Resistance to Rice Tungro Spherical Virus in Rice. H. Hibino, International Rice Research Institute, P.O. Box 933, Manila, Philippines. R. D. Daquioag, P. Q. Cabauatan, and G. Dahal. International Rice Research Institute, P.O. Box 933, Manila, Philippines. Plant Dis. 72:843-847. Accepted for publication 18 February 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0843.

Twenty-nine improved rice cultivars were evaluated in the field and in the greenhouse for resistance to infection with rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV). Many cultivars had low field infection rates with RTBV and RTSV combined but had relatively high infection rates with RTBV alone. These cultivars also had similar infections when seedlings were inoculated by leafhoppers (Nephotettix virescens) that had fed on plants infected with RTBV and RTSV. When seedlings were inoculated by leafhoppers fed on RTSV-infected plants, only IR20, IR26, IR30, and IR40 had low infection rates. TKM6, which is common in the parentages of these four cultivars, reacted in the same manner as these cultivars in the field and greenhouse. A leafhopper colony selected on IR20 increased in its ability to colonize IR20 and IR26 but did not transmit RTSV to IR20 and IR26. These results suggest that the resistance of the four cultivars to RTSV infection may not be because of resistance to the leafhopper. Possible advantages of these cultivars in tungro management are discussed.