PHOTOPERIODIC RESPONSE AND ITS EFFECTS ON CERTAIN QUANTITATIVE CHARACTERS IN TOBACCO

Abstract

The effects of the mammoth gene causing a short-day photoperiodic response in a mutant were studied in 1962 and 1966 in six genetic populations (P1, P2, F1, F2, B1 B2) derived from the cross between Mammoth Delcrest, a short-day mutation of the flue-cured tobacco variety Delcrest, and Praecox, a day-neutral pipe tobacco. The data showed the expected monofactorial segregation of day-neutral against short-day plants, the latter being recessive. Considerable amount of positive heterosis was observed for leaf width. In the inheritance of days-to-flower, in addition to the pair of alleles determining the short-day response, one to two gene groups are indicated, operating probably in an additive fashion. Two and three gene groups are indicated for leaf width and leaf length, respectively. Parameters describing additive gene effects were important for all the character tested but none of the parameters for dominance and digenic epistatic effects were significant. Evidently the segregating major gene for the mammoth character did not excessively influence the relationship of gene effects in the remaining genotype as determined by the generation-mean analysis.