scholarly journals The Length of the Intact Donor Chromosome Segment Around a Target Gene in Marker-Assisted Backcrossing

Genetics ◽  
2001 ◽  
Vol 157 (3) ◽  
pp. 1343-1356 ◽  
Author(s):  
Matthias Frisch ◽  
Albrecht E Melchinger
Keyword(s):  
Density Function ◽  
Target Gene ◽  
Chromosome Segment ◽  
Parental Origin ◽  
Recurrent Parent ◽  
Linkage Drag ◽  
Target Locus ◽  
Donor Chromosome ◽  
Recurrent Backcrossing ◽  
Marker Assisted Backcrossing

Abstract Recurrent backcrossing is an established procedure to transfer target genes from a donor into the genetic background of a recipient genotype. By assessing the parental origin of alleles at markers flanking the target locus one can select individuals with a short intact donor chromosome segment around the target gene and thus reduce the linkage drag. We investigated the probability distribution of the length of the intact donor chromosome segment around the target gene in recurrent backcrossing with selection for heterozygosity at the target locus and homozygosity for the recurrent parent allele at flanking markers for a diploid species. Assuming no interference in crossover formation, we derived the cumulative density function, probability density function, expected value, and variance of the length of the intact chromosome segment for the following cases: (1) backcross generations prior to detection of a recombinant individual between the target gene and the flanking marker; (2) the backcross generation in which for the first time a recombinant individual is detected, which is selected for further backcrossing; and (3) subsequent backcross generations after selection of a recombinant. Examples are given of how these results can be applied to investigate the efficiency of marker-assisted backcrossing for reducing the length of the intact donor chromosome segment around the target gene under various situations relevant in breeding and genetic research.

Comparative analysis of genetic background in eight near-isogenic wheat lines with different H genes conferring resistance to Hessian fly

Genome ◽  
2011 ◽  
Vol 54 (1) ◽  
pp. 81-89 ◽  
Author(s):  
S. S. Xu ◽  
C. G. Chu ◽  
M. O. Harris ◽  
C. E. Williams
Keyword(s):  
Genetic Background ◽  
Genetic Similarity ◽  
Triticum Aestivum L ◽  
Hessian Fly ◽  
Pedigree Analysis ◽  
Recurrent Parent ◽  
Linkage Drag ◽  
Near Isogenic Lines ◽  
Isogenic Lines ◽  
H Gene

Near-isogenic lines (NILs) are useful for plant genetic and genomic studies. However, the strength of conclusions from such studies depends on the similarity of the NILs’ genetic backgrounds. In this study, we investigated the genetic similarity for a set of NILs developed in the 1990s to study gene-for-gene interactions between wheat ( Triticum aestivum L.) and the Hessian fly ( Mayetiola destructor (Say)), an important pest of wheat. Each of the eight NILs carries a single H resistance gene and was created by successive backcrossing for two to six generations to susceptible T. aestivum ‘Newton’. We generated 256 target region amplification polymorphism (TRAP) markers and used them to calculate genetic similarity, expressed by the Nei and Li (NL) coefficient. Six of the NILs (H3, H5, H6, H9, H11, and H13) had the highly uniform genetic background of Newton, with NL coefficients from 0.97 to 0.99. However, genotypes with H10 or H12 were less similar to Newton, with NL coefficients of 0.86 and 0.93, respectively. Cluster analysis based on NL coefficients and pedigree analysis showed that the genetic similarity between each of the NILs and Newton was affected by both the number of backcrosses and the genetic similarity between Newton and the H gene donors. We thus generated an equation to predict the number of required backcrosses, given varying similarity of donor and recurrent parent. We also investigated whether the genetic residues of the donor parents that remained in the NILs were related to linkage drag. By using a complete set of ‘Chinese Spring’ nullisomic-tetrasomic lines, one third of the TRAP markers that showed polymorphism between the NILs and Newton were assigned to a specific chromosome. All of the assigned markers were located on chromosomes other than the chromosome carrying the H gene, suggesting that the genetic residues detected in this study were not due to linkage drag. Results will aid in the development and use of near-isogenic lines for studies of the functional genomics of wheat.

scholarly journals Introgression of the Afila Gene into Climbing Garden Pea (Pisum sativum L.)

Agronomy ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1537
Author(s):  
Oscar Checa ◽  
Marino Rodriguez ◽  
Xingbo Wu ◽  
Matthew Blair
Keyword(s):  
Pisum Sativum ◽  
Production Costs ◽  
Yield Potential ◽  
Recurrent Parent ◽  
Linkage Drag ◽  
Progeny Testing ◽  
High Biomass ◽  
Garden Pea ◽  
Pisum Sativum L ◽  
Field Peas

The pea (Pisum sativum L.) is one of the most important crops in temperate agriculture around the world. In the tropics, highland production is also common with multiple harvests of nearly mature seeds from climbing plant types on trellises. While the leafless variant caused by the afila gene is widely used in developing row-cropped field peas in Europe, its use for trellised garden peas has not been reported. In this study we describe a pea breeding program for a high-elevation tropical environment in the Department of Nariño in Colombia, where over 16,000 hectares of the crop are produced. The most widespread climbing varieties in the region are ‘Andina’ and ‘Sindamanoy’, both of which have high-biomass architecture with abundant foliage. They are prone to many diseases, but preferred by farmers given their long production season. This plant type is expensive to trellis, with wooden posts and plastic strings used for vine staking constituting 52% of production costs. The afila trait could reduce these costs by creating interlocking plants as they do in field peas. Therefore, our goal for this research was to develop a rapid breeding method to introduce the recessive afila gene, which replaces leaves with tendrils, into the two commercial varieties used as recurrent parents (RPs) with three donor parents (DPs)—‘Dove’, ‘ILS3575′ and ‘ILS3568′—and to measure the effect on plant height (PH) and yield potential. Our hypothesis was that the afila gene would not cause linkage drag while obtaining a leafless climbing pea variety. Backcrossing was conducted without selfing for two generations and plants were selected to recover recurrent parent characteristics. Chi-square tests showed a ratio of 15 normal leaved to one afila leaved in the BC2F2 plants, and 31:1 in the BC3F2 generation. Selecting in the last of these generations permitted a discovery of tall climbing plants that were similar to those preferred commercially, but with the stable leafless afila. The method saved two seasons compared to the traditional method of progeny testing before each backcross cycle; the peas reached the BC2F2 generation in five seasons and the BC3F2 in seven seasons. This is advantageous with trellised peas that normally require half a year to reach maturity. Leafless garden peas containing the afila gene were of the same height as recurrent parents and, by the third backcross, were equally productive, without the high biomass found in the traditional donor varieties. The value of the afila gene and the direct backcrossing scheme is discussed in terms of garden pea improvement and crop breeding.

Advanced backcross strategy for alien introgression for productivity enhancing traits in chickpea (Cicer arietinum L.)

2016 ◽  
Author(s):  
R. K. Bhavyasree ◽  
Sarvjeet Singh ◽  
Inderjit Singh
Keyword(s):  
Cicer Arietinum ◽  
Seed Yield ◽  
Growth Habit ◽  
Recurrent Parent ◽  
Linkage Drag ◽  
Seed Shape ◽  
Cicer Arietinum L ◽  
Advanced Backcross ◽  
Record Data ◽  
Prostrate Growth

A chickpea (Cicer arietinum L.) cultivar, GPF2, was crossed with two accessions, EC556270 and ILWC21, of its wild relative C. reticulatum with the objective to introgress productivity enhancing traits from wild to cultivated chickpea. The F1s were backcrossed to cultivated parent to generate backcross derived generations and also selfed to generate F3 progenies. In BC1F1 and BC2F1 generations, plants showing superiority for fruiting branches, pods and seed yield over the recurrent parent were recovered. A set of 77 BC1F2 and F3 progenies along with recurrent parent was grown to record data on various morphological traits, yield components and seed yield were recorded. There was significant improvement in number of pods, number of primary and secondary branches and seed yield. Some BC1F2 progenies recorded 30-32% higher seed yield as compared to recurrent parent. Many backcross progenies were superior to the cultivated parent for more than one trait. It was observed that F2 and F3 progenies were inferior as compared to the backcross derived progenies due to the undesirable characters like prostrate growth habit, seed shape and dull seed colour which were inherited from the wild parent. Results showed that the wild donors contributed several positive alleles for yield and yield contributing traits. The study also suggested that one or two backcrosses are required to reduce linkage drag of undesirable traits from the wild donors.

Genetic lag in a Meishan x Large White pig backcross population: A simulation study

2002 ◽  
Vol 2002 ◽  
pp. 59-59
Author(s):  
E.E. Wall ◽  
J.A. Woolliams ◽  
P.M. Visscher
Keyword(s):  
Linkage Drag ◽  
Large White ◽  
Donor Genome ◽  
Backcross Population ◽  
Identical By Descent ◽  
Target Locus ◽  
Trace Back ◽  
Donor Line ◽  
New Alleles ◽  
Large White Pig

Backcrossing can be used as a tool to introduce new alleles into a population. Having detected an allele of interest in a non-commercial (donor) line, backcrossing methods introduce the allele into a commercial (recipient) population whilst minimising the contribution of the less superior donor genome. Many alleles linked to the desired donor allele are incorporated into the recipient line by a phenomenon called linkage drag. Loci in the region of the target locus may trace back to a common ancestor and become identical by descent (IBD). This leads to a loss of diversity around the target locus. The linkage drag and contributions from ancestral recipient populations mean that the backcross population suffers genetic lag for commercial traits. This study aims to investigate the effect of population size and number of backcross generations on genetic lag, linkage drag and IBD around a target allele reducing back fat found in the Chinese Meishan breed when backcrossed to a commercial Large White population.

Recurrent parent genome recovery analysis in a marker-assisted backcrossing program of rice (Oryza sativa L.)

2015 ◽  
Vol 338 (2) ◽  
pp. 83-94 ◽  
Author(s):  
Gous Miah ◽  
Mohd Y. Rafii ◽  
Mohd R. Ismail ◽  
Adam B. Puteh ◽  
Harun A. Rahim ◽  
...  
Keyword(s):  
Oryza Sativa ◽  
Oryza Sativa L ◽  
Recurrent Parent ◽  
Recurrent Parent Genome ◽  
Marker Assisted Backcrossing

Escape From Repeat-Induced Point Mutation of a Gene-Sized Duplication in Neurospora crassa Crosses That Are Heterozygous for a Larger Chromosome Segment Duplication

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1581-1590 ◽  
Author(s):  
Ashwin Bhat ◽  
Durgadas P Kasbekar
Keyword(s):  
Transposable Element ◽  
Neurospora Crassa ◽  
Point Mutation ◽  
Target Gene ◽  
The Other ◽  
Chromosome Segment ◽  
Chromosome Segment Duplications ◽  
Repeat Induced Point Mutation

Abstract In Neurospora crassa the ability of an ectopic gene-sized duplication to induce repeat-induced point mutation (RIP) in its target gene was suppressed in crosses that were heterozygous for another larger chromosome segment duplication. Specifically, the frequency of RIP in the erg-3 gene due to a 1.3-kb duplication was reduced if the chromosome segment duplications Dp(IIIR > [I;II]) AR17, Dp(VIR > IIIR) OY329, or Dp(IVR > VII) S1229 were present in either the same or the other parental nucleus of the premeiotic dikaryon. We suggest that the larger duplications act as sinks to titrate the RIP machinery away from the smaller duplication. In contrast, RIP efficiency was relatively unaffected in comparably unproductive interspecies crosses with N. intermedia and N. tetrasperma. These findings offer a novel explanation for the observed persistence of the transposable element Tad in only a subset of Neurospora strains.

scholarly journals Validating a segment on chromosome 7 of japonica for establishing low-cadmium accumulating indica rice variety

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kai Wang ◽  
Tian-ze Yan ◽  
Shi-long Xu ◽  
Xu Yan ◽  
Qun-feng Zhou ◽  
...  
Keyword(s):  
Genetic Background ◽  
Safety Issue ◽  
Indica Rice ◽  
Rice Variety ◽  
Chromosome 7 ◽  
Recurrent Parent ◽  
Linkage Drag ◽  
Public Attention ◽  
Growth Duration ◽  
Cd Accumulation

AbstractCadmium (Cd) contamination of rice is a serious food safety issue that has recently been gaining significant public attention. Therefore, reduction of Cd accumulation in rice grains is an important objective of rice breeding. The use of favourable alleles of Cd accumulating genes using marker-assisted selection (MAS) is theoretically feasible. In this study, we validated a segment covering OsHMA3-OsNramp5-OsNramp1 on chromosome 7 of japonica for establishing low-cadmium accumulating indica rice variety. The OsHMA3-OsNramp5-OsNramp1jap haplotype significantly decreased grain Cd concentration in middle-season indica genetic background. The improved 9311 carrying the OsHMA3-OsNramp5-OsNramp1jap haplotype with recurrent parent genome recovery of up to 91.6% resulted in approximately 31.8% decrease in Cd accumulation in the grain and with no penalty on yield. There is a genetic linkage-drag between OsHMA3-OsNramp5-OsNramp1 jap and the gene conditioning heading to days (HTD) in the early-season indica genetic background. Because the OsHMA3-OsNramp5-OsNramp1-Ghd7jap haplotype significantly increases grain Cd concentration and prolongs growth duration, the linkage-drag between OsHMA3-OsNramp5-OsNramp1 and Ghd7 should be broken down by large segregating populations or gene editing. A novel allele of OsHMA3 was identified from a wide-compatibility japonica cultivar, the expression differences of OsNramp1 and OsNramp5 in roots might contribute the Cd accumulating variation between japonica and indica variety.

scholarly journals Disease resistance of improved MR220 lines against Pyricularia oryzae Cavara and their preliminary agronomic performance

2021 ◽  
Author(s):  
Siti Nor Aziemah Mohamad ◽  
Mohamad Bahagia Ab Ghaffar ◽  
Ahmad Sofiman Othman ◽  
Siti Norsuha Misman ◽  
Zuraida Abd Rahman ◽  
...  
Keyword(s):  
Rice Variety ◽  
Pyricularia Oryzae ◽  
Blast Disease ◽  
Management Approach ◽  
Recurrent Parent ◽  
Early Maturation ◽  
Efficient Management ◽  
Resistant Varieties ◽  
Marker Assisted Backcrossing ◽  
Group 1

Blast disease caused by Pyricularia oryzae is one of the most destructive fungal diseases of rice in Malaysia. Utilisation of resistant varieties is the most efficient management approach towards reducing yield losses. The line IRTP21683 with the Pi9 gene has shown strong resistance against the isolate MPO988.3 of pathotype P<sub>0.0</sub>, the most prevalent P. oryzae pathotype in Malaysia. Crossing of IRTP21683 was undertaken with the recurrent parent MR220, a susceptible elite Malaysian rice variety, using a marker assisted backcrossing technique with two simple sequence repeat markers, RM19776 and RM7311, as the tag for the Pi9 gene. Twenty BC<sub>3</sub>F<sub>4</sub> lines with the Pi9 gene were resistant when challenged with MPO 988.3. The cluster analysis based on seven agronomic parameters showed that the resistant BC<sub>3</sub>F<sub>4</sub> lines could be divided into four groups, of which the members in group 1 and 2 have shown comparable or better performance than MR220. Five lines in group 1, B220PI9-3-48, B220PI9-3-76, B220PI9-3-77, B220PI9-3-79 and B220PI9-3-82 showed outstanding yield performance with early maturation.

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