Near-isogenic lines (NILs) and their recurrent parent Chancellor (Co) were used to identify restriction fragment length polymorphic markers linked to powdery mildew (Blumeria graminis (DC.) E.O. Speer f.sp. tritici) resistance genes Pm], Pro2, Pro3, and Pro4 in wheat (Triticum aestivum L. em. Theli). By mapping these poIymorphic markers in F: progenies from crosses of the NILs with C, it was found that Pro1 cosegregated with a polymovphic locus detected by DNA probe CDO347; Pro2 was linked to a locus detected by probe B CD[871 with a distance of 35 cM; Pm3b was linked to a locus detected by probe BCD1434 with a distance of 1.3 cM; Pm4a cosegregated with Xbcd1231-2A(2) and Xcdod78-2A, and was closeIy flanked by Xbcd1231-2A(t) and Xbcd292-2A both wiEh a distance of 1.5 cM. Aneuploid mapping of these markers indicated that locus Xcdo347-TA is on 7AL, Xbcd187]-5D on 5DS, Xbcd1434-1A on IAS, and loci Xbcd292-2A and Xcdo678-2A are on 2AL. The same polymorphic fragments detected in the Pm3b NIL by Xbcd1434-1A were found in Pm2a NIL. using several enzyme digestions.

Restriction fragment length polymorphism (RFLP) markers were used to map male fertility restor- ing gene that was transferred from chromosome 6U of Aegilops umbeIIulata Zhuk. to wheat. Segments of ehro-mosome 6U bearing the gene that restore fertility to T. tirnopheevi Zhuk. male sterile'cytoplasm were identified in all four translocation lines by two probes, BCD2t and BCD342. Lines 040-5, 06 l-I and 0614 are T6BL.6BS-6U translocations, while Iine 2114 is a T6AL.6AS-6U translocation, Line 211~ has a much larger 6U chromo-somal segment and lower frequency of transmission of male gametes with the alien segment than the other three lines The restoring gene carried by the 6U segment in 2114 showed high expressivity and complete penetrance. This restoring gene is designated Rf6. A homoeologous chromosome recombination mechanism is discussed for the alien gene transfer

Summary. Restriction fragment length polymorphism (RFLP) markers linked to genes controlling Hessian fly resistance from Triticum tauschii (Coss.) SchmaI. were identified for two wheat (Triticum aestivum L.) germ plasm lines KS89WGRC3 (C3) and KS89WORC6 (C6). Forty-six clones wlth loci on chromosomes of homoeologous group 3 and 28 clones on those of group 6 were surveyed for polymorphisms. Eleven and 12 clones detected "E tauschii loci in the two lines, res-pectively. Analysis of F2 progenies indicated that the Hessian fly resistance gene H23 identified in C3 is linked to XksuH4 (6.9cM) and XksuG48(A) (15.6cM) located on 6D. The resistance gene H24 in C6 is linked to XcnlBCD45I (5.9eM), XcnlCD0482 (5.9cM) and XksuG48(B) (12.9cM), located on 3DL.

Gene tagging is the basis of marker assisted selection and map based cloning. To develop PCR based markers for Pm4a, a dominant powdery mildew resistance gene of wheat, we surveyed 46 group 2 microsatellite markers between Pm4a near isogenic line (NIL) CI 14124 and the recurrent parent Chancellor (Cc). One of the markers, gwm356, detected polymorphism and was used for genotyping an F2 population of 85 plants derived from CI 14124 x Cc. Linkage mapping indicated that Xgwm356 was linked to Pm4a at a distance of 4.8cM. To identify more PCR based markers for Pm4a, we also converted the restriction fragment length polymorphism marker BCD1231 linked to it into a sequence tagged site (STS) marker. The STS primer designed based on the end sequences of B CD 1231 amplified an approximately 1.6kb monomorphic band in both parents. Following digestion of the products with the four cutter enzymes HaeⅢ and Mspl, it was discovered that the band from CI 14124 consisted of at least two products, one of which had a digestion pattern different from the band from Cc. In the F2 population, the cleaved polymorphism revealed by the STS marker between the parents co segregated with powdery mildew resistance. To design Pm4a specific PCR markers, the 1.6 kb band from Cc and the fragment associated with Pm4a in CI 14124 were sequenced and compared. Based on these sequences a new PCR marker was identified, which detected a 470 bp product only in the Pm4a containing lines. These PCR based markers provide a cost saving option for marker assisted selection of Pm4a.