Sorghum (Sorghum bicolor (L.) Moench.) seeds were treated with thiram and subjected to accelerated ageing for six days. The seed quality was assessed based on germination, mould count and other biochemical parameters. The seeds treated with thiram showed a higher percentage germination when compared to that of untreated seeds from the accelerated ageing regime. The mould counts were less in thiram-treated seeds up to four days of accelerated ageing. The thiram content decreased significantly after four days of ageing. The ergosterol and free fatty acid contents increased sharply in thiram treated seeds after four days of ageing. The treated seeds showed higher formazan content after six days of accelerated ageing which was comparable with that of untreated seeds aged for four days. The lipoxygenase activity at the end of six days of accelerated ageing was higher in thiram-treated seeds when compared with that of the untreated seeds. The various seed quality parameters analysed indicated that thiram treatment could delay the seed deterioration process under adverse storage conditions.

Moulding and mycotoxin production have been studied during storage of rice at 85 and 90% relative humidity (r.h.) following treatment with cinnamon and clove oils. The clove oil-treated rice was artificially inoculated with Aspergillus flavus. Aflatoxin B1 and ochratoxin A were determined by monoclonal antibody-based enzyme-linked immunosorbent assay. Both moulding and mycotoxin were inhibited by 9 μl cinnamon oil g−1 but, with smaller doses, fungi could be isolated during the early part of storage, but not subsequently. Thus, following treatment with 3 or 6 μl cinnamon oil g−1, fungi were isolated from direct plated grains after 30 days but not after 45 days. Fungi were also isolated from washings of grain up to 30 days after treatment with 3 or 6 μl g−1, although fewer than from untreated grain. Propagules could also be detected up to 15 days after treatment with 9 μl g−1. Clove oil was much less effective than cinnamon oil in preventing moulding. After treatment with 8 μl g−1, the proportion of seeds infected with fungi and numbers of propagules in washings decreased only after 60 days' storage and with 4 μ g−1 after 90 days at both relative humidities. However, aflatoxin contamination could not be detected 90, 60 and 60 days after treatment with, respectively, 2, 4 and 8 μl g−1 at 85% r.h., although ochratoxin A was present in all treatments. At 90% r.h. aflatoxin was absent only after 90 days from treatment with 4 and 8 μl g−1. No T2 toxin was detected.

Fungal colonization and mycotoxin contamination of developing rice grains of two cultivars (IR-20 and Gowrisanna) were studied during the 1990 and 1991 crop seasons. Field and storage fungi invaded florets while they were still concealed within the boot leaf. Field fungi were most numerous from GS 65 to 77 and then decreased towards GS 91 (fully ripe). Storage fungi also decreased towards harvest. Aflatoxin B1 was detected at early growth stages but then decreased with decreasing water content. T-2 toxin increased steadily during grain development, and at harvest there was up to 210 ng toxin g-1 grain. Ochratoxin A was not detected until harvest, The incidence of toxigenic A. flavus isolates in fields of the two cultivars differed slightly, but their growth and toxin-producing ability differed greatly between seasons. A. flavus isolates collected during the 1991 crop season produced 26000 ng aflatoxin B1 ml-1 medium, much more than was produced by isolates collected during the 1990 crop season.

Aflatoxin B1 production by Aspergillus flavus was studied in yeast extract sucrose broth in the presence of cinnamon, clove, almond and cardamom oils. Growth and aflatoxin B1 production was inhibited by 0.5 mul cinnamon oil ml-1 medium and by 1 mul clove oil ml-1. Almond and cardamom oils only affected growth when their concentration exceeded 1.25 mul ml-1 medium. Aflatoxin B1 production was stimulated by 0.75 and 1 mul almond oil ml-1 medium or by 0.25 and 0.5 mul cardamom oil ml-1.