Endogenous Ethane and Ethylene Of Poa pratensis Leaf Blades and Leaf Chlorosis in Response to Biologically Active Products of Bipolaris sorokiniana

Infection of Poa pratensis leaf blades and callus tissue by Bipolaris sorokiniana increases the production of ethylene and ethane. The ethylene is responsible for most of the chlorosis that occurs during pathogenesis. The nonselective toxin(s) produced by B. sorokiniana is known to disrupt membranes and to damage chlorophyll, but it is not known whether it can induce an increase in ethylene or ethane. Research was initiated to determine the effect of a biologically-active extract of B. sorokiniana on the endogenous ethylene and ethane of intact P. pratensis leaf blades and on subsequent development of chlorosis. The extract did not increase endogenous ethylene of treated leaves, but it was associated with an increase in endogenous ethane between 24 and 96 h after treatment. Chlorophyll loss occurred 96 h after treatment and persisted for the duration of the study (168 h). The chlorophyll content of treated leaf blades ranged from 72% to 80% of control leaf blades. The observations suggest that the extract of B. sorokiniana can induce chlorophyll loss from treated leaf blades independent of an increase in endogenous ethylene by directly damaging chloroplasts with a concurrent release of ethane. The ethane is believed to be a by-product of pathogenesis.