Abstract:

It is an important approach to discover new resources of male sterile cytoplasm and to develop good quality CMS lines so as to reduce hybrid rice chalkiness, lower amylose content and substantially increase hybrid rice quality. A new male sterile cytoplasm named FA cytoplasm, which is different from WA and HL in the relationship between the maintainer line and the correspondent restorer line, has been obtained through nuclear substitution of Common Wild Rice（O. rufipogon）with the nuclear of cultivated rice by backcrosses. And the relevant CMS lines with fine rice quality, Jinnong 1A and Jinnong 2A were developed, which laid a good foundation for substantially improving the quality of hybrid rice. The subsequent breeding of the restorer line is therefore a key matching technique for the application of FA male sterile lines. In this study, the directional breeding method for male sterile restorer lines matching with FA cytoplasm was designed.
Hybridization and backcrosses were conducted by using the wild rice as non-recurrent parent and Minghui 63 as recurrent parent. The fertile genes from the wild rice were segregated, transfered, recombined and integrated into the genetic background of Minghui 63 by self-crosses of descendants to obtain a new male sterile restorer line Jinhui 1 with new male sterile cytoplasm.
The restorer line resembled Minghui 63 in agro-chaits with its spikelets completely fertile. Two hybrid rice combinations of Jinnong 1A/ Jinhui 1 and Jinnong 2A/Jinhui 1 were superior in yield compared with CK combination. All the twelve rice quality indexes approached those of fine quality rice, and the goal of greatly improving hybrid rice quality was realized.
Backcrosses could be used to input genes of recurrent parents time after time, expand genetic proportion of recurrent parents generation after generation, reduce the proportion of non-target genes from non-recurrent parents generation after generation and enlarge the genetic distance between a restorer line and a sterile line to reach the aim of improving heterosis. By using this method, fertile genes can be transferred so that any rice variety can be lead to be a male sterile restorer line, which breaks the technical bottle-neck in breeding restorer lines matching with sterile lines of the new sterile cytoplasm, greatly increases the breeding potential in the searching of restorer lines and therefore cuts a new way for the development of FA male sterile lines and fine quality hybrid rice.

Key words: Hybrid rice, cms-FA, Fine quality rice male sterile line, Male sterile restorer line