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I know that if you stress a female plant (using light, etc) enough that it will go hermie.
My question is, if you have a known male can you induce it to also go hermie? If you could would it then produce buds AND seeds like the female does?
If so, this could be a great way to get at least some bud from a male plant. If this is possible im sure someone has heard of it so does anyone know if it is possible???
Thanks,
JPG
I have not heard of someone trying to turn a male plant into a female by way of hermie.
I never even gave that a thought. Every hermie I have ever found has been a female that grew seeds on the lower part of the plant to produce seeds.
Let me know what you find out. There is a product from Dutch Masters called femalerizer or something like that. They say it will produce more female plants then just letting nature takes its course.
It's called Feminizer from Dutch Master products.
zandor pin this thread, it has alot of potential.
Polyploids: genetic diversity but they are unpredictable and usually are unstable in the first generation. They also tend to be sterile and must be propagated by clonal cuttings to be useful for subsequent breeding. No one works with the male to much
most of them go out quick. so if a male was to be brought into stress, a hermie just mite come to be. and what could we find out about them. It is all do to survival of the plant Right. it could bring the female side out...
I have a 250 MH that I'm not using and 2 JH that I don't know what they are yet, so if 1 or both of them are males I can put them in the out bulding with the light and work with them and see what happen. could be fun, to get (female) or seeds from a male plant.
let me know how that goes if you do it litespeed
When cannabis pollen is treated with ultraviolet light for one hour, the seed obtained from the resulting plants produces twice as many females as males.
Colchicine--- Tetraploidy can be induced by the mutagenic alkaloid colchicine, which is found in the autumn crocus, (colchicum autumnale). Colchicine allows a cell to double its chromosomes, but prevents meiosis (the splitting of cells), thus forcing the cells to become polyploid. When applied to cannabis, colchicine produces tetraploid plants which tend to be taller, with greater stem diameter, seed and pollen size. The THC content can increase up to 250%.
Intresting!!Quote:
Originally Posted by litespeed
Where did you find this please, is there more information?
Hemp Husbandry
Robert A. Nelson
Copyright 2000
Chapter 4
Botany & Breeding
1. Classification
2. Botanical Description
3. Trichromes
4. Phenotypes
5. Genetics
6. Polyploidy
7. Breeding
8. Light
9. Sexual Expression
10. References.
4.1 ~ Classification
Class: Angiospermae
Subclass: Dicotyledonae
Superorder: Dilleniidae
Order: Urticales
Family: Cannabinaceae
Genus: Cannabis
Species: sativa, indica
Subspecies: sativa
Varieties: ruderalis, vulgaris, spontanea, gigantea, chinensis, etc.(1-4)
4.2 ~ Botanical Description
USDA botanist Lyster H. Dewey published this official "Botanical Study of Hemp" in 1913:
"THE PLANT --- The hemp plant, Cannabis sativa L., is an annual, growing each year from the seed. It has a rigid, herbaceous stalk, attaining a height of 1 to 5 meters (3 to 16 ft), obtusely 4-cornered, more or less fluted or channeled, and with well-marked nodes at intervals of 10 to 50 cm (4 to 20 in). When not crowded it has numerous spreading branches, and the central stalk attains a thickness of 3 to 6 cm (1 to 2 in), with a rough bark near the base. If crowded, as when sown broadcast for fiber, the fluted stems are without branches or foliage except at the top or on the shortened branches, appearing fascicled, are palmately compound and composed of 5 to 11 --- usually 7 --- leaflets. The leaflets are dark green, lighter below, lanceolate, pointed at both ends, serrate, 5 to 15 cm (2 to 6 in) long, and 1 to 2 cm (3/8 to 3/4 in) wide. Hemp is dioecious, the staminate or pollen-bearing flowers and the pistillate or seed-producing flowers being borne on separate plants. The staminate plants are borne in small axillary panicles, and consists of five greenish yellow or purplish sepals opening wide at maturity and disclosing five stamens which discharge abundant yellow pollen. The pistillate flowers are stemless and solitary in the axils of the small leaves near the ends of the branches, often crowded so as to appear like a thin spike. The pistillate flower is inconspicuous, consisting of a thin, entire, green calyx, pointed, with a slit at one side, but remaining nearly closed over the ovary and merely permitting the two small stigmas to protrude at the apex. The ovary is one seeded, developing into a smooth, compressed or nearly spherical achene (the "seed"), 2.5 to 4 mm (1/10 to 3/16 in) thick and 3 to 6 mm (1/8 to 1/4 in) long, from dark gray to light brown in color and mottled, The seeds cleaned for market nearly always include some still covered with green, gummy calyx. The seeds vary in weight from 0.008 to 0.027 gram, the dark-colored seeds being generally much heavier than the light-colored seeds of the same sample. The light-colored seeds are often imperfectly developed. Dark-colored and distinctly mottled seeds are generally preferred.
"The staminate plants are often called the flowering hemp, since the pistillate flowers are rarely observed. The staminate plants die after the pollen is shed, but the pistillate plants remain alive and green two months later, or until the seeds fully developed.
"THE STALK --- The hemp stalk is hollow, and in the best fiber-producing types the hollow space occupies at least one-half the diameter. The hollow space is widest, or the surrounding shell thinnest, about midway between the base and the top of the plant. The woody shell is thickened at each node, dividing the hollow space into a series of partly separated compartments. If the stalk is cut crosswise a layer of pith, or thin-walled tissue, is found next to the hollow center, and outside of this a layer of wood composed of hard, thick-walled cells. This layer, which forms the "hurds", is a very thin shell in the best fiber-producing varieties. It extends clear across the stem below the lowest node, and in large, coarse stalks grown in the open it is much thicker and the central hollow relatively smaller. Outside of the hard woody portion is the soft cambium, or growing tissue, the cells of which develop into the wood on the inside, or into the bast and the bark on the outside. It is chiefly through this cambium layer that the fiber-bearing bast splits away from the wood in the processes of retting and breaking. Outside of this cambium is the inner bark, or bast, comprising short, thin-walled cells filled with chlorophyll, giving it a green color, and long thick-walled cells, making the bast fibers. These bast fibers are of two kinds, the smaller ones (secondary bast fibers) toward the inner portion making up rather short, fine fibers, many of which adhere to the wood or hurds when the hemp is broken, and the coarser ones (primary bast fibers) toward the outer part, extending nearly throughout the length of the stalk. Outside of the primary bast fiber is a continuation of the thin-walled stalk, chlorophyll-bearing cells free from fiber, and surrounding all is the thin bark.
"THE FIBER --- The hemp fiber of commerce is composed of the primary bast fibers, with some adherent bark and also some secondary bast fiber. The bast fibers consist of numerous long, overlapping, thick-walled cells with long, tapering ends. The individual cells, almost too small to be seen by the unaided eye, are 0.015 to 0.05 mm (3/1000 to 12/1000 in) in diameter, and 5 to 55 mm (3/6 to 2-1/8 in) long. Some of the bast fibers extend through the length of the stalk, but some are branched, and some terminate at each node. They are weakest at the nodes." (5)
4.3 ~ Trichromes
Most of the aerial parts of cannabis, especially the female bracts, possess minute hairs, or trichromes, some of which excrete glistening drops of resin, so the flowers seem to shine with sticky amber dew which has a characteristic minty odor. It is thought that cannabis produces its resin as a protective measure against ultraviolet radiation, insects or water loss. Three types of trichromes occur on cannabis:
1) Bulbous and cappitate (sessile and stalked), resin-producing, glandular hairs on the flowers, leaves and stems;
2) Non-glandular hairs having no apparent function; 3) Crystoliths which resemble the non-glandular hairs, but are shorter and contain deposits of calcium carbonate. (6-8)
4.4 ~ Phenotypes
The expression of a trait in a plant strain is termed a phenotype. The interactions of genetic potential (genotypes) and environmental conditions (ecotypes) produce unique phenotypes. The phenotype system of distinguishing varieties reconciles many of the arguments about the species of hemp, all of which can be allocated to phenotypic groups. The phenotype system is based on the analysis of the relative amounts of cannabinoids: Tetrahydrocannabinol (THC), Cannabinol (CBN), and Cannabidiol (CBD). (9-13)
The Phenotype Ratio (PR) is calculated thus:
PR= % THC & CBN
% CBD
Phenotype I: The resin is composed primarily of THC. The fresh, manicured flowers contain more than 0.3% THC, and less than 0.5% CBD. Both the male and female plants produce large amounts of the resin. Phenotype-I plants usually originate from countries south of Latitude 30o N, where the tropical climate allows a long growing season. Often it is called Cannabis indica, the variety cultivated primarily for drug use.
Phenotype II: The resin contains approximately equal amounts of THC and CBD. This group is not sharply distinguished from P-III, but P-II plants usually contain more THC than do P-IIIs, and the females are more potent than the males. P-II hemp usually originates from countries north of Lat. 30o N, and it flowers early in the summer since it is adapted to temperate climes. P-II may represent hybridization between P-I and P-III.
Phenotype III: The resin contains primarily CBD (more than 0.5%) and less than 0.3% THC. The female produces more cannabinoids than does the male plant. P-III hemp usually originates north of Lat. 30o N, and is known as Cannabis sativa, cultivated primarily for fiber and seeds.
Phenotype IV: The resin may contain large amounts of THC, and traces of Cannabigerol Monomethyl Ether (CBGM) and Cannabiverol (CBV). P-IV hemp originates in northeast Asia, and usually is known as Cannabis ruderalis.
The phenotypes rich in THC always possess Cannabichromene (CBC), sometimes in large amounts. Phenotypes rich in CBD also contain CBC.
4.5 ~ Genetics
Cannabis has a haploid number of 1n=10; its somatic number is 2n=20. Some researchers have counted 2n=18 + (XX) or (YY). In the male plants, 9 pairs of the normal genomic pairs of chromosomes are equal in size, and the tenth pair (XY) consists of one chromosome about the same size as the members of the other pairs, plus one much larger sex chromosome. Heteromorphic pairs of chromosomes have been observed in monoecious strains of cannabis. (14, 15)
K. Hirata concluded that (x) has a higher male tendency than (X), and that (y) has a higher female tendency than (Y). The (X) has a net female tendency, and (Y) has a net male tendency. The male tendency in (Y) overbalances the female tendency in (X) so that a heterogeneous (XY) male is normally male, and a (XX) plant is normally female. Female hemp genes are (XX), (XXX), and (XXXX). The (XXXY) and (XXY) individuals are female or female intersexes. The males are (XY), (XYY), and (XXYY).
S. Hennick, et al., and others assert that this classification is impractical for purposes of breeding hemp, and have developed a new classification based on the theories of Grishko, Neuer, and Migal. The sex of dioecious hemp is determined by two tightly linked genes, both with two alleles. The Y chromosome carries the male allele M and the allele l, which expresses loose inflorescence. The X chromosome carries the female allele F and the allele i (compact inflorescence). Alleles M and l dominate over F and i. A recessive third allele, with a frequency from 0.5-1%, probably exists for monoecious hemp. The sex type of monoecious hemp is determined by autosomes. The sex chromosomes of diploid cannabis carry the genotype liMF and iiFF. The theory, however, does not explain how the loose or compact types of inflorescence are determined in monoecious hemp.(16)
N.D. Migal (All-Union Res. Inst. Fiber Crops, Glukhov) studied the genotypical determination of the sex of hemp. They summarized their finding as follows:
"Monoecious and dioecious hemp plants differ from one another in many phenotypical characters. As a result, a great variety of sex types is formed, which, in some way, complicates their classification...
"While studying spontaneous sexual mutations of dioecious and monoecious hemp, some peculiarities of interaction of genetic factors of sex chromosomes and autosomes were found out. They were used in further development of the theory of genotypical sex determination in this plant... The polyfunctional nature of sex determinations connected with monoecious hemp are conditioned by interactions of gene alleles of sexual chromosomes and genetical sexual factor in autosomes of different valency...
"Chromosomal mechanism of sex determination in dioecious hemp plants does not often correspond to expected correlation of the sex types 1:1. This fact, in some way, connected with sex gene mutation in sexual chromosomes and their interaction with autosomal factors." (17, 18)
Table 4.1 ~ Cannabis Genotypes
The Sengbusch Classification system defines five degrees of monoecious forms: (1) 80-90% male flowers; (2) 60-70% male flowers; (3) 40-50% male flowers; (4) 10-30% male flowers; (5) less than 10% male flowers. The second and third degrees types are considered ideal for monoecious cultivation.
The methods developed by R. von Sengbusch and H. Neuer (1943) are the foundation of the breeding technology for monoecious hemp:
"Several trial fields were established in an effort to breed monoecious hemp in a region where no hemp is cultivated. In these fields the progeny of four strains which contain a great number of monoecious plants are cultivated. One field was devoted to plants with many male flowers and only a few female flowers; the second field, to plants with an equal number of male and female flowers.
"Investigation of the distribution of the different types of intersexuality among the progeny of these plants showed that among the progeny of the plants from the first trial field there was an increased number of plants with few female and many male flowers, while in the second field the number of plants with equal number of male and female flowers was increased. This would seem to indicate that selection for different types of intersexuality is possible. While the number of pure male plants in the first year was 10-20%, after repetition of this selection, the number of males decreased to 0.8%, indicating that the male plants have arisen by pollination with pollen of a normal dioecious plant. This result shows that it is necessary to breed and to augment the monoecious hemp in a region where no dioecious hemp varieties are cultivated.
"In the trial field II the number of normal female plants was somewhat increased (11.9%), while in the trial plot I a large number of pure male flowering plants with a female habit (25.5%) appeared, demonstrating that it is impossible to breed from plants with few female and many male flowers a non-segregating variety, and that therefore it is necessary to eliminate these plants in the breeding field before blossoming.
"Trial plot I included, besides the monoecious plants, female plants of a dioecious variety. In the trial plot II there appeared, besides the monoecious plants with the same number of male and female flowers, dioecious plants which practically were females and had only a few male flowers; female plants which arose from monoecious plants, and normal females from a dioecious variety. The progeny from the crosses between these different types were analyzed. The cross of normal females with dioecious plants yielded female plants almost exclusively. This shows that the monoecious plants have the genetic constitution xx, and that dioeciousness is dominant over monoeciousness. This dominance, however, is incomplete; in crosses between pure monoecious plants a small number of female plants arose. The monoecious plants with a very small number of male flowers in crosses with monoecious plants with an equal number of male and female flowers gave about 80% monoecious plants and only 17% female plants. The plants with the same number of female and of male flowers gave, in crosses with the same type of dioecious plants, a small percentage of females, a large percentage of monoecious plants, and a very few male flowering plants. The monoecious plants with a great number of male and a small number of female plants, crossed with the same type of monoecious plants, gave practically no female plants in their progeny, but the greatest number of male flowering plants with female habit. Because these male flowering plants with a female habit have arisen from crosses between two monoecious plants, they must also be xx plants.
"The investigation of descendants of single plants shows great variability in their composition as to sexual types; similar differences could be found between the different strains. The authors explain these observations by the hypothesis that the series of monoecious plants, beginning with the pure female and finishing with male flowering plants with female habit, involve a series of alleles of sex-realisators. The pure female plant xx has the sex-realizator F50 (XX F50F50). The sum is 100 and effects a complete suppression of male flowers. With decrease of the realisator sum the male character of the infloresence increases.
"The male flowering plants with female habit (XX F25 F25 ) have the same sum as the normal male plants (XY F50f)=50. The greater realisator value is almost wholly dominant over the smaller. This explains why in crosses between female and monoecious plants only female plants arise in the F1. The incomplete dominance of the greater realisator value also explains why in crosses between monoecious plants 5-15% female plants always arise. The number of monoecious plants with equal number of male and female flowers which produce monoecious plants is very different among single strains. For breeding therefore it is necesssary to select strains which produce a great number of 'ideal' monoecious plants.
"Two methods for this selection are described. In one the seeds are ascertained in the trial field and in the next year only these strains are cultivated together, and only the seeds from these plants are used. The other method produces results more rapidly. From all strains, those with the greatest number of 'ideal' monoecious plants are established and from these strains the ten best monoecious plants are selected. All other plants are eliminated and the selected plants are cut back. After this treatment the plants begin to sprout and flower again and produce seeds, all of which are derived from selected plants." (35, 36)
The research of W. Hoffmann cast doubt on the theory of realisator-genes:
"Several complimentary genes in the autosome influence the sexual habit of the plant. In the normal dioecious hemp the polymeric habit factors are also influenced by the XY mechanism, so that the male flowers are always combined with the male growth habit, and female flowers with the female growth habit. In the feminized and masculinized types this balance is disturbed and XY types with female growth habit and XX types with male growth habit arise. Because a continuous series exists of feminized forms with many to few male and female flowers and of masculinized forms with many to few female and and male flowers, it would seem that the genes for growth habit can also influence flower formation. The existence of different sex types in segregation proves that the genes for growth habit can also influence flower formation. The existence of different sex types in in segregation proves that the masculinization and the feminization genes are not alleles but independent genes. In the normal dioecious hemp plant, the XY mechanism assures the predominance of one factor over the others. In the intermediate forms of hemp the sum of the efficiency of the genes of the autosomes predominates so greatly that the XY mechanism is not decisive and on the lowest grade the growth habit, on further increase of the efficiency of these genes, also affects flower formation. On the assumption that both dominant and recessive genes are effective as masculinizing and feminizing genes, the large number of sexual and morphological segregates is readily explained."
4.6 ~ Polyploidy
Cannabis usually is a simple diploid plant, but polyploids having several sets of chromosomes can be produced by mutation. Polyploid cannabis usually is larger, produces more resin, and reproduces better than diploids. It is distinguishable by its darker, thicker foliage, and by microscopic analysis. Tetraploid monoecious hemp plants are selected by examination of the number and size of stomata, the number of epidermis and stoma cells, the size of pollen grains, and their number of pores. (19)
Polyploids are valuable for their genetic diversity, but they are unpredictable and usually are unstable in the first generation. They also tend to be sterile and must be propagated by clonal cuttings to be useful for subsequent breeding.
Studies by Warmke and Zhatov revealed that the normal sex ratio for diploids (2n) is nearly 1:1, but tetraploids (4n) form a new class (XXXY) and develop about 7.5 females:1 male, plus female-hermaphrodites. The XXXX is female; XXXY is female-hermaphroditic; XYYY is male-hermaphroditic, and YYYY is male. The XY determination of sex does not account, however, for the development of some monoecious strains. Seemingly, the sexual expression of hemp can be controlled by some other gene set(s) influencing different aspects of flowering. Environmental conditions also can overpower the genetic expression of Cannabis' gender, especially in the final stages of flower production. (20-23)
A. Zhatov (1979) reported these results of his research into hemp genetics:
"Change of ploidy... induced changes on some economically valuable characteristics and biological features. Tetraploid plants of dioecious hemp are characterized with sharply pronounced dioecism: plants with sexual deviations appear in the population of tetraploid hemp. Sex chromosomes of hemp on the tetraploid level play a paramount part in sex determination, but the process of determination is affected by autosomic genes...
"The viability of microspores of polyploid hemp is lower as compared with microspores of diploid hemp. During the storage, polyploid pollen loses the ability to produce pollen tubes of normal length. Selection of plants with the best regulated meiosis may raise the viability of polyploid microspores." (24, 25)
A. Zhatov, N. Migal, and other researchers have used gamma-irradiation of hempseed to mutate the subsequent plant. Presowing irradiation causes a drastic decrease in the survival rate of dioecious male plants and monoecious heterozygotic plants. Male sterility is manifested by empty pollen grains. The proportion of male plants in M1 is reduced to about 14%, and the height of plants is reduced by almost 75%. The number of branches and seed yields are increased, and the fiber content is increased by 30%. (26)
W. Hoffman and E. Knapp treated hemp seeds with x-rays, with these results:
"With increased dosage, the damage to the plants increased, the number of survivors decreased, and the sex ratio changed in favor of the females... With increased dosage, an increasing number of divergent types arose, especially of monoecious plants, and of male-like females. With increased dosage of x-rays, an increased percentage of tendrilled plants was also found... It is possible by means of x-ray treatment to change the sexuality of hemp and to get the normal dioecious hemp to a constant monoecious strain."
When hemp pollen is treated with ultraviolet light for one hour, the seed obtained from the resulting plants produces twice as many females as males.
Colchicine--- Tetraploidy can be induced by the mutagenic alkaloid colchicine, which is found in the autumn crocus, (colchicum autumnale). Colchicine allows a cell to double its chromosomes, but prevents meiosis (the splitting of cells), thus forcing the cells to become polyploid. When applied to cannabis, colchicine produces tetraploid plants which tend to be taller, with greater stem diameter, seed and pollen size. The THC content can increase up to 250%.(27)
A. Zhatov, et al., reported these findings from their research:
"The greatest % of polyploid plants is obtained when hemp plants are treated with 0.5% colchicine solution for 2 hours in the phase of cotyledon leaves. The treatment with colchicine solution inhibits growth. This inhibition continues for 2.5-3 weeks, after which the surviving plants resume normal growth and development. The guard cells in the leaves and the pollen grains of tetraploid plants are larger and the number of pores on the pollen grains are greater. Tetraploid plants are taller and the diameter of their stems, seed size and weight of 1000 seeds are greater. The anatomical structure of the stems differs from the diploid plants in a greater amount of primary and secondary fiber. The pollen viability of the tetraploid plants is lower than that of diploid plants. Vegetation period in tetraploids continues 8-15 days longer than in control plants." (28)
Colchicine also can sprayed on the seeds while they are developing on the mother plant. The flowers of plants treated in this manner should not be smoked because the concentration of colchicine may be dangerously high. A third method is to soak seeds in the solution for 2 to 4 hours. Colchicine stimulates the development of the taproot at first, but this effect ceases within a week; then the seedlings go into shock. About 30% of the survivors will be polyploid.
Colchicine can be bought, or prepared by grinding 100 grams of colchicum seeds to powder and percolating with 2 volumes of ethanol and 1 volume of water. The solution contains approximately 4 milligrams of colchicine. Label the bottle and store it safely: colchicine is toxic. Always wear rubber gloves when handling colchicine.
4.7 ~ Breeding
The great American horticulturist Luther Burbank (1849-1926) bred cannabis and suggested that other plant developers make further explorations of its possibilities. He also described his technique for breeding giant hemp:
"The hemp plant... is cultivated in this country exclusively for the fiber, its seed being almost altogether neglected. Yet the seed of this plant is prized in other countries for its oil, and its neglect here illustrates the same principle of wasteful use of our agricultural resources...
"My experiments with the hemp... have grown out of a suggestion that I made a number of years ago to a large Boston paper manufacturer, to the effect that... hemp might be used as a substitute for wood pulp in the manufacture of paper.
"The experimental work is only at its beginnings, but it seems to be of considerable promise... The hemp, as is well known, is a dioecious plant, and it may be well to mention the simple but uncommon method of making crosses. All the varieties are first planted separately; and only a few of the largest and tallest male and female plants of each variety are left to bloom. When the heads blossom, the tallest of each variety obtained from different sources are crossed with pollen of the tallest male plants.
"After two seasons of this selection and crossing of different strains from different countries, the varieties were combined by crossing, as before, by selecting the largest and tallest plants, out of which a new race was produced of giant hemp...
"Paper made from the fiber of the hemp is found not generally used heretofore, and must certainly be more prized as other pulps become scarce.
"I mention this line of investigation here merely to suggest the wide range of opportunities what will open up for the plant developer when he has learned to cooperate with workers in other industries.
"Hitherto we have been prone to take it for granted that all the valuable textile plants have been investigated and perfected. The newer studies suggest that there is still almost boundless opportunity for progress, not only through the improvement of the plants that have been utilized, but also through the introduction of species that have been ignored or neglected." (29)
In an interview with the Journal of the International Hemp Association (October 1994), the eminent Prof. Dr. Ivan Bocsa (breeder of Kompolti hemp, which gives the highest yield of fiber in the world) explained that he has bred only dioecious and unisex hybrids because self-pollinated inbreeding of monoecious hemp produces about 20% lower stem yield than dioecious varieties:
"The natural state in which hemp appears was and is dioecious. Monoeciousness is artificial in hemp, and it can only exist with the help of man, and without selection, the dioecious state will return in two or three generations. It is therefore very hard and demanding to keep 90 to 95% monoeciousness during seed multiplications. Apart from that, however, monoecious hemp is appropriate only when the crop is grown for so-called double use, i.e., when both stem and seed are harvested... In a dioecious crop, the male plants will be strongly deteriorated when the crop is harvested at seed ripeness, so in this case one needs monoecious cultivars. In Hungary... this double use is unknown. Here fibre hemp is grown as a dense crop which is harvested at the time of male flowering (â??green hempâ??), while the seed production takes place in crops grown at a low plant density and with completely different growing techniques...
"Furthermore, monoeciousness has two large disadvantages. In the first place... we have established that 20-25% of self-pollination takes place in monoecious hemp, and this is the cause of... [10-20%] lower stem yield. In the second place, in monoecious hemp, the genetic progress for fibre content is slow, because the so-called Bredemann principle cannot be used. The Bredemann principle consists of the rapid determination of fibre content in male plants before they flower, so that only the males with the highest fibre content are allowed to pollinate the female plants... In monoecious hemp this approach cannot be used, so the rate of genetic progress is only 50% or less of that in dioecious hemp. In spite of these disadvantages, we use a monoecious hemp cultivar in breeding, but only as a parent for unisexual hemp." (30)
The Bredemann Principle for the estimation of fiber content is practiced as follows:
"According to the recommended method, just before budding commences, the stalks of hundreds of male plants are vertically cut in half and the bark is stripped off. The stems are boiled for 3/4 hour in 1.5% NaOH solution, to soften the woody matter. The latter is removed mechanically, care being exercised to avoid loss of fiber. The fibrous mass is then boiled again with dilute NaOH solution, washed, dried and weighed. The woody matter may be weighed or detected by difference. As the resulting fibers are purified more than those of commerce, the weight of hemp so found should be multiplied by 1.25 before computing percentages." (31)
The testing must be performed within a narrow window of only a few days, because the plants will quickly proceed to the flowering stage. Only those males with a high fiber content are allowed to flower; the others are culled. The Bredemann method thus enables breeders to increase the fiber yield of dioecious hemp to 35% within a few generations.
The fiber content of stems is determined by sampling numerous plants from a zone situated between points 30-40% up the stem. In practice, find the middle of the stem and cut from that point downward 15%. After retting or mechanical decortication, the correlative standard of the fiber content is calculated from two weighings of the dry weight of the bark divided by the dry weight of the stem. (32)
The production index of bark fiber content makes it possible to calculate the amount of bark per unit of stem surface, and to discover which parents are productive of dry matter and rich in fiber. The index is derived from the ratio of dry weight of bark to the surface of stem (obtained from the product of height times the median diameter).
H. Neuer, R. von Sengbusch, and H. Prieger developed a rapid method of analysis to select plants for high yield of long fibers and seed:
"The stems are cut into 2 or 3 pieces, and 100 such pieces are put in special frames in which the stems of each individual plant are isolated. In these frames the stems are boiled in 0.25% NaOH for 30 minutes. The bast is removed and put in sieve-boxes which are shaken by machine for 1 hour in 2% NaOH with an addition of Persil. The individual fibers are isolated by the shaking and the perenchymous tissue is pulverized. After shaking, the fibers are washed, dried and weighed. The values so obtained are somewhat too high. For the selection of the different stem weights the fiber content classes are detected by investigating 10 plants. For each weight class the mean fiber content is ascertained and only those plants selected whose fiber content is above the mean of the corresponding weight class. Furthermore, the quantity of fibers is recorded in relation to the surface of the stem. A correlation table for fiber weight to surface of stem is made and all plants with high fiber content are examined with the aid of this second table to eliminate plants with low percentage of wood.
"In the course of the investigation this method was further developed. In order to find plants with many fibers, plants with high bast content must be selected: the stems are cooked for 30 minutes in 0.25% NaOH, and the bast is removed, washed, dried and weighed. The plants with high bast content are investigated as to fiber content to eliminate plants with high bast but low fiber content. The bast is cooked in 2% NaOH for 3 hours, washed, dried and weighed. By this method it is possible to investigate in the same time twice as many plants as by the first method.
"Comparative investigations with the different methods proved that generally high bast content corresponds to high fiber content, but that individual plants with high bast content may have few fibers. These two methods do not make it possible to investigate a very great number of plants; von Sengbusch therefore developed a microscopic method for the examination of the bast- and fiber-structure; stem cutting 3-4 cm long are put in water for 5 minutes until the bast is thoroughly soaked. The cutting then is intensively lighted, but the upper part is darkened. By this manner of illumination the parenchymous tissue remains dark, while the fiber cells show clearly. The stems are investigated by binocular microscope (50x). Plants with a thick bast layer containing many fibers are selected and investigated, by the previously described methods, as to bast- and fiber-content. Only the plants with the highest fiber content are propagated.
"For cross-pollinating hemp the breeding system is the same as that devised by Laube for rye: the seed of each selected plant is divided. In the first year, one half is sown as A-strains and tested as to quality. From the best A-strains, the remainder of the seed is sown the following years as A-strains. In the same way the B-strains are obtained and the strains with lower fiber content are eliminated. The B-strains are used for the production of material for new selection and for the production of super-elite, and elite plants and improved seed." (33)
Prof. Dr. Bocsa developed a unisex cultivar in the 1960s after hempseed for sowing became scarce:
"From the research conducted by McPhee, von Sengbusch and Hoffman we know that when a monoecious hemp plant pollinates a dioecious female the offspring (F1) consists of over 90% of females, or 3-5% of monoecious plants bearing mainly female flowers and only 3-4% of true males. This small number of males however is sufficient to ensure adequate pollination of the crop. As the stand consists mainly of seed-bearing (female and dioecious) plants, with the same habit, we called it unisexual hemp. Such a stand yields 60-80% more seeds than a dioecious cultivar. The seed produced on this stand (F2) is used as sowing seed for fibre production. We called this cultivar Uniko-B. It is, in fact, a 'single cross' between Kompolti and Fibromon, but it is the F2 generation which is commercialized. Von Sengbusch and Hoffman described the phenomenon, but they did not think of its practical use... we make the cross between Kompolti and Fibromon on a surface of 5 hectares; this yields 2500 kg of F1 seed. The F1 seed is sown on a surface of 500 hectares, yielding 400,000 kg of F2 seed, which is used to sow 3,000-3,500 hectares of fibre hemp.
"Unisexuality also can be used to exploit the effect of heterosis [hybrid vigor] which occurs when Chinese and European (Kompolti) cultivars are crossed. This heterosis can increase stem yield by 8-15%. to be able to cross two cultivars we have to construct a female parent which is 'male sterile'. A unisexual F1 can be used as such. In order to obtain a unisexual Chinese line we used Fibrimon as the donor, which was backcrossed many times until we obtained a monoecious line with a Chinese habit. We crossed this line with the original dioecious Chinese cultivar to obtain a unisexual Chinese F1... [with] an unsurpassed seed yield potential of up to 1,500-1,600 kg per hectare...
"In some of my cultivars, bark content is 38-40%; this corresponds to a bast fibre content of 32-34%. If the bark content is higher than 40% the crop may lodge...
"Fibre quality is negatively related to fibre content. As we continue to select for fibre content, we unwillingly increase the proportion of secondary fibre, which has a negative effect on fibre quality."
The fiber content of monoecious cultivars can be increased by 60-100%, up to triple the content of the parent stock, with a content of 30% or more of cleaned fibers.
Monoecious (intersex) varieties of hemp are capable of self-pollinating, which soon leads to inbreeding and depression of desired traits. The cultivation of monoecious hemp is feasible only where hemp is cultivated for both fiber and seeds, to be harvested simultaneously. The strains are not stable and so must be maintained by human intervention.
V.P. Soroka studied the formation of male reproductive system in monoecious and dioecious hemp, and reported that the differences between them at very stage of growth prove that dioecious hemp is biologically superior. (34)
Z. Loseva reported these findings:
"The degree of the manifestation and change in monoecism depends on the growing conditions. When hemp is isolated from other varieties (1.5-2 km) and when the strains are carefully separated at the right times, monoecious hemp preserves 80-90% of the monoecious plants and 0.5-1.5% of the common staminate hemp for many years. If monoecious hemp is grown along with dioecious varieties, monoecism disappears. After two years of growing under such conditions, the monoecious hemp actually becomes converted into dioecious hemp." (37)
The French strains of industrial hemp are "pseudohybrid unisexual" cultivars which are more easily produced and reliably maintained than monoecious varieties: