MOLECULAR TAGGING OF GENES FOR BROWN PLANTHOPPER RESISTANCE AND EARLINESS INTROGRESSED FROM ORYZA-AUSTRALIENSIS INTO CULTIVATED RICE, ORYZA-SATIVA

Restriction fragment length polymorphism analysis was carried out to t ag the alien genes for brown planthopper (BPH) resistance and earlines s introgressed from wild species Oryza australiensis into cultivated r ice, O. sativa L. One introgression line (IR65482-4-136-2-2), resistan t to biotypes 1, 2, and 3 of BPH and early in flowering, was selected from BC2F4 of the cross between O. sativa (IR31917-45-3-2) and O. aust raliensis (accession 100882). Recurrent parent, O. australiensis, and introgression line were surveyed for RFLP using probes of chromosomes 10 and 12. Two probes, RG457 and CDO98, detected introgression from O. australiensis. Cosegregation between introgressed characters and mole cular markers was studied in F-2 derived from the cross between the in trogression line and recurrent parent. The gene for BPH resistance is linked with RG457 of chromosome 12 at a distance of 3.68 +/- 1.29 cM, and the gene for earliness is linked with CDO98 of chromosome 10 at a distance of 9.96 +/- 3.28 cM. Such close linkage is useful in marker-b ased selection while transferring BPH resistance from introgression li ne into other elite breeding lines. Introgression at the molecular lev el indicates that the mechanism of alien gene transfer is probably gen etic recombination through crossing over rather than substitution of w hole or large segment of chromosomes of wild species.