Epigenetic determined sex change of the hemp unisexual hybrids under the influence of pho-toperiod

Abstract

Hemp (Cannabis sativa L.) is quite sensitive species to photoperiod.

The aim and tasks of the study were a comparative analysis of the phenotypic expression of sex in unisexual hybrids of the first generation hemp (dioecious hemp / monoecious) grown in field and under artificial conditions of reduced daylight hours.

Material and methods. The studies were conducted on the basis of the Institute of Bast Crops of the NAAS (Glukhov, Sumy region). Hybridization was carried out under conditions of glass house with the use of group isolators according to the scheme of dioecious hemp / monoecious. Local, selection varieties and samples of various ecological and geographical types were parent forms. F₁ hybrids were grown in the field and growers from the beginning of budding phase with a shortened daylight duration of 12 hours. The phenological phases were determined on the basis of the BBCH scale. Sex types were determined by N.D. Migal’s (1992) classification and methodology.

Results and discussion. In natural (field) conditions, the duration of a light day before the beginning of budding phase was about 15–16.30 hours. Appearance of buds (BBCH 51-59) and mass flowering (BBCH 60-65) were observed with the duration of daylight at 16.30–16 hours. The generative phase occurred in artificially created conditions with a photoperiod of 12 hours too, but the sexual structure of the hybrids was changed. The sex structure of F₁ hybrids which were grown in the field, was represented with the female plants and a small number of monoecious plants. The sex structure shifted to the female. Under the influence of the shortened daylight hours, the sexual structure of the hybrids shifted to the male, that is, the content of the female plants decreased (from 36.6 to 92.3 %), the content of monoecious sexual types increased. The emergence of male plants was observed. This regularity expression was more clearly when combined with two exposure factors (photoperiod and the removal of growth points). An epigenetically determined change of the hemp hybrids sexual structure occurs under the influence of a photoperiod. The change of the sexual structure under the influence of the photoperiod is epigenetically deterministic; such as unisexual hybrids (heterozygous for the female and monoecious sex) become almost monoecious in the phenotype and contain male plants.

Сonclusions. To establish epigenetically determined changes of sex in hemp hybrids under the influence of photoperiod.