Thornless Roses

Thornless Roses

---

Although the number of species in the genus is about , the direct ancestry of modern roses includes only species. Roses species grow as shrubs, bushes and climbing plants. Furthermore, in the industrial production of oils, essence, and other products for the pharmaceutical and cosmetic trade, thorns add to the difficulty of harvest.

Therefore, a thornless rose would be preferred by many growers, merchandisers, retailers and by the public Nobbs, Researchers have used natural mutations, conventional breeding methods and chance seedlings to breed thornless roses. Spontaneous thornless mutants of rose have been described Morey, ; Nobbs, ; Oliver, ; Druit and Shoup, This instability suggests that many thornless roses are chimeras, consisting of mutant thornless tissue that grows together with normal thorny tissue Nobbs, and Rosu et al.

The instability could also be due to transposable elements. A tissue culture method to isolate pure thornless and chimeral plants, would allow differentiation between these two possibilities. If thornless mutant plants are chimeras, tissue culture could allow us to separate the pure thornless genotype from the thorny tissue growing with it. In this way the pure thornless roses will transmit thornless genes through a sexual cycle and geneticists will have access to new genes for thornlessness. In Greek mythology, a chimera is a fire-breathing monster having the head and foreparts of a lion, the middle part of a goat and the hind parts of a dragon Neilson- Jones, In plant science, the term chimera refers to a plant which has at least two genetically different cell layers or groups growing together as a result of mutation in the apical meristem.

Mutations that occur within a plant often affect only a segment of the meristem and give rise to sectors of layers of the mutated tissue. A plant propagated from such a meristem is thus composed of two or more genetically distinct tissues mutant cell groups growing adjacent to each other in the same individual plant Neilson-Jones, and Tilney-Bassett, A chimera may develop in several different ways: Mutations are believed to be single cell events and may occur in any type of plant tissue. The location of a mutant cell is important for determining its effect on the chimeric plant.

Those in the outer layers of the apical dome are more likely to be observed than those that develop deep in the body of the plant. Mutations may be detected visually chemically, morphologically or remain unknown.

11 Stunning Rose Variety Without Thorns For Hassle-Free Gardening

Mutations for fruit color, leaf shape or color, changes in fruit and leaf size, reversion from thorny state to thornless state are easy to distinguish visually. Other mutations such as change in resistance to severe winter or changes in tolerances to salt levels may never be observed except under a stress condition such as severe winter Hartmann and Kester, ; Marcotrigiano, Chimeras have been classified in several different ways Tilney-Bassett, Plant chimeras can be classified according to their origin, induced by several factors, such as spontaneous mutations, chemical mutagens and colchicine treatments, grafting, inheritance sorting out among seedlings Hartmann and Kester, ; mixing of different groups of cell in the callus cultures; or somatic hybridization of cells in protoplast fusion experiments.

Chimeras can be classified according to their behavior as species or graft chimeras, chromosomal chimeras, nuclear gene-differential chimeras or plastid gene-differential chimeras depending upon how they are expressed in vivo Tilney-Bassett, Chimeras can be classified into three distinct groups according to their structure; mericlinal chimeras, sectorial chimeras and periclinal chimeras based on the arrangement of their histogenic layers in the apical meristem Hartmann and Kester, and Tilney-Bassett, The arrangement affects how they are expressed in vivo.

Sectorial chimeras are composed of two genetically different tissues situated side by side occupying distinct sectors of the stem. This type of chimera is often seen as distinct regions sectors on variegated plants Hartmann and Kester, The position of a lateral bud determines the segregation pattern of chimera.

The location of the mutated cell in an apical meristem determines chimeral type.

Roses By Type

If a mutation occurs in a cell on one side of the apical meristem, only a portion of the stem will be affected yielding a sectorial chimera. Any lateral shoots developing from this mutated region of the stem might be completely mutant e. The apical meristem of a periclinal chimera includes at least one complete layer of mutated cells. A chimera with a layer or two of mutated tissue that completely surrounds nonmutated tissue called periclinal chimera. Periclinal chimeras are relatively stable and are quite common.

Many thornless blackberries Rubus sp. Botanically all roses are thornless. In contrast, true thorns are modified stems or leaves and arise from deep within the tissues, so they possess vascular tissue Rosu et al. In general, when a thorny plant mutates to the thornless condition, only the epidermal cells are affected. All internal tissues remain genetically thorny. Unless a plant loses its periclinal structure, the plant remains thornless, but shoots arising form the internal tissues, will be thorny.

Shoots arising from the roots root suckers develop from the thorny internal tissues, root suckers will always have thorns Skirvin, Blackberries and raspberries Rubus spp. The actual number of prickles on a blackberry stem can be affected by light and, in general, plants grown in high light conditions have more thorns than those grown in the shade Skirvin, and Peitersen, However, there are thornless brambles, most of which arose as sports mutations on thorny plants. McPheeters and Skirvin succeeded in obtaining pure thornless shoots of TE in tissue culture. The pure thornless plants produced thornless root suckers and segregated for a dominant gene for thornlessness S te Hall et al.

The breeding of rose by conventional sexual methods is difficult, time consuming and expensive due to genetic incompatibilities, sterility, polyploidy and a relatively long generation cycle. Polyploidy is common in roses and is another drawback in rose breeding since gene segregation is complicated in polyploid species Ben-Meir and Vainstein, ; Rajapakse et al.

In spite of these complications rose breeders, produce new cultivars at a remarkable rate. The introduction and development of germplasm for thornlessness could speed the introduction of the trait into roses by both conventional sexual and molecular means. The most common types of thornless roses arose as natural mutations sports on thorny plants. Thornless sports or mutants of rose have been reported on many occasions Table 1 for many years Morey, ; Nobbs, ; Oliver, ; Druit and Shoup, ; but most have either been unstable for the thornless character Nobbs, and Rosu et al.

Nobbs and Rosu et al. Nobbs reports that there are degrees of thornlessness in roses that vary from complete thornlessness to thorny. However, completely thornless roses, which have no thorns on either stems or leaf midribs, are very rare. Roses with thornless stems and some thorn-like structures on petioles are more common than the completely thornless ones. Oliver reported finding a thornless chance seedling in which many years later reverted to a thorny condition. He assumed this reversion was a result of incomplete mutation.

Navigation menu

Later, he selected another 16 seedlings, two of which were absolutely free of thorns. Based on his experience, he did not expect them to revert to the thorny state. Druitt and Shoup, two breeders from a central Texas nursery, released a report on thornless rose breeding in They stated that although there is little information on thornless rose breeding and genetics, they found more thornless roses than they had expected. They believe that a rose should only be classified as completely thornless if it has been grown at several locations for at least 15 years without thorns reoccurring. Using this criteria on a collection Druitt and Shoup reported thornless roses in Texas, none of which has proved to be pure thornless.

There are some relatively thornless roses that are commercially available: However, these roses develop a few thorns when grown under various climates Druitt and Shoup, Reported that a putative thornless rose they tested sometimes sprouted thorns or produced thorny canes. The frequency of reversion was affected by age, extreme temperature and change in soil make up.

However, these also are not completely thornless Druitt and Shoup, Morey used mutation-inducing compounds to make many types of mutant rose. He reports that most of his mutants have been of no value for breeding because they were periclinal chimeras. The putative thornless roses reported by Nobbs and Rosu et al.

The situation remains unknown. Since no thorns were observed on the stems of regenerants and three of the regenerants were classified as almost smooth, even on their petioles. While the parent plant produced some lateral branches with recurved thorns, the authors assumed they had succeeded in obtaining a pure thornless rose by separating the chimeral tissues.

Because the chimeral status of the regenerants was unknown, the authors tried to force adventitious shoots suckers from the roots of their putative chimeral plants without success Rosu et al. The authors assumed that a periclinal chimeral thornless rose that possessed a thornless epidermis LI that overlayed a core of thorny cells LII and LIII should produce thorny, not thornless, root suckers.

In this manner these authors planned to use suckers to distinguish chimeral and pure thornless plants, but they were not successful in forcing root suckers. Three chimeral thornless rose named Thonless Isparta, Fairmount 1 and Fairmount 2. Thornless Isparta arose as a sport on a thorny plant. He found about 10 to 12 completely thornless shoots coming out of a 10 to 15 year-old thorny rose bush. Philip Dziuk on his farm in Fairmount, Illinois. In vitro regeneration and segregation methods to obtain pure thornless roses. He classified 59 plants as thornless among plants after a year of growth.

Genetics of thornlessness in rose: The genetic basis of thornlessness in roses remains largely unknown because most thornless roses are infertile making genetic investigations and thornless cultivar improvement difficult Nobbs, Thornlessness in the rose is due to cytoplasmic causes. This experiment is obviously too small to prove a point, but it suggests that the thornless character is cytoplasmically inherited and the thornless plant should be used as the seed parent Nobbs, Although some thornless roses have little commercial value due to their instability, the use of tissue culture could allow us to separate the pure thornless genotype from the thorny tissue growing with it.

In this way pure thornless forms of rose cultivars could be obtained and tested Rosu et al. In addition, if we assume that the thornless character will pass through a sexual cycle, geneticists will have access to new genes for thornlessness. These can be used in traditional breeding cycles of crosses followed by selection or through genetic engineering efforts where the thornless gene could be introduced directly to outstanding thorny cultivars to yield thornless plants.

Most researchers have used natural mutations, conventional breeding methods and chance seedlings to breed thornless roses. These procedures are time consuming, expensive and the probability of obtaining a thornless rose is low. Thus, tissue culture techniques appear to be a good way to obtain pure thornless roses without losing the desirable characters of the chimeral parent. Website design by AJ's Design Lab. All pictures on this website are protected by copyright. Most images are owned by Rosesgalore. The remainder are either in public domain, or used with permission.

If you find an image on this website that you feel is in breach of copyright, please contact us with the page URL. Wild Roses Wild or species roses. They have a natural simple beauty, with their plain 5 petal flowers and vibrant red hips. Hybrid Tea Probably the most popular type in use today. Orignally created by crossing Hybrid Perpetuals and Tea roses. Climbing Roses The climbers are not a variety, they can come from different families such as HT's, Floribundas, Antiques etc.

Rambling Roses Similar habit to the climbers, but with a few subtle and important to remember differences between them. Floribunda Well known for their prolific sprays of flowers, the floribundas are a very popular garden choice.

Smooth Touch Thornless Roses

Generally very easy care. Miniatures A great way to bring your roses indoors or onto the patio. And with a low price, you can have as many as you want!

Categories

English Roses One of the best loved varieties, David Austin's English roses are a must have for your garden. Shrub Roses This class is a "catch all" for roses that just don't fit other catagories.

• Surprise! Surprise!
• Unbridled and Unridden [The Double Rider Mens Club 4] (Siren Publishing Menage Everlasting)
• A Positively Shocking Lightning Quiz
• Discover Spirit at Any Age: An Awakening into My Spiritual Journey
• Mozart, 14 of His Easiest Piano Pieces for the Piano: A Practical Performing Edition (Alfred Masterwork Edition)
• Gifts of Love
• One Is for the Sun