Molecular Marker-assisted Selection For Bacterial Blight Resistance And Heterosis Utilization In Rice

Most of hybrid rice has no resistance to bacterial blight (BB). One or two resistance genes were transferred or pyramided into male sterile lines or restorer lines through crossing and back-crossing breeding in order to improve their resistance or durable resistance. Molecular marker-assisted selection (MAS) can provide a rapid, accurate, and efficient tool for selecting target genes in back-cross breeding. This study is to improve resistance to bacterial blight (BB) in the parents of hybrid rice by introducing Xa21 and (or) Xa23 genes both with the broad spectrum resistance to BB and using MAS in the process of back-cross and inocunation with specific strains.In addition, the situation to the development of two-line hybrid rice has been unfavourable lately because some enterprises warried about the problems on the safety techniques of seed production in two-line hybrid rice. The safety techniques of seed production in two-line hybrid rice were also made a systematic study through many years' seeding by stages at 10 days intervals to many P (T) GMS lines bred by us.The results were as follows:1) The Indica Photoperiod-sensitive Genic Male Sterile (PGMS) line '3418S (Xa21)' and Thermo-sensitive Genetic Male-sterility (TGMS) 3178S (Xa21) with BB resistance has been developed by MAS. They have similar BB resistance to the donor IRBB21 (carrying Xa21) and maintain obvious male sterility of the recipient '3418S' and 399S, the former kept the donor' good traits and had passed the provincial-level expert test and applied for the right of variety protection. The latter economic traits are also improved compared with 399S. They can be applied in two-line hybrid rice.2) The Wide Compatibility (WC) Restorer line 'R4183 (Xa21)' with BB resistance has been developed. R4183 (Xa21) has similar BB resistance to the resistant donor IRBB21, and maintains the good traits of the recurrent parent 4183. The line can be used in heterosis utilization between Indica and Japonica.3) The two homozygous resistance genes Xa21 and Xa23, both located in chromosome 11, has been firstly pyramided into a line. It has not also been reported to improve the BB resistance of a CMS line by MAS before the line has been bred. This work is more important and more difficult than improving that of a restorer line. A CMS line R106A has been developed .The line R106A and its maintainer R106 shows high resistance in whole growth stage. They will keep...