Abstract
General and specific combining ability effects were partitioned according to a proposed model to estimate general and specific combining ability effects for each parent when it is used as a female or a male in its hybrid combinations. A working example includes a full-diallel among eight parents was used so that all possible hybrid combinations were included. The objectives of this study were: (1) to compare the GCA and SCA effects before and after partitioning, (2) to evaluate the relative contribution of each parent to its cross combination when it is used as a male or female parent, (3) to estimate maternal effects in the form of GCA and SCA effects, and (4) to estimate the relationship between maternal and reciprocal effects. Results revealed that estimated GCA effects according to Griffing’s method is equal to the average of GCA effects of each parent, after partitioning, when it is used as a male and a female in its hybrid combinations. In addition, the average of the difference between female and male GCA effects would provide precise estimation of the maternal effect. This would prove that maternal effect provides precise estimation to the favorable alleles, which is mainly additive. The SCA effects calculated according to Griffing’s method is the average of SCA effects of each cross and its reciprocal. The average of the difference between SCA effects of each cross and its reciprocal, according to the proposed model, is equal to the reciprocal effect. This would prove that reciprocal effect provides precise estimation to the interaction effect between nuclear and cytoplasmic genes given that the interaction between male and female alleles inside the nucleus of the cross is similar to its reciprocal hybrid.
Highlights
The diallel cross has been proven to be of considerable value to plant breeders in making decisions concerning the type of breeding system to use and in selecting breeding materials that show the greatest promise for success (Gardner and Eberhart, 1966). Widstrom et al (1992) reported that diallel assessment of specific combining ability effects provides: 1) information about paired populations to be exposed to a reciprocal recurrent selection program; 2) the basis for choosing paired populations for extraction of new and high performing inbred lines.Griffing (1956) defined diallel crosses, which have been used extensively in plant breeding
General and specific combining ability effects are commonly based on the average effect of the parent when it is used as a female or a male in its hybrid combinations assuming that they are likely to be similar as proposed by Yates, (1947)
Partitioning of the general and specific combining ability effects would provide additional information about each parent when it is used as a female or a male in its hybrid combinations (Mahgoub, 2004)
Summary
The diallel cross has been proven to be of considerable value to plant breeders in making decisions concerning the type of breeding system to use and in selecting breeding materials that show the greatest promise for success (Gardner and Eberhart, 1966). Widstrom et al (1992) reported that diallel assessment of specific combining ability effects provides: 1) information about paired populations to be exposed to a reciprocal recurrent selection program; 2) the basis for choosing paired populations for extraction of new and high performing inbred lines.Griffing (1956) defined diallel crosses, which have been used extensively in plant breeding. General and specific combining ability effects are commonly based on the average effect of the parent when it is used as a female or a male in its hybrid combinations assuming that they are likely to be similar as proposed by Yates, (1947). Griffing’s methods 1 and 3 where crosses and their reciprocals are included, the fixed models, only one GCA effect value for each parent and one SCA effect value for each cross combination are estimated. These estimated effects do not, separately, show the contribution of each parent to the cross combination when this particular parent is used as a male or, alternatively, female
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