A potential antagonist, Bacillus amyloliquefaciens strain RC-2, against Colletotrichum dematium, mulberry anthracnose fungus, was obtained from healthy mulberry leaves by in vitro and in vivo screening techniques. Application of culture filtrate of RC-2 inhibited disease on mulberry leaves, indicating that suppression was due to antifungal compounds in the filtrate. Development of mulberry anthracnose on mulberry leaves was inhibited only when the culture filtrate was applied before fungal inoculation, and it was not inhibited by application after inoculation. These results suggest that the antifungal compounds in the filtrate exhibit a preventive effect on the disease. Peptone significantly increased production of the antifungal compounds. The culture filtrate of RC-2 also inhibited the growth of several other phytopathogenic fungi and bacteria, such as Rosellinia necatrix, Pyricularia oryzae, Agrobacterium tumefaciens, and Xanthomonas campestris pv. campestris, in vitro. From the culture filtrate of RC-2, seven kinds of antifungal compounds were isolated by high performance liquid chromatography analysis, and one of the compounds was determined as iturin A2, a cyclic peptide, by nuclear magnetic resonance and fast atom bombardment mass analysis.
Inoculation of Chinese cabbage heads with the bacterium Pseudomonas cichorii induced the production of three major phytoalexins named methoxybrassinin (l), brassinin (2), and cyclobrassinin (3), whose structures have been elucidated on the basis of spectroscopic studies and synthesis.
The isolation and structure elucidation of spirobrassinin, the first phytoalexin of oxindole structure from the daikon Raphanus sativus L. var. hortensis, is described.
The structure elucidation of a new phytoalexin, isolated from diseased mulberry leaves and designated as chalcomoracin, is described. The compound is regarded biogenetically as a Diels–Alder adduct of a chalcone, isolated newly from diseased mulberry shoots, and a substituted 2-phenylbenzofuran.
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