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Analysis of Genes for Stigma Coloration in Rice - IRRI books

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Restriction fragment length<br />

polymorphism analysis <strong>of</strong> size<br />

<strong>of</strong> chromosomal segments<br />

reta<strong>in</strong>ed around bacterial blight<br />

resistance genes <strong>in</strong><br />

near-isogenic l<strong>in</strong>es <strong>of</strong> rice<br />

S. Yoshimura, A. Yoshimura, N. Iwata, A. Saito, N. Kishimoto,<br />

M. Kawase, M. Nakagahra, and M. Yano<br />

Several genes <strong>for</strong> resistance to bacterial blight were <strong>in</strong>troduced <strong>in</strong>to rice cultivars by<br />

repeated backcross<strong>in</strong>g, and near-isogenic l<strong>in</strong>es were established (Ogawa et al 1988).<br />

We measured the sizes <strong>of</strong> the <strong>in</strong>trogressed DNA segments <strong>in</strong> some <strong>of</strong> the near-isogenic<br />

l<strong>in</strong>es by us<strong>in</strong>g a high-density map <strong>of</strong> restriction fragment length polymorphism (RFLP)<br />

markers (Kishimoto et al 1989, Yano et al 1990).<br />

The genotypes at each RFLP marker locus flank<strong>in</strong>g the resistance genes <strong>in</strong> the nearisogenic<br />

l<strong>in</strong>es were determ<strong>in</strong>ed by hybridization <strong>of</strong> labeled RFLP clones with restriction<br />

enzyme-digested genomic DNA extracted from the recurrent parent IR24, from<br />

isogenic l<strong>in</strong>es, and from donor parents. Because <strong>of</strong> the sequence divergence between<br />

IR24 and the donor parents, RFLP could be identified <strong>for</strong> the markers (Fig. 1).<br />

L<strong>in</strong>e IR-BB1 (BC 4 F 6 ; IR24*5/Kogyoku) conta<strong>in</strong>s the flank<strong>in</strong>g segment <strong>of</strong> Xa-1 on<br />

chromosome 4 from the resistant parent Kogyoku. RFLP marker Npb235 showed the<br />

genotype <strong>of</strong> Kogyoku <strong>in</strong> IR-BB1. Physiological marker Ph was also analyzed, and this<br />

locus <strong>in</strong> IR-BBI was <strong>of</strong> the Kogyoku type. There<strong>for</strong>e, the size <strong>of</strong> the flank<strong>in</strong>g segment<br />

<strong>of</strong> Xa-1 was estimated to be approximately 7.2% based on the maps <strong>of</strong> Sakaguchi<br />

(1967) and Yano et al (1990) (Fig. 2a). The l<strong>in</strong>e also possessed the segment<br />

<strong>in</strong>trogressed from Kogyoku <strong>in</strong> another region. To determ<strong>in</strong>e the genetic distance<br />

between Xa-1 and nearby RFLP markers, an F 2 population and F 3 l<strong>in</strong>es segregat<strong>in</strong>g <strong>for</strong><br />

Xa-1 resistance were analyzed. RFLP loci <strong>of</strong> XNpb102 and XNpb120 were l<strong>in</strong>ked to Xa-<br />

1 with recomb<strong>in</strong>ation values <strong>of</strong> 6.7 and 21.5%, respectively (Fig. 2a).<br />

RFLP analysis <strong>of</strong> IR-BB3 (BC 4 F 8 ; IR24*5/Chugoku 45) showed a crossover event<br />

between XNpb78 and XNpb186 on chromosome 11 <strong>in</strong> the process <strong>of</strong> develop<strong>in</strong>g this<br />

near-isogenic l<strong>in</strong>e (Fig. 2b). S<strong>in</strong>ce the segment conta<strong>in</strong><strong>in</strong>g the loci <strong>of</strong> XNpb78,<br />

XNpb181, and XNpb186 was from the resistant donor Chugoku 45 with Xa-3, Xa-3 was<br />

<strong>in</strong>ferred to be near the three RFLP markers <strong>in</strong> the l<strong>in</strong>kage map.<br />

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