Congelamento, resfriamento e conservação de sementes de abóbora (Cucurbita moschata Dusch), feijão vagem (Phaseolus vulgaris L.) e milho (Zea mays L.) obtidas de manejo biodinâmico

Abstract

The objective of this paper was to evaluate the effects of freezing and cooling on the physiological quality and storage of pumpkin seeds (Cucurbita moschata Dusch), green beans (Phaseolus vulgaris L.) and maize (Zea mays L.) produced in biodynamic systems. The seeds were frozen at -18ºC and cooled to 15ºC for two periods (36 hours and 7 days) using two types of packaging (PET bottles and special plastic vacuum bags). These seeds were evaluated initially and after the treatments for vigor, germination percentage and sanity. After the treatments the seeds were stored under ambient conditions and in a cold room. Vigor and germination were evaluated every 45 days for six months and in the sixth month the sanity test was performed. For pumpkin seeds, treatment combining the exposure time of 36 hours at -18ºC in PET packaging did not alter the physiological quality and percentage of fungi in the seeds. When submitted to -18ºC for 7 days in vacuum packaging the lowest averages were found. During storage for six months, germination and first germination count resulted in higher averages when stored under refrigeration, and seedling length averages were statistically the same regardless of storage location. Time caused a reduction in seed viability and the reduction of the genera Aspergillus and Penicillium in pumpkin seeds. For green bean seeds, treatment combining the 7-day exposure time at -18°C and PET packaging did not alter the physiological quality of the seeds and fungus contamination. The lowest averages were obtained by combining the time of 36 hours, the vacuum packing and the temperature of -18°C. The storage site was not significant, while the time was relevant for the first germination test count, reducing viability. There was a reduction of the genus Penicillium in green bean seeds after 180 days of storage in both environments. For corn seeds, the highest percentages of germination were observed in the treatment combining the time of 36 hours at 15ºC and the PET package, while for the seedling length and first count of the germination test, the exposure time of 7 days at -18ºC provided higher averages in both packages. In the sanitary evaluation of this treatment using PET packaging, there was a significant increase in contamination by the genus Fusarium. The lowest percentages of germination were obtained in the treatment combining the time of 7 days at -18ºC and the vacuum packaging. For seedling length and first count of germination test the time of 36 hours and vacuum packaging, regardless of temperature, provided the lowest averages. The storage site was not significant, while the time was relevant for all maize seed evaluations, reducing viability. In the sixth month an increase of the genus Penicillium was observed in the seeds stored in refrigeration. The results of this experiment suggest that the freezing of seeds at -18ºC in PET packages, with different exposure times that will vary according to each species, may promote an increase in seed vigor and possible maintenance of viability and sanity during storage