Application of Pseudomonas Corrugata as a Seed Treatment to Suppress Ring Rot Disease of Potatoes

Application of Pseudomonas Corrugata as a Seed Treatment to Suppress Ring Rot Disease of Potatoes

Summary

Objectives

1. Construct site-specific, antibiotic marked, non-pathogenic strains of Pseudomonas corrugata.

2. Evaluate the antimicrobial activity and survival ability of the non-pathogenic constructs.

3. Application of the non-pathogenic constructs on potato seed and evaluate their effect on the bacterium (Clavibacter michiganensis subsp. sepedonicus) in field soil.

Abstract

Transposon mutagenesis was used to develop non-pathogenic strains of Pseudomonas corrugata. Nearly 3,000 transposates were screened for antimicrobial activity and for pathogenicity in tomato plants. Of these, four transposed isolates were not pathogenic in tomatoes in preliminary (single plant) and confirmative (multiple plants) inoculations. These four isolates were identical to the wild-type parent in antibacterial and antifungal activity. Other mutant phenotypes observed were those that lost antibacterial activity, antifungal activity, or both. In these later mutants, pathogenicity was maintained.

Economic Analysis

Material and labor cost for production of the bacterial inoculum costs approximately $1.50 per pound. One pound of inoculum will treat 4 cwt of seed potato. An average increase of 50 sacks per acre was obtained. If the average price for a cwt is $4.50, then the average gain/acre would be $225. This would be about a ten-fold return on treatment costs.

Potential Benefits

Treatment with the dry formulation of Pseudomonas corrugata was readily adapted with no impact on grower handling. The bacterium was applied as one would apply any powder based fungicide. Results have also indicated that cut seed potato can be treated months in advance of planting. Since the treatment is with a bacterium, there is no introduction of chemical fungicides into the environment. Thus, the treatment addresses the need expressed by the Food Quality and Safety Act of 1996.

Farmer Adoption and Direct Impact

Other growers in the area were impressed with the progress of the treated field. They were amazed with the exhibited plant vigor and yield increases and wanted to find out what “magic” material was used to obtain these results. The cooperating grower wanted 2,000 pounds of inoculum for the 1998 growing season. We were unable to comply with this request as our resources are limited.

Producer Involvement

There were various visits by growers and chemical company field agents but no documentation was provided by the grower.

This summary was prepared by the project coordinator for the 1998 reporting cycle.