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The Soybean Phytoalexin, Hydroxyphaseollin, Induced by Fungicides. J. J. Reilly, Graduate Research Assistant, Department of Botany, University of Maryland, College Park 20742; W. L. Klarman, Associate Professor, Department of Botany, University of Maryland, College Park 20742. Phytopathology 62:1113-1115. Accepted for publication 3 April 1972. DOI: 10.1094/Phyto-62-1113.

Hypocotyls of soybeans incubated in suspensions of various fungicides contained the soybean phytoalexin, hydroxyphaseollin (HP). Fifteen of the 27 compounds tested induced detectable quantities of HP. The amounts of HP induced by eight of these compounds were quantitated. Suspensions of maneb (1 mmole/liter) induced the most HP (22 µg HP/g fresh wt of tissue), and maximal production occurred after 48-hr incubation. Two decomposition products of maneb, ethylenediamine and polyethylene (thiocarbamoyl) monosulfide, also induced HP. Butylamine, the nonfungitoxic portion of the fungicide benomyl, induced HP as effectively as did benomyl. The fungitoxic portion, benzimidazole carbamic acid, methyl ester, did not induce HP.