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 sorok iniana increases the production of ethylene and ethane. The ethylene is res ponsible for most of the chlorosis that occurs during pathogenesis. The non selective 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 in crease in ethylene or ethane. Research was initiated to determine the effec t of a biologically-active extract of B. sorokiniana on the endogenous ethy lene and ethane of intact P. pratensis leaf blades and on subsequent develo pment of chlorosis. The extract did not increase endogenous ethylene of tre ated leaves, but it was associated with an increase in endogenous ethane be tween 24 and 96 h after treatment. Chlorophyll loss occurred 96 h after tre atment 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 blad es. The observations suggest that the extract of B. sorokiniana can induce chlorophyll loss from treated leaf blades independent of an increase in end ogenous ethylene by directly damaging chloroplasts with a concurrent releas e of ethane. The ethane is believed to be a by-product of pathogenesis.