Combining ability analysis of some quantitative characters in hexaploid Triticale

Genetic interactions between wheat and rye genomes in triticale : 2. Morphological and yield characters

Six primary triticale lines were produced from two advanced breeding lines of Triticum durum and three inbred genotypes of Secale cereale. The wheat and rye parents as well as the triticale derivatives were then crossed each within the same group of species in all possible combinations. Parents, F1s, and F2 populations were used to study the inheritance of a set of morphological and yield characters. The results suggest that, in general, in triticale allelic interactions within the wheat and the rye components are suppressed in favour of intergenomic interactions. Heterozygosity in the rye genome appeared to be detrimental for triticale, whereas heterozygosity in the wheat genome only resulted in positive interactions between certain characters. The retention of a high level of heterosis for kernels per spike in the F2 generation of such hybrids indicates interactions between genes which are in the homozygous state in the rye but remain in the heterozygous state in the wheat genome. If heterozygosity in the wheat component occurs between genes in the A and B genomes (homoeoalleles), it can be fixed in true breeding lines. This condition may ultimately lead to the fixation of their benefical effect on the interaction between wheat and rye genome. Aneuploidy caused a significant decline in performance for most of the investigated characters.

Inheritance of internode and culm length in hexaploid Triticale

A diallel cross of twelve cultivars of hexaploid Triticale was made in order to study genie action types for total culm length and for the length of its different segments. Culm length, and four partial lengths of the culm were studied in the F1 and F2 generations. The analysis was made according to the Griffing, Hayman and Jinks models. Heterosis in culm length is mainly due to its upper half. Spanish cultivars have, in general, positive GCA and transmit greater height in crosses, whereas the Mexican ones show a negative GCA effect and have a tendency to decrease in height when crossed. Additivity greatly influences the inheritance of culm length, this influence being lower at the first plant internodes. The environmental component has also a large influence in the phenotypic expression of Triticale height. Dominance is only partial for the five traits studied. The predominant kind of interaction seems to be of the duplicate type. All correlations between culm length and its components are high and positive, especially the genetic ones.

A method of parental selection and cross prediction using incomplete partial diallels : Part 1: a simulation study

When a character has a large additive genetic component in its variance, general combining ability estimates may be used for predicting cross performance. Further, if emphasis is placed on the ranks of the general combining abilities in a diallel rather than on their numerical values, the incomplete partial diallel is a powerful tool for parental selection. In a self pollinating species, if general combining ability effects are equal to or greater than specific combining ability effects, 20% of the partial diallel is found to give enough information for accurate ranking of the parental general combining abilities. A generalised method for calculating general combining abilities from incomplete partial diallels is presented and tested by computer simulation over a large range of genetic population parameters.