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Sporadic occurrence of tungro in rice resistant to tungro spherical virusR. C. Cabunagan, Z. M. Flores, and H. Hibino, IRRI; and A. Muis, H. Talanca, M. Sudjak S., and
A. Bastian, Maros Research Institute for Food Crops, P.O. Box 173,Ujung Pandang, South Sulawesi, Indonesia
We studied the development of rice tungro virus (RTV) infection vectored by green leafhoppers Nephotettix spp. in rice varieties IR26, IR42, IR54, and Cisadane in 1987 dry season in Sidrap, South Sulawesi. IR26 is resistant to RTSV infection and IR42 and IR54 are resistant to the green leafhopper vector. Cisadane was the susceptible check. Seedlings (21 days old) were transplanted in 10-m2 plots at 2-3 seedlings/hill and with 20 cm between hills. RTV incidence was assessed at 14, 28, 56, and 70 days after transplanting (DT) and infected plants were plotted at 70 DT. At 70 DT, leaf samples were collected from 50 plants/plot and bacilliform virus (RTBV) and RTSV by latex serology.
RTV developed more rapidly in IR54 and IR42 than in Cisadane and IR26 (Fig. 1). RTV-infected plants appeared in patches in plots planted to IR42, IR54, and Cisadane; appearance was sporadic in plots planted to IR26 (Fig. 2).
Latex test of leaf samples collected at 70 DT showed high incidence of RTBV or RTSV or both in IR54, IR42, and Cisadane; incidence in IR26 was low. In plots planted to IR26, infection started at the border. Low RTV infection in IR26 can be explained by the inability of RTBV-infected plants to serve as virus sources for the spread of RTV infection and to the cultivar’s resistance to RTSV.
Fig. 1. Development of RTV infection and RTBV and RTSV incidence s at 70 days after transplanting in selected varieties in Sidrap, South Sulawesi, Indonesia, 1987 dry season.
Fig. 2. Distribution of RTV-infected plants in 10- × 10-m plots (2,500 hills). South Sulawesi, Indonesia, 1987 dry season.
Cabunagan RC, ZM Flores, H Hibino, A Muis, H Talanca, M Sudjak S, A Bastian. 1989. Sporadic occurrence of tungro in rice resistant to tungro spherical virus. International Rice Research Newsletter 14 (5) 13-14.