Linkage between the centromere and a gene producing nucleocytoplasmic compatibility in durum wheat

Species cytoplasm specific (scs) genes on chromosome 1A (1A(scs)) derived f rom Triticum timopheevii Zhuk. and chromosome LD (1D(scs)) derived from com mon wheat improve compatibility between the durum wheat (T. turgidum L. var . durum) nucleus and Aegilops longissima S.& M. (lo) cytoplasm. The (lo) sc s durum lines thus produced are male sterile and when crossed with durum pr oduce viable plump seeds carrying scs and inviable shriveled seeds without scs, Objectives of the present study were to determine centromere-scs linka ge distances and viability and transmission of female gametes carrying one or both scs genes. The Oo) scs durum heterozygous for 1A/1A(scs) was crosse d with the Langdon (LDN) durum disomic substitution line 1D(scs)(1A) in whi ch the 1A chromosome pair is substituted by a 1D(scs) pair. Two types of 1A + 1D double monosomic F(1)s were recovered, Oo) durum 13 " + 1'1A(scs) + 1 '1D(scs), and (lo) durum 13 " + 1'1A + 1'1D(scs), which were confirmed in p rogeny tests with normal durum. For centromere mapping, these lines were cr ossed with LDN double ditelosomic 1A (LDN dDt 1A; 2n = 30; 13 " + t " 1AS t " 1AL) and progeny examined for meiotic chromosome constitution. No telo centric t1AL(scs) arising from recombination with 1A(scs) was detected, ind icating that scs is tightly Linked to the centromere on chromosome 1A. To d etermine the transmission of female gametes carrying one or both scs genes, Oo) durum 13 " + 1'1A(scs) + 1'1D(scs) was crossed with LDN dot 1A and con trol durum. The functional female gametes carried one or both scs genes. Cr osses of Oo) durum 13 " + 1'1A + 1'1D(scs) to LDN dot 1A produced several p lants with a T1AL.1DL translocation chromosome. The formation of this chrom osome was coupled with strong selection for the scs gene on 1DL.