A multivariate analysis of morphological divergence of “seeds” (achenes) among ruderal, fibre, oilseed, dioecious/monoecious and marijuana variants of Cannabis sativa L.

Abstract

Cannabis sativa has been domesticated for stem fibre and oilseed (the two classes are both low in the euphoric cannabinoid THC and called “hemp”), and marijuana (high in THC), and also occurs as weedy, ruderal plants. Achenes (“seeds”) from herbarium collections representative of these classes were assessed for morphological characters and pericarp resistance to fracture. In contrast to ruderal plants, domesticated plants (both hemp and marijuana) possessed achenes that were significantly longer, heavier, covered with a less adherent perianth, and lacking a pronounced basal attenuation. All of these characteristics reflect traits that are advantageous in domesticated plants and are consistent with the “domestication syndrome” found in propagules of other crops. Marijuana achenes, in comparison with hemp achenes, tended to be about 26% shorter and about 32 shades darker (on a 256-bit grayscale). Achenes of fibre cultivars proved to be about 19% longer than the achenes of oilseed cultivars. Achenes of dioecious oilseed cultivars proved to be about 6% longer than the achenes of monoecious oilseed cultivars. The pericarps of hemp seeds were about 26% and about 15% more resistant to fracture than those of ruderal and marijuana plants, respectively.

Appendices

Appendix 1: Collectors and DAO accession numbers, and cultivar names (where available)

Fibre cultivars (all collected by E. Small): 132157 (Lovrin 53–65), 132162, 132163 (Tiborszallasi), 132167 (LKCSD), 135048 (Llonspdiske), 135049 (Fibrimon Truh), 135050 (Fibrimon Mittelspat), 135051 (Fibrimon Spat Eliten), 135110, 135114 (Rastislavicke), 135129 (Fibramulta 151) (All specimens were grown in a common garden in 1971 in Ottawa, as reported in Small and Beckstead 1973, and all possessed low levels of THC, < 0.3%.).

Oilseed cultivars: The 13 dioecious collections included 886530 (ESTA-1), 886532 (Victoria), 886535 (Petera), 886540 (Finola), 886541 (Georgina), 886542 (Heidron), 886543 (Hempnut), 886545 (Crag), 886546 (CFX-2), 886547 (CFX-1), 886548 (CanMa), 886551 (ARC-Express), 886553 (CRS-1). The 10 monoecious cultivars included 886531 (Yvonne), 886533 (UC-RGM), 886534 (Silesia), 886536 (Jutta), 886537 (Joey), 886538 (Ida), 886539 (Debbie), 886544 (Delores), 886550 (Canda), 886552 (Alyssa, female predominant) (The 23 oilseed cultivars were grown in a common garden in Ottawa in 2013 and were collected by E. Small and A. Ward. All were grown from pedigreed breeder’s seed. All were intended for sale in Canada for harvest of seed, and as required by law, all have proven to have very low levels of THC, < 0.3%).

Low-THC ruderal collections: The 30 north-temperate, low-THC ruderal collections included the following 17 vouchers: 131712, 131715, 131720, 131815, 131816, 131825, 131838, 131848, 131850, 132159, 132179, 132186, 132193, 132214, 132228, 132250, 135068 (These were planted in a common garden in Ottawa in 1971 from seeds obtained from ruderal populations in North America and Europe, as reported in Small and Beckstead (1973)). Also examined were the following 13 accessions collected directly from various ruderal locations in North America in the middle of the twentieth century: 158369, 743592, 743593, 743597, 743870, 743896, 743923, 743932, 743933, 743934, 743944, 743974, 743975.

Marijuana strains: The 30 marijuana accessions used included 25 vouchers at DAO grown in Ottawa in 1971, or 1973 and collected by E. Small: 131269, 131272, 131274, 131276, 131278, 131280, 131281, 131725, 131726, 131728, 131783, 131793, 131796, 131801, 131802, 131804, 131810, 131814, 131818, 131829, 131834. 131835, 131842, 131851, 132168. Also included were the following collected by S. Naraine in 2016: 1 (Biddy Early), 2 (Black Indica), 3 (Blueberry), 4 (Green Crack), 5 (Strawberry Skunk).

Appendix 2: Image analysis: MATLAB code

The images are cropped so that all pixels are representative of pericarp. The image is converted to grayscale and the grayscale cropped image is then imported to MATLAB and turned into a matrix.

• Code:

• I = imread(‘image.jpg’);  %import the image

• newI = rgb2gray(I);  %converts the image from 3 colour RGB to 256-bit grayscale

• M = mean(newI(:));  % single-precision mean of a vector

• (d) Analysis

The images were imported to MATLAB 2016b and using its enhanced image analysis, the average grayscale of the seeds were calculated.

• Code:

• I = imread(‘image.jpg’);  %import the image

• newI = rgb2gray(I);  %converts the image from 3 colour RGB to 256-bit grayscale

• Figure

• imshow (I)

• imshow(newI)

• %edge detection options

• BW1 = edge(I,’sobel’);

• BW2 = edge(I,’canny’);