Somaclonal Variation of Cytoplasmic Male Sterile Lines with Wild Rice Cytoplasm I. The Types of Somaclonal Variation from IR66707A & IR69700A

Abstract:

Male sterile rice varieties IR66707A and IR69700A from IRRI contain cytoplasm of Oryza perennis and O. glumaepatula, respectively. Their sterility can only be maintained but cannot be restored, so they are cytoplasmic male sterile. Among the total 136 somaclones, three types of mutants were obtained by somatic cell culturing from the two male sterile lines, and their F1 progenies derived from crossing with normal cultivars. They were fertile mutants (type Ⅰ), various male sterile mutants (type Ⅱ ), and female sterile mutants(type III)．In type I，among 18 clones (R₁) from the donors of hybrid F₁，two were fertile．The fertility in the R₂ generation was segregated and the ratio of fertility to sterility was 3：1， showing that the mutants were controlled by a single dominant gene． In Type II， the sterility of some clones could be restored which were quite different from the donors of male sterile lines． Among these clones a part of the sterility could not be maintained but could be converted to be fertile as the environment changed，another part was inconvertible，but restorable and incompletely maintainable，although some segregation appeared．Also in type Ⅱ，the sterility of some clones could not be restored， and were similar to the donors． It is suggested that the convertible mutants could serve as dual-purpose genic male-sterile lines in rice breeding．Type Ⅲ was completely sterile，both for male and female．