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Physiology and Biochemistry

Determination of Host-Selective Toxin Production During Spore Germination of Alternaria alternata by High-Performance Liquid Chromatography. Noriki Hayashi, Faculty of Agriculture, Nagoya University, Nagoya 464-01, Japan, Present address: Agricultural Chemical Research Laboratories, Sankyo Co. Ltd., Yasu-cho, Shiga 520-23, Japan; Kentaro Tanabe(2), Takashi Tsuge(3), Syoyo Nishimura(4), Keisuke Kohmoto(5), and Hiroshi Otani(6). (2)(3)(4)Faculty of Agriculture, Nagoya University, Nagoya 464-01, Japan, (2)Present address: Central Research Laboratories, Dainippon Ink and Chemicals Inc., Sakura-shi, Chiba 285, Japan; (5)(6)Faculty of Agriculture, Tottori University, Tottori 680, Japan. Phytopathology 80:1088-1091. Accepted for publication 16 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-1088.

The Japanese pear pathotype of Alternaria alternata, which causes black spot disease, produces multiple host-selective toxins (AK-toxins I and II) in culture; the strawberry pathotype, which causes black spot disease, also produces a series of analogous host-selective toxins (AF-toxins I, II, and III). Analysis by high-performance liquid chromatography of toxin production during spore germination showed that virulent isolate A85-10 of the Japanese pear pathotype produced about 0.02 pg of AK-toxin I per spore in the first 6 hr after germination and a trace amount of AK-toxin II after 24 hr. Most of the virulent isolates produced only AK-toxin I during the spore germination. Isolate YM-19 of the strawberry pathotype released about 0.08 pg of AF-toxin I per spore in the initial 6 hr of germination and a small but detectable amount of AF-toxin II, but no detectable AF-toxin III, within 18 hr of incubation. From the point of view of pathological importance of early host-parasite interactions, we propose that AK-toxin I and AF-toxin I, respectively, are the major toxins in yield and biological activity which play a critical role as host recognition factors at primary infection sites in each pathosystem.

Additional keywords: bioassay, Helminthosporium victoriae, victorin.