Variation In Generation Means Research Articles

Genetic effects on panicle traits of crossbred rainfed rice cultivars using generation mean analysis

The nature and magnitude of gene effects involved in expression of panicle traits in rainfed rice cultivars were estimated among a wide range of crosses using generation mean analysis. The parental lines comprised of two low-land and six upland rain-fed rice. The lowland parents were used as pollen parents and the upland genotypes were maintained as the seed parents. Crosses were made between them to obtain the F1 hybrids. Backcrosses were produced by crossing the F1 hybrids to their pollen parent to obtain BC1.1 and seed parents to produce BC1.2. The result revealed significant differences (P ≤ 0.05) among the genotypes for all the characters studied. Except for Max x CT7127-49 where P2 and F2 plants of WITA 4 x NERICA 1 that produced long panicles (29.28 and 26.13 cm) that differed significantly (P ≤ 0.05) from other generations, F1 plants produced the longest panicles in the other crosses followed by the F2 plants. For most traits, F1 generation means were higher than the mid-parent values. Significant differences observed between the F1 and F2 generation means in majority of the cases for percentage fertile spikelet and spikelet number per panicle is thought to be due to the diversity in these traits among the parental lines. The means of BC₁ and BC2 tended to be located close to those of their respective recurrent parents. Digenic epistatic model was adequate to explain variation in generation means for all the panicle traits for the pooled analysis. Most of the crosses manifested non-allelic interactions for number of spikelet per panicles and fertile spikelet per panicle and is an indication that epistasis is determined to some extent by the genotypes used for the study. Key words: Generation mean, dominance, additive, epistasis, F1, F2, parental line and backcross.

Identification of Transgressive Segregants for Yield and Its Components in Basil (Ocimum basilicumL.)

The objective of this study was to estimate gene effects and identification of transgressive segregants for five quantitative traits of seven crosses of Ocimum basilicum L. viz. EC388788 × IC333322, EC387893 × IC326711, EC388896 × IC369247, EC388887 × IC386833, EC387837 × EC338785, IC369247 × IC370846 and IC344681 × IC326735 by generation mean analysis. In cases both type of epistasis (complementary and duplicate) model was sufficient to explain variation in generation means. Generation mean analysis with three parameter model with χ2 test indicated that additive-dominance model was inadequate for all the traits like number of inflorescence, length of inflorescence, fresh herb yield, dry herb yield and oil content in all the crosses used of six parameter models to estimate the gene effects. The observed frequencies of transgressive segregants for trait oil content (4.942), fresh herb yield (11.824), dry herb yield (13.97) and length of inflorescence (5.820). A comparison of generation mean analysis for observed and predicted frequencies of transgressive segregants indicated that the potential crosses for transgressive segregants were those that had additive and dominance gene effects. The adequacies of certain models of inheritance as well as the importance and significance of gene effects and identifications of transgressive segregants for analyzed traits were dependent upon the particular crossing combination and experimental site. The present study indicated that early generation selection is effective and should be practiced for future breeding programme.

Genetic adaptability of the inheritance of the resistance to different levels of aggressiveness of Septoria tritici isolates in durum wheat

The aim of this study was to evaluate the variation in the mode of inheritance for resistance in durum wheat to Septoria tritici with the aggressiveness level of the pathogen. Material for the study involved two wheat cross-combinations and offspring populations. In each cross, the parental genotypes, F 1, F 2, BC 1P r and BC 1P s were inoculated with 15 isolates of S. tritici with different levels of aggressiveness. Generation mean analysis revealed that the mode of inheritance varied with the aggressiveness level of isolates. For less aggressive isolates, in both crosses, only additive and dominance effects were determined. When tested with isolates with moderate levels of aggressiveness, the additive-dominance model was not sufficient to explain the variation in generation means; and a di-genic epistasis model was found appropriate. For a high level of aggressiveness, both additive-dominance and di-genic epistatic models failed to explain the phenotypic variation in generation means, and probably higher order interaction or genes linkage were present. The quantification of gene effects revealed that the absolute total of epistatic effects increased with aggressiveness level of the isolate. Selection based on less aggressive isolates would be simpler, because only additive and dominance effects are implicated, but the genetic mechanism will not be stable with isolates of high aggressiveness level. Thus, selection with highly aggressive isolats is suggested for the stability of resistance to S. tritici in durum wheat.

Genetic adaptability of durum wheat to salinity level at germination stage

Faculty of Sciences, University of Tunis El Manar, Tunis from April to May 2010 to improve salt tolerance during germination stage. For this purpose, two crosses and their progenies (F1, F2, BC1Ps and BC1Pr) were used based on shoot length at different salinity levels (0, 50, 75, 100, 150 and 200 mmol/L). Significant differences for salt tolerance between means of generations were observed in all the treatments. Separate generation means analysis indicated that inheritance of resistance to salt at germination stage was dependent upon the level of salinity. With low salinity level (50 and 75 mmol/L), only additive and dominance effects were implicated in the genetic control of this trait. For moderate salinity level (100 and 150 mmol/L) in the two crosses, genetic interactions were solicited and the digenic epistatic model was sufficient to explain variation in generation means. However, for the 200 mmol/L treatment, none of these models explained the variations in generation means and probably, higher order interactions or genes linkage were solicited. The estimated values of narrow-sense heritability were dependent on the cross and the salinity level and ranged between 29 and 90%. The results of this study indicated that selection in specific environments is useful for enhancing resistance to salt, but it may not be effective in providing resistance across a wide range of environments. Keys words: Durum wheat, genetic-adaptability, salinity level.

Studies on Gene Effects in IntervarietalCrosses of Hirsutum Cotton

Basic sets of six generations of two varietal crosses of cotton were studied to estimate nature and magnitude of gene effects operative in the inheritance of yield components and fibres quality traits. Scaling tests as well as joint scaling test detected the presence of epistasis for seed cotton yield, bolls per plant, boll weight and 2.5% span length in cross LH900 x Senegal and for boll weight, ginning outturn and 2.5% span length in cross LH900 x LRA 5166. Additive-dominance model was sufficient to explain variation in generation means for the remaining traits. Inheritance pattern of various traits differed in the two crosses and additive as well as non-additive gene effects were found to be important. Keeping in view the importance of both additive and non-additive gene effects, it was suggested that sophisticated selection procedures as recurrent selection and population improvement might be followed for simultaneous improvement of yield and fibre characters.

Cytoplasmic effects on grain resistance to yellowberry in durum wheat

Parental, F<sub>1</sub>, reciprocal F<sub>1</sub> (RF<sub>1</sub>), F<sub>2</sub>, reciprocal F<sub>2</sub> (RF<sub>2</sub>), BC<sub>1</sub>P<sub>1 </sub>and BC<sub>1</sub>P<sub>2</sub> generations of four crosses involving four cultivars of durum wheat (Triticum durum Desf.) were evaluated for grain resistance to yellowberry. Significant differences were reported for F<sub>1</sub>, F<sub>2 </sub>and their reciprocals in all crosses. A generation means analysis indicated the inadequacy of additive-dominance model and additive-dominance model considering maternal effects. However, the variation in generation means in the four crosses could be explained by a digenic epistatic model with cytoplasmic effects. Cytoplasmic effects were significant and consistent in all the crosses. Dominance effects and additive × dominance epistasis were more important than additive effects and other epistatic components. The choice of a female parent possessing grain resistance to yellowberry appeared to be decisive in durum wheat breeding for resistance to this serious seed disorder.

Epistasis and Maternal Effect in Resistance to Puccinia coronata Cda. f. sp. avenae Eriks in Oats ( Avena sp.)

The objective of this paper was to investigate the mode of heredity for resistance in oats ( Avena sp .) to crown rust caused by Puccinia coronata Cda. f. sp. avenae Eriks. Eight generations of 2 crosses were used to estimate genetic effects and narrow-sense heritability (NSH). Separate generation means analysis (GMA) indicated a complex gene action controlling this trait with additive, dominance, epistatic and maternal effects (ME). The genetic model which assumed no epistasis and no ME did not accurately describe the resistance to P. coronata. In both crosses, the digenic epistatic model with ME was sufficient to explain variation in generation means for isolate CR Pc58 and isolate CR Pc46 . Additive dominance and epistatic components were negative in most cases, suggesting that gene effects contributed more to the resistance than to the susceptibility. The estimated values of NSH were 15-99% depending upon the cross and isolates. The results indicated that appropriate choice of maternal parent and recurrent selection would increase resistance to crown rust in oats.

Epistasis and genotype-by-environment interaction of grain yield related traits in durum wheat

Genetic control of the number of heads per plant, spikelets per spike and grains per spike was studied in two durum wheat (Triticum durum Desf.) crosses, Inrat 69/Cocorit71 and Karim/Ben Bechir, respectively. Separate analyses of gene effects were done using means of four generations (parents P1 and P2, F1, F2, and the two reciprocal BC1) at two sites. A three-parameter model was inadequate to explain all traits except number of heads per plant in Inrat 69/Cocorit 71 at one site. In most cases a digenic epistatic model explained variation in generation means. Dominance effects and dominance ´ dominance epistasis (l) were more important than additive effects and other epistatic components. Considering the genotype-by-environment interaction, the interactive model was applied and found adequate in all majority of cases except spiklets per spike and grains per spike in Inrat 69/Cocorit71. The results of this study indicate that maintenance of heterozygosity is useful for exploitation of epistatic effects and adaptability to varied environmental conditions for spiklets per spike and grain per spike in the cross Karim/Ben Bechir. Estimates of narrow-sense heritability indicated that the genetic effect was larger than the environmental effect. The additive effect was the largest component of genetic effects. Key words: Genetic effects, epitasis, genotype-by-environment interaction,heritability, Triticum durum.

Epistasis and genotype-by-environment interaction of grain protein content in durum wheat

Parental, F1 , F 2 , BC 1 and BC 2 generations of four crosses involving four cultivars of durum wheat (Triticum durum Desf.) were evaluated at two sites in Tunisia. A three-parameter model was found inadequate for all cases except crosses Chili x Cocorit 71 at site Sidi Thabet and Inrat 69 x Karim at both sites. In most cases a digenic epistatic model was sufficient to explain variation in generation means. Dominance effects (h) and additive x additive epistasis (i) (when significant) were more important than additive (d) effects and other epistatic components. Considering the genotype-by-environment interaction, the non-interactive model (m, d, h, e) was found adequate. Additive variance was higher than environmental variance in three crosses at both sites. The estimated values of narrow-sense heritability were dependent upon the cross and the sites and were 0%-85%. The results indicate that appropriate choice of environment and selection in later generations would increase grain protein content in durum wheat.

Gene Effects for Parameters of Peanut bud necrosis virus (PBNV) Resistance in Peanut

The objective of this study was to determine relative importance of gene effects for PBNV incidence and PBNV severity evaluated at 30, 40, 50 and 60 days after planting. Eight generations of three crosses involved three parental lines were evaluated for disease incidence (percentage of infected plants) and disease severity under natural occurrence of PBNV infection in a randomized complete block design with six replications. Evaluations were carried out at 30, 40, 50 and 60 Days After Planting (DAP). The analysis followed Hayman's model and Gamble's notations were used to describe parameters of gene effects. Joint scaling test was used to determine adequacy of the model. Additive gene effect was the most important contribution to genetic variation in generation means for both disease incidence and disease severity in the cross ICGV 86388 x IC 10. Selection for lower disease incidence and disease severity in this cross is promising. Additive gene effect and additive x additive epistatic gene effect were also important but in lower magnitude in the cross ICGV 86388 x KK 60-1 for disease incidence at 60 DAP. The presence of significant dominance gene effect in this cross for disease incidence might hinder the progress from selection. The consistent and significant additive gene effect for disease severity might provide a better selection strategy. Additive gene effect was significant for disease incidence only in the cross IC 10 x KK 60-1 at 60 DAP. Additive x dominance epistatic gene effect was also significant at 40 DAP, but no genetic parameter was significant for disease severity. This cross is considered less promising.

Quantitative inheritance of some wheat plant traits

The objective of this study was to estimate gene effects and genetic variability for some quantitative traits of two winter wheat crosses (Soissons/Zitarka and Soissons/Sana) by generation mean analysis. In most cases a digenic epistatic model was sufficient to explain variation in generation means. The additive-dominance model was adequate for plant height and grain weight per spike of the longest culm. In two cases (grain yield per plant and single grain weight) these models failed to explain variation in generation means, implying the presence of higher order interactions or interactions between linked loci. Dominance effects and additive x additive epistasis were more important than additive effects and other epistatic components. Only complementary type epistasis was observed. The estimated values of narrow-sense heritability (h2n) varied for plant height (54-81%), number of heads per plant (9-76%), number of grains per spike (11-99.8%), grain weight per spike (23-73%), grain yield per plant (21-78%) and single grain weight (49.7-72%). The adequacy of certain modes of inheritance as well as the importance and significance of gene effects and genetic components of variance for analyzed traits were dependent upon the particular crossing combination and experimental site.

Absence of Epistasis for Grain Yield in Elite Maize Hybrids

Certain maize (Zea mays L.) inbred lines are more successful than others in forming elite hybrids. This study was conducted to determine whether epistatic interactions play a significant role in hybrid performance. Statistical epistasis was measured with a modified generation means model using testcrosses. Six progeny generations (P1, P2, F1, F2, and a backcross from the F1 to each parent) were produced for all possible hybrids of a five-parent diallel in both the Iowa Stiff Stalk Synthetic (BSSS) and non-BSSS heterotic groups. Two testers were hybridized to each of the 10 possible hybrid progeny sets in both groups. Each testcross progeny set was evaluated in 10 environments. The nonepistatic model accounted for a large amount of the variation in generation means and fit the data well. Of the 40 maize testcross progeny sets studied, five resulted in a significant epistatic effect for grain yield. Four of the significant epistatic effects showed evidence of linkage, while one was due to unlinked epistatic effects. Our results suggest that parents in a hybrid cross need to be significantly different and testers need to bring out those differences to detect epistasis better by means of testcross generation means.

Absence of Epistasis for Grain Yield in Elite Maize Hybrids

Certain maize (Zea mays L.) inbred lines are more successful than others in forming elite hybrids. This study was conducted to determine whether epistatic interactions play a significant role in hybrid performance. Statistical epistasis was measured with a modified generation means model using testcrosses. Six progeny generations (P1, P2, F1, F2, and a backcross from the F1 to each parent) were produced for all possible hybrids of a five‐parent diallel in both the Iowa Stiff Stalk Synthetic (BSSS) and non‐BSSS heterotic groups. Two testers were hybridized to each of the 10 possible hybrid progeny sets in both groups. Each testcross progeny set was evaluated in 10 environments. The nonepistatic model accounted for a large amount of the variation in generation means and fit the data well. Of the 40 maize testcross progeny sets studied, five resulted in a significant epistatic effect for grain yield. Four of the significant epistatic effects showed evidence of linkage, while one was due to unlinked epistatic effects. Our results suggest that parents in a hybrid cross need to be significantly different and testers need to bring out those differences to detect epistasis better by means of testcross generation means.

Genetics of nitrate content of lettuce, 1: Analysis of generation means

The genetics of nitrate content in butterhead lettuce (Lactuca sativa L.) was studied using the mean values of five parental genotypes and several generations obtained from crosses between them. One high nitrate parental genotype was chosen and four low nitrate ones. A diallel analysis showed additive genetic effects to be the major source of variation in generation means. Estimates of additive genetic effects differed significantly between experiments, indicating genotype x experiment interactions. Effects of dominance were relatively small. The size and direction of dominance varied between experiments. Reciprocal differences were of very limited size and also varied between experiments. The inheritance of nitrate content in lettuce fitted the additive-dominance genetic model.

Inheritance of heading date, plant height, ear length and spikelets per spike in an intervarietal cross of wheat

A study to obtain information on early segregating generations of an intervarietal cross 'WG 357' X 'Tobari 66' in spring wheat on the genetics of days to heading, plant height, ear length and spikelets per spike was conducted. 'WG 357' has amber, hard and lustrous grains and is a well adapted high yielding variety of North India whereas 'Tobari 66' is red grained introduction from CIMMYT.The parental F1, F2, B1, B2, biparentals, F3 (parents of biparentals), F3 bulk and F4 bulk generations were studied in order to provide analysis of generations means (Mather 1949; Hayman 1958) and variance component analysis (Kearsay 1965; Perkins and Jinks 1970).There were highly significant differences among the generations for all the characters studied. There were significant differences among the F3 lines as well as among the biparental progenies. Only in case of ear length was the contrast between the two also significant. The mean value of most of the generations arising from the cross fell between the parental range.The three-parameter model failed to account for the variation in generation means in the case of days to heading. This character was concluded to be influenced by linkage and higher order interactions. For the other characters the three parameter model was adequate. For all characters, additive gene effects were most important as compared to dominance gene effects.The analysis of gene action as provided by the generation variance indicated that additive variance was much more pronounced as compared to dominance variance. The heritability was high for days to heading (71 per cent for narrow sense and 80 per cent in broad sense) and plant height (62 and 93 per cent in narrow and broad sense respectively.The implications of the results in breeding programmes have been discussed.

The separation of epistatic from additive and dominance variation in generation means. II.

The difficulty of specifying additive and dominance variation in the presence of epistasis is described. This difficulty can be overcome when the epistasis is at a relatively low level of intensity but when epistasis is the major source of genetic variation no measure of additive or dominance variation is possible. Heterosis in a cross between two inbred lines ofNicotiana rustica was found to be due to dominance opposed to a small extent by epistasis. The misleading nature of another method of partitioning heterosis is pointed out.

The separation of epistatic from additive and dominance variation in generation means

The difficulty of specifying additive and dominance variation in the presence of epistasis is described. This difficulty can be overcome when the epistasis is at a relatively low level of intensity but when epistasis is the major source of genetic variation no measure of additive or dominance variation is possible.

Gene Analysis by the Partitioning Method When Interactions of Genes are Involved

Previous articleNext article No AccessGene Analysis by the Partitioning Method When Interactions of Genes are InvolvedLeroy PowersLeroy Powers Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 113, Number 1Sep., 1951 Article DOIhttps://doi.org/10.1086/335691 Views: 4Total views on this site Citations: 11Citations are reported from Crossref Journal History This article was published in the Botanical Gazette (1876-1991), which is continued by International Journal of Plant Sciences (1992-present). PDF download Crossref reports the following articles citing this article:Derek A. Roff, Kevin Emerson EPISTASIS AND DOMINANCE: EVIDENCE FOR DIFFERENTIAL EFFECTS IN LIFE-HISTORY VERSUS MORPHOLOGICAL TRAITS, Evolution 60, no.1010 (May 2007): 1981–1990.https://doi.org/10.1111/j.0014-3820.2006.tb01836.xJohn K Kelly Epistasis in Monkeyflowers, Genetics 171, no.44 (Dec 2005): 1917–1931.https://doi.org/10.1534/genetics.105.041525M. C. Kharkwal, Darbeshwar Roy A Century of Advances in Plant Breeding Methodologies, (Jan 2004): 17–48.https://doi.org/10.1007/978-94-007-1040-5_2O. D. Chebotar, S. T. Chalyk The use of maternal haploids for genetic analysis of the number of kernel rows per ear in maize, Hereditas 124, no.22 (May 2004): 173–178.https://doi.org/10.1111/j.1601-5223.1996.00173.xYonatan Elkind, Avigdor Cahaner, Nachum Kedar A mixed model for the effects of single gene, polygenes and their interaction on quantitative traits. 2. The effects of the nor gene and polygenes on tomato fruit softness, Heredity 64, no.22 (Apr 1990): 205–213.https://doi.org/10.1038/hdy.1990.25PR Jackson, GT Tucker, HF Woods Testing for bimodality in frequency distributions of data suggesting polymorphisms of drug metabolism-hypothesis testing., British Journal of Clinical Pharmacology 28, no.66 (Jul 2012): 655–662.https://doi.org/10.1111/j.1365-2125.1989.tb03558.xWim J. Van Der Linden The Use of Moment Estimators for Mixtures of Two Binomials with One Known Success Parameter, Educational and Psychological Measurement 43, no.22 (Sep 2016): 321–330.https://doi.org/10.1177/001316448304300201Aly H. Mohamed, Amin S. Hanna INHERITANCE OF QUANTITATIVE CHARACTERS IN RICE. II. INHERITANCE OF PANICLE LENGTH, Canadian Journal of Genetics and Cytology 7, no.33 (Sep 1965): 406–417.https://doi.org/10.1139/g65-054G. A. Kemp EARLY-GENERATION TESTING FOR FRUIT MATURITY AND SIZE IN TOMATO CROSSES, Canadian Journal of Plant Science 43, no.33 (Jul 1963): 379–385.https://doi.org/10.4141/cjps63-070B I Hayman The separation of epistatic from additive and dominance variation in generation means, Heredity 12, no.33 (Aug 1958): 371–390.https://doi.org/10.1038/hdy.1958.36Charles M. Rick, L. Butler Cytogenetics of the Tomato, (Jan 1956): 267–382.https://doi.org/10.1016/S0065-2660(08)60504-0