|Home||Forum||Grow Guides||Gallery||Strain Guides||Links||Arcade||Rules|
|Grow Guides | Glossary | Strain Guides | Downloads|
|Breeding Basics: Phenotypes|
What is a Phenotype?|
Growers frequently use the term “phenotype” incorrectly to describe only basic sativa – or indica – like qualities. In reality, phenotypes can be much more than just these oversimplified traits. What does “phenotype” really mean?
I consider phenotypes as the observable/quantifiable representation of a given trait. Anything you can measure, categorize or otherwise observer in an individual can be considered a phenotype.
All phenotypes are the outward result of genes acting together within a plant. Sometimes a single gene controls one trait (monogenic traits); sometimes sets of genes operate together and contribute to make a whole that we consider a phenotype (polygenic traits).
There’s a wide range of leaf phenotypes, from the thin-lamina (leaf Blade) leaflets most often seen in sativas, to the wide-lamina leaflets present in indicas, with intermediate phenotypes between the two.
This diversity can be further compounded by leaves that are pinnate, webbed (duck’s foot), curly, pointy-tipped, round-tipped, or have single or double serrations along the leaf margins. Take a look at Rob Clarke’s book Marijuana Botany and you you’ll see a wide range of leaf phenotypes.
All of these phenotypes can also independently show purple leaves or green leaves. The green leaves can be further classified as lime green or dark green, thick-leaved or thin-leaved. Any of these plants may also show purple buds, green buds or even red buds, all independent of the leaf traits.
See where this is going? There can be multiple phenotypes for each and every discernible trait in a population. If you examine a pure indica population, you’ll see variations across the population with respect to many different traits.
The buds can be further broken down into many different characteristics – Highly resinous buds versus those not quite as resinous, high THC content versus high CBD content, or those with mixed CBD/THC content. This can be further expanded to low overall levels of the primary cannabinoid (THC, CBD or Mixed) or high levels of the primary cannabinoid.
What about bud density–dense, airy or somewhere in between? Large calyxes or small? Round-tipped smaller buds, or long pointy-tipped buds? Foxtails? What about large, round buds? Small pointy ones? Small, airy ones? Large, airy ones?
What about bud odors? Do the buds smell fruity, skunky or piney? If fruity, is it more citrus or berry? Buds can offer hints of grapefruit, lemon, strawberries or sandalwood. The list is virtually endless.
Let’s look at a hypothetical situation. Suppose you’re looking to breed a Thai parental line chosen for its lovely “up” high. The line was crossed with a more indica-dominant line to introduce characteristics more suited to indoor growth. An F2 population, generated by open pollination or selfing of the initial F1 cross, is grown out for further selection. Both thin- and wide-lamina plants will appear in the F2 generation. Because leaf traits are not known to necessarily segregate with the overall positive characteristics of Thais (the energetic sativa “ up” high), there is no assurance that the selection for thin leaves will in turn guarantee the chosen phenotype. The only way to select for the Thai high is post-harvest evaluation.
Only choose the plants that most closely suit your ideal. If you want potent, retain clones of every plant but keep only the clones that correspond to the most potent plants for future grows. It just depends on what you find important. Personally, when growing cannabis varieties, I look for the psychoactive content first. No matter how tasty the flowers are or how much it yields, It’s not a winner if it won’t get you nicely toasted. It’s all about priorities.
There are many possible observable phenotypes for each trait, not just two. It’s far more complex than just sativa or indica. Beware of breeders that make it seem this easy. If you don’t believe me, just grow a couple of packs of any given strain and see the many differences found in this remarkable species we all love.
This article was copied from HIGHTIMES magazine 7/05