The fungicidal and phytotoxic properties of benomyl and PPM in supplemented agar media supporting transgenic arabidopsis plants for a Space Shuttle flight experiment

Fungal contamination is a significant problem in the use of sucrose-enriche d agar-based media for plant culture, especially in closed habitats such as the Space Shuttle. While a variety of fungicides are commercially availabl e, not all are equal in their effectiveness in inhibiting fungal contaminat ion, In addition. fungicide effectiveness must be weighed against its phyto toxicity and in this case. its influence on transgene expression. In a seri es of experiments designed to optimize media composition for a recent shutt le mission, the fungicide benomyl and the biocide "Plant Preservative Mixtu re" (PPM) were evaluated for effectiveness in controlling three common fung al contaminants, as well as their impact on the growth and development of a rabidopsis seedlings. Benomyl proved to be an effective inhibitor of all th ree contaminants in concentrations as low as 2 ppm (parts per million) with in the agar medium, and no evidence of phytotoxicity was observed until con centrations exceeded 20 ppm. The biocide mix PPM was effective as a fungici de only at concentrations that had deleterious effects on arabidopsis seedl ings. As a result of these findings, a concentration of 3 ppm benomyl was u sed in the media for experiment PGIM-01 which flew on shuttle Columbia miss ion STS-93 in July 1999.