The resistance level of rice seedlings (Oryza sativa L.) to green leafhopper (GLH: Nephotettix virescens Distant) varied with age of the seedlings: seedlings of 3.2-4.0 leaf age were more resistant than 2.5 leaf age seedlings. However, Pankhari 203 and IR 42 were consistently resistant at all seedling ages examined. The resistance level of cut leaves was markedly lower than that of intact seedlings and rootless seedlings. However, IR 42 did not show, exceptionally, such changes in the resistance level.
　It was shown by the inheritance study that Pankhari 203 has one dominant resistance gene to GLH, while IR 36 and its sister line IR 42 have 2 dominant resistance genes. Of the 2 resistance genes of IR 42, it seems that one has high resistance and the other moder­ate resistance. The high resistance gene of IR 42 seemed to be independent of resistance genes in TAPL 796 and ASD 7.