Plant growth promoting substances, either from biological or chemical origin, are widely used in modern agriculture. In this context, this study evaluated the physiological quality of maize seed treated with thiamethoxam and inoculated with Azospirillum brasilense. Initially, we tested bacterial growth on medium with increasing concentrations of thiamethoxam. We also evaluated the physiological quality of seeds through morphometric measurements, emergence speed index and chlorophyll content by SPAD through a 2x3 factorial arrangement with seed inoculation with A. brasilense (100 mL per 25 kg of seed) and three doses of thiamethoxam (0, 80 and 120 ml per 60,000 seeds). Bacterial population showed a linear reduction according to increasing doses of thiamethoxam. The dose of 120 ml thiamethoxam (42 mg active ingredient) caused a decrease in several variables, while, the inoculation proved a positive activity in seedlings physiological quality. Thus, the inoculation combined with 80 ml thiamethoxam (28 mg active ingredient) show synergistic action in early development in maize seedlings.
Key words: Thiamethoxam, inoculant, plant growth promoting bacteria.
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