Soil fungal population in preharvest maize ecosystem in Río Cuarto, Argentina

NESCI, A.; BARROS, G; ETCHEVERRY, M.

Guarajá, Brasil

Congreso; X International IUPAC Symposium. Mycotoxins and Phycotoxins.; 2000

Instituto Adolfo Lutz

Progress on control has been hampered by a lack of knowledge of where Aspergillus Section Flavi and Fusarium Section Liseola exist in the maize agroecosystem and of the cultural and environmetal conditions hath influence population dynamics. To understand the conditions that might result in mycotoxigenic population increase in the soil in the maize agroecosystem, we studied during the preharvest season 1998/1999 in an experimental trial the distribution of the fungus in soil. The effect of different tillage practices was evaluated. The samples were collected from six tillage treatments: conventional tillage, reduced tillage and no tillage, with and without grazing. Treatments were randomized in a complete block design with four replicates of each treatment. The  most frequent genera isolated were Aspergillus (3.4 x 104 cfu/g), Fusarium (1.6 x 104 cfu/g), Penicillium (3.6 x 104 cfu/g), Trichoderma (5.8 x 105 cfu/g), Cladosporium (3.5 x 104 cfu/g), Alternaria (1 x 103 cfu/g). The species identified from genus Aspergillus were A. flavus, A. restricturs, A. candidus. The species from genus Penicillium were P. pinophylum, P. citreonigrum, P. implicatum, P. purpurogenum, P. mineoluteum, P. waksmanii, P. restrictum, P. rugulosum. From genus Fusarium, F. moniliforme, F. oxysporum, F. nygamai were found. There was no significant difference between treatments. Tillage practices had little impact on soilborne populations. The data showed that the pathogens were present at low levels compared with levels encountered in epidemic years in other countries. More studies will be carried out to know the different factors in the maize ecosystem that have influence on the mycotoxigenic fungi.