| H359 and Acc8558 are two indica rice varieties, which are highly susceptible and highly resistant to bacterial leaf streak (BLS), respectively. Based on a recombinant inbred (RI) population (131 lines) derived from a cross between H359 and Acc8558 and a corresponding RFLP-AFLP map, eleven QTLs conferring BLS resistance were previously mapped. Among them three QTLs exhibiting the largest effects were also detected by bulked segregant analysi (BSA) using an F2 population of the same cross. The three QTLs were located in the three marker intervals , Xpsrll6-C49 on chromosome 1.C235A-Xpsr371 on chromosome 2, R1553-C624 on chromosome 5, respectively. To further verify the three QTLs and search for PCR markers linked to them, knowable 57 SSR markers located on chronsome K 2 and 5 and being possibly near to the three QTLs were screened by BSA using a BC2 population of H359/Acc8558// H359. Six markers respectively named RM246, RM128, RM208, RM573, RM459 and RM161, were deteced to be polymorphic between the resistant and susceptible DNA pools and then mapped onto the original RFLP-AFLP map. Results show that they are all near to the marker intervals where three QTLs are located: RM128 is 7. 3cM to XpsrllG, RM246 is 2. 3 cM to C49, RM208 is 22. 4cM to C235, RM573 is 10. 7cM to C1419, RM161 is 6. 9cM to C624, RM459 is 2. 7 cM to R1553. The results demonstrate that large effect QTLs could be detected in different populations and verify the reliability of QTLs indirectly, again.After the SSR markers are added, the map lengths of chromosomesK 2 and 5 are extended by 43. IcM > 18. 2cM and 28. 6cM respectively. The problem of segregation distortion of SSR markers in the H359/Acc8558 RI populaition is also discussed.
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