G.S. Khush and A.L. Librojo
International Rice Research Institute, P.O. Box 933, Manila, Philippines
We received naked seed rice accession from Institute of Genetics, Academia Sinica, Beijing, China. It was reportedly obtained from a cross of wheat and rice. The plants looked exactly like rice. However, the glumes were papery and elongated and looked like those of wheat superflously. Since the glumes did not invest the kernel tightly as in ordinary varieties of rice, the grain appeared naked (Fig. 1).
Fig. 1 Naked Seed rice.
We crossed this naked seed rice with IR36 which has normal phenotype in this respect. The F1 was normal and the F2 population segregated in a ratio of 3 normal : 1 naked seed rice, thus showing that the naked seed rice is a monogenic recessive trait.
Naked seed rice resembled two other mutants in our collection namely op (over developed palea) and lhs (long hull sterile). op was obtained from Dr. N. Iwata and lhs from Dr. T. Kinoshita. We made the allele tests between these three mutants and as shown in Fig. 1, the F's between different mutants had mutant phenotype. These results show that op, lhs and naked seed rice are allelic. The correct gene symbol for all these mutants is lhs-1.
We also examined the meiotic chromosome complement of naked seed rice and found that it has 12 bivalents during meiosis.