Transfer of green leafhopper resistance from wild rice (Oryza minuta) to cultivated rice (O. sativa L.)
1993
Choosak Jompuk
Wide cross between cultivated rice (O. sativa, AA, 2n=24) as the female and wild rice (O. minuta, BBCC, 2n=48) as the male has been made introgression resistance to green leafhopper from wild rice into three cultivated rices. Gibberellin 75 ppm was sprayed onto pollinated panicles immediately after pollination for delaying dehescent. Rate of seed sets ranged from 14.52-25.30 %. Embryo rescue of F1 seed was made at 9-14 days after pollination. Embryo were cultured on 1/4 strength Murashige and Skoog (MS) medium supplemented with 2.0 % sucrose and 0.6 % agar at the pH of 5.8 and allowed to germination in the dark. The rate of embryo rescue ranged from 42.86-95.00 % depending on the cultivars used. Embryo with age of 13 days had high rate of rescue. Vegetative multiplication of F1 plants for use in insect resistant screening was done by culturing the young F1 planlets added with 15 mg/l benzyladenine on the MS medium. The multiplication rate of F1 plants was four limes. Another method was node multiplication by cutting nodes of vigorous F1 plants and tranplanted onto wet sand. The F1 hybrids from the three crosses were intermediate between the two parents but showed a preponderance of the traits of wild rice. They were robust and extremely vigorous. All of them were resistant to green leafhopper and had 36 chromosomes (2n=36) but completely sterile. Colchicine concentration of 0.2 % applied to the shoot tip of F1 plants partially helped improving fertility in the cross of NMS-4 x O. minuta.
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