THE GENETIC-CONTROL OF MATURITY AND SEED CHARACTERS IN SUNFLOWER CROSSES

Data from the F-1, F-2 and F-3 generations derived from four F-1 hybri ds of sunflower were analysed to determine the genetical control of el even agronomically important traits namely, flowering time (FT), final height (FH), seed set (SS), fresh seed weight (FSW), dry seed weight (DSW), 25-seed weight (SSW), head diameter (HD), head angle (HA), neck width (NW), Botrytis infection (BI) and percentage oil content (PO), with the objective of assessing their potential for producing superior recombinant lines. Comparisons of means revealed significant differen ces between the F-1 generations of crosses for all the characters exce pt FT. Model fitting indicated that these differences were attributed either to variation in the magnitude of the dominance component [h], o r the projected mean of the F-infinity generation, m. Further, all the variation in the generation means was accounted for by the m and [h] parameters and epistasis was shown to be non-existent for almost all t he traits. Analysis of the second degree statistics revealed the prese nce of additive genetic effects and most of the characters showed mode rate heritability except for HD, which was highly heritable. All the c rosses were predicted to produce significant numbers of transgressive segregants and consequently were expected to yield superior inbred lin es and second cycle hybrids either to be released as varieties as such or to be utilized in future breeding work. The overall differences be tween the crosses, however, were not highly pronounced and therefore i t was not possible to identify a cross which would yield markedly supe rior recombinant lines and F-1 crosses compared to the others.