Purification and partial characterization of a factor in cotton wax stimulating the germination of self-inhibited wheat stem rust uredospores.

Filter paper, nonabsorbent cotton, and cotton wax were found to be progressively richer sources of germination-stimulatory activity effective in counteracting the self-inhibition of Puccinia graminis var. tritici Erikss. and E. Henn uredospores. The major stimulatory component of cotton wax was purified and partially characterized. It was catalytically effective in stimulating germination and oxygen consumption of uredospores and appeared to be as active as pelargonaldehyde. Unlike most of the previously reported chemical stimulants, however, it was not active across an air gap.Although the active compound was not identified, both the ultraviolet spectrum and the nonionic and solubility properties of the active fractions were consistent with the infrared spectrum which indicated a relatively long-chained. alpha. beta unsaturated carbonyl compound such as a ketone or possibly an ester.The purification procedure involved deionization of ethanolic extracts from cotton or cotton wax on Dowex 50 (H(+)) and Dowex 1 (OH(-)) columns followed by chromatography on neutral alumina using ethylene dichloride as the developing and eluting solvent.