BIOSECURITY FOR REDUCING OCHRATOXIN A PRODUCTIVITY AND THEIR IMPACT ON GERMINATION AND ULTRASTRUCTURES OF GERMINATED WHEAT GRAINS

摘要

Ochratoxin A (OTA) is a secondary metabolite of some fungi that causes very serious problems for plants, animals and humans. Various microorganisms such as bacteria and microscopic fungi have been tested for their abilities to prevent ochratoxin A contamination or detoxify foods. In this study, Saccharomyces cerevisiae and Lactobacillus bulgaricus reduced OTA production by Aspergillus ochraceus to 40.88 μg/ml ( productivity 60.69% ) and 13.80 μg/ml (productivity 20.48% ) respectively compared with the control (67.35 μg/ml) (productivity 100%). The results clearly indicated that the seed germinibility in the presence of OTA was decreased with increasing concentration, whereas the germinibility was uncompletely ceased at high concentration (67.35 μg/ml) of OTA. The maximum amount of germination was observed in control (without OTA treatment) and at low concentration (13.80 μg/ml) within 4 days. Antioxidant enzymes catalase and peroxidase decreased in germinated grains treated with OTA. Catalase was 18.12 U/ml in grains treated with low concentration (13.80 μg/ml) of OTA while at high concentration (67.35 μg/ml), it was 12.23 U/ml compared with the control (20.33 U/ml). On the other hand, peroxidase decreased only in germinated grains treated with high concentration of OTA. The ultrastructural studies indicate that there were dramatic differences between the cells of root system of wheat seedlings of grains treated and untreated with the OTA. Cell ultrastructures of treated grains with OTA showed that the cytoplasmic membrane collapses away from the cell wall. Plasmodesmata threads were appeared in untreated cells but not formed in treated cells.