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The character of inheritance of differences in cannabinoid content in hemp (Cannabis sativa L.)
V. P. Sytnik1 and A. F. Stelmah2
1 The Institute of Bast Crops, Glukhov, Sumy region, Ukraine and 2 New York Academy of Sciences
Sytnik, V. P. and A. F. Stelmah 1998. The character of inheritance of differences in cannabinoid content in hemp (Cannabis sativa L.). Journal of the International Hemp Association 6(1): 8-9. Analyses of F2 hybrid and backcross populations from crosses between inbred monoecious and dioecious populations reveal that inheritance of cannabinoid production is controlled by closely linked, but independent genes for the biosynthesis of CBD and THC. Monohybrid segregation of cannabinoid production should simplify selection for Cannabis with particular cannabinoid phenotypes.
Introduction
In the selection process to develop
hemp (Cannabis sativa L.) varieties with less psychoactivity an important
area is to study is the inherited differences of the cannabinoid content of
hybrid crosses. The main terpenophenolic substances in hemp are cannabidiol
(CBD), tetrahydrocannabinol (THC) and the THC degradation product, cannabinol (CBN).
THC is responsible for most psychoactivity. Antibiotic qualities are present in
CBD. Other cannabinoids are not considered to be significant drugs. (Machbert
and Lukowicz 1971; Lazurevsky and Nikolaeva 1972).
At the Ukrainian Institute of Bast
Crops, new lines of non-psychoactive varieties have been created by means of
linear selection directed at lowering the cannabinoid content. Many of the lines
were non-psychoactive. The results of the selections confirm the inheritance of
cannabinoid content from the mother line. Data show that inheritance of
cannabinoid production may be by blending, polygenic and sex-linked.
The separate lines of hemp,
practically devoid of THC and CBD, obtained by several generations of
inbreeding, enabled research into the inheritance of cannabinoid content in
hybrid generations.
Materials and methods
The research on inheritance of
differences in cannabinoid content of hemp was conducted in 1991-1995 at the
Institute of Bast Crops of the Ukrainian Academy of Agrarian Sciences under
their leadership. Double crossings of lines of monoecious hemp of the variety
‘USO-45’, with almost complete absence of THC and other cannabinoids, with
families of dioecious hemp, variety ‘US-9’, containing large amounts of
cannabinoids, were completed. F1 and F2 hybrids and back crosses were tested for
cannabinoid content.
Every plant of hybrid and parental
forms was analyzed for cannabinoid content at biological maturity by the
semi-quantitative method of thin-layer chromatography. Plants were scored for
cannabinoid content.
Genetic analysis was used to compare
the modification of cannabinoid content in hybrids and parental forms. F2
hybrids and back crosses were divided into classes, based on similarity to one
of the parents (P1 or P2) or the F1 hybrids (P1 X
P2 or P2 X P1). A
correspondence to theoretical segregation was found in the F2 on P1
or P2 : (F1+P2 or P1) and in back crosses on
P1 or P2 : F2.
P1 is an inbred line I6 of monoecious 'USO-45', P2 is a family of 'US-9'. |
Results and discussion
Individual analyses of cannabinoid
contents of the offspring allowed us to divide the populations of F2 hybrids and
back crosses into groups by the level of cannabinoids (high or low) shown by one
of the parents and to determine the cannabinoid phenotype ratios. Two pairs of
reciprocal crossings were taken as examples of segregation and the data is given
in Table 1.
In the F2 generation, a
segregation of about a quarter of
the plants with low CBD and THC content equal to ‘USO-45’, can be seen
(Table 1). The remainder of the F2 offspring resemble either the F1 or the high
cannabinoid parent ‘US-9’. In the first back cross with the parental form
‘USO-45’ (BC1), low cannabinoid content plants constitute about half of the
off-spring. In the second back cross with the parental form ‘US-9’ (BC2),
half of the offspring have a high cannabinoid content equal to that of ‘US-9’.
The balance of plants in the back crosses resemble the F1.
Conclusions
Monohybrid segregation indicates the monogenic character of
cannabinoid levels in the crossed forms of ‘USO-45’ and ‘US-9’. This
could mean, that if the control of biosynthesis of the different cannabinoid
components is performed by the same gene, then the real segregation of CBD and
THC, would be exactly the same in all combinations of crossings. But since, as
is seen from Table 1, this is not true, then it is more logical to conclude that
the content of each of the cannabinoids is controlled by closely linked
independent genes.
The presence of the above mentioned source of heredity of
differences in cannabinoid components greatly simplifies the selection of hemp.
It is now possible to quickly create varieties and hybrids, that are
non-psychoactive, based on easily realized methods of selection.
References
Lazurevsky, G. V. and L. A. Nikolaeva 1972 Cannabinoids Kishinev, Moscow: 66.
Machbert G and A. W. Lukowicz 1971 Der nachweis von haschisch. Pharmazeutisch Zeitung: 15.