LAUSR

Abstract T6V#2S·6AL and T6V#4S·6DL translocation chromosomes developed from the cross of wheat and different Dasypyrum villosum accessions have good powdery mildew (PM) resistance, but their pairing and pyramiding behavior remains unclear. Results in this study indicated that the pairing frequency rate of the two differently originated 6VS chromosomes in their F 1 hybrid was 18.9% according to genomic in situ hybridization (GISH); the PM resistance plants in the F 2 generation from the cross between T6V#4S·6DL translocation line Pm97033 and its PM susceptible wheat variety Wan7107 was fewer than expected. However, the ratio of the resistant vs. the susceptible plants of 15:1 in the F 2 generation derived from the cross between the two translocation lines of T6V#2S·6AL and T6V#4S·6DL fitted well. Plants segregation ratio (homozygous:heterozygous:lacking) revealed by molecular marker for T6V#4S·6DL or T6V#2S·6AL in their F 2 populations fitted the expected values of 1:2:1 well, inferring that the pairing of the two alien chromosome arms facilitates the transmission of T6V#4S·6DL from the F 1 to the F 2 generation. A quadrivalent was also observed in 21% of pollen mother cells (PMCs) of homozygote plants containing the two pairs of translocated chromosomes. The chromosome pairing between 6V#2S and 6V#4S indicates that it will be possible to obtain recombinants and clarify if the PM resistance determinant on one alien chromosome arm is different from that on the other.