against the target pathogen. In this project, we will introduce known biocontrol genes into the well-characterized rhizobacteria Pseudomonas fluorescens Q8r1-96 and Serratia plymuthica IC1270 to broaden their range of target pathogens and enhance their antifungal and plant growth-promoting activities.

Approach:
Construct site-specific integrative expression cassettes carrying: (i) the chiA gene for a 58-kDa endochitinase, (ii) the pyrrolnitrin biosynthetic operon, and (iii) the acdS gene encoding 1-aminocyclopropane-1-carboxylate (ACC)-deaminase (which confers plant growth-promoting activity); (2) employ these constructs and an existing cassette carrying the 2,4-diacetylphloroglucinol biosynthetic operon to engineer stable recombinant strains with an expanded repertoire of beneficial activities; (3) evaluate the rhizosphere competence and antifungal activity of the wild-type and modified strains against Rhizoctonia solani, Pythium aphanidermatum, Pythium irregulare, and Gaeumannomyces graminis var. tritici on cucumber, wheat, and pea under laboratory and greenhouse conditions; and (4) use molecular and traditional approaches to monitor the persistence and impact of the introduced strains on culturable and nonculturable rhizosphere microbial populations in the greenhouse and the field. Documents BARD Grant. Log 27564. Formerly 5348-22000-012-16R (6/07).