Methods of post-harvest treatment of maize hybrids and their effect on the seed quality during long-term storage

Topicality. The seed stock creation and storage is a prerequisite in seed production of maize hybrids in order to provide sowing material in case of various adverse conditions (crop failure, natural disaster, etc.). Depending on the usage and the storage term, there are the insurance, reserve and breeding seed stocks. During storage, the seed germination may reduce; therefore, seed stock should be refreshed with seeds prepared for long-term storage. Issues. In order to prepare seeds for long-term storage, post-harvest processing aimed at forming longevity of hybrid corn seeds should be carried out. Thus, scientific and practical problem is the definition and optimization of technical and technological processes of the preparation of seeds for storage. Aim. To study the features of the formation of maize hybrid seed longevity, to establish methods and factors of post-harvest processing that ensure long-term storage and high seed quality. Materials and methods. In the experiments, we used maize hybrid seeds developed at the State Enterprise Institute of Grain Crops of NAAS. The moisture levels of the harvested seeds were different, and the seeds were processed for further long-term storage. When harvesting moisture is high, post-harvest processing includes different methods of drying, separation by fractional sieve and gravity methods, chemical treatment (seed dressing). Seeds were stored at different moisture content (7–8, 9–11, 12–14 %), in the different packages (paper, fabric, polyethylene), in the dressing and undressing state for 3–4 years. During storage, we have determined the laboratory germination by various methods, field germination, and the unity of sprout emergence. Results. We have established that the formation of longevity and seed quality of maize hybrids depend on features of harvesting and postharvest processing, such as harvest moisture, methods and temperature regimes of drying, sieve and gravity separation with the selection of various seed fractions, terms of chemical seed dressing. It was found that the laboratory seed germination indicator determined by cold test characterizes the economic suitability of maize hybrids for long-term storage. Conclusions. It was established that to obtain the high-quality seeds capable of long-term storage the following is recommended: to dry the cobs at humidity to temperature ratio of 31–36 % to 36–40 °C or 19–30 % to 40–44 °C; to grade seeds by sieving and gravity separator that to obtain two seed fractions, namely conditionally large and medium; to store undressed seed and carry out the dressing stocks immediately before sowing. Under long-term storage of untreated seeds, it is proposed to protect the seed against harmful objects with a combination of abiotic factors as low seed moisture content, cooling, limiting the oxygen access. When the maize hybrid seed with a moisture content of 9–11 % is hermetically packaged, it is guaranteed the storage period of the seed up to 3–5 years, so this method is most practical and cost-effective. It is recommended to determine the suitability of seeds for long-term storage by the germination indicators determined by the cold test. Keywords: maize seeds, germination, factors and processes of postharvest processing, long-term storage.