Aflatoxins effect on fungal populations of soil, root and leaf surface of peanut plants in the field with special reference to aflatoxins biodegradation.

摘要

The research aimed to study the role of aflatoxins contaminated peanut seeds (4, 8, 16 and 32 micro g g-1 seeds) on fungal populations of soil, rhizosphere, rhizoplane, phyllosphere and phylloplane of cultivated peanut plants for 15, 30, 60 and 120 days in the field, with special reference to aflatoxins biodegradation in soil. Mycological survey revealed that the total fungal count of soil (692.9 colonies mg-1 dry soil) was high compared with that of rhizosphere (602.9 colonies mg-1 fresh root system) and phyllosphere (103.12 colonies mg-1 fresh shoot system) based on dilution-plate method. As well as, phylloplane total fungal count (472 colonies/10 shoot segments) was rich than that of rhizoplane (288 colonies/10 root segments) based on plating-method. A total of 67 species in addition to two varieties belonging to 26 fungal genera were isolated and identified from soil (28 species of 12 genera), rhizosphere (43+1 variety of 16), phyllosphere (49+1 variety of 18), rhizoplane (15 of 10) and phylloplane (29 of 14) of peanut plants investigated (control and treated samples) on dextrose-Czapek's agar medium at 28+or-2 degrees C. Treatment of peanut seeds with different doses of aflatoxin before planting resulted in a clear effect on total fungal count of both of rhizosphere and soil, while there was no clear effect on total fungal count of rhizoplane, phyllosphere and phylloplane after different cultivation periods. The rate of aflatoxin biodegradation was dose and time dependent, that after 3 days was 40, 70, 81.9 and 89.5% at (4, 8, 16 and 32 micro g g-1 seeds), while after 7 days was 70, 81.3, 85.6 and 92.5%, respectively, whereas, after 15 days, no mycotoxin could be detected in the lowest dose (4 micro g g-1) and traces in the other remaining doses. After 30 days, completely disappearance of toxin was recorded at the different treatment doses.