The scab disease or Fusarium head blight causes a serious damage to the barley and the wheat in humid regions. However evaluating the resistance of the host plants to the scab disease is not easy, because the epidemic of the disease is largely influenced by such environmental conditions as temperature and humidity during the infection time, and the sensitivity of the host changes with developmental stage; it is most sensitive at the time of flowering. For testing the resistance of the host plants under a controlled condition, the author has developed 'cut-spike' inoculation method: At the time of flowering, spikes are taken off from the plants at the second internodes, arranged in pans with overflowing water and are inoculated with spore suspension. Spikes are kept at 25°C and at 100% humidity for two days after inoculation, and then transferred to a growth chamber where the temperature and humidity are controlled at 23∼13°C (with a sine curve) and about 95%, respectively. Illumi-nation is about 10, 000 lux during 14 hours a day. Eight days after inoculation the percentage of infected spikelets is recorded. About 5, 000 barley varieties were evaluated for seeking the resistant germplasm, and 23 highly resistant two-rowed varieties were found (Takeda and Heta). In the wheat there were three groups of resistant germplasm; winter wheat from Eastern Europe, spring wheat from China/Japan, and spring wheat from Brazil (Snijders) Scab disease resistance in barley (Takeda) and in wheat (Snijders, ) were under the control of predominantly additive minor genes. In barley heritability of the resistance was ca. 0.6 in a broad sense and was 0.4 in a narrow sense, respectively. Race differentiation due to the gene-for-gene interaction was not remarkable in barley (Takeda and Kanatani) and in wheat (Mesterhazy; Snijders and Eeuwijk). A mycotoxin, deoxynivalenol, had no relation with pathogenicity but it did with aggressiveness of the isolates (Snijders). Mutation for fungicide tolerance in Fusarium isolates developed frequently, and was easily selected by the fungicide. Therefore scab disease must be controlled by growing resistant varieties but not by the fungicides.
From the investigation of the indole metabolites of six strains of Penicillium crustosum isolated from foods in Tokyo in 1983-1984, it was clear that the tested strains were divided into two chemotypes based on mycotoxin profile: chemotyp I (the strains I-27, I-31, I-32) produced penitrems as main metabolites, whereas clavine alkaloids (f umigaclavine A, pyro-clavine, and festuclavine) were obtained from chemotype II (the strains I-28, I-29, I-30). Roquefortine C, cyclopenin, and viridicatin were the common components obtained from both chemotypes.
For a rapid screening of the aflatoxin (AF) productivity of Aspergillus flavus and related species, a competitive enzyme-linked immunosorbent assay (ELISA) using AF-specific monoclonal antibody was applied. The monoclonal antibody used was cross-reactive with AFB1 and AFG1, and showed very weak cross-reactivity with AFB2 and AFG2. The sensitivity of the assay allowed detection of 1-100 nM AFB1 and AFG1. The assay was examined to compare AF production of A. flavus and A. parasiticus strains in culture using two different liquid media, SL and YES. A total of 71 strains isolated from agricultural commodities and soils were tested. Among these, 53 strains (75%) were found to produce AFs in SL medium, while only 28 strains (39%) produced them in YES medium. These results suggest that the use of competitive ELISA detecting AFs in SL medium is applicable to the screening of large numbers of small-scale cultures.
Menadion-catalyzed hydrogen peroxide production by viable cells was proportional to viable cell number. The amount of hydrogen peroxide was measured with a chemiluminescent assay. This assay was applied as a toxicological examination for Fusarium mycotoxins. The usefulness of this assay was compared with those with the neutral red inclusion and 3-(4, 5-dimethylthyazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) reduction assays. Chemiluminescence assay was superior in speed and sensitivity to detect cytotoxicity. Intensity of cytotoxicity to HuH-6KK cell observed was in order of f usarenon-X, deoxynivalenol and nivalenol. To PC-3 and NIH3 T 3 cells, these mycotoxins showed almost the same toxicity as to HuH-6KK cell.
Seeds of Job's tears (Coix lachryrna jobi var. ma-yuen) are commonly used as herbal drug and health food in Japan, but mycotoxin contamination such as aflatoxin and zearalenone (ZEN) on Job's tears products is often problematic. Thus, a mycological examination on 35 samples of raw seed materials and commercial products of Job's tears was carried out. Aspergillus flavus, Curvularia spp., Bipolaris coicis, Fusarium pallidoroseum (=F. semitecturn), F. equiseti and F. moniliforme were detected as predominant fungi in the samples. Of the Fusarium species isolated, F. pallidoroseurn was most dominant. ZEN producing ability of these Fusariunn isolates on seeds of Job's tears in cultures was measured by HPLC analysis. The isolates of F. pallidoroseum, F. equiseti and F. moniliforme produced ZEN, with maximum yields of 55, 244 ng/g, 137 ng/g and 54 ng/g, respectively. Among tested 12 samples of the commercial Job's tears products, ZEN contamination was found in 3 hulled seeds (21; 25; and 44 ng/g), 2 crucked products (6; 29 ng/g) and 3 powdery products (23; 46 and 116 ng/g).
The effects of the elimination of fungi and mycotoxins in imported green coffee beans were examined. Each sample was divided into 3 types (22 samples each) ; 1) green coffee beans before handpicking, 2) good beans after handpicking, 3) bad beans after handpicking. All the samples were tested for both fungi and contaminations of ochratoxin-A (OCT-A). OCT-A was detected in 11 out of 22 bad samples (50%, x=6.14 ppb, range 0.08-72.7 ppb), in 7 out of 22 good samples (32%, x=0.49 ppb, range 0.08-7.67 ppb), and in 9 out of 22 samples before handpicking (41%, . x=0.79 ppb, range 0.16-7.20 ppb), respectively. Levels of OCT-A and numbers of fungi in green coffee beans were decreased by the handpicking method.
Chinese corn samples (86 samples) collected from Henan, Liaoning and Jilin Provinces were analyzed for Fusariuin mycotoxins such as fumonisins (FM), trichothecenes (TRIO) and zearalenone (ZEA). Henan samples were from Linxian and Shangqiu Counties, high-and lowrisk areas, respectively, for human esophageal cancer. The incidences of contaminated samples were 50% for FM, 58% for TRIC (principally deoxynivalenol and its 15-acetate), and 27% for ZEA, The FM level in Chinese corns was generally higher than that of TRIC. As for the mycotoxin occurrence in Linxian corns, all samples were contaminated with TRIC at a mean level of 781 ng/g, The incidence of Linxian corns contaminated with FM was about twice higher than that of Shangqiu, but was not higher than those of other Provinces. It was noted that Linxian corns were frequently co-contaminated with FM and TRIC.