Linkage and cytogenetic maps of genes controlling endosperm storage proteins and isozymes in rye (Secale cereale L.)

Genetic association of crown rust resistance gene Pc68, storage protein loci, and resistance gene analogues in oats

Segregating F(3) families, derived from a cross between oat cultivar Swan and the putative single gene line PC68, were used to determine the association of seed storage protein loci and resistance gene analogues (RGAs) with the crown rust resistance gene Pc68. SDS-PAGE analysis detected three avenin loci, AveX, AveY, and AveZ, closely linked to Pc68. Their diagnostic alleles are linked in coupling to Pc68 and were also detected in three additional lines carrying Pc68. Another protein locus was linked in repulsion to Pc68. In complementary studies, three wheat RGA clones (W2, W4, and W10) detected restriction fragment length polymorphisms (RFLPs) between homozygous resistant and homozygous susceptible F(3) DNA bulks. Four oat homologues of W2 were cloned and sequenced. RFLPs detected with two of them were mapped using F(3) and F(4) populations. Clone 18 detected a locus, Orga2, linked in repulsion to Pc68. Clone 22 detected several RFLPs including Orga1 (the closest locus to Pc68) and three RGA loci (Orga22-2, Orga22-3, and Orga22-4) loosely linked to Pc68. The diagnostic RFLPs linked in coupling to Pc68 were detected by clone 22 in three additional oat lines carrying Pc68 and have potential utility in investigating and improving crown rust resistance of oat.

Leaf-rust resistance in rye (Secale cereale L.). 1. Genetic analysis and mapping of resistance genes Pr1 and Pr2

Genetic analysis of resistance to leaf rust in rye (Puccinia recondita f. sp. secalis) led to the identification of two dominant resistance genes, Pr1 and Pr2. Both genes proved to be effective against a local leaf-rust population as well as a subset of single-pustule isolates (SPIs) the latter of which comprised SPIs with very high virulence complexity. Resistance conferred by Pr1 and Pr2 was expressed in detached-leaf tests of seedlings as well as in field tests of adult plants. Molecular marker analysis allowed us to map Pr1 in the proximal part of rye chromosome 6RL, whereas Pr2 was assigned to the distal part of chromosome 7RL. These results are discussed in view of homoeology relationships among Triticeae. A proposal is submitted for the designation of resistance genes to rye leaf rust which would avoid interference with existing gene-symboling in respect to wheat leaf-rust resistances introgressed from rye into wheat or triticale.

Refined physical mapping of theSec-1locus on the satellite of chromosome 1R of rye (Secale cereale)

The Sec-1 locus (ω-secalin) of rye (Secale cereale L.) was mapped in the satellite of the short arm of chromosome 1R using fluorescence in situ hybridization and a genomic probe called pSec2B. Sec-1 is located in the middle of the satellite at the junction of the proximal euchromatic and the distal heterochromatic regions. Double hybridization experiments using rDNA and pSec2B showed that the NOR spans over the secondary constriction of the short arm of chromosome 1R and that there is a clearly visible gap between the NOR and Sec-1. Heterologous hybridization of pSec2B to barley visualized the B-hordein locus on chromosome 1H.Key words: fluorescence in situ hybridization, physical mapping, genetic mapping, secalin, rye, B-hordein, rDNA.

Genetic linkage between cytological markers and the seed storage protein lociSec2[Gli-R2] andSec3[Glu-R1] in rye

In order to reach a higher accuracy concerning the cytological locations of the rye seed storage protein lociSec2[Gli-R2] andSec3[Glu-R1] located within chromosome arms 2RS and 1RL, respectively, the linkage relationships between the following loci were analyzed: isozyme lociGpi-R1,Mdh-R1, andPgd2, translocationT273W (Wageningen tester set, involving chromosome arms 1RS and 5RL), the telomere C-bands of chromosome arms 1RL (tL1), 2RS (tS2), and 5RS (tS5), and three interstitial C-bands in chromosome arm 1RS (iS1), in the middle of chromosome arm 1RL (iL1), and in the middle of chromosome arm 2RL (iL2), respectively. The data indicated that locusSec3 is located in the distal half of chromosome arm 1RL (between C-bandiL1 and locusPgd2), while locusSec2 is located a short distance (2.9 ± 1.4%) from the telomere C-band of chromosome arm 2RS.

A cytogenetic map on the entire length of rye chromosome 1R, including one translocation breakpoint, three isozyme loci and four C-bands

A cytogenetic map of the whole 1 R chromosome of rye has been made, with distances between adjacent markers shorter than 50% recombination. Included in the map are isozyme loci Gpi-R1, Mdh-R1 and Pgd2, the telomere C-bands of the short arm (ts1) and the long arm (tl1), two interstitial C-bands in the short arm proximal to the nuclear organizing region (NOR) (is1) and in the middle of the long arm (il1), respectively, and translocation T273W (Wageningen tester set). By means of electron microscope analysis of spread pachytene synaptonemal complexes, the breakpoint of this translocation was physically mapped in the short arm of 1R, proximal to NOR, and in the long arm of 5R (contrary to previous assumptions). The data indicated the marker order: ts1 - Gpi-R1 - is1 - T273W/Mdh-R1 - il1 - Pgd2 - tl1. A comparison between genetic and physical maps revealed that recombination is mainly restricted to the distal regions of both arms. For the translocation T273W, in heterozygotes no recombinants were observed between the translocation breakpoint and its two adjacently located markers (is1 and Mdh-R1), but recombination was not reduced in the distal regions of the chromosome. The segregations of several other isozyme and C-band markers also analyzed in the investigation presented here were consistent with observations of earlier authors concerning chromosome asignment and linkage relationships.

Mapping of genes controlling seed storage-proteins and cytological markers on chromosome 1R of rye

Rye secalins, telomeric C-bands, and telocentric chromosomes were used as markers in the progeny of a test-cross in order to determine the position of seed storage-protein genes Glu-R1 and Gli-R1 with respect to the centromere and both telomeres of chromosome 1 R in rye. These genes were linked to the centromere (32.35±3.28% and 36.27±3.37% recombination, respectively). Glu-R1 was loosely linked to the telomere of the long arm (43.63±3.47% recombination), while Gli-R1 was closely linked to the telomere of the short arm (9.80±2.08% recombination). This finding supports the possibility that rye ω- and γ-secalin genes may be located on the satellites, as has been described in wheat for genes that code similar proteins. The importance of metaphase-I pairing failure and its consequences for the estimation of the recombination fraction are also discussed.

Restriction fragment analysis of the secalin loci of rye

Analyses of wheat/rye addition lines by Southern blotting confirmed the presence of sequences related to the Sec 1, Sec 2, and Sec 3 loci on chromosomes 1R and 2R. Comparison of the 1R and 2R addition lines allowed the identification of gamma-secalin genes at Sec 1 and Sec 2, respectively, while omega-secalin and gamma-secalin genes at Sec 1 were discriminated by comparative hybridization with three probes: omega-secalin, total gamma-secalin, and 3' gamma-secalin. The high molecular weight (HMW) secalin genes at Sec 3 were identified using a homologous HMW subunit probe from wheat. Gene copy numbers were estimated as about 40-60 for omega-scalins, 5-10 for gamma-secalins, and 2 for HMW secalins. Comparison of individual plants of cv. Gazelle showed a high degree of polymorphism, particularly for sequences related to omega-secalins and HMW secalins.

Identification and mapping of the Gli-R3 locus on chromosome 1R of rye (Secale cereale L.)

The progenies of two different rye test-crosses were analyzed for secalin proteins by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) using unreduced and reduced aqueous ethanol extracts. Segregation for two high-molecular-weight secalin bands (Glu-R1 or Sec3), one ω-secalin band (Gli-R1 or Sec-1), two 40K γ-secalin bands (Gli-R1 or Sec1) and two ω-type secalin bands (new locus) were studied. One recombinant between ω- and γ-secalins was found in one test-cross. The new locus, designated Gli-R3 or Sec-4, was mapped between Glu-R1 and Gli-R1, more displaced towards Gli-R1. In test-cross 1 recombination between Glu-R1 and Gli-R3 was 33.80±3.22%, and between Gli-R3 and Gli-R1, 12.04±2.21%. In the other test-cross the map distances were relatively similar but smaller, likely due to less recombination within two different species of Secale. Genes coding for 40K γ-secalins at Gli-R1 were likely proximal to the centromere with respect to genes coding for ω-secalins at the same complex locus.

A comparison of physical distribution of recombination in chromosome 1R in diploid rye and in hexaploid triticale

Polymorphism for six C-bands on chromosome 1R was used to study the frequency and distribution of recombination along the chromosome in a diploid rye (Secale cereale L.) and in a hexaploid triticale (X Triticosecale Wittmack) derived from it. In rye, the total recombination frequency in five segments of chromosome 1R was 93.7%. Recombination was concentrated in the distal regions of both chromosome arms and was infrequent in the proximal regions. In hexaploid triticale the total recombination frequency in the same chromosome was reduced to 51.7%. In both backgrounds the distal half of the long arm showed similar recombination frequencies, 51.4% and 45.7% for rye and triticale, respectively. The remaining about two-thirds of the chromosome length showed 42.3% recombination in rye but only 6% recombination in triticale. The results demonstrate that the genetic background in which mapping is performed not only affects the total amount of recombination, but also its distribution along the chromosome length.

The cytogenetic and molecular architecture of chromosome 1R--one of the most widely utilized sources of alien chromatin in wheat varieties

Chromosome 1R of rye (Secale cereale) is one of the most intensively used sources of alien chromatin in bread wheat. It provides a source of valuable disease resistance genes and its widespread use has stimulated the development of genetic maps incorporating protein and DNA markers. Published data as well as new mapping data were combined into a consensus map by using common markers in the different mapping studies to orient the various data sets relative to each other. The consensus map provides a tentative order, and relative distances, between the genetic markers. A summary of the dispersed repetitive sequences that are now available for the detection and characterization of chromosome 1R segments in wheat is also provided.

RFLP-based genetic map of rye (Secale cereale L.) chromosome 1R

A map of chromosome 1R of rye was constructed using 16 molecular and biochemical loci. From long arm to short arm, known-function loci were placed in the order: XAdh - XLee - Glu-R1[Sec-3] - XPpdk-1R - XEm-1R-1 - XEm-1R-2 - Centromere - XNor-R1 -Gpi-R1 - XGli-R1 [Sec-1a] along with six anonymous genomic and cDNA clones from wheat. The map, which spans 106 cM with 12 loci clustered in a 15-cM region around the centromere, shows reasonably good agreement with previously published maps for the centromeric region, whereas the XNor-R1 - Gpi-R1 region gives a much larger distance than previously reported.

Biochemical evidence of a translocation between 6 RL/7 RL chromosome arms in rye (Secale cereale L.). A genetic map of 6R chromosome

The segregation of different isozymic loci was investigated in backcrosses and F2s in rye. The leucin aminopeptidase-1 (Lap-1), Aconitase-1 (Aco-1), Esterase-6 (Est-6), Esterase-8 (Est-8), and Endopeptidase-1 (Ep-1) loci were linked. The Aco-1, Est-6, and Est-8 loci have been previously located on the 6RL chromosome arm. The Lap-1 locus has been located on the 6RS chromosome arm. The results favor the gene order: Lap-1... (centromere)... Aco-1... Est-8... Est-6... Ep-1. The isoelectric focusing separations of aqueous extracts from mature embryo tissue of wheat-rye addition and substitution lines involving the chromosomes of cereal rye Secale cereale L. confirmed the gene location of locus Ep-1 on the 6RL chromosome arm. Screening of wheat-rye addition lines involving the chromosomes of Secale montanum revealed that Ep-1 locus is not located on chromosome 6R of S. montanum. These results are the first biochemical evidence of the translocation between chromosome arms 6RL/7RL in the evolution of S. cereale from S. montanum.

Encoding genes for endosperm proteins in Hordeum chilense

The endosperm proteins encoded by the genome Hch in Hordeum chilense, Tritordeum (amphiploid Hordeum chilense x Triticum turgidum), common wheat-H. chilense addition lines, and the segregating plants resulting from the cross Tritordeum x T. turgidum, were fractionated by three electrophoretical techniques: SDS-PAGE, A-PAGE, and bidimensional PAGE. Prolamin subunits with a high molecular weight (HMW) were well visualized by SDS-PAGE, the A-PAGE technique permitted good resolution for many hordeins and gliadins, and two-dimensional electrophoresis allowed new sets of bands coded by gene complexes from H. chilense chromosomes to be distinguished. The loci Hor-Hch1 (up to 11 subunits belonging to the ω-, β - and α-hordeins), Glu-Hch1 (one HMW prolamin subunit), Hor-Hch2 (one α-hordein), and Hor-Hch3 (up to four α-hordeins) were located on the H. chilense chromosomes 1Hch, 5Hch, and 7Hch.