Physiology of Rice Tungro Virus Disease: Involvement of Abscisic Acid‐Like Substance in Susceptible Host‐Virus Interactions

Abstract Stunting was severe in susceptible rice ( Oryza saliva L.) cultivar ‘Taichung Native 1’ infected with tungro virus (RTV) compared to less‐susceptible cultivar ‘IR 20’. The senescence of detached leaves of RTV‐infected susceptible cultivar incubated in water in dark was accelerated compared to the healthy leaves as measured by the loss of total chlorophyll content. The transpiration rate of RTV‐infected leaves of the susceptible cultivar was much lower than the healthy and RTV‐infected leaves of the less‐susceptible cultivar. Partially purified extracts obtained from RTV‐infected leaves effectively inhibited GA‐induced α‐amylase synthesis in barley endosperms, and rice seedling growth, and they accelerated senescence of detached rice leaves. In all the three bibassays the ABA‐like activity was significantly greater in the extracts from the RTV‐infected susceptible cultivar than in extracts from the less‐susceptible cultivar.