The CPRO Cannabis germplasm collection

Euphytica 62: 201-211, 1992

E.P.M. de Meijuer & L.J.M. van Soest
Centre for Plant Breeding and Reproduction Research (CPRO-DLO) P.O. Box
16, 6700 AA Wageningen, The Netherlands

Received 26 June 1992; accepted 19 July 1992

Key words: Cannabis, cultivars, germplasm collection, hemp, origin

Summary

A collection of more than a 150 Cannabis accessions is being established as
a source for evaluation and breeding experiments. Origin of the accessions
and maintenance of the collection are described.

Introduction

In an effort to reduce the overproduction of a too limited number of arable
food crops, several research programmes dealing with industrial crops have
been initiated in the Netherlands. The 'National Hemp Proogramme'
investigates the feasibility of hemp (Cannabis sativa L.) as a raw
material for paper pulp production. In this context breeding, agronomy,
mechanisation and processing of hemp are subject of a comprehensive study.
Two previous attempts to introduce fibre hemp in the Netherlands have been
reported (de Jonge, 1944; Friederich, 1960). Breeding of fibre hemp in
the Netherlands is unprecedented. In the framework of the current
programme, improvement of cultivars is considered necessary in order to
increase yield, quality, and disease resistance. A collection of Cannabis
accessions is therefore being established at CPRO since 1988. In this
report, the present state of the collection and its maintenance are
described.

END


Characterisation of Cannabis accessions with regard to cannabinoid content
in relation to other plant characters

Euphytica 62: 187-200, 1992

E.P.M. de Meijer, H.J. van der Kamp & F. A. van Eeuwijk

Key words: Cannabis, cannabinoids, evaluation, hemp, variation

Summary

Ninety seven Cannabis accessions were evaluated for cannabinoid content and
non-chemical plant characters. Variation within populations for
cannabinoid content, and consistency of chemical characters at the
population level were investigated. The relationship between chemical and
other plant characters was very limited. Leaflet width and phenological
data can be used for a rough prediction of the chemical phenotype on a
population level. Various combinations of cannabinoid content and other
economic plant characters were observed, thus a breeding programme will not
be hampered by strict linkage. For a selection programme a direct analysis
of cannabinoids will be inevitable.

Introduction

The presence of stimulants in Cannabis has attracted a lot of scientific
attention in the past decades. Several theories have been proposed for the
biological function of the cannabinoid containing resin for the plant
itself. A relation was suggested with antibiotic activity (Krejci, 1970)
and drought and heat tolerance (Schultes, 1970). Warm, dry and windy
conditions were believed to induce a higher density of resin glands where
the biosynthesis of cannabinoids takes place. Murari et al. (1983)
estimated higher contents of cannabinoids in the same varieties when grown
in a continental climate than in a maritime climate.

The presence of psychoactive components is considered as an
important reason for the decline of fibre hemp cultivation in the course of
the 20th century (Bredemann et al., 1957; Dempsey, 1975). Due to
legislation, hemp cultivation is prohibited in many countries. Only in
France, Eastern Europe, the former USSR and China cultivation of fibre hemp
is still continued. In the former USSR a low content of psychoactive
compounds is one of the priorities in hemp breeding (Virovets et al.,
1987; Gorskhova et al., 1988). In the context of the Dutch National Hemp
Programme a collection of Cannabis accessions was established (de Meijer &
van Soest, 1992). Selected accessions of this collection will be used in a
breeding programme. In addition to the existing fibre hemp cultivars other
Cannabis strains may provide desired characters such as a long vegetative
growth, and resistance to pests and diseases. However, the psychoactive
potency of new cultivars should be below acceptable levels. Therefore a
screening for cannabinoid content is part of the evaluation of newly
introduced accessions. A relation between cannabinoid content and easily
visible plant characters would allow an indirect recognition of accessions
with respect to psychoactive potency. Close linkage of cannabinoid content
and agronomic characters would have an impact on the breeding programme.
The relation between chemical and morphological or physiological parameters
was therefore evaluated.

END


Optimisation of breeding for agronomic traits in fibre hemp (Cannabis
sativa L,) by study of parent-offspring relationships

Euphytica 78: 69-76, 1994

Sebastiaan Hennink

CPRO, Wageningen, The Netherlands

Key words: hemp, heritability, mass selection, THC, yield, Cannabis sativa
L.

Summary

In the framework of a comprehensive Dutch research project the feasibility
of hemp cultivation for paper pulp production is being investigated. This
project also includes a hemp breeding programme which was initiated at
CPRO-DLO in 1990. Hemp breeding is primarily aimed at improving bast fibre
production since bast fibre is qualitatively superior to woody core fibre
for paper pulp production. The progress of the ongoing breeding programme
is hampered by the lack of knowledge on the inheritance of agronomic
traits.
The following traits were examined on 252 parental plants in 1991
and subsequently on their progenies in 1992; fibre content, plant height,
date of flowering, stem diameter and cannabinoid contents. For each trait
heritabilities were estimated and direct and indirect effects of artificial
selection were studied.
The heritability of bast fibre content was high and mass selection
proved to be an efficient method causing no undesirable influence on other
characters. Characters not directly related to bast fibre yield such as
date of flowering, plant height and stem diameter were shown to have
disadvantages as selection criteria for the improvement of bast fibre
yield.
The cannabinoids THC and CBD were studied, as the acceptance of
hemp cultivation requires a low level. The content of THC, the
psychoactive component can be successfully reduced by mass selection, but
it is not certain that mass selection is the most efficient method.

Introduction

In the framework of a comprehensive Dutch research project the feasibility
of hemp cultivation (Cannabis sativa L.) for paper pulp production is
being investigated. This project also includes a hemp breeding programme
which was initiated at CPRO-DLO in 1990. The progress of the ongoing
breeding programme is hampered by the lack of knowledge on the inheritance
of agronomic traits.

Traditionally only the bast fibre was used for rope and cloth
production, while the woody core was considered as waste. When hemp is
grown for fibre production, seed is sometimes considered a valuable
by-product.
For paper production both bast fibre and woody core fibres can be
utilized. The quality of paper made from bast fibre is superior to that
from woody core fibre. Therefore, hemp breeding for paper production has
primarily aimed at improved bast fibre production. The yielding (fibre)
capacity can be improved directly by selection for yield components, i.e.
stem yield and bast fibre content, or indirectly by selection for
characters such as date of flowering, plant height or stem diameter
(Hoffman, 1957). Late flowering cultivars produce greater fibre yields
than early flowering cultivars due to a longer vegetative growing period
(van der Werf, 1993). For annual fibre crops a strong relationship between
plant height and stem yield is often reported, for instance, in kenaf total
dry matter yield is closely associated with plant height (Muchow, 1979).

Breeding of fibre hemp has been subject of many studies
(Bredemann, 1938; Hoffman, 1957; Bocsa,1958; Bocsa, 1969). Since the
1920's bast fibre content has more than doubled from approximately 12-15%
to 25-35% (Bredemann, 1922; Bredemann, 1938; Heimann, 1990). Breeders in
Hungary and France discontinued selection for increase of bast fibre
content, since further increase of bast fibre content is accompanied by an
increase of secondary bast fibre. This would decrease quality for cloth
and rope production (Bocsa, personal communication, 1991). In contrast
high bast fibre levels have no negative effect on paper quality.

For political and social acceptance of large scale hemp
cultivation, the content of cannabinoids, especially
delta-9-tetrahydrocannabinol (THC), should be minimal. Plants containing,
at initial seed maturity less than 0.3% THC in the dry matter of the female
inflorescense are considered to have no psychoactive potency (De Meijer et
al., 1992), individual plants can have THC levels above the tolerated
maximum, although the overall population has an acceptable level.

A successful breeding programme for the reduction of cannabinoid
contents was initiated in the former USSR in the 1970's. Cultivars
completely lacking THC were obtained. In the 1980's breeders in France and
Poland also started breeding for low cannabinoid contents. In France new
selections of existing cultivars were released having a THC content less
than 0.07% instead of the original content of 0.1-0.3% (van der Werf,
1992).
Mass selection is a common breeding method in hemp, indicating that
the heritability of traits under selection are high. No studies have
reported any estimates of realized or narrow-sense heritabilities.
Evidently the maximisation of the response to selection is never
considered.

The use of knowledge on relations among characters is also seldom
considered. The relationship between narcotic components and other
characteristics has been subject of some studies. De Meijer et al.
(1992) found no apparent relation except for a weak correlation between
leaflet width and THC content. Small et al. (1976) found only a weak
association between a large set of characters and narcotic components using
multivariate analyses. It is never reported that hemp breeding was
hampered by unwanted relationships between characters.
In the present paper parent-offspring (HS-families) relationships
for relevant agronomic traits are used to estimate genetic parameters such
as narrow-sense heritability. With the aid of artificial selection the
estimated genetic parameters are verified and relationships between
characters assessed. The response to selection for the observed traits
will be discussed in relation with the optimisation of yield capacity.


INDEX

HOME