Male-Hermie Question

Parent Stock: (Dioecious) x (Monoecious) = F1 Generation: (Unisexual) x (Monoecious) = F2 Generation: Marketable Seeds. Dioecious cultivars are bred as follows: Parent Stock: (Dioecious Female) x (Monoecious Male) = F1 Generation: (Female 1) x (Monoecious male) = F2 Generation: (Female 2) x (Monoecious Male) = F3 Generation: (Stable Dioecious Cultivar).

Male plants with insufficient fiber content are removed from the crop before they pollinate; thus, the females are fertilized by the best males only. The seeds of females with the best fiber content are sown the next spring. The selection process is repeated annually.

G.S. Stepanov reported on characteristics of heterosis in unisexual hemp hybrids which he obtained by crossing maternal dioecious hemp with the paternal monoecious form:

"The F1 generation consisted almost completely of female plants (88.3-98%). Heterosis was established for seed yield, which represents a complex expression of many interrelated reproductive qualities. A discrete character of heterosis for elements of productivity is suggested, based on the height and weight of stem, weight of seeds and weight of fiber." (38, 39)

In a report on the "Phenonemon of unisexuality and heterosis in first generation hemp hybrids", Stepanov declared:

"Intervarietal hybridization of dioecious forms with monoecious forms is a highly effective means for increasing the yield of hemp. The unisexual hybrids are promising for use under commercial conditions, since they can be harvested without hand-picking of staminate hemp, and they have a high yield of stems, seeds and fiber. Depending on the combination, heterosis can be noted either only for individual elements of the structure or for an entire complex of characters...

"The F1 unisexual hybrids of hemp obtained from crossing dioecious and monoecious varieties most often manifest heterosis in seed yield. The hybrid plants (as compared to the parental forms) are characterized by a higher homeostasis of development... Heterosis has a discrete nature in relation to elements of productivity."

In his "Evaluation of hybridization capacity of hemp cultivars in breeding for heterosis", Stepanov reported:

"Common and specific capacities for hybridization in hemp cultivars are slightly different genetically. Specific capacity for hybridization of the crossing components is of the greatest significance for heterosis manifestation in the first generation hybrids. To obtain a high heterosis effect it is necessary to choose for breeding in the first turn the cultivars with high specific capacity for hybridization...

"When crossing varieties that are equal in height, the variation scope in hemp varietal hybrids exceeds the limits of the ranged series of the parental forms. The highest heritability index (0.79-0.87) is obtained in simple and complex hybrids. To create heterosis hybrids both parents should be selected out of the tall-stalked varieties." (40, 41)

Breeding techniques can be used to stabilize a seed line, to incorporate a desirable trait, or to remove an undesirable charcteristic. The simple process of "line breeding" serves well to maintain the stability of a seed line. Select at least several female plants for seed production, and pollinate only a few of their flowers. If the variety is very inbred, it is advisable to collect pollen from several male plants in order to preserve any diversity in the seedline. Thus, the line can be stabilized for several more generations.

The method of "back-crossing" can be used to stabilize new hybrid seedlines, but it takes several generations to do so. As the name implies, seeds from an earlier generation are crossed with those of later crosses. A second generation (F2) hybrid female is crossed with an F2 male to produce the F3 seed. The F2 and F3 seeds are planted and a worthy F2 female is crossed with a choice F3 male. A male is selected from each subsequent generation (F4, F5, etc.) to be backcrossed with a female grown from F2 seed.

Stepanov reported on the "Variability and heritability of principal elements of productivity in intercultivar hemp hybrids" in 1977:

"The significant effect of backcrosses of paternal forms on the degree of the determination of characters in hemp hybrids was studied. Maternal forms have such an effect for simple and complex intervarietal hybrids. The highest phenotypical variability obtained was connected with the number and weight of seeds per plant. The effect of genotype on the phenotypical manifestation of symptoms is evidently a result of simple and complex intervarietal crosses, so it is easier to make the selection of populations of such hybrids than in back population because environmental conditions insignificantly hide hereditary differences among plants." (42)

In 1978, however, Stepanov reported on "The ineffectiveness of the back-crossing method selection of hemp for heterosis":

"In back crossings the additive effect of the genes predominates. The selection of the characters controlled by the additive genes leads to the homozygous increase of the population and reduced vitality of the plants. The repeated crossings of the heterozygous hybrid plants with the parental form homozygous for the recessive gene increases the quota of the genes of the latter. It results in the intermediate type of inheritance for all the elements of the backcross hybrid productivity...

"The use of the inbreeding method in hemp breeding... as a method of differentiating a heterogenous population and selection of the most valuable biotypes is the first stage in the creation of controlled heterosis. The investigated hemp cultivars were heterozygotic not only for numerous characters but also for combining ability, which even after 5-fold self-pollination was manifested in different families to a different degree. The magnitude of combining ability of the line was higher, the more strongly it was differentiated genotypically relative to all other lines. In the first stages of practical breeding, the inbreeding methods can be used in creating heterotic variety-line hybrids.

"Heritability of main productivity elements and their anticipated gain in populations of various types of intervarietal hemp hybrids... plant height and fiber content in a stem, are highly-heritable irrespective of the crossing types. Low heritability is typical of such integral characters, as the number and weight of seeds from one plant; they are modified depending on the growth conditions. The higher the heritability coefficient, the greater the genetic gain of characters. Other conditions being equal, selection is more efficient. From the theoretical view point the expected gain of all the productivity elements at simple and complex intervarietal crossing is considerably higher than at reciprocal ones." (43-45)

M.A. Fedin reported concerning "The efficacy of gametocides inducing male sterility" in 1984:

"The heterotic breeding method is more effective than the methods used before. The breeding process is shorter. It is possible to produce the necessary quantity of hybrid seeds in a shorter period." (46)

K. Goncharova and N. Migal observed "Deviations in meiosis in four sources of hemp male sterility":

"Microsporocytes dying off, migration of the chromosomes beyond the borders of the spindle division in the metaphase and anaphase, lagging chromosomes in the anaphase, formation of the micronuclei in the telophase, and asynchronous division of the microsporocytes." (47)

N.D. Migal also studied the inheritance of the length of the vegetative period:

"Families with different intervals between ripening of male and female plants were revealed in dioecious hemp. This permits breeding for simultaneously ripening forms by selecting families with a minimum interval." (48)

Migal's research also revealed another useful finding:

"The dwarfs of monoecious hemp represent a recessive mutation form valuable for studying peculiarities of natural mutagenesis and changes in the development of sex expression." (49)

The intersexual form of male sterility in the plants of monoecious hemp is characterized by a complete lack of pollen. It is inherited by the next posterity through the monofactorial type of inheritance, which makes it possible to use it as a maternal form in the process of hybridization.

The transition of male to female flowers can be accomplished by wounding the infloresences of male plants. The anther lobes will transform into ovules. The earlier this process begins, the more normal is the development of female flowers. Bisexual flowers also are obtained. (50)

R. Savelli and N. Soster reported the induction of monophylly by wounding hemp:

"[Wounds were inflicted by] extirpation of the apex of the principal bud, cutting of lateral branches, cutting back the plant at various heights, and in all cases total exfoliation... High mortality resulted. The best cases of monophylly occurred in plants cut back 20-25 cm from the ground. Lateral buds grew rapidly in place of the terminals removed. Monophylly is homologized with a juvenile form. The wounding was ineffective in changing the sex ratio."

Monoecy of hemp also can be induced by control of soil moisture. Z. Loseva grew hemp in different watering regimes, with these results:

"Soil moisture of 60-80% proved most suitable for the establishment of monoecy. The seed yield increased with the increased soil moisture. In order to obtain a more widespread monoecy and higher seed yields, hemp should be grown on fertile low-lying fields...

"When the monoecious variety is grown during a shorter day, a smaller number of monoecious plants and lower seed yields are obtained. On the other hand, lengthening of the day, improvement of the water regime, and reasonable ratio of NKP favors a rise in the percentage of monoecious plants and an increase in the seed yields." (51, 52)

Loseva and Arinshtein found these conditions to be optimal for monoecious hemp:

"When grown isolated from other hemp varieties and varietal purity maintained, monoecious hemp consists of 98-99% of monoecious and simultaneously ripening plants. If pure seed is not used, next year the percentage of common fimble will increase 4-6% and a year later to 8-12%. Monoecious hemp cannot be grown on seed plants without isolation or alongside dioecious varieties. The greatest number of monoecious hemp plants was observed under natural day length (79-90%); the smallest, under a short day (32-63%). Consequently the transfer of monoecious hemp varieties into shorter day conditions results in a reduction of seed yield, owing to the decrease in monoecious plants. Optimal conditions for monoecy development are attained by complete mineral fertilizer replacement and by soil moisture equal to 69-80% of the total moisture capacity." (53)

4.8 ~ Light

Cannabis' rate of growth is proportional to the intensity of the light it receives, and is inversely proportional to the length of the photoperiod.

Cannabis responds to light in accordance with the intensity, wavelength, and photoperiod. Cannabis is a "short-day" species: it flowers when the photoperiod decreases to about 8 hours. The plant requires at least 3 hours of light daily just to survive, and at least 8 hours daily to thrive. While the plant is young, up to 3 months old, it responds vigorously to increasingly longer periods of light (up to 16 hours). Daily photoperiods of 16 hours or more will cause cannabis to grow indefinitely in a vegetative phase. The plant will grow about 25% faster under 24-hour lighting. Nutrient consumption increases proportionately. (54)

The photoperiod must be shortened to less than 10 hours to induce flowering and complete the growth cycle. Cannabis flowers quickest with a photoperiod of 8 hours. Thus, mature plants will develop flowers within 2 weeks of short-day treatment. Immature plants require up to one month of long nights to induce flowering. A short light period usually will bring cannabis into bloom within a month after emerging from the ground, but of course the plants will be very small. Short photoperiods inhibit the growth of stems and foliage, leaves produce fewer serrations in the margins. Flowering is hastened. The number of serrations correlates well with the degree of lighttime treatment.

Erratic lighting will confuse cannabis. V. Sofinskaya studied the conditioning of hemp with lighttime, and observed the following effects:

"The decrease in day length favored the acceleration of light stage completion but was unfavorable to plant growth. A prolonged short-day treatment resulted in a greater growth delay and in stunted plants, especially when plants were grown under short-day conditions since their emergence. Sharp changes of light conditions during the light stage resulted in various morphological alterations and in the appearance of hemp forms widely differing in habitat. Changes in light conditions during the light stage caused transgression in the normal course of the stadial plant development, resulting in considerable morphological changes of infloresence development as well as in the shape and size of leaves." (55)

Cannabis must not be disturbed during its night; unscheduled illumination during the dark period will inhibit flowering. Total darkness is required. The flowering response of hemp is controlled by the length of the dark night, not by the length of daylight. As little as 0.03 footcandles (FC) of red light interrupting the dark period will inhibit the anthesis of hemp. A long night thus becomes two short nights separated by an extremely short day, such as 1 minute of illumination.

Very long nights cause hemp flowers to ripen more quickly. This technique is most effective after the 4th week of the flowering phase. Far red light (supplied by incandescent spotlights) can reduce the time required for the flowering phase by about one week.

Cannabis will grow with as little as 800 FC of light, but the growth will not be vigorous. A minimum of 1500 FC is required for a healthy crop. When grown in a short-day regime under low-intensity light, cannabis becomes starved for photons. The hypocotl elongates excessively during the first 2 weeks after the plant emerges. It may reach a height of 6 inches before any internode leaves develop in the plumule. If the illumination is intensified, the plants may survive, and they will develop a clockwise spiral twist in the cotyledon.

Low light levels also produce smaller, thinner leaves, elongated internodes, reduced concentrations of chlorophyll, and less dry weight. High levels of light shorten the growth period, stimulate branching and budding, and increase the production of red anthocyanin pigments. Excessive light causes dessication, bleaching due to photodestruction of chlorophyll, and then necrosis.

Laser light has similar effects. G. Krustev, et al., used a He-Ne laser (632.8 nm/15 & 30 minutes) and a nitrogen laser. The sowing qualities of the seed are improved, the phases of plant development are shortened, the plants are more vigorous, and the yield of seeds and stems. (83)

Rejuvenation --- The growth cycle of cannabis usually lasts about 16 weeks. When cultivated indoors, however, cannabis can be rejuvenated after it has bloomed and begins to go into senile decline. Some varieties are very amenable to rejuvenation after their flowers have been harvested. The plants should be cut back to the second branching node. Let as many leaves as possible remain, and a few buds. Give the plants at least 18 hours of light daily. New meristems will develop within three weeks. Extra nutrients (especially N) must be supplied at this time, or the new flowers will be male. The process can be augmented with foliar sprays of Indole Acetic Acid (IAA) or Napthalene-AA. The soil should also be treated with the hormones. Hemp can be rejuvenated repeatedly with such treatment, thus living several times longer than usual. Even without continuous-light rejuvenation, female hemp may live several months longer after flowering if the plant remains unpollinated. If female plants become senile between rejuvenations, then sex-reversals usually occur, especially under the influence of short-day photoperiods after the continuous-light treatment. In such a case, about 90% of the females reverse to male or hermaphroditic intergrades. (56-60)

Rejuvenated cannabis blossoms from the terminal bud or from lateral buds below the infloresence. Usually the first few leaves on rejuvenated plants are entire (smooth edged). After several such leaves have developed, subsequent leaves again have the usual serrations. When grown under continuous light, the phyllotaxy of the branches changes from opposite to alternate at some point after the seventh node. Plants grown with normal long-days do not change their phyllotaxy until 12 internodes have developed. Rejuvenated plants are very sensitive to tobacco smoke and can be killed by it.

D. Kohler researched the effects of short and long days on hemp morphology, and found another way to rejuvenate cannabis, based on its response to light:

"In short-day and long-day hemp the first leaves are simple and comparatively broad, the later are divided, their leaflets being comparatively narrow. The size of the leaves following one another is continuously increased. Plants begin to flower (qualitatively reacting short-day hemp in short-day only). The shape of the leaves produced in the infloresence is determined in the first days of flowering: they become more and more simple and their leaflets comparatively broader. The leaf size is influenced by the length of day. The leaves of plants kept in flower-inducing daylength grow less and less due to competition between reproductive and vegetative organs, whilst the leaves of flowering plants, which are transferred into longer day, grow larger and larger. In this case the latest leaves are of the same size and shape as the earliest one; a second life-cycle starts, whilst the plants in the original daylight are dying. Considering the photoperiodic response of hemp, leaf-size is a measure of the physiological age. With monoecious hemp a certain leaf size is necessary for the formation of male flowers. If female plants are put into longer day during blossom, they do imitate the male habit." (61)

Ocra Wilton found a correlation of cambial activity with cannabis' flowering and regeneration:

"A study was made of cross-sections of all the internodes from the tips to the bases of the stems... When Cannabis sativa has reached an advanced stage of reproductiveness, the meristematic tissue of the stem tends to become entirely differentiated into xylem and phloem elements. This anatomical condition is a possible explanation of the death of such plants at the close of one reproductive cycle. The cessation or decline of cambial activity which accompanies the production of flowers in C. sativa progresses from the region of the infloresence toward the base of the plant, which it may or may not reach depending on the degree of reproductiveness which the plant attains. Vigorously vegetative plants have an active cambium throughout their stems... a certain amount of at least potentially meristematic tissue is necessary for a renewal of vegetative growth in stems."

Photoperiodism ---- Photoperiodic control can be very useful to the cannabis breeder. If yield is not important (as is often the case in the early stages of a breeding program), the time required for the life cycle can be greatly reduced by using short photoperiods. Thus, several generations of plants can be produced each year. Under such conditions, cannabis will flower when it is only a few inches tall. (62)

Photoperiodic control makes it possible to synchronize the flowering dates of male and female plants, thus making possible their cross-breeding. Most importantly, photoperiodic control enables breeders to stimulate the production of male flowers on female plants. Self-pollination can be accomplished only by means of such flowers. Male flowers on female hemp do not contain the Y (male) chromosome; they produce only female pollen. When this is used to fertilize female flowers on female plants, they will produce purely female seeds. The pollen from male flowers is of two kinds, and usually produces a ratio of males 1:1 females. A few viable seeds can be obtained from female flowers produced on male plants and self-pollinated, but such seeds are only weakly fertile and produce mostly female plants.

The following procedure will produce seeds which will grow 100% female hemp:

Cultivate two separate groups of female plants indoors. The plants should receive at least 50 watts of light per square foot of growing area. One group must not receive more than 7 hours of light daily. This will induce male flowers to manifest on the female plants. The second group of females must receive about 16 hours of light daily to ensure that no male flowers develop on them. The long photoperiod also inhibits the development of flowers so much that the short-day plants will mature 2 or 3 weeks before the long-day group. Therefore, begin cultivating the long-day females at least 2 weeks before planting the short-day plants.

As the two groups approach maturity, remove any males which may appear. A few weeks before the male hemp begins to flower, the internodes of the stem begin to elongate very quickly. The dominant male enzyme andrase produces thin plants with a tuft of leaves at the top. The leaves are smaller than those of the females, and have fewer leaflets (usually 5). Tiny buds sometimes appear in the nodes about 2/3 up the stalk. The future sexual expression of hemp may be determined by examining these premature flowers. If the buds remain erect, the plant is female. If the buds droop, the plant is male.

When clusters of female buds begin to appear on plants in the long-day group, cover each bud with a transparent plastic bag sealed with a rubber band around the stem below the bud cluster, so as to protect the flowers from accidental pollination.

When male buds appear on some of the female plants in the short-day group, cover each bud with a transparent bag sealed with a rubber band around the stem below the bud cluster, so as to protect the female flowers from accidental pollination.

When male buds appear on some of the females in the short-day group, carefully cut off every male bud and store them in a glass jar. Any new male buds which appear also must be pruned. Within a few days the anthers of the clipped buds will open and release pollen. Collect this pollen and apply it with a thin brush to the stigmas of the bagged flowers in the long-day group. Because this pollen contains only female chromosomes, the fertilized female flowers on the long-day female group will develop seeds which will produce only female plants.(63-66)

Another method of manipulating the gender of cannabis involves treatment of the male pollen with ultra-violet light for about 1 hour. This doubles the ratio of the females to males, perhaps by neutering the weaker male chromosomes. (67, 68)

The viability of hemp pollen can be preserved by the method of Migal and Arinshtein:

Storage of pollen in a refrigerator will protect breeding material for 38-45 days, which is important for crossing different varieties of hemp. Hemp pollen can also be stored in the dark placing it in a desiccator over calcium chloride or concentrated sulfuric acid. Here the pollen grains retain the viability to germinate for 12-18 days. The pollen of dioecious varieties of hemp retain viability longer than the pollen of monoecious varieties. (69)

G. Davidyan found these effects of light on the root development of hemp:

"The growth of the root system in hemp was found to be more intensive than that of the stem at the vernalizaton and light stages. The root system is less vigorous in short than in long day conditions. At the stage of rapid development --- the beginning of budding up to flowering --- an intensive stem and root system growth is observed. The root system of female hemp plants is superior in vigor to that of male plants." (70)

4.9 ~ Sexual Expression

The sexual expression of cannabis is determined by its genetic makeup, and by its metabolic temper, which is regulated by the male enzyme andrase and the female enzyme gynase. Environmental conditions (light, nutrients, soil and water) may suppress the formation of the dominant enzyme, and allow the opposite sex to express itself partially (hermaphroditism) or completely (sex reversal). (71, 72)

E. Galoch found that cytokinin is important for the sexual expession of hemp:

"Transition of female and male hemp plants from the vegetative to the generative phase is associated with a rise in cytokinin level while that of male inflorescences proceeds at a decreasing cytokinin level. The activity of cytokinins apparently is associated with an enhancement of the female tendency..." (73)

Gibberellin will inhibit the formation of flowers on cannabis, but sometimes it will otherwise cause the growth of fertile female flowers on genetically male plants. Silver nitrate or cobalt chloride causes masculinization of flowers of female hemp, possibly due to blockage of ethylene synthesis. High levels of N salts --- and long photoperiods --- have a masculinizing effect on hemp.(74-76)

According to K. Conrad, there are sex-linked differences of the auxin content in male and female hemp plants:

"During blossoming the vegetative parts of the males contain more auxin than those of the females. In the dying leaves and stems a remarkable increase of auxin can be observed." (77)

J. Heslop-Harrison studied auxin and sexuality in Cannabis:

"Dioecious hemp plants were grown to an age of 20 days in a day-length of 21-22 hours, then given an inductive treatment of ten 8-hour days to initiate flowering. After return to long days and during the period of differentiation of flower buds, a total of 0.5 gr lanolin paste containing 0.5% NapthaleneAcetic Acid (NAA) was applied to leaves at the 3rd and 4th nodes. In genetically male plants, female plants were subsequently formed in sites which would normally be occupied by males, a result which appears to be regulated by the level of native auxin in the vicinity of meristems during the period of differentiation of flower primordia. Secondary effect of auxin treatment were evident in an over-all reduction in intensity of heteroblastic development, the trend towards a reduction of leaf lobing and serration which normally accompanies plants passing through a period of flowering than in untreated controls." (78)

Nitrogen fertilizers masculinize the phenotype by stimulating the formation of male flowers. The proportion, number and degree of monoecious plants increases with increasing N, and the total N content is always higher in monoecious individuals than it is in females. (79)

Treatment of hempseed with ethylene gas will increase the resulting number of female plants by about 50%. Ethylene is produced by certain plants (i.e., bananas, cucumbers and melons), and these can be used to treat hempseed in a simple manner. About two weeks before you plan to sprout the seeds, place them in a paper bag or envelope and put that in a plastic bag with the peels of a ripening banana or cucumber. Replace the peels after a couple of days, and change the bags to prevent mold.

Hempseed can be feminized while they are forming on the plant. Fruit peels are spread around the area for two weeks before the plants enter the flowering phase. Remove the skins when the plants begin to flower. Otherwise, treatment with Etephon will accomplish the same effect.

When hempseed is treated with the female hormone estrogen, percentage of females that are produced will increase by about 10%. Dissolve a birth control pill in water and soak the seeds overnight in the solution. After the initial soaking, continue to treat the seeds by sprouting them on a paper towel soaked in the solution. (80)

A.I. Zhatov tested the effects of ethrel on hemp:

"Treatment of hemp plants with an aqueous solution of ethrel changed the ratio of male to female flowers. The greatest effect was observed when plants were treated during flowering of male flowers." (81)

Electricity also can change the sexual expression of cannabis; B.R. Lazarenko and I.B. Gorbatovskaya reported:

"Under the influence of the electrical current, the numerical proportions between hemp plants of different sexes was changed by comparison with the control to give an increase of female plants by 20-25%... The characteristics acquired by the plants in electrically treated soils are transmitted by inheritance to the third generation..." [emphasis added] (82)

Photoperiodism is a most useful tool with which to control the sexual expression of cannabis. For example, J. Limberk made a careful study of lighttime on the sexual index of hemp, and reported thus:

"Male plants usually flowered earlier than female. Female plants flowered only when the period of daylight was shorter than 14 hours; male plants flowered even when the day was longer than 14 hours. Reduction of light intensity in the first stages of plant development lead to increases of female plants by 4.3%. Intersexual plants (22-30% of the total) were present in conditions of 11-13 hours light per day. Grafting of plants did not change sex."

Monoeciousness effected by short days is not fixed in the descendants. (84)

The probable future sex of a pre-floral hemp plant can be guessed at by calculating the Leaf-Mass Index (LMI): Count the points (3, 5, 7) on 3 leaves in the center of a cluster. Divide that number by 3 to determine the average number of points. Repeat the process several times, and figure that average also. Multiply the two averages to determine the LMI. A high LMI indicates that the plant will be female.

The phyllotaxy changes to alternate just before the onset of flowering. Then the sex of the plant can be determined by making a close examination of the upper nodes of the main stem. The onset of flowering is indicated by the appearance of undifferentiated primordial buds behind the stipules at the nodes of the petioles (along the stem at the base of branches). Within a few days they differentiate. The male pistils are flat or knobby with a curved shape and 5 open petals about 5 mm. long; they have a single tiny stalk. Overlapping vegetation often disguises their appearance.

The female develops pairs of flowers surrounded by pointed bracts of protective leaves that will enclose the seed. The female stigma usually appear as 2 fuzzy white hairs forming a "V" that protrudes from a bract. Resinous hairs (glandular trichromes) cover the calyx (2-6 mm long).

4.10 ~ References
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