Improvement Rice Resistance To Bacterial Blight And Blast By Molecular Marker-assisted Selection

The bacterial blight (BB) and blast, two of most serious rice diseases and often becoming popular in rice planting areas, have been leading to great damage of production. Developing resistant varieties is considered very effective and economical strategy to control them. Molecular marker-assisted selection (MAS), an high-efficient breeding system, is widely used to improve characters in many crops. The purpose of this study is to improve blast resistance of R18.the elite japonica restore line, and pyramiding Pi9(t), Xa21 and/or Xa23 gene by MAS and tradition breeding .The major results are as followed:1 .Improvement the blast resistance of R18The blast resistance of R18 was improved by being crossed and backcrossed with 75-1-127 which confer blast resistance gene Pi9(t). The elite resistance lines were selected by MAS and confered stronger resistance and broader spectrum than R18 by artificial inoculation of multiple Pyricularia Oryzae Cav. strains. The resistance spectrum and resistance level are similar to the donor varieties, 75-l-127and conspicuously stronger than R18. While the impoved R18 (with Pi9(t) gene) retained main agronomic traits of R18. Some resistance lines had good agronomic characters in the seed-setting rate, 1000-grain weight and total grains weight aspects and express good restoring ability through hybridizing with sterile line 9201A and 80-4A.2. Pyramiding Pi9(t) and Xa21 , Pi9(t) and Xa23 genesThrough hybrid between resistance varity 75-1-127(with Pi9(t) gene) and M12(with Xa21 gene) , 75-1-127(with Pi9(t) gene) and CBB23 (with Xa23 gene) by molecular marker-assisted selection (MAS), the lines which conferred the broad spectrum resistance genes Xa21 and Pi9(t),genes Xa23 and Pi9(t)were obtained. The lines express high resistance to bacterial blight and blast and show same spectrum and similar resistant level as donor varieties by artificial inoculation of multiple strains. The gene can express normaly in the pyramiding lines.3. Pyramiding Xa21 and Xa23 genesThe elite lines with Xa21 and Xa23 genes were obtained by MAS. By artificial inoculation of 7 popular bacterial blight races of China and Anhui popular race, the lines conferred better resistance than donor varieties of Xa21 or Xa23 genes.4. Pyramiding Pi9(t) ,Xa21 and Xa23 genes The lines with 3 elite resistant genes Pi9(t), Xa21 and Xa23 were developed. They express high resistance to blast and had same spectrum and similar resistant level with 75-1-127 and had stronger resistance level to bacterial blight than donor of Xa21 or Xa23 genes at the same time.