The Correlation between Severity of Disease Symptoms and the Accumulation of Viral Antigen and Acidic Pathogenesis‐related Proteins in the Leaves of Thorn‐apple Plants Infected with Different Isolates of Potato Virus X

The isolates of potato virus X causing disease symptoms of different severity in thorn-apple plants (Datura stramonium L.) can be categorized in terms of the increase in antigen accumulation, as follows: strong, medium and weak. Extracts from leaves of healthy plants and of those infected with separate virus isolate did not differ in set of acidic pathogenesis-related (PR) proteins as shown by discontinuous non-denaturating polyacrylamide gel electrophoresis. Within 2 weeks after inoculation the total content of PR-proteins in leaves of plants infected with weak or medium isolates was higher than in the healthy ones but after 3 weeks these differences became negligible. The plants infected with the strong isolate had higher total content of PR-proteins than healthy plants and plants infected with weak or medium isolates during 3 weeks. It is proposed that the greater the damage to the plant caused by virus infection, the more PR-proteins are accumulated.