HYDROXYPROLINE-RICH GLYCOPROTEIN ACCUMULATION IN TMV-INFECTED TOBACCOSHOWING SYSTEMIC ACQUIRED-RESISTANCE TO POWDERY MILDEW

Tobacco cv. Havana 425, with systemic-acquired resistance (SAR) to an otherwise compatible Erysiphe cichoracearum DC. race after TMV infecti on, was infected with TMV basally (4th and 5th leaves) and the hydroxy proline-rich glycoproteins (HRGPs) were determined in two experiments (experiment 1 and experiment 2) by analysing cell wall hydroxyproline (Hyp) in the 6th leaf. In basal TMV infected plants Hyp content (mu mo l(-1) FW) was greater than in controls in both experiments: the increa se was significant at all times except 16 days after TMV inoculation i n experiment 1; the pool of data of experiment 2 was also significantl y increased. In TMV protected + E. cichoracearum challenged leaves com pared to untreated controls significant increases in Hyp were also not ed between the pools of data in both experiments. No differences were found between Hyp content in protected compared to protected + challen ged leaves in both experiments. These results show accumulation of HRG Ps in Havana tobacco associated with TMV infection and SAR activation against E. cichoracearum. The accumulation appears to be due to the in ducer, since no further increase was detected in protected leaves afte r challenging.