| Abstrakt: |
The potential value of fruiting branches (sympodia) of intermediate length in an ideotype for a high‐yielding line of F1hybrid cotton grown for stripper harvest led us to research for modifier genes that affect the expression of alleles at the two known major gene loci (cl1and cl2that exert primary control over sympodial length. Six stocks of Gossypium hirsutumL., and two G. barbadenseL. stocks representing three basic branching habits, normal (Cl1Cl1Cl2Cl2), cluster (cl1cl1cl2cl1Cl2), and short branch (Cl1Cl1cl2cl2), were crossed in all possible one‐way combinations to assess the expression of the mutant alleles in the F1generation in various genetic backgrounds. Lateral internode distance to the first fruiting form (square) was measured at the ninth vertical node in the parental and F1field‐grown populations. Twenty of the 25 crosses showed full dominance of the normal allele over the mutant allele. However, five of the crosses were bimodal with a progeny class of intermediate length occurring in addition to a dominant normal length class. This was interpreted to mean that one or both of the parental lines involved harbored a gene that modified the dominance relationships between the normal and mutant genes conditioning sympodial length. Modified activity in cluster (cl1) expression was observed in four crosses, and modified short‐branch (cl2) expression was detected in one cross. |
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