Abstract
Pre-inoculation of soybean seeds with Bradyrhizobium spp. associated with polymers could be an alternative to the conventional inoculation performed at the day of sowing. The objectives of this study were i) to determine whether the HiCoat® technology (peat inoculant + liquid inoculant + polymer) allows the survival of B. elkanii after storage of the inoculated seeds, and ii) to evaluate whether the pre-inoculation and seed treatment reduces the physiological quality of seed and soybean yield. Soybean seeds were treated with different fungicides and insecticides associated with pre-inoculation using HiCoat® and the seeds were stored at room temperature. The survival of B. elkanii was reduced over time with standard inoculation, however there was above 2 x 106 colony-forming units of B. elkanii per seed at 60 days after inoculation with HiCoat®. Seed germination, number of nodules per plant, mass of nodules, yield, number of grains per plant and number of pods per plants were not significantly affected by the pre-inoculation and seed treatments. Our findings indicated that the fungicide and insecticide associated with HiCoat® can be used to treat and to pre-inoculate seeds that can be stored for up to 71 days without compromising the nodulation of plants and soybean yield. Key words: Industrial seed treatment, biological nitrogen fixation, storage period, fungicide, insecticide, polymer, HiCoat, Glycine max.
Highlights
Inoculation of nitrogen-fixing bacteria of the Bradyrhizobium genus in soybean is a common practice in Brazil (Alves et al, 2003; Zilli et al, 2010)
Since little is known about the use of a new technology (HiCoat®) developed with the aim of enabling pre-inoculation of soybean seeds treated with fungicides and insecticides, the objectives of this study were i) to determine whether the HiCoat® technology allows the survival of B. elkanii after storage of the inoculated seeds; and ii) to evaluate whether the pre-inoculation and seed treatment with fungicides and insecticides reduces the physiological quality of seed and soybean yield
The number of colony-forming units (CFU) recovered from soybean seeds was significantly affected by seed packing, seed treatment, storage period and all the interactions (Table 2)
Summary
Inoculation of nitrogen-fixing bacteria of the Bradyrhizobium genus in soybean is a common practice in Brazil (Alves et al, 2003; Zilli et al, 2010). These bacteria are capable of fixing atmospheric nitrogen and provide it to the plant in exchange for photoassimilates (Bergersen, 1997; Fagan et al, 2007). Seed treatment with insecticides and fungicides has often been performed to protect the seeds from pests, seed-borne and soil-borne pathogens (Goulart 1998), but the toxicity of these products has been considered a risk to people who manipulate the treated seeds as well as for the bacteria inoculated on the seeds with the purpose of fixing nitrogen. New technologies need to be explored with the aim of overcoming these challenges
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