The initial response of barley to challenge by leaf rust ( Puccinia hordei Otth.): some factors in RNA metabolism related to resistance

Abstract

In seedlings of barley ( Hordeum vulgare L.) inoculated with leaf rust ( Puccinia hordei Otth.) the resistance response of cultivar DSIR 725-02 is suppressed by exposure to actinomycin D. For the susceptible cultivar Zephyr, actinomycin D allows only slightly better growth of the pathogen. In both cases the optimum time for application of the actinomycin D is 8–12 h after innoculation with the pathogen. Infection of the barley with rust is found to cause an increase in the proportion of monosomes and a decrease in the proportion of polysomes in the total leaf ribosome population. This change, relative to healthy seedlings is found in both resistant and susceptible hosts. The fraction of large polysomes ( n >4) in the polysome population remains constant in both cases. The data is discussed in relation to the role of RNA in the resistance response.