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1) Rice and Wheat Institute, Fujian Academy of Agric. Sciences, Fuzhow, Fujian Province, Peoples Republic of China and
2) Intenational Rice Research Institute, P.O. Box 933, Manila, Philippines
IR54, a rice variety developed at IRRI and released in 1980, was
identified as an effective restorer of cytoplasmic genetic male sterile lines
(viz., Zhen Shan 97A, V20A, V41A) possessing 'WA' cyto-sterility system. We
studied the inheritance of its fertility restoration ability in the cross:
Zhen Shan 97A/IR54. Progenies of Zhen Shan 97A (PI), IR54 (P2), Zhen Shan
97A/IR54, (F1, F2)and Zhen Shan 97A/Zhen Shan 97A/IR54 (BC 1 F1) were
analyzed with regard to pollen and spikelet fertility. The F\1\ showed pollen
and spikelet fertility similar to the restorer parent, IR54, indicating that
restoration ability was dominant and the cytoplasmic-genetic sterility system
of Zhen Shan 97A was sporophytic in nature. With regard to pollen fertility,
determined by staining with 1% IKI solution, the F\2\ population segregated
into fully fertile (like IR54), fertile (70-95%), partially fertile (1-70%)
and completely sterile (like Zhen Shan 97A) giving a good fit to digenic
ratio 9:3:3:1 (Table 1). The backcross segregation conformed to 1:1:1:1
ratio. Segregation for spikelet fertility in F\2\ and backcross generations
(Table 2) conformed to the results on pollen fertility. It appears that the
restoration ability of IR54 is governed by two independent major genes, one
of them has a stronger fertility restoration ability than the other, such
that if both genes are present, fertility is like the restorer line, IR54; if
the gene with stronger fertility restorattion ability is present alone
fertility is somewhat reduced, but if the gene with weaker restoration
ability is present alone, plants show partial fertility ranging between 1-70%
(for pollen) and 1-30% (for spikelet). The plants possessing the double
recessive genotype are completely sterile like Zhen Shan 97A.
Table 1. Frequency distribution for pollen fertility (%) in parental
F\1\, F\2\ and BC\1\F\1\ populations of the cross Zhen Shan 97A/IR54
Table 2. Frequency distribution for spikelet fertility in parental F\1\,
F\2\ and BC\1\F\1\ populations of the cross Zhen Shan 97A/IR54
