Agriculture Reference
In-Depth Information
varieties that will produce very little hurds and
free up the ground earlier.
These varieties potentially may be best
adapted to the production of hemp seed. Their
use will require the validation of an economic
model for a hemp crop that does not produce
fibre.
The chosen plants reproduce by cross-
pollination.
This technique presents the advantage of
being cheap and efficient, as it works through
a large number of individuals and has a short
reproductive cycle (in terms of generations).
Selection for THC concentrations and
fibre concentration using recurrent phenotypic
techniques produces good dependable results
(Fig. 4.14).
In practice, this technique requires mother
plants to be selected according to phenotype.
The outcome can then be tested and studied in
a specially adapted plot. Testing of descendent
plants allows a definitive choice to be made
and the selected families are retained and used
as stock for future generations.
This technique is cheap and rapid (although
slower than the technique described previ-
ously). Unfortunately, it is less easy to manipu-
late and must be reserved for the functions to
which it is best suited.
In both cases, these techniques do not
allow a significant homogenization of genetic
material, the resulting varieties remain improved
populations (i.e. genetically heterogeneous).
HEMP OIL
.
Hemp is known to bear an oil-rich
oil is seen between plants. During the 1990s,
the potential for a selection programme was
evaluated. This programme focused on the oil
content (%), and specifically the oleic oil con-
tent. In particular, attempts were made to
increase the content in
-linolenic acid.
Initial results were very encouraging. Lines
were identified with seeds containing up to
45% oil compared to the more usual 30-35%,
while lines containing >5%
γ
-linolenic acid
(2-3% found in classic lines) were also identi-
fied. As of the 1990s, this material had not
been brought to commercial use because the
market was not developed and its size remained
uncertain.
12
The selection of industrial hemp must take
into account a number of important criteria.
These must respond and adapt to the needs of
the two lines of cultivation, while producing
end products that can satisfy several industrial
uses.
This represents a difficult challenge and
requires that reasonable compromises be struck
in order to satisfy the different end users while
still maintaining economic viability.
γ
Creation of composite varieties
A composite variety (also known as synthetic)
is an artificial population resulting from con-
trolled reproduction across several generations
to produce a limited number of lines that
generally are not pure lines and are chosen for
their own desirable agronomic properties, as
well as those they offer to cross mixes.
The creation of composite varieties
(Fig. 4.15) requires:
•
The selection of a starting group of phe-
4.3.4 Selection techniques
notypes through a process of mass
selection.
The creation of partially homozygous lines
Mass selection method
•
Given the lack of means available and the avail-
ability and usefulness of simple techniques,
mass selection techniques have long been used
to breed hemp. Two such techniques are still
used today.
When selecting for maturity and monoec-
ity, selection is effected by recurrent selection
of the individual phenotype (Fig. 4.13).
The phenotype is therefore chosen based on
the visual recognition of genetic characteristics.
through self-fertilization across several
generations. The number of generations
will vary in relation to the economic
importance of the species and the hope of
a return on the investment. This process
allows favourable plant characteristics to
be preserved and undesirable characteris-
tics eliminated, leading to a homogeniza-
tion of the plants. The best parents are
selected simultaneously.
