36.Mapping of hybrid sterility gene S17 of rice (Oryza sativa L.) by isozyme and
     RFLP markers
     J. WAN1, H. IKEHASIH2, M. Sakai1, H. Horisue1 and T. IMBE’
    1) National Agriculture Research Center, Tsukuba, 305-8666 Japan
    2) Faculty of Agriculture, Kyoto University, Kyoto, 606-01 Japan

    The semi-sterility of F1 hybrids between indica and japonica varieties of rice has been attributed to an allelic interaction at S5 locus, where indica and japonica varieties have S5’ and S5’, respectively, and some javanica varieties have a neutral allele, S5”. (Ikehashi and Araki 1986). Through varietal screening, a series of new loci for causing female gamete abortion were found, in other groups of rice hybrids. Similar allelic interactions were found at loci S7, S8,S9, S15 and Si6 respectively, on chromosomes 4,6,7, 12 and 1. All of them causes the sterility independent of each other (Wan and Ikehashi 1995, Wan et a!. 1996). Penuh Barn II is identified as one of javanica varieties which show hybrid steril

ity in crosses tojaponicas (Ikehashi and Araki 1987). The locus for the sterility between Penuh Baru II and japonica was identified as Si 7 by isozyme markers (Wan and Ikehashi 1995). S17 causes female gamete abortion.
    In this report the locus Si7 for hybrid sterility between Penuh Barn II and Japonicas, was deterniined with isozyme and RFLP marker analyses.
    F, population of a three way cross, Akihikari I CY85-26 II Penuh Barn II, was used for genetic analyses and tested marker genotypes. CY85-26 is a Chinese variety developed from a cross of Peidi I C57, and is known to be a wide compatible variety (WCV). Akihikari is a japonica tester variety. Penuh Baru II is a javanica variety from Indonesia. Two F, populations, Akihikari I Penuh Baru II and Penuh Barn 11/ CY85-26 were used as check.
    According to the method to analyze one-locus allelic interaction which causes F, semi-sterility (Ikehashi and Araki 1986), a three-variety cross was studied to confirm the 1:1 segregation of fertile versus semi-sterile plants as shown in Table 1. To determine co-segregthon of isozymes or RFLP marker loci with spikelet fertility, the F, population of the three-way cross were grown at National Agriculture Research Center in 1997. The spikelet fertility was determined by counting fertile and sterile spikelets on the upper half of 3-4 panicles for each plant.
    The F, population of AkihikarilCY85-26//Penuh Barn II showed segregation for sterility (Table 1), and the level of spikelet fertility was significantly correlated with marker loci, Pox, Sdh1, RG413 and C751of chromosome 12, indicating an allelic interaction at the Si7 locus. The F, hybrid of Akihikari/Penuh Barn II showed semi-sterility (40.3%). But the F1 hybrid of Penuh Barn Il/ CY85-26 (WCV) showed normal fertility (9 1.3%).
    For mapping of isozyme and RFLP markers Mapmaker/3.0 was used (Fig. 1). The

 
recombination values between Si 7 and the isozyme marker loci Sdh1, Pox2, Acpl and Acp2, and 12 RFLP markers were calculated from the progeny of Akihikari/CY85-26// Penuh Barn H. The assumed recombinants are underlined in Table 1, and the recombination frequencies are shown in Fig. 1. Previously reported recombination frequencies between Sdh1 and Pox2, between Sdhl and Acpi, and between Acpl and Pox2 were 16.6%, 35.6% and 23.9%, respetively (Ishikawa et al. 1992, Causse et al. 1994). Thus, the present estimates were in good agreement with those reported earlier.
 


 

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