for some that may not know what traits are this read from mj botany should help .thank you r.c.c
An Advanced Study: The Propagation and Breeding of Distinctive Cannabis
by Robert Connell Clarke
Chapter 3 - Genetics and Breeding of Cannabis
List of Favorable Traits of Cannabis in Which Variation Occurs
1. General Traits
a) Size and Yield
e) Disease and Pest Resistance
g) Root Production
2. Seedling Traits
3. Leaf Traits
4. Fiber Traits
Taste and Aroma
Persistence of Aromatic Principles and Cannabinoids
h) Trichome Type
i) Resin Quantity and Quality
j) Resin Tenacity
k) Drying and Curing Rate
I) Ease of Manicuring
m) Seed Characteristics
q) Cannabinoid Profile
6. Gross Phenotypes of Cannabis Strains
a) Size and Yield - The size of an individual Cannabis plant is determined by environmental factors such as room for root and shoot growth, adequate light and nutrients, and proper irrigation. These environmental factors influence the phenotypic image of genotype, but the genotype of the individual is responsible for overall variations in gross morphology, including size. Grown under the same conditions, particularly large and small individuals are easily spotted and selected. Many dwarf Cannabis plants have been reported and dwarfism may be subject to genetic control, as
it is in many higher plants, such as dwarf corn and citrus. Cannabis parents selected for large size tend to produce offspring of a larger average size each year. Hybrid crosses between tall (Cannabis sativa-Mexico) strains and short (Cannabis ruderalis-Russia) strains yield F1 offspring of intermediate height (Beutler and der Marderosian 1978). Hybrid vigor, however, will influence the size of offspring more than any other genetic factor. The increased size of hybrid offspring is often amazing and accounts for much of the success of Cannabis cultivators in raising large plants.
It is not known whether there is a set of genes for "gigantism" in Cannabis or whether polyploid individuals really yield more than diploid due to increased chromosome count. Tetraploids tend to be taller and their water requirements are often higher than diploids. Yield is determined by the overall production of fiber, seed, or resin and selective breeding can be used to increase the yield of any one of these products. However, several of these traits may be closely related, and it may be impossible to breed for one without the other (gene linkage). Inbreeding of a pure strain increases yield only if high yield parents are selected. High yield plants, staminate or pistillate, are not finally selected until the plants are dried and manicured. Because of this, many of the most vigorous plants are crossed and seeds selected after harvest when the yield can be measured.
B) Vigor - Large size is often also a sign of healthy vigorous growth. A plant that begins to grow immediately will usually reach a larger size and produce a higher yield in a short growing season than a sluggish, slow-growing plant. Parents are always selected for rich green foliage and rapid, responsive growth. This will ensure that genes for certain weaknesses in overall growth and development are bred out of the population while genes for strength and vigor remain.
c) Adaptability - It is important for a plant with a wide distribution such as Cannabis to be adaptable to many different environmental conditions. Indeed, Cannabis is one of the most genotypically diverse and phenotypically plastic plants on earth; as a result it has adapted to environmental conditions ranging from equatorial to temperate climates. Domestic agricultural circumstances also dictate that Cannabis must be grown under a great variety of conditions,
Plants to be selected for adaptability are cloned and grown in several locations. The parental stocks with the highest survival percentages can be selected as prospective parents for an adaptable strain. Adaptability is really just another term for hardiness under varying growth conditions.
d) Hardiness - The hardiness of a plant is its overall resistance to heat and frost, drought and overwatering, and so on. Plants with a particular resistance appear when adverse conditions lead to the death of the rest of a large population. The surviving few members of the population might carry inheritable resistance to the environmental factor that destroyed the majority of the population. Breeding these survivors, subjecting the offspring to continuing stress conditions, and selecting carefully for several generations should result in a pure-breeding strain with increased resistance to drought, frost, or excessive heat.
e) Disease and Pest Resistance - In much the same way as for hardiness a strain may be bred for resistance to a certain disease, such as damping-off fungus. If flats of seedlings are infected by damping-off disease and nearly all of them die, the remaining few will have some resistance to damping-off fungus. If this resistance is inheritable, it can be passed on to subsequent generations by crossing these surviving plants. Subsequent crossing, tested by inoculating flats of seedling offspring with damping-off fungus, should yield a more resistant strain.
Resistance to pest attack works in much the same way. It is common to find stands of Cannabis where one or a few plants are infested with insects while adjacent plants are untouched. Cannabinoid and terpenoid resins are most probably responsible for repelling insect attack, and levels
of these vary from plant to plant. Cannabis has evolved defenses against insect attack in the form of resin-secreting glandular trichomes, which cover the reproductive and associated vegetative structures of mature plants. Insects, finding the resin disagreeable, rarely attack mature Cannabis flowers. However, they may strip the outer leaves of the same plant because these develop fewer glandular trichomes and protective resins than the flowers. Nonglandular cannabinoids and other compounds produced within leaf and stem tissues which possibly inhibit insect attack, may account for the varying resistance of seedlings and vegetative juvenile plants to pest infestation. With the popularity of greenhouse Cannabis cultivation, a strain is
needed with increased resistance to mold, mite, aphid,- or white fly infestation. These problems are often so severe that greenhouse cultivators destroy any plants which are attacked. Molds usually reproduce by wind-borne spores, so negligence can rapidly lead to epidemic disaster. Selection and breeding of the least infected plants should result in strains with increased resistance.
f) Maturation - Control of the maturation of Cannabis is very important no matter what the reason for growing it. If Cannabis is to be grown for fiber it is important that the maximum fiber content of the crop be reached early and that all of the individuals in the crop mature at the same time to facilitate commercial harvesting. Seed production requires the even maturation of both pollen and seed parents to ensure even setting and maturation of seeds. An uneven maturation of seeds would mean that some seeds would drop and be lost while others are still ripening. An understanding of floral maturation is the key to the production of high quality drug Cannabis. Changes in gross morphology are accompanied by changes in cannabinoid and terpenoid production and serve as visual keys to deter-
mining the ripeness of Cannabis flowers.
A cannabis plant may mature either early or late, be fast or slow to flower, and ripen either evenly or sequentially.
Breeding for early or late maturation is certainly a reality; it is also possible to breed for fast or slow flowering and even or sequential ripening. In general, crosses between early-maturing plants give rise to early-maturing offspring, crosses between late-maturing plants give rise to late-maturing offspring, and crosses between late- and early-maturing plants give rise to offspring of intermediate maturation. This seems to indicate that maturation of Cannabis is not controlled by the simple dominance and recessiveness of one gene but probably results from incomplete dominance and a combination of genes for separate aspects of maturation. For instance, Sorghum maturation is controlled by four separate genes. The sum of these
genes produces a certain phenotype for maturation. Although breeders do not know the action of each specific gene, they still can breed for the total of these traits and achieve results more nearly approaching the goal of timely maturation than the parental strains.
g) Root Production - The size and shape of Cannabis root systems vary greatly. Although every embryo sends out a taproot from which lateral roots grow, the individual growth pattern and final size and shape of the roots vary considerably. Some plants send out a deep taproot, up to 1 meter (39 inches) long, which helps support the plant against winds and rain. Most Cannabis plants, however, produce a poor taproot which rarely extends more than 30 centimeters (1 foot). Lateral growth is responsible for most of the roots in Cannabis plants. These fine lateral roots offer the plant additional support but their primary function is to absorb water and nutrients from the soil. A large root system will be able to feed and support a large plant. Most lateral roots grow near the surface of the soil where there is more water, more oxygen, and more available nutrients. Breeding for root size and shape may prove beneficial for the production of large rain- and wind-resistant strains. Often Cannabis plants, even very large ones, have very small and sensitive root systems. Recently, certain alkaloids have been discovered in the roots of Cannabis that might have some medical value. If this proves the case, Cannabis may be cultivated and bred for high alkaloid levels in the roots to be used in the commercial production of pharmaceuticals.