Breeding for Disease and Insect Resistances in Keng Rice

Abstract

Tainung 67 was crossed with Tetep, Carreon, Dawn and other donor parents followed by 3 to 4 consecutive backcrossings to Tainung 67 for improving its blast resistance. A genetic study on the BC1F1's revealed that Tetep was most numerous in the genes resistant to 4 races of the blast fungus tested. An upland blast nursery with corn border lines facilitated the screen-testing of breeding lines. Many new selections from this breeding program were resistant to the blast disease and outyielded Tainung 67. Tainung 67 was also crossed with yellow dwarf resistant Firooz, followed by 2 consecutive backcrossings to Tainung 67. From the segregating progenies of these backcross hybrids, 11 new strains resistant to yellow dwarf were selected. The yields of 2 strains surpassed that of Tainung 67. The brown planthopper resistance of a Oryza rufipogon was tranes-ferred to Ponlai by 2 consecutive breeding programs. TNGY8849, a final selection that was resistant to blast and brown planthoppers, is being recommended for registration. Various other varieties possessing Bph 1, bph 2, Bph 3 and bph 4 were also crossed with Tainung 67, followed by 2 consecutive backcrossings. The resistant strains selected from the segregating materials of these hybrids are being tested in the preliminary yield trial. Several japonica cultivars showed resistance in a test for white-backed planthopper resistance, including moderately resistant Tainung 67. A breeding program and the genetic study related with the resistance are in progress. Twenty-one double cross F1's between the lines selected mostly from the above mentioned backcross breeding programs were subjected to anther culture cooperated with tissue culturists. A total of 1,567 green AC, plants derived from the anther culture gave only 230 diploid AC1S, lines for screen-testing. The rate of this diploid recovery was greatly improved later. Segregation patterns of blast, planthopper resistances and shattering habit of rice grains among the AC1S1 lines showed that the combination of different desirable traits by double crossing followed by anther culture will he successful and readily useful.