Tobacco mosaic virus-induced increase in abscisic acid concentration in tobacco leaves: intracellular location and relationship to symptom severity and to extent of virus multiplication

Abscisic acid (ABA) concentration was increased 1·1 to five-fold in Samsun tobacco infected with six strains of tobacco mosaic virus (TMV) which produced mosaic symptoms of widely different severity and which multiplied to different extents. The ABA accumulation was more closely related to the severity of mosaic symptoms (r = 0·93; 4 degrees of fredom, df) than to the extent of virus multiplication (r = 0·39, 4 df). The increase in ABA concentration was located outside the chloroplast; virus infection had little effect on, or reduced, chloroplastic ABA concentration.

Tobacco mosaic virus infection inhibited plant growth. Reduction in growth rate was related both to increase in extrachloroplastic ABA concentration (r = 0·69, 4 df) and to virus accumulation (r = 0·73, 4 df). It is concluded that both these factors are important in the inhibition of growth produced by TMV infection.