INFLUENCE OF METHYL-p-HYDROXYBENZOATE, CHLORTETRACYCLINE, AND CERTAIN TRACE METALS ON GERMINATION OF UREDOSPORES OF MELAMPSORA OCCIDENTALS JACKS.

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Abstract
Less than 1% of the uredospores of Melampsora occidentalis Jacks., a poplar rust, germinated on distilled water. However 31% of the spores germinated on a solution of 80 p.p.m. of methyl-p-hydroxybenzoate at the optimal temperature of 15°–16 °C. When cobalt or nickel ions were added, further increases of 4 and 14% germination were obtained. The maximum effect (60% germination) was found with optimum amounts of methyl-p-hydroxybenzoate, nickel salt, and 25 p.p.m. chlortetracycline in combination, although the antibiotic and the heavy metal salt had no effect by themselves. No spore stimulation was found with compounds related to methyl-p-hydroxybenzoate and with other rust species.