Triple test cross analysis in F2 populations of four barley crosses (original) (raw)
Triple test cross analysis in two wheat crosses
Heredity, 1976
Modified triple test cross analysis described by Jinks and Perkins (1970) has been applied to the study of additive, dominance and epistatic components of genetic variance for five metric traits, namely final plant height, ear length, number of spikelets per spike, number of grains per spike and grain yield per plant, in two wheat crosses (Kalyan Sona x Norteno 67 and Norteno 67 x WL 212). The results of the analysis reveal that the epistatic component is an important element in both the crosses for all the five characters.
ESTIMATION OF SOME GENETIC PARAMETERS FOR YIELD AND ITS COMPONENTS IN SOME BARLEY GENOTYPES
This investigation was carried out at Sakha Agricultural Research Station, ARC, Egypt during the two growing seasons (2009/2010 and 2010/011). Four lines and three testers were used to develop barley hybrids for yield and its components. Through this study, general and specific combining ability, genetic parameters, heritability and genetic advance from selection were studied for plant height, spike length, no. of spikes/plant, no. of grains/spike, 100-grain weight and grain yield/plant. Data revealed that most of the variance due to the lines, testers and line x testers were highly significant for most studied traits. On the other hand, positive and negative heterosis over better parent and mid-parent were detected for most traits indicating that parental genotypes were genetically diverse. Potence ratio estimates showed partial and over dominance in most traits. The parents L 4 considered as good combiners for plant height, no. of grains/spike, 100-grain weight and grain yield/plant. Also, the parent L 3 is considered as good combiner for spike length, no. of spikes/plant, no. of grains/spike and grain yield/plant. Heritability in broad sense values were found to be high in magnitude for most of the studied characters on the other side, heritability in narrow sense were found to be low to moderate of these traits. From the results, it could be concluded that the two crosses: (L 1 x T 3 ) and (L 3 x T 3 ) are the best for yield and most of its components. So using these crosses in breeding programs for high yielding production would be useful.
Genetic analyses were performed to uncover the supremacy of additive, dominance and epistasis genetic variances following triple test cross analysis involving three testers (P1, P2 and F1) and four lines of rice. Epistasis was found to be an integral part of genetic variation for days to flowering, plant height, number of tillers per plant and yield per plant. The partitioning of total epistasis revealed that i type (additive x additive) were highly significant for days to flowering whilst j and l type (additive x dominance and dominance x dominance) were important for plant height with predominant effect of i type interaction. j and l type epistasis also played significant role in the inheritance of number of tiller per plant and yield per plant respectively. The additive and dominance effects were highly significant for number of grains per panicle and grain weight per panicle with the exception of 1000-grain weight where dominance effects were non-significant coupled with highly ...
Quantitative inheritance of some wheat plant traits
Genetics and Molecular Biology, 2004
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.
Genetics
Linkage relationships between loci affecting quantitative traits (QTL) and marker loci were examined in an interspecific cross between Lycopersicon esculentum and Lycopersicon pimpinellifolium. Parental lines differed for six morphological markers and for four electrophoretic markers. Almost 1700 F-2 plants were scored with respect to the genetic markers and also with respect to 18 quantitative traits. Major genes affecting the quantitative traits were not found, but out of 180 possible marker x trait combinations, 85 showed significant quantitative effects associated with the genetic markers. The average marker-associated main effect was on the order of 6% of the mean value of the trait. Most of the main effects were apparently due to linkage of QTL to the marker loci rather than to pleiotropy. Fourteen of the traits showed at least one highly significant effect of opposite sign to the overall difference between the parental lines, demonstrating the ability of this design to uncover cryptic genetic variation. Significant variance and skewness effects on the quantitative traits were found to be associated with the genetic markers, suggesting the possible presence of loci affecting the variance and shape of quantitative trait distribution in a population. Most marker-associated quantitative effects showed some degree of dominance, generally in the direction of the L. pimpinellifolium parent. When the significant marker-associated effects were examined in pairs, 12% showed significant interaction effects. The results of this study illustrate the potential usefulness of this type of analysis for the detailed genetic investigation of quantitative trait variation in suitably marked populations.
The impact of epistasis in the heterosis and combining ability analyses
2021
The current theoretical knowledge concerning the influence of epistasis on heterosis is based on simplified multiplicative model. The objective of this study was to assess the impact of epistasis in the heterosis and combining ability analyses, assuming additive model, hundreds of genes, linkage disequilibrium (LD), dominance, and seven types of digenic epistasis. We developed the quantitative genetics theory for supporting the simulation of the individual genotypic values in nine populations, the selfed populations, the 36 interpopulation crosses, 180 doubled haploids (DHs) and their 16,110 crosses, assuming 400 genes in 10 chromosomes of 200 cM. Epistasis only affects population heterosis if there is LD. Only additive x additive and dominance x dominance epistasis can affect the components of the heterosis and combining ability analyses of populations. Both analyses can lead to completely wrong inferences regarding the identification of the superior populations, the populations wi...
GENE EFFECTS FOR QUAL I TA TIVE TRAIT US ING THREE TEST ERS IN TO MATO (Lycopersicon esculentum Mill
Three testers, BT-17 and PS-1 and there hybrid (BT-17 × PS-1) were crossed to 15 inbred lines to develop the experimental material The modified triple test-cross analysis was applied to estimate additive (D), dominance (H) and epistatic component of genetic variance for ten quantitative traits of tomato.. Overall epistasis was important for number of seeds/fruit and number of locules/fruit for both the season except number of seeds/fruit in spring-summer season Significant estimate of both additive and dominance component were observed for all the characters except total soluble solids in both the season for additive and total soluble solids in autumn-winter season for dominant component. The F value was positive and significant for total soluble solids in autumn-winter season showing isodirectional nature of dominance. Significant of additive components and F parameter showing increasing effect on the characters, indicates that pedidree selection would be effective for improvement of such traits.