Somaclonal Variation and Vegetative Selection

  • Cooper: Selection of corn, watermelon, etc. (1799)
    A complaint is very general, that potatoes of every kind degenerate, at which I am not surprised, when the most proper means to produce that effect is constantly practiced; to wit, using or selling the best, and planting the refuse; by which means, almost the whole of those planted are the produce of plants the most degenerated. This consideration induced me to try an opposite method. Having often observed that some plants or vines produced potatoes larger, better shaped, and in greater abundance than others, without any apparent reason, except the operation of nature, it induced me to save a quantity from such only, for planting the ensuing season, and I was highly gratified in finding their production exceed that of the others, of the same kind, planted at the same time, and with every equal advantage, beyond my expectation, in size, shape, and quantity; by continuing the practice, I am satisfied that I have been fully compensated for all the additional trouble.
  • Arthur: Physiological basis for the comparison of potato production (1892)
    The potato tuber is physiologically the resting state of a branch having a number of buds. Each tuber possesses a certain amount of reserve force, partly in the form of starch, and partly in other forms designated as vigor. The reserve force of the tuber is greatest at the apical (seed) end and becomes less toward the base; it increases with the size of the tuber and with its natural roughness; and it may be made more available by wilting the tuber, exposing it to cold, or facilitating the absorption of moisture. Dividing the tuber divides the reserve force, and increases the number of lines in which it is distributed, or in other words, the number of plants to which it gives rise.
  • Webber: Improvement of plants by selection [USDA Yearbook for 1898]
    For several years Messrs. B. T. Galloway and P. H. Dorsett, of the Division of Vegetable Physiology and Pathology, have been carefully selecting violet cuttings to determine to what extent the plants can by this means be improved in productiveness, vigor, and ability to resist disease, etc. The results already obtained show that productiveness is remarkably increased, and they also clearly demonstrate that violets can be gradually improved by a continuous selection of the cuttings used in propagation and of the plants from which these are obtained.
  • Powell: Bud Variations (1899)
    I have in mind a Currant plantation which contains some 10,000 bushes of Fay's Prolific, which came directly or indirectly through cuttings from twenty-five Fays, purchased at 1 dol. each some ten or twelve years ago. The original bushes were uniform in size, and heavy bearers. As the Fay currant was one of the best varieties extant twelve years ago, and the plants were scarce, the cheapest way to secure a plantation was to take cuttings from a few bushes. In the haste for a large number of plants, the new wood was cut from these bushes every fall. When more bushes were established, they were divided into cuttings as fast as new wood was made. Little attention was paid to the bearing capacity of the bushes in the second generation, from which the cuttings were taken, because the original twenty-five were exceptionally heavy bearers. The result at the present time is 12,000 Fays, some of which are tremendous bearers, others light bears, while still others produce no fruit at all.
  • Goff: Vegetative selection of potatoes (1899)
    It is believed that these experiments, reaching as they do through fourteen years, are sufficient to demonstrate the principle that vigor in the potato plant, as in other plants, may be maintained and increased by selection. The potato grower must decide how far he can benefit by this principle. Heretofore he has attained the end by purchasing, as often as his varieties fail, new varieties, in which vigor has been enhanced by careful breeding.
  • Buttenshaw: Vegetative Selection (1906)
    'The object of the experiment is to ascertain whether the saccharine content of the sugar-cane can be effected by selection of cuttings.' These experiments consist in selecting two series of canes— (1) canes rich in sucrose, called 'High' canes, and (2) canes poor in sucrose, called 'Low' canes. The experiments have now been in progress for four years. Each year the ten richest canes have been selected from the high plot and the ten poorest front the low plot. This represents an attempt to obtain two divergent series— 'one tending to increased richness, and the other to decreased richness.' ln making the selection, the canes are examined by cutting off the basal portion in the middle of the fifth internode from the base, crushing this basal portion in the Chatanooga mill, and determining the amount of sugar by means of the polariscope in the sample of juice so obtained. ... The difference on canes planted in 1900 and 1904, in pounds of sucrose per gallon, has increased from .597 to .876, an increase of 46 per cent. Similarly, the difference on canes reaped in 1901 and 1904 has increased from .020 to .199.
  • Macoun: Hill Selection of Potatoes (1918)
    After a variety has been originated, and after its general characteristics have been sufficiently fixed to introduce it, a variety may be changed, to some extent, by careful selection. This may be undertaken for the purpose of increasing the yield or to obtain a variety which is earlier or later, shallower in the eye, or of better shape. Selection may also be made to obtain a potato which is more resistant to disease and drought, better in quality, or with a higher percentage of starch, but while selection is desirable there needs to be more experimental evidence to show that marked, permanent changes in a variety can be made in this way.
  • Michurin: Propagating fruit trees (1929)
    ... we may come across a sport deviation (bud variation) of one of the buds of a cutting (this, in general, happens rather rarely in old, long-existent varieties of plants, but in hybrids, particularly at a young age, up to ten years, sport deviations must be regarded as a common occurrence).
  • Bosley: The Nurseryman's Rose Responsibility (1937)
    At first, points of difference in a deteriorated variety are very small. They are like forks in a road, quite close together and yet one fork may lead you far astray. For example, I began to notice that Rev. F. Page-Roberts was just an ordinary yellow rose—a long way from the beautiful two-toned rose it is pictured. We set about to find the most highly colored blooms, and to cut bud-wood from only those very sticks. Continuing this over a number of years, Rev. F. Page-Roberts began to look like its color illustration.
  • Hjort: Sporting Tendencies of Newer vs. Older Roses (1938)
    Summing up the evidence, it is plain that newer roses sport much more freely than the older ones, and probably finish sooner. It is quite probable that this feature links up with longevity in the various classes. The older Tea roses have shown little inclination to sport, and are, under favorable conditions, very long-lived.
  • Prokofyeva: Heterochromatization (1947)
    The regularities of heterochromatization, namely, (1) its increase in active regions adjoining the inert ones, (2) its suppression in inert regions inserted into active ones, (3) its varying length in active regions adjoining the inert ones, due to the latter's sensitivity, (4) its suppression at temperatures of 14 and 30° C., and (5) its increase in the progeny with the age of female parents, are all in full accord with the regularities of crossing-over.
  • O'Rourke: Effect of Juvenility on Plant Propagation (1951)
    In Citrus, and to a slight degree in Malus and some other plant species, seedlings may be produced from embryos which arise entirely from the maternal nucellar tissue surrounding the embryo sac, and subsequently develop within the embryo in the normal way to produce viable seed. The resulting seedlings will therefore be of exactly the same genetic constitution as the seed parent and may he considered clonal since they have been produced by asexual means. Frost (8) and Hodgson and Cameron (13) have reported that such "young clones" produced by apogamy are more juvenile in appearance and characteristics than the "old clones" from which they arose. Buds taken from seedling "new clones" produce more vigorous trees which come into fruiting later than those grown from buds taken from "old clones" of the same variety. The time of fruiting of any clone is apparently associated with the mature growth phase, and as Spinks (15) has pointed out, it cannot be hastened to any degree by treatments and environmental influences. The ease of production of vegetative individuals of uniform genetic constitution and of high vigor has been hailed by Cook (3) as an opportunity for a new field of research in plant science.
  • Burdick: Tomato Haploids (1951)
    Recalling that the original haploid was y, colorless skin, it is hard to explain the appearence of yellow skinned fruits in these doubled haloids. Other plant characters gave some indication of segregation also.
  • Zimmerman: Rose 'Sports' from Adventitious Buds (1951)
    A new kind of rose (sport) appeared on a branch of Briarcliff variety. The new rose flower was single and pink. The parent plant was a double pink. When plants of the sport were propagated from stem cuttings, they continued to show the same characteristics. When plants were propagated from root cuttings involving adventitious buds, they reverted to the original Briarcliff variety.
  • Breese, et al. Somatic selection in perennial ryegrass (1965)
    An experiment has shown that the rate of tillering (= asexual reproduction) in perennial ryegrass can be significantly altered by selection within clones. The response to this somatic selection depended on the age of the clone such that response was obtained in young clones raised from seedlings but not in clones with a long history of uninterrupted asexual propagation. The response was also dependent on the genotype of the clone and there was some evidence to suggest that the somatic lability of genotypes was predisposed by a history of adaptation to asexual propagation previous to the sexual cycle. The responses could be attributed to changes in the plasmon and were inferred to be potentially adaptive. The significance of these results in relation to sward dynamics is discussed.
  • Darlington & Mather: Somatic Mutation (1969)
    Most old vegetatively propagated plants such as pelargoniums and potatoes have become chimaeras owing to somatic mutation at some time in their history. When they are propagated from root-cuttings (or from disbudded tubers) shoots grow out of the concealed inner layers which reveal the chimerical structure and the ancient mutations of these plants.
  • Dayton: Adventitious shoots on apples (1970)
    The technique of forcing adventitious shoots was used to test for genetic mutations in the internal wood of Golden Delicious, Mclntosh and several strains of Red Delicious. Disbudding had no effect on Golden Delicious, but one or more adventitious shoots formed on all the treated Mclntosh and Red Delicious trees. Of 25 trees developed from adventitious shoots, 15 exhibited fruit or tree characters more or less different from the source variety. Results from investigations of changes in fruit pigmentation indicated that cells may carry mutations affecting two or more characters and that the internal wood-may be heterogeneous, containing two or more kinds of genetically different tissues.
  • Hall, et al.: Isolation of thornless loganberry by meristem culture (1986)
    'Thornless Loganberry' (TL) is a periclinal chimeral blackberry in which a layer of mutant (thornless) epidermis surrounds a core of wild-type (thorny) tissue. Due to its chimeral arrangement, TL produces thorny adventitious root cuttings and thorny offspring. To separate the chimera into its components parts, meristems of TL were grow in vitro on modified Murashige and Skoog medium to yield callus and adventitious shoots. One of these shoots has survived, flowered, and produced thornless offspring from seed. The importance of this non‑chimeral TL is discussed.
  • Larkin & Snowcroft: Somaclonal Variation (1988)
    The cell culture system was readily established with an astonishing capacity for plant regeneration. Toxins were isolated and a bioassay was developed. One of us (Larkin) remembers well an embarrassing number of weeks in 1980. During the development of the bioassay, suitable susceptible parental sugarcane plants became unavailable. In their place a small group of regenerants from cultures of that genotype were used. These had not been exposed to toxin in culture. To our extreme annoyance a couple of those plants gave "resistant" reactions to the bioassay. The expectation of their being susceptible was so strong that the compelling initial conclusion was that the bioassay was unreliable. For some weeks these results were not conveyed to anyone. As true control plants and a fresh isolation of pathotoxin became available, the assays were repeated many times. The assay method was indeed vindicated and the presumptive resistant regenerants were also confirmed.
  • Lloyd: In vitro Rosa shoots (1988)
  • Arene: A comparison of the somaclonal variation level of Rosa hybrida L. cv Meirutral plants (1993)
  • Kaeppler: Epigenetics and Somaclonal Variation (2000)
    Detailed phenotypic analyses in later studies showed that quantitative variation is also frequently found among regenerant-derived progeny. Quantitative variation has been described for many phenotypes including plant height, plant biomass, grain yield, and agronomic performance. A generalization of studies that have assessed quantitative variation is that quantitative variation is frequent and inheritance studies indicate alteration of numerous loci.
         LoSchiavo et al. (1989) ... In this study, methylation levels were also developmentally regulated, being "reset" as cells were induced to embryogenesis.
  • Canli & Skirvin: Thornless rose (2003)
    Abstract: To isolate a pure thornless rose, a thornless sport of Rosa multiflora ('Fairmount 1') was established in tissue culture. To determine whether the sports were chimeral and consisted of both thorny and thornless tissue, the regenerants obtained in the tissue culture studies were assessed for the thorny or thornless condition both in vitro and ex vitro. Chimeral plants were expected to yield both thorny and thornless regenerants. Among these regenerants we expected to obtain a pure thornless rose. All tissue culture experiments with 'FM1' yielded both thorny and thornless regenerants, clearly demonstrating that 'FM1' is chimeral. TDZ significantly affected segregation both in vitro and ex vitro. The percentage of thorny plants was highest at 14.4 µM TDZ and lowest with control (0 µM TDZ). The linear relationship between increasing TDZ concentrations and percentage of thorny plants at vitro was significant. These results show rose chimeras can be separated into their component genotypes by growing them on media with high concentrations of TDZ (3.6, 5.4, 7.2 and 14.5 µM TDZ). Also among 240 plants from the TDZ experiments, 21 plants were classified as thornless after a seven months in the greenhouse.
  • Vegetative Selection
  • Epigenetics, Gene Silencing, RNAi