Combining ability for crude protein in six selected inbred x Triticosecale genotype

English: The objective of this study was to study the combining ability, heritability and additive genetic correlation of various crude protein characteristics in a selected fixed population. Three treatments were used to obtain grain production. The control treatment was left uncut; the cut 1 treatment had one cut of vegetative material before left for grain production while the cut (1+2) treatment had two consecutive cuts before the plants were allowed to produce grain. Characters measured for grain in all treatments were grain yield, percentage crude protein and crude protein yield. Characters measured for the vegetative material were percentage crude protein and crude protein yield. The total herbivore utilisable crude protein yield where the total crude protein yield of the vegetative material was combined with the grain crude protein yield of the cut (1+2) was also determined. Highly significant differences were shown between both genotypes and treatments for vegetative and grain characters when the phenotypic means of parents and offspring were evaluated in factorial analyses. The F1 progeny of a 6 x 6 half diallel cross were evaluated in the combining ability analyses using the Method 4, mixed model B analysis of Griffing (1956b), because only one reading per plot was obtainable for each of the characteristics measured. In the combining ability analyses of the F1 progeny, highly significant and significant differences were shown for gca effects and sca effects respectively when vegetative crude protein yield was evaluated in the cut 1 treatment. The σ2 gca/σ2 sca ratio differed between treatments and was higher for vegetative crude protein yield in the cut 1 treatment than in the cut (1+2) treatment. No significant differences between gca effects or sca effects could be found for grain yield or grain crude protein yield in the analyses of variance for any of the treatments. A significant difference between gca effects was shown for the combination character, total herbivore utilisable crude protein yield. With the aim of evaluating the combining ability effects to select parents for a better dual purpose triticale cultivar and to identify possible good hybrid combinations in mind, selections could be made with the available data of the cut 1 treatment as basis. When the variance components, heritabilities and correlated responses were calculated, the decision to base selection on the vegetative crude protein yield of the cut 1 treatment was confirmed. This character showed highly significant additive genetic correlations with both the total vegetative crude protein yield and the total herbivore utilisable crude protein yield.