TY  - PRO
AU  - Madatova,M.
AU  - Bedoshvili,D.
ED  - Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT)
ED  - 
TI  - Combining ability of tetrapolid wheat genotypes based on two-factor variance analysis
U1  - 633.1147 
PY  - 2004///
CY  - Tbilisi (Georgia)
PB  - CIMMYT
KW  - Crossbreeding
KW  - Environmental factors
KW  - Germplasm
KW  - AGROVOC
KW  - Wheat
KW  - Yields
KW  - Genotypes
KW  - Hybrids
KW  - CIMMYT
N1  - Abstract only
N2  - Testing progeny obtained by crossing one parent with many others shows variation in yield, which is found across the all hybrid combinations. Therefore, combining ability is expressed in two ways: General Combining Ability (GCA) ref1ects an average contribution of a genotype in a series of hybrid combinations compared to contributions of other genotypes, and Specific Combining Ability (SCA) characterizes individual contribution to a certain cross in relation to its contributions to other crosses with an array of specified lines. Through the statistical analyses it is established that both GCA and SCA depend on the year and environment (genotype/environment interaction). It is shown that GCA is less dependent on environmental variability and is more stable than SCA and therefore, esti- mation of SCA requires more prolonged multi-year and multi-location testing ofthe progeny. GCA and SCA may change depending on genetic variability in germplasm. GCA and SCA differ by their genetic nature. GCA is determined by additive effects of the hereditary factors, while SCA is determined by epistasis, dominance and over-dominance. GCA and SCA are estimated through crosses ofthe analyzed material with testers. A set of 15 tetraploid wheat genotypes in- cluding 6 Iranian and 9locallines characterized by a number of the favorable traits was used in our study. The material was tested on an irrigated plot of KSEB during three years. The initial stage of statistical analysis ( analyses of variance ) revealed significant effect of the genotypes on variability in yield (Rokitskiy, 1973; Lakin, 1980). Total variance was partitioned into variances explained by the effects of the genotype, replication and random error. The ratio of the mean-square value of the genotypic variance to the error mean-square formed the basis for drawing conclusions on significance of the differences detected between the genotypes. The variance analysis, effects and variability in CA were calculated with the formulas (Turbines, Ho- tyleva, 1974). To estimate GCA of the individual lines, the effects of GCA showing a deviation from the average value were compared. Deviations from the average values produced effects with both the positive and negative sign. High GCA suggests higher yield compared to low GCA. To estimate SCA, deviations from GCA of parental lines were calculated and explained as a result of specific interaction of genes ( dominance, epistasis ). Where SCA estimates are equal to O, the hybrid performance is determined by GCA of the parents, i.e. Byadditive genes. The SCA estimates significantly differ from each other if the difference between them is higher than the standard deviation. If the difference is less than the standard deviation, the SCA estimates are not significantly different from each other. The results of the analysis show that high variability in GCA and SCA exist among the studied lines. Given that the mean square-value deviation for GCA is several times higher than that of SCA, it may be asserted that the additive effects of the genes are more important than the non-additive effects in inheritance of number of grains per spike
ER  -