Genetic analysis of photoperiodism in primitive upland cotton (Gossypium hirsutum L.)

Restriction fragment length polymorphism (RFLP) analyses were used to compare commercial cotton (Gossypium hirsutum L.) and photoperiodic primitive accessions of upland cotton to determine if a marker for photoperiodism could be identified. Photoperiodic plants require a short day to initiate flowering. Six accessions from four races and one cultivar were studied. There were 468 probe/enzyme combinations used, yielding 605 polymorphisms. Comparisons were made to link polymorphisms to photoperiodic flowering response and evaluate the differences among lines. There was a wide range of flowering among lines, but only a few polymorphisms were found when applied across all photoperiodic and flowering parents. Accessions were crossed to a cultivar, selfed and backcrossed to each parent. The F;Classical genetic analysis indicated varying numbers of genes controlling photoperiodism. Three accessions segregated for one dominant gene causing non-flowering (T256, T126, T140); whereas the other line (T48) showed a single recessive gene. The segregation in the cross with T324 most closely fit a 13:3 F2 ratio indicating two genes for photoperiodism.;There are genes controlling earliness and lateness of flowering. T256 and T126 have one dominant gene for early flowering. T140 and T324 have one dominant gene for late flowering. T2 and T48 have two dominant genes for time of flowering.;Quantitative genetic estimates were made of the number of genes controlling the time of flowering and the heritability of the traits. The Warner method to estimate heritability indicated that variation in flowering had a genetic component. Segregation ratios suggested that the number of genes involved in flowering was very close to estimates using the Wright method with one or two genes controlling photoperiodism and one or two genes controlling time of flowering.