The awns in wild rices are considered advantageous because these protect rice grains from animal attack and play an important role in seed dispersal (Takahashi et al. 1986). Long awn is one of the typical characters of an Australian wild rice, O. meridionalis During the process of developing O. meridionalis introgression lines (Kurakazu et al. (2001), we observed that plants having awned spikelets segregated in two BC₄F₂ populations (A and B). The parent of BC₄F₂ population A retained the O. meridionalis chromosomal segment on chromosome 5, while the parent of BC₄F₂ population B retained the O. meridionalis chromosomal segment on chromosome 4. To determine the locations of the genes for awn on RFLP map, RFLP analyses were conducted in these BC₄F₂ populations.

In population A, segregation analysis between awn character and RFLP markers on chromosome 5 revealed that awn co-segregated with RFLP marker R569. At R569 locus, 32 awnless plants were homozygous for Taichung 65 alleles. Out of 39 awned plants, 35 plants were heterozygous and 4 plants were homozygous for O. meridionalis. This result indicated that awn character was controlled by a single dominant gene; this gene was designated as An7(t). Linkage analysis using RFLP markers near R569 revealed that An7(t) was located between Y1060L and C249 with map distances of 1.0 and 5.8 cM, respectively (Fig.1).

Population B segregated into 32 awnless and 40 awned plants. Segregation analysis between awn character and RFLP markers on chromosome 4 revealed that awn character was associated with RFLP marker XNpb237. At XNpb237 locus, out of 40 awned plants, 33 plants were heterozygous and 7 plants were homozygous for O. meridionalis. All 32 awnless plants were homozygous for Taichung 65 except for one plant which was heterozygous.This heterozygous plant was considered as a recombinant between the awn character and XNpb237 locus. This result indicated that awn in this population was controlled by a single dominant gene; this gene was designated as An8(t). Linkage analysis suggested that An8(t) was located between XNpb237 and C891 with map distances of 1.0 and 5.2 cM, respectively (Fig. 2). Populations B and A showed segregation distortions wherein the frequencies of O. meridionalis homozygous alleles around the regions of An8(t) and An7(t), respectively, were reduced.

So far, six genes for awn have been reported. Genes An1, An2 and An3 were located on chromosomes 4, 5 and 3, respectively (Nagao and Takahashi 1963). An4 gene was located on chromosome 8 (Sato et al. 1996). Genes of An5(t) and An6(t) were located on chromosomes 3 and 8, respectively. These two genes were assumed to be allelic with An3 and An4 respectively (Takano et al. 2001). An7(t) and An8(t) were located on the same chromosomes as An2