Abstract
A new substance named phleichrome was extracted from culture filtrate of the causal organism of timothy purple spot. Phleichrome increased in the culture filtrate until 20th day in the dark, while it did up to 15th day and then decreased in the light. When applied to timothy leaf blades, phleichrome [>10^<-4>M] produced lesions similar to purple spot naturally produced by the pathogen. The reaction of timothy to phleichrome did not differ with resistance or susceptibility of tested clonal lines. Phleichrome was also toxic to some of leaf-surface microorganisms of timothy, and its effect on bacteria was stimulated by the light, especially at 260 or 274nm, i.e. maximum absorption wavelength of phleichrome. The photodynamic reaction of phleichrome on the micro-flora of timothy leaf surface is discussed in relation to the pathogenesis of timothy purple spot.
