Linked digenic epistasis in the inheritance of tillering and yielding ability in a cross of wheat

1984 ◽  
Vol 26 (2) ◽  
pp. 209-213 ◽  
Author(s):  
J. D. Patel ◽  
K. S. Bains
Keyword(s):  
Genetic Variation ◽  
Quantitative Traits ◽  
Triticum Aestivum L ◽  
Transgressive Segregation ◽  
Crossing Over ◽  
Repulsion Phase ◽  
Generation Means ◽  
Gene Dispersion ◽  
Biparental Mating ◽  
Duplicate Epistasis

The nature of genetic variation in an intervarietal cross ('WG 377' × 'Sonalika') of bread wheat (Triticum aestivum L. em Thell.) was determined for grain yield and tillers per plant by analyzing 21 generation means and 36 family variances. For both traits, duplicate epistasis of linked loci in the pairs and gene dispersion was observed through the analysis of 21 generation means. The analysis of generation variances further suggested repulsion phase linkages for the gene pairs. The additive genetic component was significant for both traits in each of the analyses. Prevalence of gene dispersion suggested the possibility of high transgressive segregation. However, the task of exploiting additive genetic variation would be difficult because of duplicate epistasis and repulsion phase linkages. Considering these results a breeding procedure like biparental mating among a large number of superior F2 plants which encourages crossing-over is suggested.Key words: Triticum, linked epistasis, quantitative traits, additive effects, tillering.

scholarly journals UNEQUAL CROSSING OVER AT THE rRNA TANDON AS A SOURCE OF QUANTITATIVE GENETIC VARIATION IN DROSOPHILA

Genetics ◽  
1980 ◽  
Vol 95 (3) ◽  
pp. 727-742 ◽  
Author(s):  
R Frankham ◽  
D A Briscoe ◽  
R K Nurthen
Keyword(s):  
Genetic Variation ◽  
Selection Response ◽  
Crossing Over ◽  
Wild Type ◽  
X Chromosomes ◽  
Unequal Crossing Over ◽  
Quantitative Genetic ◽  
Y Chromosomes ◽  
Homozygous Line ◽  
Minimum Estimate

ABSTRACT Abdominal bristle selection lines (three high and three low) and controls were founded from a marked homozygous line to measure the contribution of sex-linked "mutations" to selection response. Two of the low lines exhibited a period of rapid response to selection in females, but not in males. There were corresponding changes in female variance, in heritabilities in females, in the sex ratio (a deficiency of females) and in fitness, as well as the appearance of a mutant phenotype in females of one line. All of these changes were due to bb alleles (partial deficiencies for the rRNA tandon) in the X chromosomes of these lines, while the Y chromosomes remained wild-type bb+. We argue that the bb alleles arose by unequal crossing over in the rRNA tandon.—A prediction of this hypothesis is that further changes can occur in the rRNA tandon as selection is continued. This has now been shown to occur.—Our minimum estimate of the rate of occurrence of changes at the rRNA tandon is 3 × 10-4. As this is substantially higher than conventional mutation rates, the questions of the mechanisms and rates of origin of new quantitative genetic variation require careful re-examination.

scholarly journals Inherited Differences in Crossing Over and Gene Conversion Frequencies Between Wild Strains of Sordaria fimicola From “Evolution Canyon”

Genetics ◽  
2001 ◽  
Vol 159 (4) ◽  
pp. 1573-1593
Author(s):  
Muhammad Saleem ◽  
Bernard C Lamb ◽  
Eviatar Nevo
Keyword(s):  
Genetic Variation ◽  
Gene Conversion ◽  
Spontaneous Mutation ◽  
Crossing Over ◽  
Natural Genetic Variation ◽  
Evolution Canyon ◽  
Wild Strains ◽  
Sordaria Fimicola ◽  
First And Second Generation ◽  
Consistent Direction

Abstract Recombination generates new combinations of existing genetic variation and therefore may be important in adaptation and evolution. We investigated whether there was natural genetic variation for recombination frequencies and whether any such variation was environment related and possibly adaptive. Crossing over and gene conversion frequencies often differed significantly in a consistent direction between wild strains of the fungus Sordaria fimicola isolated from a harsher or a milder microscale environment in “Evolution Canyon,” Israel. First- and second-generation descendants from selfing the original strains from the harsher, more variable, south-facing slope had higher frequencies of crossing over in locus-centromere intervals and of gene conversion than those from the lusher north-facing slopes. There were some significant differences between strains within slopes, but these were less marked than between slopes. Such inherited variation could provide a basis for natural selection for optimum recombination frequencies in each environment. There were no significant differences in meiotic hybrid DNA correction frequencies between strains from the different slopes. The conversion analysis was made using only conversions to wild type, because estimations of conversion to mutant were affected by a high frequency of spontaneous mutation. There was no polarized segregation of chromosomes at meiosis I or of chromatids at meiosis II.

scholarly journals HSP90 affects the expression of genetic variation and developmental stability in quantitative traits

2008 ◽  
Vol 105 (8) ◽  
pp. 2963-2968 ◽  
Author(s):  
T. A. Sangster ◽  
N. Salathia ◽  
S. Undurraga ◽  
R. Milo ◽  
K. Schellenberg ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Quantitative Traits ◽  
Developmental Stability

Components of Genetic Variation Associated with Second and Third Chromosome Gene Arrangements in Drosophila melanogaster

Genetics ◽  
1987 ◽  
Vol 116 (1) ◽  
pp. 87-97
Author(s):  
James A Ferrari
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Low Temperature ◽  
Interaction Effect ◽  
Quantitative Traits ◽  
Development Time ◽  
Gene Arrangement ◽  
Optimal Conditions ◽  
Experimental Conditions ◽  
Chromosome Gene

ABSTRACT The effects of naturally occuring combinations of second and third chromosome gene arrangements of Drosophila melanogaster on two quantitative traits were partitioned into parameters of additive, dominance and interaction components of genetic variation. Development time and preadult survival of the gene arrangement genotypes were measured under four experimental conditions. Gene arrangement effects, when significant, were predominantly additive under all conditions. Experimental conditions, however, did influence gene arrangement effects. A second chromosome effect on development time was detected when amount of food or temperature was reduced, but not under optimal conditions. A third chromosome additive effect on development was observed under all experimental conditions. A consistent interaction effect between second and third chromosome gene arrangements was detected only at low temperature. Gene arrangement effects on survival were not as consistent as for development time, but also depended on experimental conditions.

scholarly journals Quantitative and molecular genetic variation in sympatric populations of Medicago laciniata and M. truncatula (Fabaceae): relationships with eco-geographical factors

2007 ◽  
Vol 89 (2) ◽  
pp. 107-122 ◽  
Author(s):  
MOUNAWER BADRI ◽  
HOUCINE ILAHI ◽  
THIERRY HUGUET ◽  
MOHAMED ELARBI AOUANI
Keyword(s):  
Genetic Variation ◽  
Genetic Variability ◽  
Local Adaptation ◽  
Quantitative Traits ◽  
Gene Diversity ◽  
Sympatric Populations ◽  
Widespread Species ◽  
Geographical Factors ◽  
Significant Difference ◽  
Selection For

SummaryMedicago laciniata is restricted to south of the Mediterranean basin and it extends in Tunisia from the inferior semi-arid to Saharan stages, whereas M. truncatula is a widespread species in such areas. The genetic variability in four Tunisian sympatric populations of M. laciniata and M. truncatula was analysed using 19 quantitative traits and 20 microsatellites. We investigated the amplification transferability of 52 microsatellites developed in M. truncatula to M. laciniata. Results indicate that about 78·85% of used markers are valuable genetic markers for M. laciniata. M. laciniata displayed significantly lower quantitative differentiation among populations (QST=0·12) than did M. truncatula (QST=0·45). However, high molecular differentiations, with no significant difference, were observed in M. laciniata (FST=0·48) and M. truncatula (FST=0·47). Several quantitative traits exhibited significantly smaller QST than FST for M. laciniata, consistent with constraining selection. For M. truncatula, the majority of traits displayed no statistical difference in the level of QST and FST. Furthermore, these traits are significantly associated with eco-geographical factors, consistent with selection for local adaptation rather than genetic drift. In both species, there was no significant correlation between genetic variation at quantitative traits and molecular markers. The site-of-origin explains about 5·85% and 11·27% of total quantitative genetic variability among populations of M. laciniata and M. truncatula, respectively. Established correlations between quantitative traits and eco-geographical factors were generally more moderate for M. laciniata than for M. truncatula, suggesting that the two species exhibit different genetic bases of local adaptation to varying environmental conditions. Nevertheless, no consistent patterns of associations were found between gene diversity (He) and environmental factors in either species.

scholarly journals MEIOTIC BEHAVIOR OF COMPOUND AUTOSOMES IN FEMALES OF DROSOPHILA MELANOGASTER: INTERCHROMOSOMAL EFFECTS AND THE SOURCE OF SPONTANEOUS NONSEGREGATION

Genetics ◽  
1980 ◽  
Vol 96 (2) ◽  
pp. 455-470
Author(s):  
Hideh Harger ◽  
David G Holm
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Inverse Correlation ◽  
Proximal Region ◽  
Crossing Over ◽  
X Chromosomes ◽  
Repulsion Phase ◽  
Base Level ◽  
Exchange Processes ◽  
Spontaneous Frequency

ABSTRACT In females of Drosophila melanogaster, compound autosomes enter the repulsion phase of meiosis uncommitted to a particular segregation pattern because their centromeres are not restricted to a bivalent pairing complex as a consequence of crossing over. Their distribution at anaphase, therefore, is determined by some meiotic property other than exchange pairing, a property that for many years has been associated with the concept of nonhomologous pairing. In the absence of heterologous rearrangements or a free Y chromosome, C(3L) and C(3R) are usually recovered in separate gametes, that is as products of meiotic segregation. Nevertheless, there is a regular, albeit infrequent, recovery of reciprocal meiotic products (the nonsegregational products) that are disomic and nullosomic for compound thirds. The frequency of these exceptions, which is normally between 0.5 and 5.0%, differs for the various strains examined, but remains constant for any given strain. Since previous studies have not uncovered a cause for this base level of nonsegregation, it has been referred to as the spontaneous frequency. In this study, crosses between males and females whose X chromosomes, as well as compound autosomes, are differentially marked reveal a highly significant positive correlation between the frequency of compound-autosome nonsegregation and the frequency of X-chromosome nondisjunction. However, an inverse correlation is found when the frequency of nondisjunction is related to the frequency of crossing over in the proximal region of the X chromosome. These findings have been examined with reference to the distributive pairing and the chromocentral models and interpreted as demonstrating (1) that nonsegregational meiotic events arise primarily as a result of nonhomologous interactions, (2) that forces responsible for the segregation of nonhomologous chromosomes are properties of the chromocentral region, and (3) that these forces come into expression after the exchange processes are complete.

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