HydroxyproUne-rich Glycoprotein Accumulation in TMV-infected Tobacco Showing 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 infection, was infected with TMV basaily (4"ʹ and 5"ʹ leaves) and the hydro xyproline-rich glycoproteins (HRGPs) were determined in two experiments (experiment 1 and experiment 2) by analysing cell wall hydroxyproline (Hyp) in the 6"ʹ leaf. In basal TMV infected plants Hyp content (/imol"ʹ FW) was greater than in controls in both experiments: the increase was significant at all times except 16 days after TMV inoculation in experiment 1; the pool of data of experiment 2 was also significantly increased. In TMV protected + E. cichoracearum challenged leaves compared to untreated controls significant increases in Hyp were also noted between the pools of data in both experiments. No differences were found between Hyp content in protected compared to protected -f challenged leaves in both experiments. These results show accumulation of HRGPs in Havana tobacco associated with TMV infection and SAR activation against E, cichoracearum. The accumulation appears to be due to the inducer, since no further increase was detected in protected leaves after challenging