FAN, SHUGUO*, CHENGYE LIANG, AND HONGXIAN LIU. South China Institute of Botany, Academia Sinica, Guangzhou 510650, P. R. China. - Factors influencing the in vitro screening of male-sterile variants in rice (Oryza sativa L.).
Young panicles from 11 rice varieties, Zhenshan 97A (WA type
cytoplasmic male-sterile (CMS) line, indica), Zhenshan 97B (WA type
maintainer line, indica), IR24, IR26, Taiyin 1 and Minghui 63 (WA type
restorer line, indica), Hongyuan A (HL type CMS line, indica), Baoyuan
A (BT type CMS line, indica), Nanguangzhan (genic male-sterile (GMS)
line, indica), Nongken 58s (photoperiod-sensitive genic male-sterile
rice (PGMR), japonica) and W6154s (thermosensitive genic male-sterile
rice (TGMR), indica), were cultured on different media. Regenerated
plants were obtained. Pollen fertility was examined. Factors
influencing the in vitro screening of male-sterile variants were
discussed. The main results were as follows: During the eight years
of 1991~1998, 78 cases of male-sterile mutants (or variants) in seven
varieties (Zhenshan 97A, Zhenshan 97B, IR26, Hongyuan A, Baoyuan A,
W6154s and Nanguangzhan) were found, in which 74 cases belonged to R1
generation and four to R2 generation. Genotype was the main reason in
the course of inducing male-sterile variants. Male-sterile variation
was found in all rice varieties except Nongken 58s, IR24, Zhenshan 97A
and Taiyin 1 in R1 generation. Dedifferentiation of explants was
essential to producing male-sterile variation, and 2,4-D played a
decisive role in this course. The frequency of male-sterile variation
in somaclones might be affected by the duration of subculture passage.
The frequency of male-sterile variation in R2 generation (around 2%)
was higher than that in R1 generation (around 1%). The higher
frequency of male-sterile variation in R2 generation showed that the
mutant frequency of one site of a pair of genes from the wild type was
much higher than that in a homozygous mutant (two sites of a pair of
genes undertaking mutant at the same time). Based on the result of
this experiment, the authors suggested that some chemicals in the
medium might cause the mutant during culture in vitro.
Key words: cytoplasmic male sterility (CMS), genic male sterility (GMS), in vitro screening, indica, japonica, Oryza sativa L.