Field and Agroinoculation Screening for Resistance against MYMV in Mungbean Backcross Populations

Several mice with generalized lymphadenopathy were found in the CBA/KlJms (CBA) colony maintained at our institute. A new mutant strain of mice that develop massive lymphoid hyperplasia at 100% incidence within 5 mo after birth was established by crossing these diseased mice. Genetic studies on lymphadenopathy were conducted in F1, F2, and backcross populations from crosses between mutant CBA (CBA-m) and various inbred strains of mice. The results supported the control of lymphadenopathy by a single autosomal recessive gene. Since C3H/He-gld/gld (C3H-gld), MRL/MpJ-lpr/lpr (MRL-lpr), and C3H/HeJ-lpr/lpr (C3H-lpr) mice develop the same type of lymphoid hyperplasia, allelism of the mutant gene with gld or lpr was tested by investigating lymphadenopathy in F1 and backcross populations from crosses between CBA-m and C3H-gld, MRL-lpr, or C3H-lpr mice. The gene was confirmed to be allelic with lpr but not with gld. Interestingly, however, the mutant gene interacted with gld to induce less severe lymphadenopathy. Thus, the mutant gene was named lprcg, an lpr gene complementing gld in induction of lymphoproliferation. The genetic conclusion was supported by the same profile of surface markers of lymphoid cells with gld/gld, lpr/lpr, lprcg/lprcg, lprcg/lpr, and +/gld +/lprcg genotypes, as well as by massive lymph node hyperplasia and high titers of autoantibodies in the first four genotypes, but slight hyperplasia and insignificant autoantibody production in the last. The discovery of lprcg provided strong genetic evidence for the parallels between anomalous phenotypes of gld and lpr, and CBA/KlJms-lprcg/lprcg mice will contribute to elucidation of the mechanism of induction of the same abnormal differentiation and functions of lymphocytes by gld and lpr.

Download Full-text

High-density linkage map around the root aerenchyma locus Qaer1.06 in the backcross populations of maize Mi29 × teosinte “Zea nicaraguensis”

Breeding Science ◽

10.1270/jsbbs.59.427 ◽

2009 ◽

Vol 59 (4) ◽

pp. 427-433 ◽

Cited By ~ 27

Author(s):

Yoshiro Mano ◽

Fumie Omori

Keyword(s):

Linkage Map ◽

High Density ◽

Root Aerenchyma ◽

Backcross Populations ◽

High Density Linkage Map

Download Full-text

Marker-Assisted Introgression in Backcross Breeding Programs

Genetics ◽

10.1093/genetics/144.4.1923 ◽

1996 ◽

Vol 144 (4) ◽

pp. 1923-1932 ◽

Cited By ~ 10

Author(s):

Peter M Visscher ◽

Chris S Haley ◽

Robin Thompson

Keyword(s):

Quantitative Trait ◽

Genetic Model ◽

Phenotypic Selection ◽

Inbred Lines ◽

Breeding Programs ◽

Coupling Phase ◽

Breed Difference ◽

Backcross Populations ◽

Backcross Breeding ◽

Marker Spacing

The efficiency of marker-assisted introgression in backcross populations derived from inbred lines was investigated by simulation. Background genotypes were simulated assuming that a genetic model of many genes of small effects in coupling phase explains the observed breed difference and variance in backcross populations. Markers were efficient in introgression backcross programs for simultaneously introgressing an allele and selecting for the desired genomic background. Using a marker spacing of 10–20 cM gave an advantage of one to two backcross generations selection relative to random or phenotypic selection. When the position of the gene to be introgressed is uncertain, for example because its position was estimated from a trait gene mapping experiment, a chromosome segment should be introgressed that is likely to include the allele of interest. Even for relatively precisely mapped quantitative trait loci, flanking markers or marker haplotypes should cover ∼10–20 cM around the estimated position of the gene, to ensure that the allele frequency does not decline in later backcross generations.

Download Full-text

Genetic Architecture of a Morphological Shape Difference Between Two Drosophila Species

Genetics ◽

10.1093/genetics/154.1.299 ◽

2000 ◽

Vol 154 (1) ◽

pp. 299-310 ◽

Cited By ~ 11

Author(s):

Zhao-Bang Zeng ◽

Jianjun Liu ◽

Lynn F Stam ◽

Chen-Hung Kao ◽

John M Mercer ◽

...

Keyword(s):

Interval Mapping ◽

Additive Effect ◽

Parameter Estimates ◽

Effect Estimate ◽

Interspecific Difference ◽

Posterior Lobe ◽

Complete Dominance ◽

Backcross Populations ◽

History Of ◽

Trait Locus

AbstractThe size and shape of the posterior lobe of the male genital arch differs dramatically between Drosophila simulans and D. mauritiana. This difference can be quantified with a morphometric descriptor (PC1) based on elliptical Fourier and principal components analyses. The genetic basis of the interspecific difference in PC1 was investigated by the application of quantitative trait locus (QTL) mapping procedures to segregating backcross populations. The parental difference (35 environmental standard deviations) and the heritability of PC1 in backcross populations (>90%) are both very large. The use of multiple interval mapping gives evidence for 19 different QTL. The greatest additive effect estimate accounts for 11.4% of the parental difference but could represent multiple closely linked QTL. Dominance parameter estimates vary among loci from essentially no dominance to complete dominance, and mauritiana alleles tend to be dominant over simulans alleles. Epistasis appears to be relatively unimportant as a source of variation. All but one of the additive effect estimates have the same sign, which means that one species has nearly all plus alleles and the other nearly all minus alleles. This result is unexpected under many evolutionary scenarios and suggests a history of strong directional selection acting on the posterior lobe.

Download Full-text

Cosegregation of Single Genes Associated with Fertility Restoration and Transcript Processing of Sorghum Mitochondrial orf107 and urf209

Genetics ◽

10.1093/genetics/150.1.383 ◽

1998 ◽

Vol 150 (1) ◽

pp. 383-391 ◽

Cited By ~ 1

Author(s):

Hoang V Tang ◽

Ruying Chang ◽

Daryl R Pring

Keyword(s):

Fertility Restoration ◽

Mitochondrial Gene ◽

Pollen Viability ◽

Single Gene ◽

Dominant Gene ◽

Nuclear Gene ◽

Male Sterile ◽

Reading Frame ◽

Transcript Processing ◽

Backcross Populations

Abstract Defective nuclear-cytoplasmic interactions leading to aberrant microgametogenesis in sorghum carrying the IS1112C male-sterile cytoplasm occur very late in pollen maturation. Amelioration of this condition, the restoration of pollen viability, involves a novel two-gene gametophytic system, wherein genes designated Rf3 and Rf4 are required for viability of individual gametes. Rf3 is tightly linked to, or represents, a single gene that regulates a transcript processing activity that cleaves transcriptsof orf107, a chimeric mitochondrial open reading frame specific to IS1112C. The mitochondrial gene urf 209 is also subject to nucleus-specific enhanced transcript processing, 5′ to the gene, conferred by a single dominant gene designated Mmt1. Examinations of transcript patterns in F2 and two backcross populations indicated cosegregation of the augmented orf107 and urf209 processing activities in IS1112C. Several sorghum lines that do not restore fertility or confer orf107 transcript processing do exhibit urf209 transcript processing, indicating that the activities are distinguishable. We conclude that the nuclear gene(s) conferring enhanced orf107 and urf209 processing activities are tightly linked in IS1112C. Alternatively, the similarity in apparent regulatory action of the genes may indicate allelic differences wherein the IS1112C Rf3 allele may differ from alleles of maintainer lines by the capability to regulate both orf107 and urf209 processing activities.

Download Full-text

Molecular Mapping of Segregation Distortion Loci in Aegilops tauschii

Genetics ◽

10.1093/genetics/149.1.319 ◽

1998 ◽

Vol 149 (1) ◽

pp. 319-327 ◽

Cited By ~ 1

Author(s):

J D Faris ◽

B Laddomada ◽

B S Gill

Keyword(s):

Segregation Distortion ◽

Molecular Mapping ◽

Aegilops Tauschii ◽

Distorted Segregation ◽

F2 Population ◽

Male Gametes ◽

Skewed Segregation ◽

Segregation Ratios ◽

Backcross Populations ◽

Intraspecific Hybrids

Abstract Distorted segregation ratios of genetic markers are often observed in progeny of inter- and intraspecific hybrids and may result from competition among gametes or from abortion of the gamete or zygote. In this study, 194 markers mapped in an Aegilops tauschii F2 population were surveyed for distorted segregation ratios. Region(s) with skewed segregation ratios were detected on chromosomes 1D, 3D, 4D, and 7D. These distorter loci are designated as QSd.ksu-1D, QSd.ksu-3D, QSd.ksu-4D, and QSd.ksu-7D. Three regions of segregation distortion identified on chromosome 5D were analyzed in two sets of reciprocal backcross populations to analyze the effect of sex and cytoplasm on segregation distortion. Extreme distortion of marker segregation ratios was observed in populations in which the F1 was used as the male parent, and ratios were skewed in favor of TA1691 alleles. There was some evidence of differential transmission caused by nucleo-cytoplasmic interactions. Our results agree with other studies stating that loci affecting gametophyte competition in male gametes are located on 5DL. The distorter loci on 5DL are designated as QSd.ksu-5D.1, QSd.ksu-5D.2, and QSd.ksu-5D.3.

Download Full-text