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Detection of Rice Tungro Bacilliform Virus by Polymerase Chain Reaction for Assessing Mild Infection of Plants and Viruliferous Vector Leafhoppers. Y. Takahashi, National Agriculture Research Center, Tsukuba, Ibaraki 305, Japan, Present address: Institute of Japan Plant Protection Association, Ushiku, Ibaraki 300-12, Japan; E. R. Tiongco(2), P. Q. Cabauatan(3), H. Koganezawa(4), H. Hibino(5), and T. Omura(6). (2)(3)(4)International Rice Research Institute, P. O. Box 933, Manila, Philippines; (5)(6)National Agriculture Research Center, Tsukuba, Ibaraki 305, Japan. Phytopathology 83:655-659. Accepted for publication 17 February 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-655.

The polymerase chain reaction (PCR) was 103104 times more sensitive for detecting rice tungro bacilliform virus (RTBV) DNA extracted from infected rice plants than was enzyme-linked immunosorbent assay (ELISA). The greater sensitivity of PCR enabled the detection of the virus in individual RTBV-exposed leafhoppers, Nephotettix virescens, a semipersistent vector of RTBV. Detection of RTBV in the vector by ELISA has been impossible. To evaluate resistance to RTBV, seedlings of rice cultivars Utri Merah, Utri Rajapan, or Balimau Putih, were inoculated with RTBV, and infection of the cultivars with the virus was indexed by PCR and ELISA. When inoculated seedlings with no clear symptoms were tested by ELISA, only some seedlings of the three cultivars produced positive reactions, and their ELISA values were generally low. When DNA extracted from the same leaf samples was amplified by PCR, RTBV DNA was detected in all plants that reacted in ELISA. In addition, among the plants that produced ELISA values lower than 0.05, a value twice the average of the uninfected controls and considered noninfected with RTBV, 19% of Utri Merah, 4.2% of Utri Rajapan, and 60% of Balimau Putih plants were positive according to PCR. These results indicate that ELISA failed to detect RTBV in many infected rice plants with tolerance to the virus. The results clearly demonstrate the effectiveness of PCR as a method for evaluating rice cultivars for tolerance or resistance to RTBV.

Additional keywords: diagnosis, evaluation of resistance and tolerance.