Final report for LNE21-430R
Project Information
Hemp is a new and profitable crop for cannabinoids. Hemp is a diploid, dioecious species, and female plants are desired, since their inflorescences produce the greatest quantity of cannabinoids. When female plants are pollinated, they set seed, which significantly reduces cannabinoid yield. Despite farmers best efforts to remove male plants from their fields, crops remain susceptible to pollen drifting from neighboring farms or feral plants. One way to eliminate seed set is to develop triploid hemp, which produce gametes with imbalanced chromosomes that are non-viable. There are many horticultural examples of triploids that are sterile including watermelon, banana, citrus, and hops. My lab developed triploid hemp plants and it needs to be demonstrated that triploids will not set seed, maintain high cannabinoid content, and that their horticultural production potential is sufficient to allow farmers to successfully grow the crop. This project will compared triploid plants to standard diploid plants both in the greenhouse and the field. In the greenhouse, controlled pollination studies using genetically male pollen tested plant sterility. Plant performance and cannabinoid production was also evaluated. In the field, horticultural performance and ability to resist pollen under real world conditions was evaluated. Many northeast farmers have completely lost their hemp crop due to inadvertent pollination by plants found in the wild or on nearby farms. Triploid hemp proved to be nearly seedless, and will enable farmers to grow high cannabinoid yielding hemp without risk of crop loss due to pollination and seed set. As part of the process of fully vetting the performance of triploid hemp, a research farmer tested plants in their annual variety trials. Farmers participated in annual online workshops where they viewed research results and provided feedback on the findings.
Evaluate the sterility and growth performance of triploid hemp plants developed through breeding. Greenhouse and field studies will be conducted to confirm that triploid hemp is infertile or exhibits reduced fertility. Sterile triploids would allow northeast farmers to grow hemp without the risk of seed set reducing cannabidiol (CBD) yield or hemp escaping cultivation to the wild. In addition to sterility, triploid hemp will likely possess greater yield and CBD content. Adoption of seedless triploid hemp would improve sustainability and profitability for northeast hemp farmers.
Research
2021 Greenhouse sterility and field performance studies
A greenhouse study was conducted to compare seed production ability of one diploid (2x) female genotype of ‘Wife’ and two triploid (3x) female genotypes of ‘Wife’. Plants were started from cuttings from stock mother plants. Plants were potted into 7.33 L containers with peat-based medium (Metro-Mix 830; Sun Gro Horticulture, Agawam, MA, USA). Containers were top-dressed with 15N–3.9P–10K controlled-release fertilizer [CRF (Osmocote Plus 5- to 6-month formulation; Everris NA, Dublin, OH, USA)]. Plants were fertigated with a 20N–8.7P–16.6K water-soluble fertilizer (Peters 20–20–20; Scotts, Marysville, OH, USA), providing 100 mg·L-1 N at each watering. Plants were grown in a greenhouse with set points of 21/17°C day/night temperature thresholds and photoperiod control provided by supplemental lighting using 1000-W high-pressure sodium lamps (Phantom HPS 100W; Hydrofarm, Petaluma, CA, USA) and blackout curtains. The experimental unit (EU) was a single potted plant and plants were arranged in a randomized complete block design (RCBD) with 11 replications. Plants were grown under 18-h photoperiod for 14 d and then 12-h photoperiod for 62 d. Pollen was provided by 11 2x male plants of ‘Youngsim10’ that were started from seed and potted as described. Male plants were grown in the same greenhouse as female plants, but they were not randomized with female plants. Hand pollinations were conducted for 12 terminal inflorescences per female plant. In addition, pollen was dispersed by air flow from greenhouse fans and venting. Male plants were discarded following anthesis. On day 56 of the study plant height, number of shoots and total shoot length was measured per plant. All seeds per plant were harvested. For 3x plants, all seed produced was counted and for 2x plants the number of seed produced per plant was estimated using the weight of a random subsample of 100 seeds. The number of filled seeds were determined for a random subsample of 60 seed, and this value was used to calculate percent filled seed per plant. Seed caliper was measured for eight filled seed per plant. Cannabinoid content of dry flower was analyzed by high-performance liquid chromatography at The University of Connecticut (UConn) Center for Environmental Sciences and Engineering [CESE (Storrs, CT, USA)].
Video 1. Hand pollination in the greenhouse
A field study to evaluate sterility of four 3x genotypes and one 2x genotype (control) was installed in June 2021. However, this planting perished because of extreme rainfall (that more than doubled the historic average) and flooding in summer 2021 in Connecticut and other parts of the northeast due to four storms that that came up the East Coast.
2022 Greenhouse Performance Study
A greenhouse trial was conducted to evaluate the performance of four 3x female genotypes compared to four 2x female genotypes. The 3x genotypes were: ‘Abacus’ x ‘Kentucky Sunshine; ‘Wife’ x ‘Kentucky Sunshine’; ‘Tangerine’ x ‘Kentucky Sunshine’; and ‘Wife’ x ‘Wife’. The 2x genotypes were: ‘Abacus’; ‘Kentucky Sunshine’; ‘Tangerine’; and ‘Wife’. Plants were started from cuttings from stock mother plants and potted into 7.33 L containers as described. The EU was a single potted plant and plants were arranged as a RCBD with four replications. Plants were grown under 18-h photoperiod for 10 d and then 12-h photoperiod for 42 d. On day 38 of the study plant height, number of shoots, and total shoot length per plant were measured. On day 41 of the study stem caliper, measured at 3 cm above the medium surface, was recorded per plant. At harvest, plants were cut at the stem base, allowed to dry at room temperature for 14 d and weighed, then flowers were separated from stems and leaves and weighed. Percent flower weight was calculated by dividing flower dry weight by plant dry weight and multiplying by 100%. Cannabinoid content of dry flower was analyzed as described.
2022 Field Sterility Study
A field study was conducted to evaluate sterility of five 3x female genotypes compared to four 2x female genotypes. The female 3x genotypes were: ‘Purple Star’ x ‘Wilhelmina’; ‘Tsunami’ x ‘Wife’; ‘Purple Star’ x ‘Wife’; ‘Wife x ‘Purple Star’; and ‘Kentucky Sunshine’ x ‘Wife’. The 2x female genotypes were: ‘Tsunami’ x ‘Wilhelmina’; ‘Purple Star’ x ‘Wife’; ‘Abacus’ x ‘Wife’; and ‘Wife’ x ‘Wife’. Male 2x plants of ‘Purple Star’ × ‘Youngsim10’ and ‘Youngsim10’ were included in the field planting to provide pollen. Female plants were started from seed and male plants from cuttings from stock plants. Plants were potted in 1.04 L containers in the same potting medium described, and grown in a greenhouse under 18-h photoperiod for 24 d before transplanting to the field on 31 May 2022. The ploidy level of plants was confirmed by flow cytometry prior to transplanting in the field. The field planting was located at the UConn Plant Science Research and Education Facility in Storrs, CT (lat. 41.79544°N, long. -72.22836°W). The field soil was a Paxton and Montauk fine sandy loam with 6.7% organic matter and pH 5.9. The EU was a single plant and plants were arranged as an RCBD with 10 replications. Each block included 10 genotypes, nine female genotypes (five 3x and four 2x) and one male genotype, either ‘Purple Star’ × ‘Youngsim10’ or ‘Youngsim10’, such that 5 blocks had ‘Purple Star’ × ‘Youngsim10’, and 5 blocks had ‘Youngsim10’. Plants were grown in rows with 1.8-m spacing on center between rows and 1.2-m spacing on center within rows. To facilitate manual irrigation, two blocks were established per planting row, so there was a total of five rows. To ensure that pollen presence was strong, an additional male plant of ‘Youngsim10’ was installed per planting row between the two blocks, thus forming a row of five male plants that bisected the planting. In total 105 plants were installed of which 90 were female and 15 were male (10 plants of ‘Youngsim 10’ and five plants of ‘Purple Star’ × ‘Youngsim10’). Plants were fertilized twice, at time of planting and again on 7 Jul 2022, with 10 g of granular fertilizer (All Purpose 10N–4.4P–8.3K; Greenview, Lebanon, PA, USA) per plant each time. Fertilizer was broadcast around the base of the plant by hand. Plants were irrigated by hand as needed throughout the growing season. Weeding was by rototiller between rows and by hand within rows. Peak anthesis was noted for male plants when approximately 50% of flowers were open, based on visual observation of inflorescences. Plants were harvested when seeds appeared ripe and approximately 50 d after onset of terminal flowering (when a minimum of three pistils bearing stigmas were visible at the shoot tips), which varied by genotype. For photoperiod-sensitive genotypes, a subsample consisting of four terminal inflorescences per plant were harvested, dried in an air circulating oven at 45°C for 24 hours, weighed, and had seeds removed. Terminal inflorescences were 20 to 25 cm long measured from the terminal apex of the shoot inward. Seeds were weighed and seed percent of floral biomass was calculated. The number of filled seeds per plant was determined using a random subsample as described and percent filled seed was calculated. For the two photoperiod-insensitive (autoflowering) genotypes the entire plant was harvested by cutting at the stem base, and all seeds per plant were counted. The ploidy level of 30 filled seeds, selected at random, per 3x photoperiod-sensitive genotype was determined using flow cytometry.
2023 Greenhouse Performance Study
A greenhouse trial was conducted to evaluate the performance of four 3x and three 2x genotypes. The 3x genotypes were: ‘Kentucky Sunshine’ x ‘Wife; ‘Purple Star’ ; ‘Purple Star’ x ‘Wife’; and ‘Wife’ x ‘Purple Star’. The 2x genotypes were: ‘Purple Star’; ‘Purple Star’ x ‘Wife’; and ‘Wife’. Plants were started from seed and potted into containers as described for greenhouse study 1. The EU was a single potted plant and plants were arranged as a RCBD with six replications. Plants were grown under 18-h photoperiod for 35 d, then 15-h photoperiod for 21 days, then 12-h photoperiod for 30 d. The critical photoperiod varied for the genotypes used in this study, therefore plants were harvested at three weeks after the onset of terminal flowering. Data collection was conducted as described for greenhouse study 1. On day 57 of the study stem caliper was measured as described and on day 67 of the study plant height, number of shoots and total shoot length were measured.
2023 Crosses
Controlled crosses using growth chambers were conducted to produce 2x and 3x seed of the same cultivar or hybrid from two cultivars for to use in a future greenhouse experiment to directly compare 2x and 3x counterparts with similar genetic background. Crosses to produce 2x and 3x seed of the genotypes ‘Purple Star’; ‘Tsunami’ x ‘Wife; and ‘Purple Star’ x ‘Wife’ were conducted.
2024 Greenhouse Performance Study
A greenhouse trial was conducted to evaluate the performance of 2x and 3x genotypes of ‘Purple Star’, ‘Tsunami’ x ‘Wife, and ‘Purple Star’ x ‘Wife’. Methods were as described for the 2023 greenhouse performance study.
Statistical analysis
Data were subjected to analysis of variance (PROC GLIMMIX) and mean separation with Tukey’s honestly significant difference (HSD) test (P ≤ 0.05) using statistical software (SAS version 9.4; SAS Institute, Cary, NC, USA).
In the greenhouse, 3x genotypes of ‘Wife’ produced approximately 99.5% fewer filled seeds than 2x ‘Wife’ did (Table 1). Seed produced by plants of 3x genotype ‘Wife’-6 (4x) × ‘Wife’ (2x) had larger caliper than those produced by ‘Wife’ (2x). There were not enough filled seeds produced by plants of 3x genotype ‘Wife’-1 (tetraploid; 4x) × ‘Wife’ (2x) to measure caliper. Percent cannabidiol (CBD) and tetrahydrocannabinol (THC) of 3x genotypes of ‘Wife’ were the same or slightly lower than 2x ‘Wife’.
Table 1.
|
Genotype |
Ploidy |
Seeds (no.) |
Filled seeds (%) |
Unfilled seeds (%) |
Seed caliper (mm) |
Plant ht (cm) |
Shoots per plant (no.) |
Total shoot length (cm) per plant |
CBD (%) |
THC (%) |
|
Wife (2x) |
2x |
3010.3ai |
88.5 a |
11.5 c |
4.6 b |
98.5 a |
19.0 a |
829.3 a |
7.4 a |
0.37 a |
|
Wife-1 (4x) × Wife (2x) |
3x |
99.0 b |
8.8 b |
91.2 a |
- |
66.2 b |
10.0 b |
375.5 b |
6.0 b |
0.26 b |
|
Wife-6 (4x) × Wife (2x) |
3x |
118.3 b |
14.2 b |
85.8 b |
5.2 a |
71.2 b |
13.0 b |
441.0 b |
7.4 a |
0.38 a |
iMean separation within column, indicated by different letters, by Tukey’s honestly significant difference (HSD) test at P≤0.05
In the field, pollen was provided by the male 2x genotypes ‘Purple Star’ × ‘Youngsim10’ and ‘Youngsim10’. Anthesis for ‘Purple Star’ × ‘Youngsim10’ ranged from 22 Jun to 31 Aug, with peak anthesis from 6 July to 3 Aug. Anthesis for ‘Youngsim10’ ranged from 17 Aug to 20 Sep, with peak anthesis from 31 Aug to 14 Sep. Plants of genotype ‘Purple Star’ × ‘Youngsim10’ flowered earlier than plants of ‘Youngsim10’, because this genotype had a photoperiod-insensitive parent, ‘Purple Star’. The period of anthesis for the two male genotypes overlapped for 14 d, from 17 Aug to 31 Aug. The male plants in the planting provided a continuous supply of pollen over an 84-d period, which covered anthesis for all nine female genotypes in the study. Seed production as a percent of floral biomass ranged from 52.6% to 57.1% from 2x photoperiod-sensitive genotypes, and 86.1% to 87.5% of seeds were filled (Table 2). Seed production from 3x photoperiod-sensitive genotypes was significantly less at 6.7% to 18.0% of floral biomass, and 26.5% to 34.0% of seeds were filled. For the photoperiod-insensitive genotypes, 3x plants of genotype ‘Purple Star’ (4x) × ‘Tsunami’ (2x) produced 98.5% fewer filled seeds than 2x plants of genotype ‘Tsunami’ (2x) × ‘Wilhelmina’ (2x). According to seed producers, yields of 1,000 seeds per plant from photoperiod insensitive 2x cultivars is supraoptimal (personal communication, Adam Davidoff, Founder, Atlas Seed, Sebastopol, CA, USA). Plants of photoperiod-insensitive 2x genotype ‘Tsunami (2x) × ‘Wilhelmina’ (2x) produced approximately 1,300 filled seeds per plant, which indicates that the study plants were well challenged with pollen. In reality, a flower crop is unlikely to experience the heavy pollen exposure provided the study planting. Flower growers report that unexpected male flowers in a crop can result in 50 to 200 seeds per plant, which renders the inflorescences unsalable as smokeable product. An acceptable rate is 10% this value or 5 to 20 seeds per plant (personal communication, Adam Davidoff, Atlas Seed). Photoperiod insensitive 3x genotype ‘Purple Star’ (4x) × ‘Tsunami’ (2x) produced approximately five filled seeds per plant. It is probable that other 3x cultivars developed will demonstrate similar seed production when exposed to unexpected pollen. In the field planting approximately equivalent amounts of 2x and 3x progeny were produced per 3x genotype (Table 2). This finding was not surprising, since meiosis in triploids results in unbalanced segregation of chromosomes and aneuploid gametes.
Table 2.
|
Genotype |
Ploidy |
Photoperiod sensitivity |
Sampled dry floral biomass (g) |
Seed weight (g) of sample |
Seed production (% of floral biomass) |
Seeds (no.) |
Filled seeds (%) |
Total progeny tested by flow cytometry (no.) |
Progeny [% of progeny tested (no.)] |
|
|
|
|
|
|
|
|
|
|
|
|
2x |
3x |
|
|
Abacus (2x) × Wife (2x) |
2x |
Sensitive |
66.8 |
38.1 |
57.1 ai |
- |
86.1 a |
- |
- |
- |
|
|
Purple Star (2x) × Wife (2x) |
2x |
Sensitive |
102.4 |
53.6 |
52.6 a |
- |
87.5 a |
- |
- |
- |
|
|
Tsunami (2x) × Wilhelmenia (2x) |
2x |
Insensitive |
- |
19.8 |
- |
1803.2 a |
75.5 a |
- |
- |
- |
|
|
Wife (2x) × Wife (2x) |
2x |
Sensitive |
48.9 |
26.5 |
54.5 a |
- |
86.7 a |
- |
- |
- |
|
|
Kentucky Sunshine (4x) × Wife (2x) |
3x |
Sensitive |
45.1 |
4.3 |
10.1 c |
- |
26.5 bc |
30 |
13 (43) |
17 (57) |
|
|
Purple Star (4x) × Wife (2x) |
3x |
Sensitive |
74.3 |
5.2 |
6.7 c |
- |
34.0 b |
30 |
14 (47) |
16 (53) |
|
|
Purple Star (4x) × Wilhelmenia (2x) |
3x |
Insensitive |
- |
0.2 |
- |
26.6 b |
16.6 c |
- |
- |
- |
|
|
Tsunami (4x) × Wife (2x) |
3x |
Sensitive |
109.6 |
19.6 |
18.0 b |
- |
30.9 bc |
30 |
14 (47) |
16 (53) |
|
|
Wife (4x) × Purple Star (2x) |
3x |
Sensitive |
85.0 |
11.1 |
13.0 bc |
- |
29.9 bc |
30 |
19 (63) |
11 (37) |
|
iMean separation within columns, indicated by different letters, by Tukey’s honestly significant difference (HSD) test at P≤0.05
Seven 2x genotypes and eight 3x genotypes were evaluated for multiple plant growth and flower traits over two greenhouse studies. Overall, 2x and 3x genotypes performed similarly with a few exceptions. In the first study, 3x plants of ‘Abacus’ (2x) × ‘Kentucky Sunshine’ (4x) and ‘Wife’ (2x) × ‘Kentucky Sunshine’ (4x) had larger stem caliper than most 2x plants. CBD content from 3x genotype ‘Abacus’ (2x) × ‘Kentucky Sunshine (4x) was greater than from other genotypes, except from its 2x parent ‘Abacus’ (Table 3). ‘Abacus’ (2x) also had greater percent flower weight than other genotypes, except ‘Tangerine’ (2x). In the second study, 2x and 3x plants of ‘Purple Star’ were the smallest, which was not unexpected, since they are photoperiod insensitive (Table 4). However, they did exhibit percent flower weight above 20%. This attribute is desirable to growers, because plants with a greater ratio of flower to stem and foliage are easier to harvest (personal communication, Heather Darby, Extension Professor, University of Vermont, Burlington, VT, USA).
In 2022, 3x genotypes ‘Tsunami’ (4x) × ‘Wife’ (2x) and ‘Wife’ (4x) × ‘Purple Star’ (2x) were included in field trials at the University of Vermont (Burlington, VT, USA). Plants performed equivalent to, or better than, 14 industry-standard 2x cultivars and six 3x cultivars developed by Oregon CBD [Independence, OR, USA]. Plants of 3x ‘Tsunami’ (4x) × ‘Wife’ (2x) exhibited the greatest percent flower weight at 46.6%.
Table 3.
|
Genotype |
Ploidy |
Plant ht (cm) |
Shoots (no.) |
Total shoot length (cm) |
Stem caliper (mm) |
Plant dry wt (g) |
Flower dry wt (g) |
Flower dry wt (%) |
CBD (%) |
THC (%) |
|
Abacus |
2x |
62.8 ci |
10.5 c |
468.8 ed |
10.9 c |
102.7 ab |
53.3 ab |
52.5 a |
11.9 ab |
0.47 a |
|
Kentucky Sunshine |
2x |
80.3 bc |
14.5 abc |
576.5 cde |
12.9 bc |
115.9 ab |
42.4 ab |
36.8 bc |
9.2 cde |
0.29 b |
|
Tangerine |
2x |
99.2 ab |
16.5 a |
724.0 abc |
11.7 c |
148.9 ab |
67.6 a |
44.8 ab |
7.9 de |
0.24 b |
|
Wife |
2x |
111.3 a |
16.0 a |
732.3 abc |
12.9 c |
99.3 ab |
32.5 ab |
33.3 c |
10.2 bcd |
0.40 a |
|
Abacus (2x) × Kentucky Sunshine (4x) |
3x |
121.5 a |
15.3 ab |
843.3 a |
16.8 ab |
176.9 a |
60.7 ab |
35.3 bc |
14.2 a |
0.48 a |
|
Tangerine (2x) x Kentucky Sunshine (4x) |
3x |
83.5 bc |
14.5 abc |
628.8 bcd |
14.7 abc |
116.4 ab |
38.3 ab |
32.5 c |
8.5 ed |
0.27 b |
|
Wife (2x) x Kentucky Sunshine (4x) |
3x |
115.0 a |
14.8 ab |
774.8 ab |
17.2 a |
166.1 ab |
47.9 ab |
27.8 c |
11.4 bc |
0.40 a |
|
Wife (4x) x Wife (2x) |
3x |
75.8 bc |
11.5 bc |
441.0 e |
12.6 c |
71.6 b |
24.4 b |
34.0 bc |
7.3 e |
0.29 b |
iMean separation within column, indicated by different letters, by Tukey’s honestly significant difference (HSD) test at P≤0.05
Table 4.
|
Genotype |
Ploidy |
Photoperiod sensitivity |
Plant ht (cm) |
Shoots (no.) |
Total shoot length (cm) |
Stem caliper (mm) |
Plant dry wt (g) |
Flower dry wt (g) |
Flower dry wt (%) |
CBD (%) |
THC (%) |
|
Purple Star (2x) × Purple Star (2x) |
2x |
Insensitive |
45.0 ci |
7.0 d |
180.3 c |
10.3 c |
35.0 c |
9.1 d |
25.9 a |
. |
. |
|
Purple Star (2x) × Wife (2x) |
2x |
Sensitive |
114.5 ab |
22.2 a |
1199.3 a |
21.8 a |
478.3 a |
42.8 bc |
8.9 c |
9.9 a |
0.37 a |
|
Wife (2x) × Wife (2x) |
2x |
Sensitive |
105.3 b |
20.0 bc |
936.3 b |
17.0 b |
401.7 ab |
50.6 b |
12.6 bc |
6.3 b |
0.22 b |
|
Kentucky Sunshine (4x) × Wife (2x) |
3x |
Sensitive |
127.2 ab |
21.2 ab |
1121.7 a |
21.2 a |
451.7 a |
69.4 a |
15.4 bc |
9.5 a |
0.33 a |
|
Purple Star (4x) × Purple Star (2x) |
3x |
Insensitive |
58.0 c |
7.0 d |
222.0 c |
10.1 c |
38.1 c |
7.9 d |
20.7 ba |
. |
. |
|
Purple Star (4x) × Wife (2x) |
3x |
Sensitive |
139.4 a |
19.0 bc |
1107.2 ab |
19.0 ab |
336.7 b |
45.9 bc |
13.6 bc |
8.3 ab |
0.30 ab |
|
Wife (4x) × Purple Star (2x) |
3x |
Sensitive |
116.3 ab |
18.7 c |
951.0 b |
18.8 ba |
378.3 ab |
32.0 c |
8.5 c |
6.4 b |
0.30 ab |
iMean separation within column, indicated by different letters, by Tukey’s honestly significant difference (HSD) test at P≤0.05
A final greenhouse study compared 2x and 3x genotypes for the same parental cultivar cross and found few differences between 2x and 3x counterparts (Table 5). The 3x genotypes ‘Tsunami’ (4x) × ‘Wife’ (2x) and ‘Wife’ (4x) × ‘Purple Star’ (2x) from this study were included in field trials at the University of Vermont (Burlington, VT, USA). Plants performed equivalent to or better than 14 industry-standard 2x cultivars and six 3x cultivars developed by Oregon CBD (Independence, OR, USA) (Darby 2023). Plants of 3x ‘Tsunami’ (4x) × ‘Wife’ (2x) exhibited the greatest percent flower weight at 46.6%. We found that greenhouse-grown 3x plants of ‘Tsunami’ (4x) × ‘Wife’ (2x) had a lower percent flower weight than their 2x counterparts, less total shoots, and smaller shoot length (Table 5). These findings suggest that differences in plant growth and flower production between 2x and 3x cannabis are most likely attributable to genotype, not ploidy. Furthermore, parental combination can influence important traits like cannabinoid content and percent flower weight. Several of our 2x and 3x genotypes were derived from photoperiod insensitive and photoperiod-sensitive parents, or from parents with divergent backgrounds; therefore, enhanced performance observed for these genotypes may be partially attributable to heterosis.
Table 5.
|
Genotype |
Ploidy |
Photoperiod sensitivity |
Plant ht (cm) |
No. shoots |
Total shoot length (cm) |
Stem caliper (mm) |
Plant dry wt (g) |
Flower dry wt (g) |
Flower dry wt (%) |
CBD (%) |
THC (%) |
|
Purple Star (2x) × Purple Star (2x) |
2x |
Insensitive |
47.0 ai |
5.9 a |
160.6 a |
7.9 a |
23.6 a |
7.1 a |
30.0 b |
8.8 a |
0.36 a |
|
Purple Star (4x) × Purple Star (2x) |
3x |
Insensitive |
51.8 a |
6.3 a |
186.0 a |
8.0 a |
24.2 a |
8.0 a |
33.7 a |
8.9 a |
0.38 a |
|
Purple Star (2x) × Wife (2x) |
2x |
Sensitive |
85.3 a |
15.6 a |
706.4 a |
14.1 a |
138.6 a |
29.4 a |
19.9 a |
11.8 a |
0.53 a |
|
Purple Star (4x) × Wife (2x) |
3x |
Sensitive |
98.7 a |
14.0 a |
660.0 a |
13.7 a |
155.0 a |
26.5 a |
16.7 a |
9.9 a |
0.44 a |
|
Tsunami (2x) × Wife (2x) |
2x |
Sensitive |
117.4 a |
17.6 a |
1026.8 a |
20.0 a |
272.5 a |
54.4 a |
24.1 a |
9.5 a |
0.40 a |
|
Tsunami (4x) × Wife (2x) |
3x |
Sensitive |
110.2 a |
14.6 b |
788.5 b |
18.4 a |
212.9 a |
36.5 a |
17.1 b |
9.7 a |
0.40 a |
iMean separation within column, within counterpart, indicated by different letters, by Tukey’s honestly significant difference (HSD) test at P≤0.05 (n=8, except for percent CBD and THC where n=4).
In conclusion, 3x plants demonstrated reduced seed production but similar plant growth and flower production compared with 2x plants. Although 3x plants may develop a small number of filled seeds in the presence of pollen, there is low risk of large crop losses caused by seed set. The optimal cross direction for producing 3x seed is 4x × 2x because the 2x × 4x cross exhibits triploid block. When developing 4x plants, cryptic chimeral mixoploids can occur. If these are used as parents in the 4x × 2x cross, then the progeny will be a mix of 2x and 3x. For photoperiod-sensitive cultivars, a prolonged period of testing can identify cryptic chimeral mixoploids, but this is not possible for photoperiod-insensitive cultivars.
Education & Outreach Activities and Participation Summary
Educational activities:
Participation Summary:
2021
On December 9, 2021, a virtual field day/workshop was conducted, which included educational presentations about what is triploid hemp, how is triploid hemp seed produced, and triploid hemp sterility and performance. After each presentation there was a lengthy and dynamic discussion with attendees about the project and results of the research to date. There were 20 attendees of which 15 were farmers or in industry, and 5 were extension educators. The advisory group for this project, consisting of 3 growers and 3 extension educators, attended this event and participated in the discussions. Based on the post meeting evaluation questionnaire, which included retrospective questions, respondent (n=9) knowledge about what is triploid hemp increased from 3.6 (on a scale of 1=no understanding to 5=great understanding) before the workshop to 4.9 after the meeting. Respondent knowledge about how triploid seed is produced and triploid sterility and performance increased from 3.0 before the workshop to 4.8 after.
I provided a presentation about this project for the 2nd Annual Hemp Science & Technology Virtual Symposium, which aired on December 1, 2021. There were 360 registered for the event and 99 attended the session live. The session was made available to registrants to watch for one year.
2022
I provided a presentation about this project for the 2022 Industrial Hemp Conference hosted by the University of Vermont on March 15, 2022. A meeting to share information about the project with stakeholders is in planning for late winter/spring 2023.
2023
On May 16, 2023, a second virtual field day/workshop was conducted, during which stakeholders learned breeding strategies to produce early flowering triploid and diploid hemp cultivars and how autoflowering gene dosage impacts flowering timing. After each presentation there was a lengthy and dynamic discussion with attendees about the project and results of the research to date. There were 30 attendees of which 11 were farmers or in industry, and 19 were extension educators or researchers. The advisory group for this project, consisting of 3 growers and 3 extension educators, attended this event and participated in the discussions. Based on the post meeting evaluation questionnaire, which included retrospective questions, attendee (n=13) knowledge about early flowering triploids increased from 2.0 (on a scale of 1=no understanding to 5=great understanding) before the meeting to 4.6 after the meeting. Attendee knowledge about the impact of autoflowering gene dosage on flowering timing increased from 3.2 before the meeting to 4.2 after the meeting.
Two presentations were delivered in 2023. The first was at the University of Connecticut Cannabis Symposium in Storrs, Connecticut on March 16, 2023. The second was at the annual conference for the American Society for Horticultural Science, in Orlando, Florida on August 4, 2023.
In 2023 research findings about triploid hemp flowering performance were published in the Journal of the American Society of Horticultural Science, which is an open access publication. https://doi.org/10.21273/JASHS05293-23
2024
A presentation was delivered to the Hemp Symposium in Connecticut: Hemp Sustainability, and Justice through a Circular Economy in CT. The advisory group for this project met following this meeting with some member attending in person and other virtually.
In 2024 research findings about triploid hemp sterility were published in the Journal of the American Society of Horticultural Science, which is an open access publication. https://doi.org/10.21273/JASHS05359-23
Learning Outcomes
Stakeholders that attended workshops and presentations reported increased knowledge about triploid hemp sterility and performance. Grower knowledge of triploid hemp increased 36%, of triploid hemp seed production and sterility increased 60%, and of early flowering triploids increased 130%.
Growers expressed interest in the triploid plant material produced by the project since one genotype in particular produced the greatest floral dry weight out of 22 total varieties tested in the 2022 University of Vermont Hemp Flower Variety Trials (https://www.uvm.edu/d10-files/documents/2024-08/2022_Hemp_Flower_Variety_Trial.pdf).
The research article published in the Journal of ASHS in 2023 has garnered 2476 views and 2074 downloads to date. The research article published in the Journal of ASHS in 2024 has garnered 1506 views and 1235 downloads in the past year.