Pseudomonas lachrymans Adsorption, Survival, and Infectivity Following Precision Inoculation of Leaves

Abstract

Precise quantities of P. lachrymans suspensions were deposited on leaf surfaces and the effects of drying and other factors were measured. Assay of survival was by dilution plating of wash water and by direct counts of infections on the inoculated leaves. Both techniques had a minimum detection level of about 1000 cells/leaf. Over a range of 104-1011 cells/4 cm2 a constant proportion (93%) of the inoculum was adsorbed, indicating nonspecific adsorption sites. During a 16 h post-inoculation drying period, survival was highest on pubescent suscept (cucumber) leaves, less on pubescent nonhost (potato) leaves, and least on glaborous nonhost (pear) leaves; both leaf surface morphology and innate plant resistance influenced the death rate. The pathogen''s resistance to dry conditions governed survival on all 3 crops after the initial drying period; death rates were similar on all 3 crops. On cucumber, survival after drying for up to 16 h was less at 10.degree. C than at 25.degree. C. With increasing periods of artificial dew on leaves before inoculation, short-term survival of the pathogen decreased.