Industrial processes of treated corn seeds for maintenance of physiological quality and their impact on storage

Abstract

The seed treatment is an important technique used in corn crops as it provides protection to seeds and seedlings. However, there have been reports of phytotoxicity caused by insecticides in seedlings, mainly stored, which promotes interest in research to provide information for the production sector, from the seed production to the processes and products used for phytosanitary treatments. Thus, three studies were carried out with the objectives of 1) assess different operational processes for corn seed treatment in terms of seed physiological and treatment functional quality during storage; 2) evaluating physiological and morphoanatomical traits in different seed treated with neonicotinoid insecticides and stored, that contributes to the maintenance vigor and storage potential.; and 3) to characterize how improvements in the last 50 years of agronomic traits associated with the quality, technology, and genetics of corn seeds reported in the Ohio Corn Performance Test (OCPT) were relevant to increasing corn yield. The treatment processes and the arrangement of the active ingredients with the seeds affected the maintenance of the treated corn seeds quality. The use of the fungicide plus polymer (FP) in the first stage aid to maintain vigor and mitigate phytotoxicity in the seeds and seedlings, especially during 12 months of storage. In these lines, the stratified process of FP/Insecticide/Dry powder is indicated for favoring the maintenance of vigor for up to 12 months of storage, being similar to the FP treatment. Functional quality of treatment dust release, plantability and coating is not an impediment to the use of industrial seed treatment processes with component stratification. Seed lots not treated with neonicotinoid insecticides showed superior performance compared to treated and stored lots. The active ingredients imidacloprid + thiodicarb and thiamethoxam showed a greater phytotoxic effect, greater negative impact on germination and vigor, especially in the sensitive and low initial vigor genotypes. The initial seed lot vigor affects tolerance to neonicotinoid insecticide treatment and storage. The corn genotypes vary in their tolerance to neonicotinoid seed treatment and storage. There is relationship between ultrastructural analyses, such as greater pericarp thickness and starch granule size, with a trend toward greater vigor and storage tolerance of insecticide-treated seeds. Over the past 50 years, the OCPT an increase of 10.3% (or 0.66% year-1

) in seedling

emergence and an increase of 66% or 34 thousand plants ha-1

(equivalent to 694 plants year-1 ) in final stand population, with positive correlations r= 0.64 and r= 0.82, both variables with yield, in addition to the evolution of the number of transgenic events, phytosanitary products for seeds and planting technologies, contributed to an 84.7% increase in grain yield, from 7.91 Mg ha-1 in 1972 to 14.6 Mg ha-1

in 2021 provided by synergistic responses to new genotypes,

technologies, seeds and management practices.