Cyclopentanone derivatives, isoterrein (3) and terrein (4), were isolated along with nortryptoquivalone (1) and aszonalenin (2) from Neosartorya fischeri IFM52672. Isoterrein (3) was identified with the synthetic one by the analysis of the spectroscopic investigation and the first example of the isolation from natural source.
In the screening for new antifungal substances against pathogenic filamentous fungi and yeasts, a naturally new compound, 2,4-dihydroxy-3-methylacetophenone (2), was isolated along with tryptoquivaline I (1) from the methylene chloride-methanol (1:1) extract of Aspergillus fumigatus IFM 54246, obtained from a Brasilian soil, screened by possessing the antifungal activity against Aspergillus fumigatus, Aspergillus niger, Candida albicans and Cryptococcus neoformans. The structure of 2 was determined from the analysis of the spectroscopic investigation. Compound 2 showed the broad antifungal activity against A. fumigatus, A. niger, C. albicans, and C. neoformans, whereas tryptoquivaline I (1) showed the inhibition only against A. fumigatus. The main antifungal substance in the extract of the A. fumigatus strain was considered to be compound 2.
Fusarium head blight (FHB) or scab is one of the most serious disease for the wheat production in Hokkaido, the northern most part of Japan. Wheat production in Hokkaido accounts for about 60% of domestic wheat in Japan and yield losses resulting from rain damage, pre-harvest sprouting and FHB, are estimated at 10–20% of total production. Since some Fusarium produce mycotoxins, the government applied guideline levels of 1.1 mg/kg for DON in raw cereals for human consumption and feed material, 1.0 mg/kg in feed for various animal species and 4.0 mg/kg for cattle older than 3 months in 2002. Unlike Honshu district, there is no rainy season, humidity is usually low in the grain filling season except near the seashore or the river in Hokkaido. But it has become more frequent for wheats to be exposed to continuous rain during the maturing stage and the resistance to FHB of Hokkaido varieties is moderate to weak, not sufficient to avoid a contamination with DON. Selection and evaluation of FHB resistance are conducted by several methods, such as inoculation of a suspension of Fusarium spores onto wheat heads or inoculation by oat cultures with mist irrigation and a single floret injection method. Developing resistance lines, we also use Asian materials, such as Sumai 3, Japanese landrace and breeding materials developed at Kyushu agricultural research center, Brazilian varieties and European materials. Every materials have many inferior characters for Hokkaido conditions. Low yield potential, long culm, low qualities, susceptiveness to cold, snow molds and pre-harvest sprouting. Breeders and pathologists are actively screening and developing good resistance varieties and genetic material with excellent resistance to FHB. And DON accumulation of these material are low. The yield potential of these breeding lines are lower than‘Hokushin’, a leading variety in Hokkaido and they are still inferior in some traits, snow molds resistance, culm strength and quality. The improvement of these traits is being investigated.
Fusarium head blight (FHB) and deoxynivalenol (DON) contamination have been great concern in wheat production in Hokkaido since a guideline level for DON was established. Chemical control is one of the effective measures to reduce FHB and DON levels. We recommend following five fungicides: tebuconazole, propiconazole, kresoxim-methyl, iminoctadine-acetate, and thiofanate-methyl. These fungicides reduce both FHB and DON levels. As the timing of fungicide application is decisive to reduce FHB level, the first application should be started at beginning of flowering. The frequency of fungicide application is also important especially for DON control. Three and four applications at one-week intervals are recommended for winter wheat and spring wheat, respectively. These recommendations have so far been approved by wheat growers and reduced both FHB and DON levels practically. However, wheat grower's demand for reducing application frequency is increasing. Further investigations are required to establish the control by fewer fungicide applications.
Deoxinivalenol(DON) concentration ratio in wheat is likely to increase during the storage stage of so called 2stage-drying. The risk of DON -increase seems to be without reference to kernel moisture content (14-18% w.b.). The increase occurred remarkably in high level of initial DON concentration over 2mg/kg. Rapid drying can prevent increase of DON concentration. DON contaminated grain can be removed by some physical treatments. Sizer, gravity separator and optical (near-infrared light) sorter can reduce the concentration of DON effectively. In gravity separation, the DON concentration of samples (pre-separation, accepted and rejected) are in inverse proportion to its volume weight. So the target DON concentration by gravity processing can roughly be estimated from volume weight of accepted sample.
In May 2002, the provisional standard value of deoxynivalenol (DON) in wheat was decided at 1.1mg/kg by Ministry of Health, Labor and Welfare in Japan. Marketing of wheat with more than 1.1mg/kg was prohibited as unsafe for human consumption. As Hokkaido is a major area of wheat production in Japan, this decision became the most important problem for farmers. To solve this problem, we have been conducting many trials. After the DON standard was set in May 2002, we immediately established a system to check DON levels in each lot of products going to market. In 2003, we proved the efficiency of the ELISA system and shared this system to other Agricultural Co-operatives. As a result, checking the product's DON concentration is possible during acceptance from farmers and/or during regulation; for example, sieving, blending, etc. In addition, many techniques have been developed by Hokkaido prefecture agricultural experimental stations, such as: 1 - Selection of varieties displaying low DON accumulation; 2 - Developing effective sorting systems by combining sieving and gravity separation; and 3 - Effective combination of chemicals during ripeness. Currently, these techniques have been used in many farmers and Agricultural Co-operatives to supply a safe wheat product to consumers. In this report, we summarize our activities, especially the construction of the system to verify DON concentration.