25. RFLP mapping of a new resistance gene for green rice leafhopper in Kanto PL10

1) Department of Lowland Research, National Agricultural Research Center for Kyushu Okinawa Region, NARO; Chikugo, 833-0041 Japan
2) Japan International Research Center for Agricultural Sciences, Tsukuba, 305-8686 Japan
3) Hokuriku Research Center, National Agricultural Research Center, NARO; Joetsu, 943-0193 Japan
4) Joetsu, 943-0154 Japan

Kanto PL10, resistant line to green rice leafhopper (GRH), was bred from crosses between SML17 and Nipponbare. Its cross combination is represented as SML17/3*Nipponbare. In the present study, we determined the chromosomal location of a new GRH resistance gene in Kanto PL10.

For the linkage analysis of the GRH resistance gene with rice RFLP markers, we used 87 F2 plants derived from the cross between Kanto PL10 and Nipponbare. To evaluate GRH resistance, we employed a newly developed technique, in which both nymph survival and growth rates were used as criteria (Hirae et al. 2002). 87 F2 plants showed a discrete distribution, segregating into 69 resistant and 18 susceptible plants (Fig. 1). The segregation ratio fitted to a 3:1 ratio (chi2=0.97), indicating that the GRH resistance was controlled by a single dominant gene. From the result of progeny test using F3 strains, 69 resistant plants were classified into 17 homozygote and 52 heterozygote.

To determine the chromosomal location of the resistance gene, we first analyzed the graphical genotype of Kanto PL10 using 144 markers. Several segments originated from SML17 were detected. Segregation of the markers located in these segments and the resistance gene was

analyzed with the software MAPMAKER/EXP ver.3.0. RFLP analysis using F2 plants showed that the resistance gene was located between Y3635R and C708 on chromosome 4 (Fig. 2). So far, five genes for resistance to GRH have been mapped on rice chromosomes using RFLP or simple sequence repeats (SSR) markers, Grh1 on chromosome 5(Tamura et al. 1999), Grh2 and Grh4 on chromosome 11 and 3, respectively (Fukuta et al. 1998; Yazawa et al. 1998), Grh3 (t) on chromosome 6 (Saka et al. 1996), and Grh5 on chromosome 8 (Fujita et al. 2003). There have been no genes for resistance to GRH on chromosome 4. Therefore, we designated the new resistance gene as Grh6 (Green rice leafhopper resistance 6).


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