The assessment of non-pathogenic related effects of the seed treatment Stamina on germinating maize under cold stress
Maize is an important crop grown in the Midwest. Low temperatures in this region can cause irreversible damage to maize, limiting stand establishment and ultimately affecting yield. Fungal contamination also contributes to poor stand establishment, affecting yield. A new seed treatment fungicide for maize (Stamina) has shown positive effects on maize plants under cold stress, not related to protection against fungi. The goal of this project was to determine whether the seed treatment Stamina protects maize seedlings from cold stress or freezing injury by enhancing superoxide dismutase (SOD) activity in maize seedlings. In this study, three seed treatments (Stamina and a binding agent, binding agent only, and no treatment) were used for each of three seed lots. Seeds were planted and grown at 10°C for seven days, followed by four days at 25°C. At the end of the four days at 25°C, seedlings were moved back to 10°C for ten days to provide additional stress. Seedling height, dry weight, and SOD were measured at the end of the 25°C treatment (Point A), as well as at the end of the second stress (Point B). Freeze injury was measured at Point B at three temperatures: -1.0°C, -1.5°C, and -2.0°C. Stamina treated seedlings were taller and contained greater SOD activity at Point A, compared to seedlings treated with binders or no treatment. Stamina treated seedlings were taller and heavier than seedlings treated with binders or no treatment at Point B, but no differences in SOD activity were found. The effects of temperature, seed lot, and treatment were variable over all levels in the freezing assay. Variability in injury was most evident at -1.5°C. These results indicate Stamina provides protection against oxidative stress at Point A, evidenced by increased SOD activity. This leads to greater performance in seedling height. Mean relative growth rate measurements indicate Stamina is providing some level of protection against the chilling stress at Point B, as Stamina treated seedlings are both taller and heavier, even though SOD activity is not enhanced. It is difficult to assess the effectiveness of Stamina on freeze injury due to inconsistencies in freeze injury on seedlings treated with binders. Seed lot differences were important across all aspects of the study, having an effect on seedling height, dry weight, SOD activity and freeze injury.