Interesting Article on Inheritence of Chemical Phenotype

DNA markers in Cannabis

Today, the concept of Cannabis as a monotypic genus is widely accepted; taxonomical, morphological, and biometrical studies confirm the continuity of its gene pool despite the extremely high variation found within and between populations (SMALL et al. 1976 ?; DE MEIJER and KEIZER 1996 ?). In the last few years, the existence of just a single species within the genus has been confirmed by molecular marker studies that show a limited segregation of the different groups within the genus Cannabis and an extremely high degree of polymorphism, estimated to be of the same magnitude within and between populations (FAETI et al. 1996 ?; FORAPANI et al. 2001 ?). Within some of the best-known hemp cultivars, e.g., Carmagnola, the degree of polymorphism was estimated by randomly amplified polymorphic DNA (RAPD) markers to involve ?80% of the markers scored, and the data suggested a huge reservoir of variation within even the most selected Cannabis strains considered during the study. Finally, within the dioecious populations, the presence of a high number of male-specific markers, presumably associated with the Y chromosome, was found by RAPD and amplified fragment length polymorphism analysis (MANDOLINO et al. 1999 ?, MANDOLINO et al. 2002 ?; FLACHOWSKY et al. 2001 ?).

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Constitution of inbred lines:

All parentals used in this study were doubly inbred plants (S2's) obtained through the self-fertilization of selected female clones from the Cannabis collection of HortaPharm B.V., The Netherlands. The original plants had either CBD or THC as the predominant cannabinoid. The 00.45.1 clone was an exception, having both CBD and THC in similar amounts. The clones were obtained through in vivo propagation of lateral branches. An individual from each clone was partially sex reversed according to the procedure described by MOHAN RAM and SETT 1982 ? and allowed to self-pollinate in isolation. In many cases it was possible to collect sufficient viable seed to constitute a first-generation inbred line (S1), which was completely female and showing the same chemotype as the parental clone. The 00.45.1 S1, however, segregated into pure CBD, mixed CBD-THC, and pure THC individuals. Here, further inbreeding was restricted to the pure CBD plants. An S2 generation was produced from some of the S1 plants, using the same procedure described above. The work focused on six S2 lines, briefly described in Table 1. A leaf sample was collected for DNA analysis from 10 to 20 plants per S2.

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Table 1. Characteristics of the parental inbred lines

Production of F1's and F2's:?Seven individual plants belonging to the six S2 lines with contrasting chemotypes were chosen to produce hybrid F1's. The individual female plants used as pollen parents were partially sex reversed and placed in isolation cabinets with the seed parent plants. The crosses performed are summarized in Table 2.

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Table 2. Pedigrees and codes of the studied progenies

The next season, a variable number of individual plants of the four different F1's were grown and their chemotype was determined. Again, leaf samples from 5–20 plants belonging to the four F1's were taken for molecular analysis. Ten F1 plants (3 plants from cross 99.3, 3 from 99.4, 1 from 99.5, and 3 from 99.6; Table 2) were again treated to obtain partial sex reversion, isolated, and allowed to set F2 seed. The seeds were sown and a variable number of F2 mature plants, ranging from 35 to 118, were evaluated for chemotype; leaf samples were again collected for DNA analysis. During three seasons (1998–2000), the complete cycle from the parental S2 inbred lines to the different F2 progenies was accomplished under similar greenhouse conditions and strict isolation. Confirmation of the genetic femaleness of all the plants was based on the absence of any male-specific marker.

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**Aim of the work

This study aims to clarify the inheritance of cannabinoid chemotype, by isolating pure CBD and pure THC inbred lines. A simple inheritance model was proposed after making crosses between the chemotypically contrasting lines and examining a number of F1 and F2 progenies. An RAPD analysis of the parental lines and their offspring was performed and a number of chemotype-associated markers were described.

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The uniformity of F1 chemotypes and the F2 segregation ratios demonstrate the presence of a single locus, which is referred to as B, showing simple Mendelian inheritance of the two alleles, BD and BT, evidenced by this study. The model proposes that a pure CBD plant has a BD/BD genotype at the B locus, while a pure THC plant has a BT/BT genotype. F1 and 50% of the F2 plants are therefore heterozygous BD/BT, with the two alleles being codominant and therefore simultaneously expressed in the hybrids. The hypothesis of two alleles at one locus was accepted by 2 tests for all the F2's examined (Table 4). This model agrees with the assumption of a monogenic inheritance as expressed by BECU et al. 1998 .

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Today, the concept of Cannabis as a monotypic genus is widely accepted; taxonomical, morphological, and biometrical studies confirm the continuity of its gene pool despite the extremely high variation found within and between populations (SMALL et al. 1976 ?; DE MEIJER and KEIZER 1996 ?). In the last few years, the existence of just a single species within the genus has been confirmed by molecular marker studies that show a limited segregation of the different groups within the genus Cannabis and an extremely high degree of polymorphism, estimated to be of the same magnitude within and between populations

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Grat3fulh3ad said:

I found this to be a very interesting assertion... any comments?

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CannaBuilding said:

Alright i read it, veyr interesting

Just a couple of questions the plants that lean more the CBD are indica dominant i presume? the THC dominant are sativa? Im just assuming, cause i know when THC breaks down to CBD you get more of a couchlock feeling hence indica sort of effect

Correct me if im wrong

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SativaBelieva said:

So CBD-dom/THC-dom hybrids will be the strongest?

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