|Vavrina, C. S.|
|Roberts, P. D.|
|Ontermaa, E. O.|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2003
Publication Date: 1/1/2004
Citation: Vavrina, C., Roberts, P., Burelle, N.K., Ontermaa, E. 2004. Greenhouse Screening of Commercial Products Marketed as Systemic Resistance and Plant Growth Promotion Inducers. HortScience. 39(2):433-437. Interpretive Summary: Research objectives were to evaluate the effects of commercially available products claiming systemic resistance (SR) properties on tomato transplants, and to define the range of capabilities of these SR products in reducing damage by foliar and soilborne pathogens. This information could facilitate strategies for the integration of these products into production systems, and assist vegetable growers by providing objective evaluation of their efficacy in reducing disease. Materials with varied mechanisms of SR activation, including biologically based products (fungi and bacteria), pathogenesis-related proteins, organic amendments, chemical elicitors, nutritional supplements, and plant growth regulators, were evaluated to determine if they elicited the same plant growth and disease suppression responses under similar circumstances. Results indicated that the plant growth promotion (PGP) and SR effects on tomato transplants and young seedlings are material specific and may be dependent on physiological age of the plant at treatment application. Interactions between PGP and SR effects implied a significant response relationship between the acquired disease resistance and plant growth that was illustrated by a reduction of plant growth with strong SR activation. Application timing and plant sensitivity to the SR stimulus are important to the end user. A better understanding of these factors has the potential to markedly improve the consistency of treatment responses with these materials.
Technical Abstract: Six greenhouse trials of five commercial products marketed as systemic resistance (SR) and plant growth promotion (PGP) inducers were evaluated on tomato over a 21 month time period. The effect of the inducers on treated plants was measured by monitoring plant growth and disease suppression after inoculation with either plant pathogenic bacteria or nematodes. The commercially available SR/PGP inducers included a bacterial suspension [Companion (Bacillus subtilis GB03)], two plant defense elicitors with nutrients [Keyplex 350DP plus Nutri-Phite, and Rezist with Cab'y], natural plant extracts [Liquid Seaweed Concentrate and Stimplex] and a synthetic growth regulator [Actigard 50W]. Growth enhancement was noted in some trials, but the aspect of growth affected often varied with trial. Response to Actigard treatment included significant suppression of bacterial spot (Xanthomonas campestris pv. vesicatoria [Xcv]) in five of the six trials and a combined PGP and SR response that suppressed both disease and nematode damage with Keyplex 350DP plus Nutri-Phite combined treatment. Companion, Keyplex 350DP plus Nutri-Phite and Seaweed products induced only partial disease suppression of bacterial spot in inoculated tomato plants. The alpha keto acids plus nutrients (Keyplex 350DP plus Nutri-Phite) increased plant growth by 14.3% and improved root condition compared to the UTC following exposure to nematodes. Results are encouraging if not consistent and with a greater understanding of the SR system and the conditions related to product efficacy such materials may becomes effective tools for production agriculture.